Abstract
To evaluate the behavior of the relevant microbial populations during stretched cheese production, quantitative microbiological analysis was performed during the critical steps of the preparation. The obtained data distributions proved statistically significant increases in all indicators, on average by 4.55 ± 0.64 log CFU/g of presumptive lactococci counts, 4.06 ± 0.61 of lactobacilli, 1.53 ± 0.57 log CFU/g of coliforms, 2.42 ± 0.67 log CFU/g of Escherichia coli, 1.53 ± 0.75 log CFU/g of yeasts and molds, and 0.99 ± 0.27 log CFU/g of presumptive Staphylococcus aureus, from the early stage of milk coagulation until curd ripening (0–24 h). The following steaming/stretching process caused reductions in viable counts with the most significant inactivation effect on coliform bacteria, including E. coli (−4.0 ± 1.0 log CFU/g). Total viable counts and yeasts and molds showed 2 and almost 3 log reduction (−2.2 ± 1.1 log CFU/g and −2.6 ± 0.9 log CFU/g), respectively. The lowest decreases in presumptive S. aureus counts were estimated at the level of −1.50 ± 0.64 log CFU/g. The counts of yeasts and molds showed the best indicatory function during the entire storage period of vacuum-packaged cheeses at 6 °C.
Highlights
The pasta filata cheeses share a unique processing step, when the curd is immersed in hot water or salt brine and mechanically stretched to a plastic consistency which can be formed or molded into a variety of shapes [1]
This work provides the data distributions and variabilities of microbiological indicators of 20 raw milk curds steamed and stretched according to an artisanal procedure during laboratory preparation. They include the counts of lactococci and lactobacilli (LBC), total viable count (TVC), coliforms (CFM), E. coli (EC), presumptive S. aureus, and yeasts and molds (Y&M) at each relevant manufacturing step: in raw milk, fresh cheese curd after coagulation, whey, cheese curd after 24 h of fermentation, before the steaming and stretching, and in fresh stretched cheese
Applying the concept of a Food Safety Objective [27], the steps associated with the increase (IG) or reduction (R) of microbial counts are identified in order to provide performance criteria for the artisanal production steps, including the initial microbial load in raw material (H0)
Summary
The pasta filata cheeses share a unique processing step, when the curd is immersed in hot water or salt brine and mechanically stretched to a plastic consistency which can be formed or molded into a variety of shapes [1]. Some of this type of cheese are soft or semisoft and usually consumed fresh or after a brief period of ageing (e.g., fresh Mozzarella, low-moisture Mozzarella, and Scamorza). Stretching describes the mechanical treatment of the curd following cooking [2]
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