1 Introduction
1.1 Palm oil as a food lipid and biomass-derived resource
Palm oil is one of the most important biomass-derived oil resources in the global food, oleochemical, and bio-based industrial systems. According to the 2025 data, it accounted for 34.2% of production among the major vegetable oils worldwide [
1], highlighting its exceptional contribution to the global edible-oil supply. Its strategic importance derives not only reflected in production scale, but also in the high oil productivity, efficient land-use performance, stable year-round supply, and broad compatibility with food processing, oleochemical conversion, and biomass valorization [
1,
2]. Its semi-solid nature, excellent oxidative stability, and compatibility with fractionation and blending make palm oil widely applicable in cooking and frying oils, bakery fats, margarines, shortenings, confectionery fillings, and other structured food products [
1]. Meanwhile, the processing residues also generates lipid and lignocellulosic streams that may be further converted into renewable energy, bio-based materials, and food-related packaging resources [
3].
However, palm oil also faces significant controversy. It is criticized for its relatively high saturated fatty acid (SFA) content, potential nutritional risks, refining-derived contaminants, and sustainability concerns [
1,
2,
4]. Its nutritional and safety attributes are jointly determined by raw-material quality, triacylglycerol (TAG) molecular structure, fatty acid positional distribution, minor bioactive compounds, processing strategies, and final food application [
5]. Therefore, palm oil should be evaluated as a process-responsive biomass lipid system rather than a uniform commodity oil.
1.2 Current limitations, scope, and novelty of this review
Existing reviews have provided substantial insights into palm oil nutrition, processing, food safety, and sustainability [
1,
6,
7]. However, these topics are often evaluated as relatively independent issues. Nutrition-oriented assessments commonly emphasize palmitic acid intake, serum lipid profiles, and cardiovascular risk [
8,
9], whereas processing reviews generally describe extraction, refining, fractionation, and lipid modification as separate unit operations [
1,
6,
10]. Safety-focused studies, in turn, have concentrated mainly on 3-monochloropropane-1,2-diol esters (3-MCPDEs), glycidyl esters (GEs), and their mitigation [
7,
11]. This separation obscures how raw-material quality and processing severity jointly alter triacylglycerol (TAG) architecture, fatty acid positional distribution, minor bioactive components, oxidation status, crystallization behaviour, functional performance, digestive fate, and contaminant formation [
12-
15].
To address this gap, the present review adopts an integrated structure–processing–nutrition–safety framework and evaluates palm oil as a defined, process-responsive biomass lipid system rather than as a uniform commodity oil. It examines how milling, refining, fractionation, interesterification, storage, and thermal use reshape palm oil structure and subsequently influence physicochemical functionality, nutrient retention, digestion, oxidation, and safety outcomes [
16,
17]. The review first establishes the native structural basis of palm oil, including its fatty acid composition, TAG species,
sn-position distribution, minor bioactive components, crystallization behaviour, and solid-fat network formation. It then links processing-induced transformations with nutritional performance and contaminant formation, before assessing engineering strategies such as moderate refining, precursor control, enzymatic lipid restructuring, AI-assisted process optimization, and biomass valorization. By connecting molecular structure, processing history, nutrition, safety, and sustainability, this review aims to provide a systematic basis for defining product-specific processing conditions and supporting the development of higher-value palm-oil products.
2 Native Structural Characteristics of Palm Oil: The Starting Point for Quality Engineering
2.1 Lipid composition and TAG architecture
Oil palm fruit provides two chemically distinct oil resources because different anatomical parts of the fruit accumulate lipids with different molecular identities (Fig. 1). Palm oil is extracted from the fleshy mesocarp, whereas palm kernel oil is obtained from the inner kernel. Although both originate from the same oil palm fruit, they should not be treated as interchangeable oils. Palm oil is the dominant commercial product in terms of production volume and is mainly used in edible-oil systems, frying oils, bakery fats, margarines, shortenings, confectionery fats, and structured lipid products [
18]. Palm kernel oil is produced in much smaller quantities but has high value in oleochemical, surfactant, confectionery, coating fat, and specialty-fat applications because of its lauric-fat characteristics [
1,
19]. Palm oil is a palmitic–oleic-rich mesocarp oil, typically containing about 40%–45% PA, 38%–43% oleic acid (OA), 9%–12% linoleic acid (LA), and 4%–5% stearic acid [
20]. This balanced distribution of saturated and monounsaturated long-chain fatty acids gives palm oil its semi-solid consistency, oxidative stability, crystallization capacity, and suitability for fractionation into palm olein, palm stearin, and palm mid-fraction [
14,
21]. By contrast, palm kernel oil is a lauric-rich kernel oil, commonly containing approximately 45%–52% lauric acid (C12:0), 14%–18% myristic acid (C14:0), 7%–10% PA, 13%–18% OA, and smaller amounts of caprylic, capric, stearic, and LA [
22,
23]. This short- and medium-chain SFA profile makes palm kernel oil closer to coconut oil, resulting in sharper melting behavior, higher saturation, and different functionality in confectionery and oleochemical uses [
18].
The physicochemical and nutritional properties of edible oils are fundamentally determined by fatty acid molecular structure and their distribution on the glycerol backbone. In palm oil, PA and OA are the dominant fatty acids and are mainly esterified into characteristic TAG species, such as POP (1,3-dipalmitoyl-2-oleoylglycerol), POO (1-palmitoyl-2,3-dioleoylglycerol), PLP (1,3-dipalmitoyl-2-linoleoylglycerol), PLO (palmitoyl-linoleoyl-oleoylglycerol) and related palmitic–oleic TAGs [
24]. These TAG structures determine the melting behavior, crystallization, fractionation performance and application of palm oil [
25,
26]. More importantly, the acyl distribution at the
sn-1,
sn-2, and
sn-3 positions influences lipase-mediated hydrolysis, intestinal absorption, and subsequent metabolic fate [
27]. PA located at the
sn-2 position is generally associated with more efficient intestinal absorption and a lower tendency to form insoluble soaps with divalent mineral ions, thereby exerting less interference with intestinal homeostasis and mineral bioavailability [
28]. Therefore, the physiological activity and nutrition of palm oil should be understood from the integrated perspective of fatty acid composition, TAG molecular structure, site-specific digestive release, and intestinal microenvironment interactions, as further discussed in the following section on palm oil digestion and absorption [
29].
2.2 Minor bioactive components
The nutritional and functional value of palm oil is determined not only by fatty acid composition and TAG structure, but also by the concentration and species of minor bioactive components. Compared to other vegetable oils, palm oil, particularly crude and red palm oil, has a distinctive lipid-soluble bioactive profile characterized by the coexistence of carotenoids, vitamin E (tocopherols, tocotrienols), phytosterols, squalene, and other unsaponifiable constituents [
26,
30]. Despite constituting less than 1% of the oil phase, these constituents profoundly influence its color, oxidative stability, and nutritional quality (Table 1) [
31]. Red palm oil contains approximately 500–750 mg·kg
−1 carotenoids, 600–1000 mg·kg
−1 total vitamin E compounds, and 325–365 mg·kg
−1 phytosterols, although these values depend on cultivar, fruit maturity, extraction, and refining history [
32-
34]. Carotenoids in palm oil are important lipid-soluble bioactives with provitamin A activity, and their conversion into retinoids contributes to vision, epithelial integrity, immune regulation, and normal growth and development [
35]. Tocopherols and tocotrienols, particularly the tocotrienol-rich vitamin E fraction of palm oil, exert antioxidant and anti-inflammatory activities
in vivo and may help regulate lipid oxidation, cellular redox balance, and cardiometabolic health [
36,
37].
