Safety improvement of the open sun dried Egyptian Siwi dates using closed solar dryer

Abstract

Egyptian Siwi dates dried using the open sun drying is exposed to different contaminants. So, the current study aims to use the closed solar dryer to improve Siwi date safety. The impact of washing and closed solar drying on the levels of microbial load, aflatoxins and heavy metals in Egyptian Siwi dates (ESD), in comparison to traditional open sun drying methods were examined. Two different drying techniques were employed to dry 300 kg of ESD. The microbial load was assessed following the two drying procedures. The levels of aflatoxins and heavy metals were analyzed using High-performance liquid chromatography (HPLC) and Inductively Coupled Plasma (ICP) techniques, respectively, after both drying methods. Additionally, the influence of storage time on the microbial load of the ESD was also evaluated using standard methods. The findings of the current study demonstrated that the closed solar drying significantly reduced the total bacterial and fungal counts by 96 % and 93 %, respectively, when compared to open sun-drying. No aflatoxins were detected in both fresh Siwi dates and Siwi dates dried using closed solar drying. However, after open sun drying, two aflatoxins; aflatoxin B1 (AFB1) and aflatoxin G1 (AFG1), were detected in the ESD, with concentrations of 0.95 and 0.23 μg kg−1, respectively. The closed solar drying significantly decreased the levels of lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), chromium (Cr), zinc (Zn), manganese (Mn), and iron (Fe) in the dried dates by 96 %, 94 %, 48 %, 71 %, 64 %, 4 %, 26 %, and 7 %, respectively, when compared to open sun drying. The stored Siwi dates that was exposed to the open sun drying showed a higher increase in bacterial (4.86 log CFU/g) and fungal (4.46 log CFU/g) counts. However, the stored Siwi dates that was exposed to the closed solar dryer showed a lower increase in bacterial (3.21 log CFU/g) and fungal (2.51 log CFU/g) counts. So, the duration of storage significantly impacted the microbial loads of the closed solar dried dates as compared to open sun drying. Overall, closed solar drying reduced the levels of investigated contaminants and extended the shelf life of ESD, thereby enhancing their safety for human consumption.