Impact of Blanching and Two Drying Methods on the Nutritional, Organoleptic and Microbiological Properties of Fresh Onions of the Galmi Violet Variety Sold on the Markets of Korhogo (Côte D’Ivoire)

Abstract

The aim of this work is to contribute to the reduction of post-harvest losses of fresh onions, with a view to enhancing their value. To this end, the influence of two drying methods (sun and shade), organoleptic qualities and microbiological characteristics were studied. Onions were subjected to two types of pre-treatment (boiling water blanching and steam blanching) and to 7 days drying at a temperature of 33°C in the sun and at room temperature. The results of biochemical analysis reveal that drying significantly reduces the water content of fresh onions from 83.23% to 14.49%. There was also a variation in ash content from 1.84 to 4.84%, titratable acidity from 5.48 to 42.91 mEq/100g, total polyphenol content from 718.19 to 2170.28 mg EAG/g and flavonoid content from 30.25 to 136.01 mg EQuer/g of dried onions. The results of the sensory analyses show that the steam-bleached and sun-dried samples were more appreciated by tasters for their color, taste and odor. Microbiological characteristics indicate the presence of aerobic mesophilic germs (1.30.10^1 to 7.06.10^5 CFU/g), total coliforms (5.80.10^1 CFU/g), yeasts and molds (1.10^1 to 1.81.10^1 CFU/g) and an absence of fecal coliforms, E. coli and ASR. All these results are an added value for onion processing and will help reduce post-harvest losses.