https://doi.org/10.37229/fsa.fjh.2024.06.15

Washington Navel orange (Citrus sinensis, L. Osbeck) is the most popular among citrus species. Producers and traders face losses of about 20–40% after harvest due to factors such as mechanical damage, microbial spoilage, and improper handling during storage and transportation. Therefore, proper handling and storage becomes crucial to maintain the quality, freshness, and delay spoilage of oranges. This study was conducted during the 2022/2023 and 2023/2024 seasons to evaluate the efficacy of preharvest foliar applications of silicon oxide at (0.50, 1.00 and 1.50) %, and postharvest dipping in jojoba wax at (25, 50 and 75) % on the quality and storability of Washington Navel orange fruits stored at 5 ^◦C with 85-90% relative humidity. Results showed that, prolonged cold storage significantly increased fruit weight loss, decay percentage, and TSS/acid ratio, especially in control fruits, while firmness and vitamin C content gradually declined. Treated fruits showed better quality retention, particularly those treated with silicon oxide at 1.50% and jojoba wax at 75%, which were the most effective in minimizing weight loss and decay and maintaining fruit firmness. Jojoba wax at 50% and 75% significantly preserved vitamin C levels, while the highest TSS content was observed in jojoba wax-treated fruits. Acidity was best maintained with jojoba wax at 75%, followed by silicon oxide at 1.50%, contributing to a more favorable TSS/acid ratio. Total and reducing sugars increased in control fruits but were significantly suppressed by treatments, especially jojoba wax at 75%, whereas, non-reducing sugars showed no consistent trend. Overall, silicon oxide at 1.50% and jojoba wax at 75% were the most effective treatments for preserving the physical and chemical quality of Washington Navel orange fruits under cold storage.