Palm oil minor bioactives are highly processing-sensitive, and their degradation or removal during milling and refining reduces antioxidant capacity and distinguishes crude, red, and fully refined palm oils [
32,
33]. In a mild physical-refining process operated at 170 °C, red palm olein retained up to 80% of the carotene and vitamin E originally present in crude palm oil [
31,
38]. The mildly processed crude palm oil contained 52% more carotene, 57% more squalene, and 2.8-fold higher antioxidant capacity than high-heat processed oil [
39]. During palm oil fractionation, lipid-soluble bioactive compounds tend to be retained preferentially in the liquid olein fraction, whereas their levels are generally lower in palm stearin [
30,
40]. The higher abundance of bioactive molecules in palm olein makes it more suitable as an edible oil for improving nutritional quality, while also providing a safer and more nutritionally favorable option for food-processing applications [
41]. A systematic evaluation of lipid molecular composition and minor bioactive retention is therefore essential for guiding moderate processing strategies that preserve health-relevant constituents, control quality-deteriorating factors, and improve the overall nutritional, functional, and safety profile of palm oil.
2.3 Crystallization behavior and solid fat network formation
The physicochemical functionality of palm oil is primarily governed by how its characteristic TAG molecules crystallize and organize during cooling [
25]. Among palmitic–oleic TAG moleculars, palmitic-rich TAGs such as PPP (1,2,3-tripalmitoylglycerol) and POP have relatively high melting points and crystallize earlier during cooling, providing the initial crystalline framework of the fat phase [
42]. In contrast, more unsaturated TAG such as POO, PLO, and OOO (1,2,3-trioleoylglycerol) have lower melting points and remain in the liquid phase over a wider temperature range [
13,
43]. The balance between these high- and low-melting TAG fractions determines the melting profile, minor bioactive content, and application of palm oil [
21,
44].The molecular symmetry and acyl-chain composition of TAGs further influence crystallization kinetics and crystal structure transformation [
25,
45]. Symmetric saturated–unsaturated–saturated TAGs, such as POP, tend to pack more regularly and contribute to relatively stable crystal formation [
46] TAG containing more unsaturated acyl chains, such as POO and PLO, disturb ordered packing and reduce crystal growth rate, thereby increasing fluidity and softening the fat matrix [
47]. During cooling, palm-based fats may initially form less stable α crystals, which can subsequently transform into β′ or β forms depending on cooling rate, TAG composition and final storage temperature [
48]. A higher proportion of POP-type TAG generally favours the formation of fine and stable crystal structures, while excessive accumulation or uncontrolled transformation of high-melting TAGs may promote coarse β crystals [
44,
46]
Palm-based fats can crystallize in α, β′, and β polymorphs, which differ in molecular packing, thermodynamic stability, and crystal morphology. The α form is the least stable and usually appears first during rapid cooling; its loose packing and small crystals favour nucleation but undergo rapid transformation. The β′ form has intermediate stability and generally forms fine crystals that develop dense networks with good oil-binding capacity and plasticity. The β form is the most stable and highly ordered, but excessive growth of large β crystals may cause graininess, fat bloom, or oiling-out [
14,
40].
In palm-oil systems, the prevailing polymorph and network structure depend strongly on TAG composition and processing history. Dry fractionation changes the distribution and crystallization behaviour of high- and low-melting TAGs in palm olein and palm stearin [
34]. Enzymatic interesterification of palm olein and palm kernel stearin improves lipid-phase compatibility but may promote β′–β transformation and a less compact crystal network [
10]. By contrast, interesterification of palm stearin, coconut oil, and peony seed oil produced a medium- and long-chain TAG(MLCT)-containing margarine fat with a β′ crystal form suitable for plastic-fat applications [
41]. Molecular-compound formation in palm olein/OPO-rich blends further demonstrates that specific TAG interactions can redirect polymorphic transitions and functional performance [
38]. Thus, palm-oil functionality is governed by TAG distribution, polymorphic state, crystal size, and network connectivity rather than SFA or solid fat content alone.
3 Processing-Induced Structural Changes in Palm Oil
3.1 Early processing: milling, sterilization and crude oil quality
The initial quality of crude palm oil is determined not only by fruit maturity and oil yield, but also by the coupled control of moisture, temperature, and residence time during early processing [
49,
50]. After harvesting, bruising, detachment, delayed transport, and storage disrupt mesocarp tissues and expose TAG to endogenous lipases. In the presence of available water, lipase-mediated hydrolysis converts TAG into free fatty acids (FFA), diacylglycerols (DAG), and monoacylglycerols (MAG) [
51]. This transformation increases oil acidity, alters the interfacial properties of the crude-oil matrix, and may worsen subsequent oxidation and bleachability performance, thereby creating a more reactive system before refining [
50,
51].
Temperature control serves a distinct but complementary function. Sterilization must provide sufficient temperature-time exposure to inactivate lipases, soften the mesocarp, facilitate fruit detachment, and support oil release [
52]. However, temperature must not be viewed merely as a tool for water reduction. Insufficient heating allows hydrolysis and FFA accumulation to persist. Conversely, excessively severe or prolonged heating can degrade valuable minor bioactive compounds, while simultaneously driving up energy consumption [
31,
53]. The relevant objective is therefore not maximum heating, but the minimum thermal load required to achieve effective enzyme inactivation, efficient oil release, and acceptable crude-oil quality [
31,
52].
Pressing and clarification further determine the stability of the extracted oil. Along with neutral lipids, crude oil may retain water, suspended solids, phospholipids, gums, trace metals, and other polar impurities [
54]. Residual water can sustain hydrolytic deterioration, while metals and suspended particles may promote oxidation during storage or subsequent heat treatment [
55,
56]. Clarification and dewatering therefore function not merely as physical separation steps, but as upstream stabilization operations that reduce matrix instability and decrease the transfer of impurities and reactive precursors into downstream refining [
57]. From this perspective, moderate processing is not yet a standardized technical definition, but a product-specific principle for balancing impurity removal, temperature-time exposure, phytonutrient retention and energy efficiency. Data-enabled monitoring may eventually assist in identifying processing windows that maintaining the quality required for later refining and food use [
4,
11].
