ASSESSMENT OF MICROBIAL SPOILAGE OF ONION (ALLIUM CEPA) DURING STORAGE

Abstract This study assessed the microbial spoilage of onion (Allium cepa) during storage under ambient laboratory conditions (30–35°C and 60–70% relative humidity). Fresh onion bulbs were purchased from three different locations within Damaturu metropolis—Household Retailer, Bayan Tasha, and Sunday Market. The onions were cut and exposed to simulate common market and household storage practices. Physical changes were observed daily, while microbial isolation and identification were conducted using Nutrient Agar and standard microbiological techniques (Gram staining). The results showed that visible signs of spoilage began within 48 hours, with complete decay by the seventh day. Bacterial counts ranged from 1.68×10⁻² to 1.98 CFU/g, indicating significant microbial proliferation. Gram staining revealed both Gram-positive and Gram-negative organisms, with Gram-negative bacteria being dominant. The study concluded that cutting and exposing onions accelerate microbial spoilage due to increased surface moisture, oxygen exposure, and nutrient availability. It recommends minimizing cutting before storage, maintaining hygienic handling, adopting cold storage or sealed containers, and applying natural antimicrobials such as neem or garlic extracts to extend shelf life. These findings align with previous studies (Agi et al., 2020; Malilima & Peter, 2022; Torimiro et al., 2020), confirming that post-harvest handling and environmental conditions strongly influence onion spoilage.