Utilization of antibacterial edible coating and nano-silver to enhance the quality of fresh and dried onion

Abstract

The effect of edible coating on shelf life of fresh and dried onion was studied using different coating materials. such as Carboxy methyl cellulose (A) - alginate (B) - starch (C) – carboxy methyl cellulose incorporated into nano-silver (D) - alginate incorporated into nano-silver (E) - starch incorporated into nano-silver (F) - nano-silver (G). Chemical analysis included (moisture content, total soluble solids, total sugars, total phenol content, vitamin C), and microbial analysis included (total count of bacteria, fungi and yeasts) were determined. The results indicated that the lowest percentage of weight loss at the end of the storage period was an average of 0.12%, 0.16% for fresh onions (whole - slices) for treatment (D). The lowest percentage weight gain for dried onion was an average of (0.03%) for treatment (D)at the end of the storage period. The fresh onion color value 277 did not change until the end of the storage period for the treatments (D, E, F, G). Also, the color value was constant until the end of the storage period for the dried onion slices under all treatments except for the control treatment where the average color value decreased up to 313. It was noticed that treatment (D) preserved the largest percentage in both total soluble solids, total sugars, total phenols, vitamin C and also pungency until the end of the storage period of fresh and dried onion samples. Lowest value for total bacterial count was an average 1.91 CFU x 10-2 /g for the treatments (D, E, F, G) this is in the case of fresh onions (whole – slices). Also, these treatments kept dried onion slices without bacterial growth until the end of the storage period. The lowest value for the total count for fungi and yeasts was with a mean 0.97 CFU x 10-2 / g for the treatments (D, E, F, G) this is in the case of fresh onions (whole - slices) for treatment. Also, these treatments kept dried onion slices without fungi and yeast growth until the end of the storage period. Sensory evaluation of the quality overall acceptability was excellent for all treatments (D, E, F, G). It was observed that the treatments (A, B, C) were average and that the control samples were not acceptable. The moisture content decreased from 86% to 9% during the drying period, which ranged between 4-6.5 hours under the influence of different treatments, while the drying rates in the first stage of the drying process ranged between 0.494 to 0.3196 Kg/ hour under the influence of different treatments, while was lowest specific energy consumption during the drying process is 12.61 Kj / (Kg at treatment (G). The lowest cost of evaporating one kilogram of water during the drying process was 1.71 LE/Kg for treatment (G) and the largest percentage of moisture absorption during rehydration was 56.8% for treatment G.