3.2 Refining as selective purification and structural transformation
Refining converts crude palm oil into edible and application-specific products by removing undesirable impurities while simultaneously reshaping its molecular composition and structural environment [
58,
59]. Unstable constituents in crude palm oil affect not only sensory attributes and basic quality parameters, but also storage stability, processing tolerance, acylglycerol integrity, and the formation of risk factors during subsequent refining and thermal treatment [
60,
61]. Therefore, palm oil refining should not be understood simply as impurity removal, but as a process-induced reconstruction of the oil matrix (Table 2). Different refining stages modify palm oil quality through distinct molecular pathways (Fig. 2). Degumming reduces phospholipids, gums, residual water, suspended solids, and metal-associated impurities that may destabilize the crude-oil matrix or promote oxidation [
59,
62]. Deacidification removes FFA and improves oil quality by reducing free fatty acid content,while enhancing smoke point, flavour, and storage stability [
63]. However, this step does not remove DAG and MAG, the hydrolytic condition of the oil should therefore be assessed through the broader acylglycerol profile [
64]. Bleaching removes pigments, residual soaps, trace metals, oxidation products, and polar compounds through adsorption, but this step can also cause substantial losses of carotenoids and other minor bioactive constituents [
31,
62]. Deodorization imposes the highest thermal load and strongly affects FFA stripping, acylglycerol transformation, bioactive-compound degradation, and the formation of 3-MCPD esters and GEs [
60,
61]. Under high-temperature conditions, FFAs and chloride species may promote partial-acylglycerol protonation, cyclic oxonium formation, and subsequent chloride substitution, thereby generating 3-MCPD esters. DAGs react more readily than MAGs, whereas GE formation follows a distinct pathway dominated by the thermally induced intramolecular rearrangement of DAGs [
65]. Because crude palm oil may contain relatively high chloride and DAG levels, precursor burden and deodorization severity jointly determine contaminant formation, providing the mechanistic basis for the control strategies discussed in Section 5.2 [
65].Thus, each refining stage alters not only the chemical purity of palm oil, but also its nutritional profile, oxidative status, thermal reactivity, and structural functionality.
Palm oil refining comprises multiple sequential operations rather than a single step, with pretreatment, bleaching, and deodorization acting as distinct control points. Pretreatment and bleaching remove phospholipids, metals, pigments, soaps, and contaminant precursors, but may also reduce carotenoids and other minor lipids in palm oil [
31,
62]. Deodorization removes residual FFAs and volatiles, whereas excessive thermal exposure promotes bioactive degradation, acylglycerol rearrangement, and 3-MCPD ester and GE formation [
59,
61]. The refining sequence should therefore balance purification, nutrient retention, oxidative stability, contaminant control, and product-specific functionality [
58,
59].
3.3 Fractionation and crystallization as functionality engineering
Palm oil fractionation separates pre-existing TAG populations according to their melting and crystallization behavior. This process produces palm olein, palm stearin, and palm mid-fraction with distinct solid fat content, melting profiles, crystallization properties, and food-processing functions [
66]. In selected food formulations, greater use of lower-melting olein fractions may help control saturated fat intake while maintaining the required product functionality [
67,
68]. During controlled cooling, TAGs containing relatively more C16:0 crystallize preferentially into the solid phase, whereas TAG richer in C18:1 and C18:2 are retained in the liquid phase [
69,
70]. Crystallization temperature, cooling rate, holding time, agitation, viscosity, and solid–liquid separation therefore determine the degree of compositional enrichment, fraction yield, and product purity [
21,
71].
Palm olein is the lower-melting liquid fraction and contains less C16:0 than palm mid-fraction and stearin. Olein fractions contained 32%–36% C16:0, 49%–52% C18:1, and 8%–9% C18:2, whereas the corresponding stearin fractions contained 49%–53% C16:0, 10%–11% C18:1, and 21%–26% C18:0 [
13,
72]. The relatively higher oleic and LA proportions of palm olein support its fluidity and use in cooking oils, frying media, and liquid blends. Palm stearin, in contrast, provides the higher solid fat content and crystal-network strength required as a hard-stock component in margarines, shortenings, bakery fats, and other structured-fat systems [
73,
74]. Palm mid-fraction is obtained by further fractionation and is enriched in selected TAGs, particularly POP-type species, making it useful in confectionery fats and cocoa-butter-equivalent formulations [
74,
75].
The temperature applied during fractionation is a decisive determinant of this compositional separation [
69,
70]. Representative solvent-free studies have examined crystallization and separation between 10 and 25 °C, whereas solvent-aided crystallization has been evaluated at approximately 10–18 °C [
13,
21]. Within the latter system, lower crystallization temperatures favoured saturated TAG enrichment in stearin, while higher temperatures promoted retention of unsaturated TAG in olein. 10 °C produced the highest stearin yield and 18 °C the highest olein yield under the reported conditions [
13,
69]. These temperatures should be interpreted as process-specific examples rather than universal operating targets because the optimal range depends on feedstock composition, solvent use, agitation, residence time, and separation method. Fraction selection should therefore be guided by PA enrichment, TAG profile, melting behaviour, oxidative stability, and intended application rather than SFA content alone. This composition-directed separation provides tailored substrates for subsequent blending and interesterification [
71,
73].
3.4 Interesterification and structured lipid design
The core purpose of palm oil interesterification is not to change the total fatty acid composition, but to rearrange TAG molecular species and
sn-position distribution, thereby simultaneously modulating physicochemical behaviour, processing adaptability, and digestive–metabolic properties [
71,
76]. Recent studies indicated that palm oil-based interesterification had evolved from a conventional approach for preparing plastic fats into a platform for precise structured-lipid design, including single-oil molecular rearrangement, DAG enrichment, MLCT construction, and
sn-2 palmitate-enriched lipid synthesis [
77,
78] (Table 3). Chemical interesterification is usually catalyzed by alkaline catalysts such as sodium methoxide and promotes relatively random acyl exchange among TAG molecules at elevated temperatures. Its advantages include rapid reaction, low cost, and good industrial scalability, making it suitable for technical fats such as shortenings and margarines. However, it has weak positional selectivity and requires post-treatment to remove the catalyst, and may be accompanied by saponification, neutral-oil loss, or accumulation of partial acylglycerols [
79]. By contrast, enzymatic interesterification commonly uses immobilized lipases, especially
sn-1,3-specific lipases such as Lipozyme TLIM. This provides greater potential for preserving or designing specific
sn-2 structures, although enzyme cost, acyl migration, water activity, and scale-up stability remain important constraints [
15,
80]. A direct comparison using RBD palm oil–RBD palm kernel oil blends showed that chemical interesterification with 0.2% sodium methoxide at 110 °C for 30 min caused more extensive TAG redistribution than enzymatic treatment with 4 wt.% Lipozyme TLIM at 70 °C for 6 h. In the 50:50 blend, chemical interesterification reduced LaLaLa, POO, and POP from 11.00%, 14.28%, and 15.61% to 5.15%, 4.87%, and 5.18%, respectively, whereas enzymatic interesterification produced less extensive, predominantly
sn-1,3-selective rearrangement and finer crystals [
81]. In a continuous packed-bed reactor, increasing the temperature from 50 to 90 °C or decreasing the palm-olein flow rate from 40 to 4.5 g·min
−1 promoted acyl migration and increased saturated fatty acids at the
sn-2 position; higher flow rates better preserved the native positional distribution, while limited initial FFA formation was attributed to water associated with the immobilized lipase [
77].
