Growth and growth boundary model with terms for melting salts to predict growth responses of Listeria monocytogenes in spreadable processed cheese

Milk-derived antimicrobial peptides incorporated whey protein film as active coating to improve microbial stability of refrigerated soft cheese

Nisin is the first FDA-approved antimicrobial peptide and shows significant antimicrobial activity against Gram-positive bacteria, but only a weakly inhibitory effect on Gram-negative bacteria. The aim of this study was to prepare whey protein-based edible films with the incorporation of milk-derived antimicrobial peptides (αs2-casein151-181 and αs2-casein182-207) and compare their mechanical properties and potential application in cheese packaging with films containing nisin. These two antimicrobial peptides showed similar activity against B. subtilis and much higher activity against E. coli than bacteriocin nisin, representing that these milk-derived peptides had great potential to be applied as food preservatives. Antimicrobial peptides in whey protein films caused an increase in film opaqueness and water vapor barrier properties but decreased the tensile strength and elongation at break. Compared to other films, the whey protein film containing αs2-casein151-181 had good stability in salt or acidic solution, as evidenced by the results from scanning electron microscope and Fourier transform infrared spectroscopy. Whey protein film incorporated with αs2-casein151-181 could inhibit the growth of yeasts and molds, and control the growth of psychrotrophic bacteria present originally in the soft cheese at refrigerated temperature. It also exhibited significant inhibitory activity against the development of mixed culture (E. coli and B. subtilis) in the cheese due to superficial contamination during storage. Antimicrobial peptides immobilized in whey protein films showed a higher effectiveness than their direct application in solution. In addition, films containing αs2-casein151-181 could act as a hurdle inhibiting the development of postprocessing contamination on the cheese surface during the 28 days of storage. The films in this study exhibited the characteristics desired for active packaging materials.

Influence of Emulsifying Salts on the Growth of Bacillus thuringiensis CFBP 3476 and Clostridium perfringens ATCC 13124 in Processed Cheese

Processed cheese is a dairy product with multiple end-use applications, where emulsifying salts play a fundamental role in physicochemical changes during production. Moreover, some of these salts may be a strategy to control spoilage and pathogenic microorganisms, contributing to safety and shelf life extension. This study aimed to evaluate the in vitro inhibitory activity of two emulsifying salts (ESSP = short polyP and BSLP = long polyP) against Bacillus thuringiensis CFBP 3476 and Clostridium perfringens ATCC 13124, and to compare the in situ effects of two emulsifying salts treatments (T1 = 1.5% ESSP and T2 = 1.0% ESSP + 0.5% BSLP) in processed cheeses obtained by two different methods (laboratory- and pilot-scales), during 45-day storage at 6 °C. C. perfringens ATCC 13124 growth was not affected in vitro or in situ (p > 0.05), but both of the treatments reduced B. thuringiensis CFBP 4376 counts in the tested condition. Counts of the treatments with B. thuringiensis CFBP 3476 presented a higher and faster reduction in cheeses produced by the laboratory-scale method (1.6 log cfu/g) when compared to the pilot-scale method (1.8 log cfu/g) (p < 0.05). For the first time, the inhibitory effect of emulsifying salts in processed cheeses obtained by two different methods was confirmed, and changes promoted by laboratory-scale equipment influenced important interactions between the processed cheese matrix and emulsifying salts, resulting in B. thuringiensis CFBP 4376 growth reduction.

From Cheese-Making to Consumption: Exploring the Microbial Safety of Cheeses through Predictive Microbiology Models

Cheeses are traditional products widely consumed throughout the world that have been frequently implicated in foodborne outbreaks. Predictive microbiology models are relevant tools to estimate microbial behavior in these products. The objective of this study was to conduct a review on the available modeling approaches developed in cheeses, and to identify the main microbial targets of concern and the factors affecting microbial behavior in these products. Listeria monocytogenes has been identified as the main hazard evaluated in modelling studies. The pH, a_w, lactic acid concentration and temperature have been the main factors contemplated as independent variables in models. Other aspects such as the use of raw or pasteurized milk, starter cultures, and factors inherent to the contaminating pathogen have also been evaluated. In general, depending on the production process, storage conditions, and physicochemical characteristics, microorganisms can grow or die-off in cheeses. The classical two-step modeling has been the most common approach performed to develop predictive models. Other modeling approaches, including microbial interaction, growth boundary, response surface methodology, and neural networks, have also been performed. Validated models have been integrated into user-friendly software tools to be used to obtain estimates of microbial behavior in a quick and easy manner. Future studies should investigate the fate of other target bacterial pathogens, such as spore-forming bacteria, and the dynamic character of the production process of cheeses, among other aspects. The information compiled in this study helps to deepen the knowledge on the predictive microbiology field in the context of cheese production and storage.