Physicochemical and Biochemical Changes in Fresh Onion (Allium cepa L., Alliaceae) Bulbs Produced from Four Dry-Seasonal Varieties in Korhogo, Northern Côte d’Ivoire

Aims: Onions are fresh vegetables whose post-harvest storage life is closely related to the variety and season of production. The study aims to investigate the effect of storage upon the nutrients in fresh onion bulbs for better management of the local onion production.

Study Design: Fresh onion bulbs of four dry season varieties, namely Dayo, Safari, Red Star and Red Jewel, were produced and stored to study variations in physicochemical and biochemical properties during storage.

Place and Duration of Study: The study was carried out in the experimental site and laboratory of the University Peleforo GON COULIBALY for four (4) months from June to September 2022.

Methodology: Bulbs of all four varieties were bagged after production and stored in a warehouse at ambient conditions. During the storage, the physicochemical and biochemical descriptors in onion samples were assessed at 30 days intervals. The statistical treatment consisted of comparing the means using the ANOVA test, studying the correlation between the parameters analyzed and principal components analysis at the 5% significance level.

Results: The results revealed significant changes of the parameters assessed from the investigation, according to both the storage duration and onion variety (p<0.001). The lipid and protein contents increased from overall onion bulbs during the storage. Dayo and Safari onion bulbs recorded more significant dry matter (11.59 and 13.19g/100g FM) than the Red varieties (9.70 to 11.31 g/100g FM). The total polyphenols content also increased in Red Star onion bulbs from 43.86 to 53.62 mg/100g FM at day 120 but decreased from the other onion varieties. According to the Principal Components Analysis, Red Star and Red Jewel onions on days 60, 90 and 120 displayed the highest levels of phenolic compounds.

Conclusion: Dayo and Safari bulbs with greater dry matter rates during storage appear as suitable for storage. Nevertheless, the polyphenols profiles increased from the Red Star and Red Jewel onions and are also appreciable. Data on production potential and post-harvest losses could better guide variety selection.