From a structural-design perspective, interesterification of single palm oil or palm fractions can rearrange dominant TAGs such as POP, POO, and PLP, thereby changing the ratio of high- and low-melting TAG, the SFC curve, crystallization behavior, and polymorphic transition. This improves the suitability of palm-based fats for plastic-fat systems and broadens their application scenarios [
71,
80]. For example, in palm olein and fully hydrogenated palm oil systems, enzymatic interesterification can generate new TAGs such as PLS and SOS, reduce SFC, and improve spreadability and end-product adaptability [
25,
79]. Glycerolysis–interesterification further converts palm oil into DAG-enriched structured lipids. In a representative study, palm oil and glycerol were reacted at a 1:1 mass ratio using 4 wt.% Lipozyme TLIM at 65 °C and 400 r/min for 6 h. Prior positional rearrangement stabilized saturated fatty acids at the
sn-2 position and reduced their migration during glycerolysis, thereby altering DAG composition and the crystallization and thermal properties of the resulting DAG fraction [
59]. Palm-based DAG oil may exhibit higher melting point and better oxidative stability than conventional palm oil, but its intestinal digestion can be slower during the intestinal phase. Therefore, DAG-rich palm lipids should be evaluated not only as functional oils, but also as molecular systems with distinct digestion, absorption, and metabolic characteristics [
12,
71]. Another important nutritional direction is the enzymatic preparation of
sn-2 palmitate-enriched structured lipids. PA can be preferentially enriched at the
sn-2 position, while oleic, linoleic, or other unsaturated fatty acids (UFA) are introduced at the
sn-1,3 positions to generate OPO, OPL. These structured lipids are widely relevant to infant formula. Thus, enzymatic restructuring of palm-based fats can shift palm oil from a general fat ingredient toward a nutritionally targeted structural lipid [
17,
82]. Multi-oil interesterification mainly aims to construct MLCT-rich structured lipids. When palm olein is combined with palm kernel stearin or coconut oil and then enzymatically rearranged, newly formed MLCTs can reduce eutectic incompatibility between the original lipid phases. However, these MLCT-rich systems may also show greater susceptibility to β′–β polymorphic transition and form less dense crystal networks [
25]. In a peony seed oil–palm stearin–coconut oil system, for instance, MLCT content increased from 2.92% to 11.38%, the slip melting point decreased from 45.9 °C to 33.5 °C, and a β′ crystal form suitable for functional margarine was obtained [
76].
Overall, palm oil structured-lipid design should integrate TAG species,
sn-position distribution, MLCT formation, crystal polymorphism, network structure, and digestive–metabolic behavior into a unified optimization framework. Its value lies in modifying palm oil through molecular rearrangement to improve both processing performance and nutritional functionality, rather than judging palm-based fats solely by their saturated fatty acid content [
12,
48,
80].
4 Nutritional Quality of Palm Oil Determined by Structural Features
4.1 Molecular structure, digestion and absorption
The digestive behavior and nutritional effects of edible oils are fundamentally determined by their molecular structure [
83,
84]. For palm oil, the major nutritional controversy arises from its relatively high PA content. Excessive intake of PA-rich fats may contribute to lipid accumulation and increase the risk of lipid metabolic disorders under certain dietary and physiological conditions [
8]. However, the nutritional evaluation of palm oil should not rely only on total PA content or saturated fatty acid proportion. Lipid digestion, intestinal absorption, and interactions with the gut microenvironment are also critical determinants of its physiological effects [
83,
84]. In palm oil, fatty acids are esterified at specific positions on the glycerol backbone rather than existing as free molecules. This positional distribution directly affects lipid digestion [
17,
29]. Pancreatic lipase preferentially hydrolyzes fatty acids at the
sn-1 and
sn-3 positions, generating FFA and
sn-2 monoacylglycerols. Since PA in native palm oil is mainly distributed at the
sn-1,3 positions, it is readily released as free PA during intestinal digestion [
25]. Owing to its long-chain saturated structure and low aqueous solubility, free PA is less efficiently incorporated into mixed micelles and can form poorly soluble soaps with calcium, magnesium, or iron. This may reduce fatty acid and mineral bioavailability and may further influence micelle formation, intestinal transport, microbial metabolism, and gut barrier homeostasis [
29,
85].
By contrast, PA located at the
sn-2 position is more likely to remain as 2-palmitoyl MAG after digestion [
16,
86]. Meanwhile, a reduced release of PA during intestinal digestion may lower the formation of insoluble fatty acid soaps with calcium, magnesium, and iron, thereby improving mineral bioavailability and reducing the saponification burden in the intestinal lumen. Therefore, the health relevance of palm oil should be understood from the integrated perspective of fatty acid type, acyl positional distribution, digestive release form, and intestinal interaction. This structure-based framework provides a rational basis for evaluating palm oil nutrition and for guiding structured-lipid design, mild processing, enzymatic modification, and food-specific nutritional optimization [
16,
83,
86].
4.2 PA exposure and nutrition
PA is a major long-chain saturated fatty acid involved in energy storage, membrane lipid composition, protein palmitoylation, and lipid-mediated cellular signaling [
85]. However, adverse nutritional effects cannot be assigned to a single dietary PA threshold. Risk may increase when PA contributes to a dietary pattern in which total SFA or energy intake exceeds recommended levels, or when endogenous PA accumulation exceeds metabolic handling capacity, thereby disturbing lipid homeostasis and promoting lipotoxic stress, inflammation, and insulin resistance [
87,
88]. Since PA is the predominant saturated fatty acid in palm oil, it represents the main basis of nutritional concern surrounding palm oil consumption. Nevertheless, the health relevance of palm oil cannot be inferred from PA content alone. Palm oil supplies PA within a complex TAG matrix that also contains OA, LA, partial acylglycerols, and minor bioactive components [
89]. Moreover, circulating and tissue PA does not originate exclusively from dietary palm oil. Under long-term high-carbohydrate dietary patterns, especially when energy intake exceeds metabolic demand, carbohydrates can be converted into fatty acids through hepatic
de novo lipogenesis, with palmitate as a major synthetic product [
85,
90]. Human metabolic studies have shown that short-term carbohydrate overfeeding can markedly increase hepatic
de novo lipogenesis, while reviews on carbohydrate-induced lipogenesis and fructose metabolism further indicate that excess sugars, particularly fructose-rich diets, can promote triglyceride synthesis, hepatic lipid accumulation, and obesity-related metabolic dysfunction [
90]. These findings provide important context for interpreting the controversy surrounding palm oil: PA exposure and its metabolic consequences reflect both dietary fat intake and endogenous synthesis associated with excess carbohydrate and energy intake, rather than palm oil consumption alone [
87,
90].
Experimental studies provide mechanistic evidence that excessive exposure to free PA can impair metabolic regulation. In cell and animal models, high concentrations of unesterified palmitate have been associated with lipid accumulation, ceramide-related signaling, oxidative stress, endoplasmic-reticulum stress, mitochondrial dysfunction, inflammatory activation, and impaired insulin signaling [
91-
93]. These findings explain how saturated fatty acid overload may aggravate metabolic dysfunction in susceptible tissues. However, they should not be directly equated with the effects of consuming palm oil in ordinary diets, because many models use isolated free PA, supraphysiological concentrations, short exposure periods, or simplified cellular systems that do not reflect the TAG-bound form, digestive process, food matrix, and systemic regulation of dietary lipid metabolism.
Human nutritional interpretation should therefore consider exposure dose, dietary replacement, and metabolic context. Because no PA-specific upper intake level has been established, excessive dietary exposure is more appropriately interpreted against total SFA recommendations; the World Health Organization recommends limiting SFA intake to no more than 10% of total energy [
88]. In a 12-week randomized trial of adults with central obesity, red palm olein (RPOO) supplied 20% of energy in an approximately 2400-kcal diet. Based on its 37.28% PA and 42.2% SFA composition, this corresponded to approximately 19.9 g PA d
−1 (7.5% of energy) and 22.5 g SFA d
−1 (8.4% of energy) from the test oil [
94]. Compared with extra virgin olive oil (EVOO), RPOO produced similar high-sensitivity C-reactive protein and most inflammatory responses, but resulted in approximately 10% higher low density lipoprotein (LDL) cholesterol and an 8% higher total-to-high density lipoprotein (HDL) cholesterol ratio, while increasing plasma carotenoids [
94]. This exposure should not be regarded as a universal adverse-effect threshold because responses depend on the comparator fat, background diet, food matrix, and metabolic status. Replacing partially hydrogenated fats with palm-based fats may reduce trans-fat exposure, whereas replacing polyunsaturated fatty acid (PUFA)- or Monounsaturated fatty acid (MUFA)-rich oils may produce less favourable lipid responses [
79]. Palm oil should therefore be evaluated within its overall dietary and metabolic context rather than by PA or SFA content alone [
87].
