Roseline Esi Amoah

Aim: This study assessed the physicochemical, microbial, aflatoxin, bioactive, and aroma intensities of dried ginger (Zingiber officinale 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, Bacillus cereus, 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, and Bacillus cereus 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.

Human beings have battled with oxidative stress and its related illnesses such as inflammatory diseases, heart diseases, and even cancer for decades. Spices and herbs are known for their anti-inflammatory and antioxidant properties that could mitigate oxidative stress. However, post-harvest loss of such spices make their production seasonal and solar drying could curtail this problem. Solar drying of ginger will add value and reduce post-harvest loss, yet consumer preference needs to be established. This study carried out a survey by administering semi-structured questionnaires to 398 willing respondents in the Accra metropolis to seek information on the knowledge of the health benefits and sicknesses that consumers had used ginger to treat as well as the acceptability of solar dried ginger locally. Respondents enumerated 22 illnesses in the category of anti-inflammatory disorders, stomach discomfort, weight loss, and an aphrodisiac which they had used ginger to cure. More than half of respondents (74.3%) had used ginger to cure upper respiratory infections with an almost unanimous response to the local production of dried ginger for all-year availability.

A comparison of concrete solar dryer (CSD) to stainless steel solar dryer (SSSD) in terms of the effect of drying and 10 vinegar pretreatment on antioxidant activities of ginger rhizome using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity method, Ferric Reducing Antioxidant Power (FRAP) Assay, and total antioxidant methods was investigated. The effect of the two solar dryers and open-sun drying (OSD) on bioactive compound composition of the 10 vinegar pretreated sliced ginger using ethanol and aqueous extracts with GCMS/MS identification was also evaluated. The antioxidant activities of ethanol and aqueous extract of the 10 vinegar pretreated ginger using FRAP, DPPH, and total antioxidant methods were all higher than that of the dried samples, with CSD having the highest antioxidant activities among the dried methods. Drying reduced the main bioactive compound, which is gingerol, from 47.97 in the fresh sample to 32.49 in the OSD sample. The CSD sample demonstrated close likeness to the fresh sample with regard to retaining the highest gingerol and α-zingiberene. Hence, CSD can be adopted for commercial processing of ginger to reduce postharvest losses of the crop.

Ginger (Zingiber officinale Roscoe) rhizomes are mostly used as spice and medicine due to their high aroma intensity and medicinal bioactive compounds. However, the volatile compounds of ginger, partly responsible for its aroma and medicinal properties, can be affected by the pretreatment, drying method, and extraction processes employed. The objective of this study was to assess the effects of pretreatment and drying on the volatile compounds of yellow ginger variety at nine months of maturation. The effect of potassium metabisulfite (KMBS) and blanching pretreatment and drying on the volatile compounds of ginger using head space solid-phase microextraction with GCMS/MS identification (HS-SPME/GCMS/MS) was investigated. KMBS of concentrations 0.0 (control), 0.1, 0.15, 0.2, and 1.0 and blanching at 50°C and 100°C were used for pretreatment and dried in a tent-like concrete solar (CSD) dryer and open-sun drying (OSD). The different concentrations of KMBS-treated fresh ginger rhizomes did not result in any particular pattern for volatile compound composition identification. However, the top five compounds were mostly sesquiterpenes. The 0.15 KMBS-treated CSD emerged as the best pretreatment for retaining α-zingiberene, β-cubebene, α-farnesene, and geranial. The presence of β-cedrene, β-carene, and dihydro-α-curcumene makes this study unique. The 0.15 KMBS pretreatment and CSD drying can be adopted as an affordable alternative to preserve ginger.

This study evaluated the influence of 10% vinegar and solar drying using two solar dryers and open‐sun drying on the microbiological quality of ginger (Zingiber officinale Roscoe) rhizome. The rhizomes were analyzed for bacterial, mold, and Salmonella populations in the raw state, which were water‐washed and soaked in 10% vinegar, and in dried form. The fungal population was isolated and identified. Fresh and dried ginger rhizome contained both bacterial and fungal population in the range of 3.0 x 10² ± 1.14 x 10² to 2,180 x 10⁹ ± 70.7 x 10⁹ CFU/g. The stainless steel solar dryer had fewer fungal loads among the drying methods. Aspergillus and Penicillium species of mycotoxin‐producing potential were identified. The 10% vinegar as pretreatment showed no significant difference (p ≤ .05) in the bacterial population reduction but in the fungal population reduction. Growth of fungi in fresh and dried ginger extracts was lower compared with growth in Potato Dextrose Broth.

Pretreatment of fruit and vegetables is necessary to reduce microbial proliferation and to preserve color of the produce. The effect of drying and pretreatment with potassium metabisulfite (KMBS) of concentrations 0.0%, 0.1%, 0.15%, 0.2%, and 1.0% and blanching at 100°C and 50°C using a tent‐like concrete solar (CSD) dryer as compared to open‐sun drying (OSD) of yellow ginger rhizomes was investigated using routine methods. The total color change and residual sulfur dioxide (SO₂) were analyzed. KMBS reduced the yeast and mould load significantly from 3.6 × 10⁴ ± 1.4 × 10³ CFU/g in 0.0% (control) to 5 ± 2.12 × 10⁴ CFU/g for the 1.0% KMBS. Overall, the CSD had fewer microbial loads than the OSD but it was not significant. Aflatoxins and Salmonella sp. were not detected in any of the samples. The sulfur dioxide residue (SO₂) for KMBS pretreated samples increased as the concentration of KMBS increased with the CSD retaining slightly higher amount than the OSD. The total color change index increased with increase in KMBS, and drying further increased the total color change index. On the whole, the blanched samples had the least color change among the pretreatments with 100°C CSD showing the least change among the dried samples.