Efeitos da lavagem e da sanitização com ácido peracético ou luz ultravioleta sobre a ultraestrutura da casca e características microbiológicas de ovos de consumo

Abstract

The present study examined the effect of egg washing and different disinfection methods on eggshell ultrastructure, on abundance and taxonomic diversity of microorganisms on eggshells, and on egg content, immediately after treatment and after 15 days of storage. A total of 600 eggs were collected from 53-week-old Bovans White® hens, housed in cages, using an automated egg collection system. Selected eggs were randomly assigned to treatments using a factorial scheme 2 × 3: as follows: a) unwashed eggs: without sanitization (WS), sanitized with peracetic acid ([PAA]; 355 ppm; 0.5 mL/egg), and sanitized with ultraviolet C radiation ([UVC]; 254 nm; 2.067 μw/cm2 , 5s), and b) washed eggs (W): WS, PAA, and UVC. A total of 24 eggs were collected for ultrastructural evaluation of the shell, with four eggs per treatment. Measurements were made of the mammillary, palisade, vertical crystal and cuticle in the apical, equatorial, and basal eggshell layers, then average values of the three measurements were calculated. Eight samples of four eggs each were collected to count total mesophilic aerobic microorganisms, Enterobacteriaceae, molds, and yeasts in the shell, contents after 48 hours and contents after 15 days of storage at room temperature. After culturing the microorganisms, morphologically different colonies were selected for identification by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF). Washing reduced the cuticle thickness of eggs (p<0.05) and the use of APA reduced the thickness of the calcified region (p<0.05). Eggs washed and sanitized with APA or UVC showed significant (p<0.05) reduction of shell aerobic mesophilic microorganism counts when compared to eggs washed only. The contents of W-WS eggs showed the lowest contamination by total mesophilic aerobes (p<0.05). The contents of WS eggs, regardless of washing, was free of Enterobacteriaceae. After 15 days of storage at room temperature, the counts of total mesophilic aerobic microorganisms, molds and yeasts were lower (p<0.05) in the contents of washed eggs. The contents of eggs subjected to UVC radiation showed the lowest mold and yeast counts (p<0.05). Eggs washed and sanitized with UVC showed the lowest count of Enterobacteriaceae in the contents after 15 days of storage. Counts of mesophilic aerobes, Enterobacteriaceae, molds and yeasts of the contents after 15 days of storage increased in almost all treatments, however, to a lower degree in W-UVC treatment. On eggshells, the phyla Firmicutes and Proteobacteria were the most prevalent. There was a reduction of bacteria of the Enterobacteriaceae family and an increase of Staphylococcaceae after washing the eggs. In the contents, Firmicutes was most prevalent in the unwashed eggs 13 and Proteobacteria was predominant in washed eggs. The genus Enterobacter was most prevalent in the contents of the washed eggs. No Salmonella was identified on either the shell or the contents of the eggs. By having the lowest bacterial counts on the shell and contents, and the lowest mold and yeast contamination on the egg contents after 15 days of storage, washing associated with the use of UVC can be considered the method of choice in sanitizing consumption eggs. Key words: Microorganisms count; Peracetic Acid; Ultraviolet; MALDI TOF