Revestimento proteico de soro de leite com nanopartícula de montmorilonita incorporado de antimicrobiano para aplicação em ovos

Abstract

A film-forming solution was developed from a whey protein isolate (WPI) with montmorillonite nanocomposite (MMT) and sodium metabisulfite incorporated as an antimicrobial. The choice of antimicrobial was based on the determination of the minimum inhibitory concentration of seven preservatives (sodium metabisulfite, malic acid, sodium sulfite, sodium nitrite, benzoic acid, sodium benzoate and sodium bisulfite) against Salmonella Enteritidis. The solution was optimized (0.01 mg MMT. mg-1 WPI and 0.41 mg glycerol. mg-1 WPI) through a rotational central composite design and applied to white eggs in the form of coating. Thus, this work aimed to evaluate the effect of this coating effect on the internal, external, microbiological quality and visual appearance of the eggs. In order, to evaluate the internal quality of the eggs, 324 white eggs, class A, Extra type, from 76-weekold laying hens were used in a completely randomized design, following an 2 x 9 factorial scheme (2 treatments coated and uncoated eggs; and 9 storage time 0, 7, 14, 21, 28, 35, 42, 49, 56 days), with three replicates of 108 eggs. The eggs were stored at 25 ± 3 °C and relative humidity of 70 ± 5%, and analyzed for the following parameters: weight loss; percentage of shell, yolk and albumen; Haugh unit (HU); yolk index (GI); pH of the yolk and albumen; foam stability and overrun. The external quality evaluation was performed with 150 white eggs, Class A, Extra type, from 77-week-old laying hens, equally distributed between the two treatments. The color, structure and hydrophilicity of the shell were determined, as well as the eggs' resistance to breaking. For the microbiological evaluation, shells of 20 white eggs, class A, Extra type, from 78-week-old laying hens were used, being inoculated with S. Enteritidis, Aspergillus sydowii and Penicillium paxilli, and distributed among the treatments. The egg shells were stored at 25 ± 5 ºC and relative humidity of 75 ± 5% for up to five days and analyzed every 24 hours for microbial growth. For the sensory experiment 20 white eggs, class A, large type, acquired in the Lavras city were used. The eggs were divided between the two treatments and evaluated about appearance by customers of a supermarket. The coated eggs had lower values of albumen pH, yolk percentage and weight loss, and higher values of UH, IG, foam stability and overrun, when compared to uncoated eggs. The coating showed no antimicrobial activity against any of the microorganisms tested. Sensory analysis showed that coated eggs were preferred over uncoated ones. The coating neither influenced the shell color nor the breaking resistance, but had its hydrophilicity increased. WPI coating may be an alternative for maintaining the quality of white eggs stored at room temperature (~ 25 °C).