Effect of Preservation Methods and Storage Duration on the Microbiological Quality and Economic Feasibility of Giza 6 Onion (Allium cepa L.)

Abstract

This study evaluated the effects of four preservation and treatment methods—traditional storage, refrigerated storage, natural drying, and oven drying—during storage periods of 2, 4, and 6 months on the microbiological quality of Giza 6 onion (Allium cepa L.), together with a simplified economic evaluation of the four treatments. Microbiological indicators included total microbial count, coliform bacteria, Escherichia coli, and yeasts and moulds, with results expressed as CFU/g. Microbial load increased markedly under traditional storage after six months, reaching 5×10³ CFU/g for total count, 1.6×10³ CFU/g for coliforms, and 2×10³ CFU/g for yeasts and moulds. Refrigerated storage was more effective than traditional storage in limiting growth during the early and intermediate stages, whereas natural drying maintained relatively low levels. Oven drying recorded the lowest microbial load and the most stable pattern; total count remained at 100 CFU/g or below the counting limit, coliforms and E. coli were not detected, and yeasts and moulds remained below 100 CFU/g. E. coli was not detected in any treatment. Because some results were constrained by counting/detection limits (<10 and <100) and others were recorded as “not detected,” the microbiological data were presented descriptively without converting them to zero or directly subjecting them to numerical ANOVA. Economically, natural drying achieved the highest net profit (250 Libyan dinars) and the highest return on cost (500%) under the prices and costs used, whereas refrigerated storage retained the greatest quantity of marketable fresh product. The results indicate that the preferred preservation method depends on the objective: oven drying was best for microbiological stability, natural drying for calculated profitability, and refrigeration for maintaining the quantity of fresh product.