Effect of chitosan molecular weight and type of plasticizer in edible coating on internal quality and eggshell morphology

To investigate the effect of molecular weight of chitosan and the type of plasticizer used in the composition of edible coating on internal quality parameters and morphology of eggshell, an experiment with 125 eggs in a completely randomized design with 5 treatments included uncoated eggs (control), coated based on chitosan with high molecular weight (450 kDa) or low molecular weight (65 kDa) and the use of glycerol or sorbitol and 3 replicates was conducted. Coating was done by immersion method and the eggs were stored at ambient temperature for 4 weeks. The internal quality parameters of eggs including weight loss (WL), Haugh unit (HU), yolk index (YI) and albumen pH were evaluated weekly. At the end of the storage period, scanning electron microscope (SEM) micrograph were prepared for eggshell morphology. The results showed that the edible coating based on chitosan improved significantly (P<0.05) all the evaluated parameters. At the end of the week 4, among these, the lowest values of WL (7.01 ± 0.90) and pH of albumen (8.90 ± 0.15) and the highest values of HU (± 3.23) 63.80) and YI (0.34 ± 0.06) were seen in eggs containing high molecular weight chitosan-sorbitol coating (P<0.05). In the SEM micrograph, more integrated and less porous and fractured in the mentioned group. Therefore, in order to improve the quality of edible coating based on chitosan as a biocompatible packaging to increase the storage time of eggs, chitosan with higher molecular weight and sorbitol as plasticizer are recommended.