4.3 Bioactive retention and function
The nutritional value of crude and red palm oil is influenced not only by fatty acid composition and TAG structure, but also by minor lipid-soluble bioactive components [
95,
96]. Carotenoids provide the characteristic red-orange colour of crude and red palm oil and contribute provitamin A activity as well as antioxidant protection in the lipid phase [
97]. Tocopherols and tocotrienols constitute the vitamin E fraction, with palm oil being particularly notable for its tocotrienol-rich profile relative to many tocopherol-dominant vegetable oils [
98]. These compounds may contribute to oxidative protection and have been associated with antioxidant, anti-inflammatory, and lipid-modulating activities [
95]. Phytosterols may contribute to cholesterol-related nutritional function, whereas squalene and coenzyme Q10 provide additional antioxidant-related and nutraceutical value [
99,
100]. These constituents differentiate crude or red palm oil from highly refined palm oil, although their biological relevance depends on their concentration, chemical stability, and processing conditions.
Retention data illustrated that bleaching and deodorization affected these compounds through different mechanisms. Bleaching is a major adsorption-related loss point for carotenoids [
101,
102]. Evidence showed that carotenoid losses during bleaching ranged from approximately 20% to 50%, depending particularly on bleaching-earth type and dosage. Deodorization imposes the highest thermal load under severe conditions of 240 °C for 20 min, carotenoid removal exceeds 98%. In contrast, a mild process combining bleaching with deodorization at 165 °C for 20 min retains 81.5% of carotenoids [
103]. In the same mild-refining study, vitamin E declined by only 1.5%, although losses of approximately 25%–37% have been reported across physical refining systems, indicating a stronger dependence on deodorization severity and steam exposure [
103]. The objective of moderate refining is therefore not maximal retention of every minor constituent, but the preservation of biologically relevant compounds as far as possible while maintaining impurity removal, oxidative stability, sensory quality, and contaminant control. This balance explains different palm oil products should not be considered nutritionally equivalent in realistic food matrices and digestion models [
4,
7,
104].
4.4 Health implications: a structure-based interpretation
The health implications of palm oil should be interpreted according to exposure dose, TAG structure, and processing state. Palm-derived products are not nutritionally equivalent because red palm oil, refined palm oil, palm fractions, interesterified fats, and repeatedly heated oils differ in fatty acid exposure, TAG composition, bioactive retention, oxidation status, and contaminant burden [
105,
106].
Dose and comparator fat are particularly important. In a 12-week randomized trial of adults with central obesity, red palm olein (RPOO) supplied 20% of total energy, corresponding to approximately 19.9 g PA d
−1 from the test oil. Compared with extra virgin olive oil, RPOO resulted in approximately 10% higher LDL cholesterol and an 8% higher total-to-HDL cholesterol ratio, although most inflammatory responses were similar [
94]. Thus, this dose represents a reported human exposure rather than a universal adverse-effect threshold. Replacing partially hydrogenated fats with palm-based fats may reduce trans-fat exposure, whereas replacing unsaturated oils may produce less favourable lipid responses [
79,
94,
107].
TAG positional structure also affects digestion. PA at the
sn-1,3 positions is preferentially released as free PA and may form calcium soaps, whereas
sn-2 PA is retained mainly as 2-monoacylglycerol. Human infant studies have linked
sn-2-palmitate-enriched formulas with reduced fecal fatty acid soaps and altered calcium and lipid absorption, although these findings cannot be directly extrapolated to adult cardiovascular outcomes [
28,
84]. Palm-based DAG oil also shows different intestinal digestion from conventional palm oil, but long-term human evidence remains limited [
12]. Processing further modifies exposure: red palm oil retains carotenoids and vitamin E, whereas repeated heating generates oxidized and polymerized lipids [
95,
108-
110]. Palm oil health assessment should therefore specify dose, TAG and
sn-position structure, comparator fat, processing state, thermal history, and target population.
5 Engineering Strategies to Optimize Palm Oil Nutrition and Safety
5.1 Mild refining and low-temperature deodorization
Precision refining seeks to remove compounds that compromise sensory quality, stability, and safety without imposing unnecessary thermal or adsorptive stress on the oil [
104,
111]. Mild refining should be understood as a controlled processing window rather than insufficient purification. Deodorization is the principal thermal control point to remove residual FFA and odour-active compounds [
77]. Lowering cumulative heat exposure through shorter residence time, stable vacuum, efficient steam stripping, improved heat transfer, and oxygen exclusion may limit degradation of heat-sensitive constituents and reduce thermally driven contaminant formation [
77]. These adjustments must still achieve adequate deacidification, volatile removal, sensory neutrality, and shelf stability (Table 4). Red palm oil and other nutritionally differentiated products may prioritize carotenoid and tocotrienol retention, whereas refined palm olein intended for frying requires a more neutral flavour profile, low residual acidity, and stable high-temperature performance. The appropriate refining window must therefore be selected according to product function rather than by applying one universally “mild” process.
In mild refining system, bleaching followed by deodorization at 165 °C for 20 min retained 81.5% of carotenoids and caused only a 1.5% decline in vitamin E, whereas carotenoid removal exceeded 98% under severe deodorization at 240 °C for 20 min [
103]. These results indicated that carotenoid preservation was particularly sensitive to the combined effects of bleaching and thermal treatment, while vitamin E retention depended strongly on subsequent deodorization severity and steam exposure. They provide a practical benchmark showing that reduced cumulative heat exposure can preserve biologically relevant constituents when purification requirements have been controlled. Low-severity deodorization is most effective when combined with precursor-oriented conditioning before the final thermal stage [
112]. Stable vacuum, efficient but controlled steam stripping, narrow residence-time distribution, uniform heat transfer, and oxygen exclusion can improve volatile removal without relying solely on higher temperature or longer holding time. Process-optimization studies further indicated that simultaneous adjustment of pretreatment, bleaching, and deodorization variables could lower 3-MCPD and GE formation while maintaining acceptable refined-oil quality, although the optimal response differs between contaminant classes [
11,
112]. The engineering objective is therefore not minimum refining intensity, but the lowest verified severity that satisfies product-specific requirements for safety, sensory quality, oxidative stability, residual FFA control, and retention of relevant bioactive compounds.temperature alone is not a universal solution, particularly when incoming oil contains a high precursor burden. Vacuum and steam conditions determine whether volatile compounds can be removed efficiently at lower temperatures.Excessive steam use may increase energy demand or aggravate hydrolytic effects when process control is inadequate. Short-time vacuum-based stripping and intensified vapour-removal approaches may offer further reductions in thermal exposure, but their effects on contaminant mitigation, bioactive retention, energy use, and product consistency remain to be evaluated at industrial scale [
112].
The appropriate refining intensity depends on product function. Red palm oil and other functional products may prioritise retention of carotenoids and tocotrienols, whereas general cooking oils require a balance between neutral flavour, oxidative stability, and low contaminant risk. Industrial fats may demand greater compositional consistency and sensory stability. Precision refining should consequently define a product-specific thermal window rather than impose a single low-temperature profile on all palm-based oils [
77,
104,
111].
