Modeling of Listeria innocua, Escherichia coli, and Salmonella Enteritidis inactivation in milk treated by gamma irradiation.

Measuring microbial inactivation in food is useful for food technology as it allows for predicting the growth or death of microorganisms. This study aimed to investigate the effect of gamma irradiation on the lethality of microorganisms inoculated in milk, estimate the mathematical model of inactivation of each microorganism, and evaluate kinetic indices to determine the efficient dose in the treatment of milk. Raw milk samples were inoculated with cultures of Salmonella enterica subsp. enterica serovar Enteritidis (ATCC 13076), Escherichia coli (ATCC 8739), and Listeria innocua (ATCC 3309), irradiated at doses of 0, 0.5, 1, 1.5, 2, 2.5, and 3 kGy. The fitting of the models to the microbial inactivation data was performed using the GinaFIT software. The results demonstrated a significant effect of irradiation doses on the population of microorganisms, with the application of a dose of 3 kGy, a reduction of approximately 6 logarithmic cycles is observed for L. innocua and 5 for S. Enteritidis and E. coli. The model with the best fit was different for each microorganism studied: for L. innocua, the model was log-linear + shoulder; for S. Enteritidis and E. coli, the model that showed the best fit was the biphasic. The studied model fitted well (R2 ≥ 0.9; R2 adj. ≥ 0.9 and smallest RMSE values) for the inactivation kinetics. The lethality of the treatment, considering a reduction in the 4D value, was achieved with the predicted dose of doses of ±2.22, ±2.10, and ±1.77 kGy, for L. innocua, S. Enteritidis, and E. coli, respectively.

Cyto-genotoxic and oxidative effects of a continuous UV-C treatment of liquid egg products.

UV-C treatment of food is a promising non-thermal processing technology to improve food safety and preservation. Most of the chemical constituents of food absorb UV-C light that can lead to chemical modifications and quality changes. This work investigated the effects of UV-C treatment of liquid egg products on lipid, protein oxidations and potential cyto- and genotoxic effects on intestinal epithelial cells in vitro. Egg preparations (egg white, yolk, liquid whole egg) were treated with UV-C (254 nm, volumetric doses between 0 and 115,619 J L(-1)) using a commercial UV-C processing unit equipped with a Dean Flow reactor. UV-C treatment at high doses (from 32,181 J L(-1), about 2 times higher than that needed to inactivate 5 log of relevant microorganisms) showed an increased lipid oxidation in egg yolk and slight effects in liquid whole eggs; this was confirmed by slightly but not statistically significant increased peroxide values. UV-C induced also slight protein damage, characterised by the total sulfhydryl group reduction. These UV-C-induced oxidative modifications in egg preparations however did not cause any increase in the cyto- or genotoxic (DNA strand breaks) effects in intestinal Caco-2 cells.