The quality of dehydrated ginger (Zingiber officinale Roscoe) on the market of Ghana

Abstract

Aim: This study assessed the physicochemical, microbial, aflatoxin, bioactive, and aroma intensities of dried ginger (Zingiberofficinale Roscoe) sold on the Ghanaian market to determine its quality and wholesomeness for human consumption. Methods: Powdered and sliced dehydrated ginger open-sun dried were purchased from different markets and analysed for moisture, total ash, and acid insoluble ash (AIA) using standard methods. The samples were further analysed for microbial quality: aerobic plate count (APC), yeast and mould,Bacilluscereus, faecal coliform, and total aflatoxins to ascertain overall quality. Also, the flavour and bioactive compounds were evaluated using head space solid-phase microextraction (HS-SPME) and solvent extraction methods, respectively. Results: The moisture content of all sliced samples was significantly higher than that of the powdered ginger, which exceeded the acceptable limit of 12.0% d.b. The APC was in the range of 1 × 10⁶ ± 1 × 10⁶ colony forming unit (CFU)/g to 1.69 × 10⁸ ± 1.77 × 10⁷ CFU/g and yeast and mould, 1.50 × 10¹ ± 0.21 × 10¹ CFU/g to 3.40 × 10³ ± 1.41 × 10² CFU/g with 42.9% having faecal coliform > 1.10 × 10³ most probable number (MPN)/g. The yeast and mould of the powdered samples were significantly higher than the sliced samples, andBacilluscereus was too numerous to count in 50% of the powdered samples. Total aflatoxin content was a maximum of 3.68 ± 0.01 ppb and aflatoxin B1 (AFB1) of 1.64 ± 0.77 ppb, with flavour compounds being mostly sesquiterpenes with α-zingiberene as high as 47.42%. The bioactive compounds isolated were mostly α-zingiberene and gingerol in fractions of 33.72% and 30.82%, respectively. Conclusions: The high microbial contamination of dehydrated ginger on the market calls for proper monitoring and preservative methods to prevent foodborne illnesses and the use of solar dryers for improved microbial quality.

Keywords

dehydrated ginger / flavour compounds / bioactive compounds / microbial quality / aflatoxins

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