Numerical modeling of thermal inactivation parameters of Escherichia coli O157:H7 in pretreated watermelon juice

Abstract

Aim: This work focused on numerical modeling of thermal inactivation parameters ofEscherichiacoli O157:H7 in pretreated watermelon fruit juice as influenced by processing conditions. The work aimed to enhance microbiological safety and information of the product. Methods: Mature and fresh watermelon fruits were sourced, graded, and processed into juice under hygienic conditions. The extracted juice was pasteurized and allowed to cool. Prior to thermal treatments, the juice was sterilized, cooled, and inoculated withEscherichiacoli O157:H7. The inoculated samples were then subjected to different treatments. The effect of pH (4.5, 5.5, and 6.5) and temperature (70℃, 80℃, and 90℃) on thermobacteriological properties was investigated. Meanwhile, Design Expert 13 for Windows was used for experimental layout for interactive impact of pH and inactivation temperatures. All experiments were conducted in triplicate. Thermal inactivation curves ofEscherichiacoli O157:H7 in the juice samples were obtained by plotting the number of survivors (CFU/mL) against time, and the correspondingD-value was obtained. Other thermobacteriology parameters were subsequently calculated using appropriate equations. The data obtained were fitted into a model using Design Expert 13 for Windows. Results: Thermal inactivation data obtained showed that the thermal inactivation curve ofEscherichiacoli O157:H7 in pretreated watermelon juice had a linear interactive effect as temperature and pH varied. As temperature (70–90°C) and pH (4.5–6.5) varied, thermobacteriology parameters such asD-value,F-value,z-value and activation energy ranged from 11.8–23.4 min, 23.6–46.8 min, 8–9.6°C, 32.49–42.03 kJ/mol, respectively. The results showed thatEscherichiacoli O157:H7 in pretreated watermelon juice demonstrated significant inactivation at a higher temperature of 90℃ and a lower pH of 4.5. Conclusions: This study provided valuable data that could be employed as a guide for the potential food industry, scientists, and engineers in order to improve the consumption safety of the product.

Keywords

pre-treated watermelon juice / thermal inactivation / Escherichia coli O157:H7 / modeling parameters

References

[1] Ruxton CHS, Myers M. Fruit Juices: Are They Helpful or Harmful? An Evidence Review. Nutrients. 2021;13:1815.

[2] Renner SS, Wu S, Pérez—Escobar OA, Silber MV, Fei Z, Chomicki G. A chromosome—level genome of a Kordofan melon illuminates the origin of domesticated watermelons. Proc Natl Acad Sci U S A. 2021;118:e2101486118.

[3] FAO. World Food and Agriculture—Statistical Pocketbook 2020. FAO; 2020.

[4] Nadeem M, Navida M, Ameer K, Iqbal A, Malik F, Nadeem MA, et al. A comprehensive review on the watermelon phytochemical profile and their bioactive and therapeutic effects. Korean J Food Preserv. 2022;29:546-76.

[5] Dhaliwal MS. Classification of vegetable crops. In: Handbook of Vegetable Crops (3rd Ed.). Kalyani Publishers; 2017. pp. 12-7.

[6] FAO. FAOSTAT: Crops and livestock products—Watermelons, world production. FAO; 2021.

[7] Kim CH, Park MK, Kim SK, Cho YH. Antioxidant capacity and anti—inflammatory activity of lycopene in watermelon. Intl J Food Sci and Techno. 2014;49:2083-91.

[8] Chidozie AA, Chidiebele E, Egboka TP, Iroka CF. Nutritional composition of boiled and unboiled watermelon: A Comparative Study. Asian J Bio Sci. 2024;18:118—23.

[9] Adepoju AO, Ologan O. Post—harvest loss along the watermelon value chain in the tropics. Intl J Veg Sci. 2021;27:461-71.

[10] Praise ET, Azubuike AC, Roseline EC, Finan IC. Nutritional composition of boiled and unboiled watermelon: A comparative study. Asian J Bio Sci. 2025;18:118—23.

[11] Munir MT, Mtimet N, Guillier L, Meurens F, Fravalo P, Federighi M, et al. Physical Treatments to ControlClostridiumbotulinum Hazards in Food . Foods. 2023;12:1580.

[12] Aneja KR, Dhiman R, Aggarwal NK, Aneja A. Emerging preservation techniques for controlling spoilage and pathogenic microorganisms in fruit juices. Int J Microbiol.2014;2014:758942.

[13] Sharma M, Beuchat LR, Doyle MP, Chen J. Survival of salmonellae in pasteurized, refrigerated calcium—fortified orange juice. J Food Prot. 2001;64:1299-304.

[14] Umelo C, Wisdom E, Chioma E, Odimegwu EN, Akajiaku L, Ehirim FN, et al. Effect of heating at different temperatures and times on the bacterial/fungi count and sensory properties of bottled watermelon (CitrullusLanatus) Juice . IOSR J Environ Sci Toxicol Food Technol. 2019;13:23-31.

[15] Ike CC, Odinakachi OH, Kalu AD. Bio—preservation of processed watermelon (Citrulluslanatus) juice using Lactobacillus species isolated from processed fermented maize (akamu) . GSC Bio and Pharm Sci. 2020;10:126-36.

[16] Adeniran HA, Adeniyi DM, Taiwo KA. Microbiological properties of probioticatedkununzaki drink enriched with cocoa powder . Euro J Agric and Food Sci. 2020;2:1-9.

[17] Toledo RT. Fundamentals of food process engineering. Springer; 2007. pp. 310-1.

[18] Mazzotta AS. Thermal inactivation of stationary—phase and acid—adaptedEscherichiacoli O157:H7,Salmonella andListeriamonocytogenes in fruit juices . J Food Protection. 2001;64:315-20.

[19] Araghi LR, Mishra L, Adhikari A, Singh RK. Inactivation kinetics ofEscherichiacoli K12 in selected fruit juices determined by thermal—death—time disks . J Food Process Eng. 2024;47:e14734.

[20] Saubade F, Cossec N, Giguelay Gesret L, Kouamé C, Ellouze M, Gerard C, et al. Heat resistance of five spoilage microorganisms in a carbonated broth. Food Microbio. 2024;122:e104545.

[21] Li H, Gänzle M. Some like it hot: Heat resistance ofEscherichiacoli in food . Front Microbiol. 2016;7:1763.

[22] Lee J, Kaletunç G. Evaluation of the heat inactivation of Escherichia coli and Lactobacillus plantarum by differential scanning calorimetry. Appl Environ Microbiol. 2002;68:5379—86.

[23] Sruthy GN, Sandhya KR, Kumkum CR, Mythri R, Sharma M. Chapter 10—Thermal processing technologies for food. In: Current Developments in Biotechnology and Bioengineering. Elsevier; 2022; pp. 263-300.