5.2 Precursor removal before deodorization
Contaminant mitigation should begin with crude-oil quality control, rather than relying on corrective treatment after contaminants have formed. [
102,
113,
114]. Rapid processing after harvest, reduction of fruit bruising and loose-fruit deterioration, effective lipase inactivation, clarification, dewatering, and protected storage can limit TAG hydrolysis before refining. The direct outcome of these measures is a lower burden of FFAs, DAGs, MAGs, residual moisture, suspended solids, and oxidation-promoting impurities entering the refinery [
113,
114]. In a palm-pressed mesocarp fiber oil refining study, a two-step water-degumming, acid-degumming, and neutralization sequence reduced FFA from 6.36% in crude oil to below 0.25%, while phosphorus declined from 901 ppm to approximately 23 ppm [
103]. These results indicated that pretreatment improved feedstock quality and reduced the burden on downstream refining, although such improvements should not be assumed to have produced a proportional decrease in GE formation.
Chloride-oriented mitigation should focus on precursor removal before the final high-temperature stage. Water washing, efficient phase separation, optimized degumming, and avoidance of chloride introduction from processing aids, cleaning chemicals, or equipment contact are practical control measures [
115-
117]. For example, water degumming reduced chloride content from 24 ppm to below 10 ppm, and the resulting oil contained less than 0.3 ppm of combined 2- and 3-MCPD esters before further refining [
103], indicating that chloride reduction should be analytically verified rather than inferred from final contaminant levels [
118]. A pilot-scale chemical-refining process combining neutralization, water washing, and lower deodorization temperature reduced 2-MCPD esters, 3-MCPD esters, and glycidyl esters to 0.42, 0.78, and 0.99 mg·kg
−1, corresponding to reductions of 49%, 52%, and 73%, respectively [
4]. These results show that precursor control and reduced thermal severity can jointly mitigate multiple contaminants, although MCPD esters and glycidyl esters respond differently. Effective safety control should therefore integrate low-hydrolysis crude-oil production, removal of water, solids, phospholipids, metals, and chloride-related impurities, control of FFAs and partial acylglycerols, and final deodorization at the lowest verified severity compatible with product quality. This strategy shifts palm-oil safety management from post-formation correction to preventive process design [
65,
102].
5.3 Adsorption, membrane, enzymatic and catalytic strategies
Selective separation technologies can provide direct mitigation when conventional pretreatment does not sufficiently reduce the contaminant burden or precursor reactivity of palm oil. Tailored adsorption has the clearest evidence in palm-oil systems [
119,
120]. In bleaching trials, HCl-treated activated carbon reduced 3-MCPD content by approximately 80% and GE content by approximately 97% [
120]. Beta zeolites reduced 3-MCPD ester by up to 86%, while a synergistic beta-zeolite/activated-carbon system achieved a 94% reduction in 3-MCPD ester together with a 75% reduction in GE [
119]. These results demonstrated that adsorbent selection can be directed toward specific contaminant classes rather than limited to conventional decolourization [
121]. Excessive adsorption may also cause neutral-oil loss and remove carotenoids, tocopherols, tocotrienols, and other valuable minor constituents. In crude palm oil, polyethersulfone ultrafiltration has been investigated as a degumming approach, with phospholipid removal being strongly influenced by membrane structure, operating temperature, and transmembrane pressure [
122]. Centrifugal clarification also improved gum separation, with optimal laboratory performance reported at 1400 r/min for 40 min [
123]. These methods reduced gums, suspended solids, phospholipid-associated materials, and polar impurities, thereby lowering downstream refining stress [
121].
Targeted chemical intervention during thermal refining may provide an additional control route when specific contaminant classes remain difficult to suppress through precursor removal alone. In a reported palm-oil deodorization trial conducted at 250 for 2 h, potassium acetate reduced 3-MCPD esters by 98.7% and GEs by 48.6%, whereas sodium hydrogencarbonate, sodium acetate, and sodium carbonate reduced 3-MCPD esters by more than 80% but did not reduce GEs [
65]. These salts probably suppress 3-MCPD ester formation mainly by neutralizing FFAs and other acidic species and converting them into sodium or potassium soaps, thereby reducing proton availability and limiting the formation of HCl and chloride-mediated acylglycerol intermediates. Bicarbonates and carbonates additionally release CO
2 and H
2O during neutralization. Potassium acetate may be advantageous because potassium soaps are more water-soluble and can be removed more readily by subsequent washing than sodium soaps. However, the mechanism responsible for its partial reduction of GEs remains unresolved because GE formation is primarily associated with the thermal intramolecular rearrangement of DAGs rather than the acid–chloride pathway [
65,
124]. Enzymatic degumming and lipase-catalysed esterification remain relevant upstream options because they may reduce phospholipid-associated impurities or convert FFAs under milder conditions, but direct evidence that they lower final 3-MCPD ester or GE concentrations in palm oil remains limited [
125]. Selective adsorption, physical separation, and targeted chemical intervention should therefore be integrated according to the specific contaminant profile, product specification, bioactive-retention requirement, and food-grade feasibility of the refining system [
112,
126].
5.4 Digital process control and predictive modeling
Digital process control and predictive modeling provide a technical basis for defining moderate processing windows in palm oil refining (Fig. 3) [
127]. Unlike conventional refining, which largely depends on fixed temperature–time settings and endpoint quality inspection, AI-assisted processing integrates raw-material characteristics, process parameters, contaminant formation, nutrient retention, sensory quality, and energy consumption [
128,
129]. This approach is particularly relevant to palm oil because its nutritional quality and safety are highly sensitive to refining severity. Insufficient refining may leave residual FFAs, odor-active compounds, pigments, and pro-oxidant impurities, whereas excessive thermal treatment can degrade carotenoids, tocopherols, and tocotrienols while promoting the formation of 3-MCPD esters and GEs [
112]. Thus, the key challenge is not to minimize processing intensity, but to identify product-specific conditions that balance safety, nutrition, quality, functionality, and sustainability.
A practical AI-assisted refining framework should be built on an integrated process database covering crude-oil quality, pretreatment, bleaching, deodorization, contaminant levels, and final product attributes [
130]. Relevant compositional variables include FFAs, moisture, phosphorus, chloride-related precursors, DAGs, MAGs, carotenoids, tocopherols, and tocotrienols, while process variables include water dosage, acid dosage, degumming temperature, bleaching-earth dosage, deodorization temperature, residence time, vacuum level, steam flow, and specific energy consumption [
131,
132]. These variables represent the chemical and engineering determinants of under-refining, appropriate refining, or over-refining. Existing optimization studies support this concept. Response surface optimization of palm oil physical refining showed that 3-MCPD ester formation could be reduced while maintaining acceptable refined-oil quality, although trade-offs with color and oxidative stability remained [
133]. Degumming optimization similarly reduced GE and 3-MCPD ester formation while preserving basic oil quality [
114], confirming that palm oil refining is a multi-factor and multi-objective process [
113].
