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)
Oulaï Dehegnan Patricia *
Laboratory of Biotechnology and Valorization of Agroressource and Natural Substances, Département de Sciences Biologiques, Université Peleforo Gon Coulibaly, P, O. Box 1328 Korhogo, Ivory Coast.
Libra Michel Archange
Laboratory of Biotechnology and Valorization of Agroressource and Natural Substances, Département de Sciences Biologiques, Université Peleforo Gon Coulibaly, P, O. Box 1328 Korhogo, Ivory Coast.
Kodjo Noelle
Laboratory of Biotechnology and Valorization of Agroressource and Natural Substances, Département de Sciences Biologiques, Université Peleforo Gon Coulibaly, P, O. Box 1328 Korhogo, Ivory Coast.
Ouattara Hadja Djeneba
Laboratory of Biotechnology, Training and Research Unit of Biosciences Faculty, Felix Houphouet Boigny Univerity, P,O.Box 582 Abidjan 22, Ivory Coast.
Cissé Mohamed
Laboratory of Biotechnology and Valorization of Agroressource and Natural Substances, Département de Sciences Biologiques, Université Peleforo Gon Coulibaly, P, O. Box 1328 Korhogo, Ivory Coast.
Niamké Lamine Sébastien
Laboratory of Biotechnology, Training and Research Unit of Biosciences Faculty, Felix Houphouet Boigny Univerity, P,O.Box 582 Abidjan 22, Ivory Coast.
*Author to whom correspondence should be addressed.
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.
Keywords: Onion, drying, pre-treatment, high perishability, post-harvest losses, preservation