Machine-learning models, including random forest, support vector regression, artificial neural networks, gradient boosting, and hybrid mechanistic–data driven models, can further predict contaminant levels, nutrient retention, oxidative stability, residual FFAs, color, and energy demand from integrated process data [
134]. Multi-objective tools such as Pareto-front analysis, desirability functions, genetic algorithms, and model predictive control can then define refining windows for different products [
135]. For example, red palm oil may prioritize carotenoid retention and mild thermal exposure, whereas frying olein may require stronger deodorization and oxidative stability [
136]. Digital twins offer an additional implementation route by integrating real-time sensors, laboratory data, predictive models, and optimization algorithms to simulate how refining conditions affect contaminants, nutrients, energy demand, and product quality [
137]. Although still emerging in edible-oil refining, these technologies can support palm-oil-specific digital platforms [
138]. Overall, AI-assisted refining can shift palm oil processing from endpoint correction toward proactive, data-driven, and sustainability-oriented process design.
6 Palm Oil Biomass Valorization: Linking Food Quality With Circular Bioeconomy
6.1 Oil palm residues as renewable biomass resources
Oil palm biomass should not be treated as a uniform waste stream because its residues differ substantially in origin, availability, moisture content, and chemical composition [
139,
140]. Fronds and trunks are generated mainly during pruning, harvesting, and replanting, whereas empty fruit bunches (EFB), mesocarp fibers (MF), palm kernel shells (PKS), and palm oil mill effluent (POME) are concentrated around milling operations (Table 5). In a reported 2023 biomass availability profile, oil palm fronds represented the largest stream at approximately 63.40 million tons, followed by trunks (9.83 million tons), MF (7.57 million tons), EFB (7.20 million tons), and PKS (4.37 million tons) [
139]. These values show that resource abundance alone does not determine valorization priority. EFB, MF, fronds, and trunks are mainly lignocellulosic fiber resources, whereas PKS is a denser carbon-rich fraction. POME, as a high-moisture liquid stream, is more suitable for anaerobic digestion, nutrient recovery, and water-management routes than for dry carbon-material production [
141,
142].
Composition provides a clearer basis for allocating biomass to high-value applications. EFB contains approximately 38.3% cellulose, 35.3% hemicellulose, and 22.1% lignin, supporting its use in fiber, pulp, nanocellulose, composite, and carbohydrate-conversion routes [
139,
143]. In contrast, PKS contains lower cellulose and hemicellulose contents but approximately 50.7% lignin, together with a dense and durable structure [
139]. PKS should therefore be regarded primarily as a carbon-rich aromatic resource rather than as a conventional fiber feedstock. Its high lignin content supports conversion into biochar, activated carbon, porous carbon, catalyst supports, and solid fuels [
143]. More broadly, lignin should not be considered only as a barrier to cellulose recovery. As the major renewable aromatic biopolymer in oil palm biomass, it can also provide phenolic compounds, aromatic-value products, functional carbon materials, and chemical precursors [
143,
144]. Composition-guided allocation of cellulose-rich and lignin-rich residues is therefore essential for efficient circular palm-oil processing [
140].
6.2 Valorization routes relevant to palm oil quality and safety
Oil palm residues can be valorized through routes that directly or indirectly support palm oil quality and safety (Fig. 4). Lignin-rich and carbon-rich PKS is particularly suitable for carbonization and adsorbent development, whereas EFB, MF, fronds, and trunks provide cellulose- and hemicellulose-rich feedstocks for fiber-based materials [
139,
145]. However, raw biomass cannot be directly regarded as an effective refining aid or packaging substrate. PKS generally requires carbonization followed by steam, carbon dioxide, microwave-steam, or chemical activation with phosphoric acid or KOH to develop pore structure, surface area, and adsorption sites [
145]. Further hydrothermal treatment, mineral loading, or polymer- and amine-based functionalization may adjust surface acidity/basicity and oxygen-containing groups, thereby improving affinity toward selected impurities. In contrast, cellulose-rich residues are more appropriately converted through delignification, fibrillation, nanocellulose production, surface modification, or blending with biodegradable polymers to improve mechanical strength, grease resistance, and barrier performance [
146-
148].
In palm oil processing, modified PKS-derived carbons may serve as supplementary clarification or refining-support materials rather than direct replacements for conventional bleaching earth [
149]. Their potential value lies in reducing suspended solids, pigments, residual soaps, trace metals, oxidation-related compounds, and selected polar impurities before high-temperature deodorization. A CPO clarification study showed that carbonized, phosphoric-acid-activated, and thermally reactivated PKS carbon improved crude-oil quality; under the reported conditions, 5 wt.% activated PKS carbon at 80 °C produced the lowest FFA value of 3.86 wt.% [
69,
150]. This supports the feasibility of converting lignin-rich milling residues into functional materials for real palm-oil matrices. Nevertheless, this evidence does not directly prove control of 3-MCPD esters, glycidyl esters, chloride-related precursors, neutral-oil loss, carotenoid retention, or food-contact safety. Thus, PKS- and EFB-derived carbons should be viewed as tunable adsorbent platforms whose selectivity must be verified against the actual impurity profile and safety requirements of the target oil.
Cellulose-rich oil-palm residues provide a complementary pathway for biodegradable packaging and protective materials. Fiber-, pulp-, and nanocellulose-based substrates can be developed into molded pulp, coating layers, reinforcing fillers, and composite packaging structures for lipid-containing foods [
145,
148,
151]. Their relevance to palm oil quality lies in controlling oxygen exposure, light transmission, moisture transfer, grease permeation, oil migration, and volatile oxidation products, thereby influencing oxidative stability and shelf life [
152,
153]. Because untreated palm fibers are often porous and hydrophilic, surface coatings, multilayer designs, hydrophobic modification, nanocellulose reinforcement, biopolymer blending, or antioxidant-active components may be required for oil-rich food applications [
139,
152,
153]. Overall, carbon materials may support upstream oil purification, whereas fiber-based materials may protect refined oils during storage and distribution. Both routes require validation in real oil or real food systems, together with migration assessment, bioactive-retention analysis, food-contact compliance, and techno-economic evaluation before industrial scale-up [
153,
154].
6.3 Circular processing concept
Closed-loop palm oil processing can be defined as an integrated system in which selected residues are converted into functional materials, renewable energy carriers, and process-supporting products that are reintegrated into refining, storage, packaging, wastewater treatment, or non-product-contact operations. The concept does not require complete recirculation of every material stream. Its purpose is to retain value within the production system while reducing reliance on virgin materials, external energy, and disposal-oriented waste management [
155].
In such a system, POME-derived biogas may support biomass drying or process heat [
156-
159]; carbonized residues may provide adsorbents for oil clarification or wastewater polishing [
160,
161], recovered antioxidant fractions may be incorporated into stabilization or packaging strategies [
162,
163], and fiber-derived materials may protect oxidation-sensitive products during storage [
154]. These pathways should be evaluated as an interconnected process network rather than as isolated valorization technologies [
155].
Circularity does not automatically ensure food safety or environmental benefits. Biomass-derived materials may require additional energy for activation, purification, or regeneration, while advanced packaging structures can complicate recycling or composting [
154,
164]. Implementation should therefore be assessed through combined criteria that include contaminant control, nutritional retention, oxidative stability, energy demand, waste reduction, product functionality, food-grade compliance, and economic feasibility [
157,
159,
165]. This integrated perspective provides the basis for future assessment frameworks linking palm oil quality, safety, and sustainability.
7 Future Perspectives
7.1 Palm oil structural quality index
Palm oil assessment should move beyond isolated indicators such as fatty acid composition, acid value, or a single contaminant concentration [
166]. A Palm Oil Structural Quality Index (POSQI) may provide a conceptual, structure-informed framework that integrates TAG architecture, fatty acid positional distribution, minor bioactives, oxidation status, contaminant burden, solid fat behaviour, processing history, and application-specific functionality [
25,
167]. Its purpose would be to connect molecular and supramolecular structure with product quality across red palm oil, refined cooking oil, frying olein, hard stock, and confectionery fat [
19,
168]. Because standardized indicators, validated weights, and large comparative datasets remain limited, POSQI should be regarded as a decision-support concept rather than a mature scoring or regulatory system.
7.2 Shifts in processing strategies driven by property changes
Palm oil modification mainly focused on improving physicochemical properties and processing adaptability, such as melting behavior, solid fat content, crystallization rate, polymorphic stability, plasticity, spreadability, and oxidative stability [
169]. These objectives supported the wide use of palm-based fats in margarine, shortening, bakery fats, confectionery fats, and frying systems [
19]. However, lipid functionality is not determined only by macroscopic processing performance. The molecular structure of lipids, including fatty acid composition, TAG species,
sn-position distribution, partial acylglycerol content, and crystal network organization, also governs digestion, absorption, intestinal interaction, and metabolic response [
166]. Therefore, future palm oil modification should shift from physical property-driven processing toward nutrition-oriented molecular design. The main strategies may include several directions. First, enzymatic interesterification can be used to regulate TAG structure and
sn-position distribution, especially to enrich
sn-2 palmitate or introduce UFA at specific positions, thereby improving lipid absorption and reducing intestinal soap formation [
17]. Second, glycerolysis–interesterification can generate DAG-rich palm-based structured lipids with altered digestive kinetics, oxidative stability, and potential metabolic benefits. Third, multi-oil interesterification can combine palm oil or palm fractions with medium-chain, lauric, oleic, or PUFA-rich oils to construct MLCTs or nutritionally balanced structured lipids [
80,
168]. Fourth, mild refining, fractionation, blending, and oleogelation can be integrated to reduce excessive thermal damage while maintaining product functionality [
166,
170,
171]. Finally, AI-assisted optimization would function as a decision-support layer by learning the relationships between feedstock composition, processing conditions, and multiple product responses. Models could integrate TAG species, DAG/MAG content, enzyme dosage, temperature, residence time, cooling rate, vacuum, and energy use to predict TAG redistribution, solid fat content, crystal polymorphism, oxidative stability, 3-MCPD ester and GE formation, and nutrition-related proxies such as
sn-2 palmitate retention or in vitro digestibility [
12,
133,
169]. Multi-objective algorithms could then identify Pareto-optimal processing windows according to product-specific priorities rather than maximizing a single response [
135]. When coupled with online sensing and digital twins, these recommendations could be updated as raw-material quality or process conditions change [
134,
137]. However, simultaneous palm-oil validation across all these endpoints remains limited. Thus, future palm oil processing should not simply aim to make fats harder, softer, or more stable. It should develop structure-defined palm-based lipids with controlled processing performance, digestive behavior, and health-oriented functionality [
172].
7.3 Safer refining through multi-objective optimization
Future refining should be optimized across multiple objectives rather than against a single contaminant or quality target [
173-
175]. Contaminant mitigation, bioactive retention, oxidative stability, sensory neutrality, energy demand, neutral-oil yield, and technological functionality must be considered simultaneously [
173,
176,
177]. Chloride-containing precursors, FFA, DAG, MAG, metals, and oxidation products form an interconnected precursor network before deodorization; controlling only one component is unlikely to provide robust risk reduction [
112]. Process analytics, rapid screening, hybrid models, and data-enabled optimization may help identify product-specific refining windows [
178,
179]. The value of low-temperature deodorization, selective adsorption, membrane separation, and enzymatic processing depends on performance in real oils, scalability, and food-grade validation rather than on laboratory-level removal efficiency alone [
175-
177,
180,
181].
7.4 Integrating palm oil with sustainable food packaging and biomass materials
Palm fibers, cellulose-rich fractions, and nanocellulose may provide substrates for sustainable packaging and functional materials that protect palm oil-containing foods from oxygen, light, moisture transfer, oil migration, and volatile oxidation products [
182-
184]. Palm-derived antioxidant fractions could also support active packaging or oxidative protection, provided that their composition, stability, release behaviour, sensory effects, and food-contact safety are established [
185-
187]. Material development should be evaluated through oxidation control and shelf-life protection in real lipid-rich foods rather than mechanical performance or chemical antioxidant activity alone [
162,
163,
186]. Bio-based packaging does not automatically provide superior environmental or safety performance; barrier properties, migration, recyclability or compostability, and life-cycle impacts remain decisive [
184,
187,
188].
7.5 Building a risk–benefit–sustainability assessment model
A palm oil risk–benefit–sustainability assessment model (PO-RBSA) could provide a decision framework linking nutritional quality, contaminant risk, oxidative stability, food functionality, environmental performance, and economic feasibility [
112,
189,
190]. Safety requirements must operate as non-compensatory gates: nutritional, functional, or environmental advantages cannot offset unacceptable contaminant concentrations, oxidation status, or food-contact risks [
4,
191,
192]. Comparisons should use equivalent functional units, such as frying capacity, solid-fat performance, shelf-life protection, or nutritional service, rather than one kilogram of oil alone [
189,
193]. Life-cycle assessment, techno-economic analysis, and multi-criteria decision analysis may support comparisons among refining pathways, fat substitutions, packaging systems, and biomass-utilization routes, but their conclusions depend on transparent weights, realistic supply-chain data, scenario analysis, and regional validation [
145,
194,
195]. Palm oil should ultimately be evaluated as a defined product with a defined processing history, food use, and assessment boundary [
190,
191].
8 Conclusions
Palm oil should be understood not simply as a commodity edible oil, but as a process-responsive biomass lipid resource whose quality is determined by molecular structure, processing strategies, food application, and sustainability context. Its high productivity, semi-solid functionality, oxidative stability, and compatibility with fractionation and modification make it strategically important for food systems and bio-based industries. However, its nutritional and safety evaluation cannot rely solely on PA content, saturated fatty acid proportion, or single-contaminant indicators. The structural features of palm oil, including TAG composition, sn-position distribution, minor bioactive components, crystallization behavior, and solid fat network formation, govern its physicochemical properties, digestive fate, nutritional performance, and industrial functionality. Processing further reshapes these attributes. Milling, refining, fractionation, interesterification, thermal use, and storage may improve edible quality and application performance, but may also cause bioactive loss, oxidation, acylglycerol transformation, or formation of 3-MCPD esters and glycidyl esters. Therefore, palm oil processing should shift from maximum purification or simple functionality adjustment toward moderate, structure-informed, and product-specific engineering.
Future palm oil development should integrate molecular design, mild refining, precursor control, enzymatic modification, AI-assisted optimization, and biomass valorization. Structured lipids such as sn-2 palmitate-rich TAGs, DAG-enriched oils, and MLCTs provide new routes for improving both processing adaptability and nutritional functionality. Meanwhile, oil palm residues can be converted into adsorbents, packaging materials, energy carriers, and other bio-based products, linking palm oil quality control with circular bioeconomy. Overall, a structure–processing–nutrition–safety–sustainability framework is essential for advancing palm oil from a controversial tropical oil toward a high-value biomass lipid platform.
The Author(s) 2026. This article is published by Higher Education Press.
PDF
(5781KB)
