The Effect of Temperature on Physicochemical and Microbiological Aspects of Serrano Artisanal Cheese Ripening

Abstract

The serrano artisanal cheese (SAC) is a traditional raw milk dairy produced in southern Brazil. The maturation temperature plays a crucial role regarding the cheeses' microbiological and physicochemical features and has been underexplored when it comes to unpasteurized milk dairy in Brazil. The objective of the present work is to evaluate the effect of ripening temperature on foodborne bacteria (total and thermotolerant coliforms, positive coagulase Staphylococcus and the production of its enterotoxin, Listeria monocytogenes, Escherichia coli and Salmonella spp.) and physicochemical attributes (moisture, water activity, pH, acidity and sodium chloride concentration) of SAC during maturation at 5ºC-20ºC for up to 60 days. Metagenomic analysis was also evaluated through the rDNA 16S method at ripening time of 0-60 days. The samples were safe for L.monocytogenes, E.coli, Salmonella spp. and staphylococcal toxin. The physicochemical parameters reached legal boundaries as follows: moisture, after 30 days at 5ºC; fat, after 30 days at 12.5ºC and 20ºC; fat at dry extract, after 30 days at 12.5ºC or 15 days at 5ºC. The microbiological features indicate that positive coagulase Staphylococcus reached legal conditions after 30 days when cheeses were ripped at 12.5ºC and 20ºC; thermotolerant coliforms after 30 days at 12.5ºC and 20ºC; and total coliforms after 15 days at 20ºC. Lower temperatures lead to lower inactivation rates, and Staphylococcus did not reach legal parameters at 5ºC positive coagulase regarding moisture, water activity HIGHLIGHTS• SAC was free of staphylococcal toxin during ripening.• Staphylococcus group did not reach legal parameters when cheeses were ripped at 5ºC.• 20ºC and 12.5ºC for 30 days seems the ideal conditions to reach legal parameters.• Main acid lactic bacteria were Enterococcus sp. and Lactococcus sp.

Unveiling Safety Concerns in Brazilian Artisanal Cheeses: A Call for Enhanced Ripening Protocols and Microbiological Assessments

“…However, in most studies, Salmonella sp. [ 12 , 15 , 18 , 28 , 33 , 35 , 36 , 48 , 49 ] and L. monocytogenes [ 10 , 13 , 18 , 33 , 36 , 40 , 48 , 49 ] were absent in the various kinds of artisanal cheese surveyed. It is worth noting, though, that Allaion et al [ 34 ] detected 8 positive samples (out of 100) for Salmonella by PCR, but only one was confirmed by the culture-dependent method.…”

“…Concerning the Serrano cheese produced in Santa Catarina state, two of the studies in the reviewed literature [ 15 , 41 ] demonstrated that 60 days of ripening may not be enough to meet the legal parameters since L. monocytogenes was present at 35 [ 41 ] and 60 days [ 15 ] of ripening. However, for Serrano cheese produced in Rio Grande do Sul state, Souza et al [ 68 ], Pretto et al [ 48 ], and Ströher et al [ 49 ] indicated a minimum ripening time ranging from 30 to 33 days, which is a much shorter ripening period that can still reach acceptable microbiological levels than those required by Normative Instruction SEAGRI N° 7 [ 63 ]. It is important to highlight that Ströher et al [ 49 ] demonstrated that the refrigerated temperature (5 °C) determined by IN 7/2014 is not adequate for ripening this type of cheese.…”

“…However, for Serrano cheese produced in Rio Grande do Sul state, Souza et al [ 68 ], Pretto et al [ 48 ], and Ströher et al [ 49 ] indicated a minimum ripening time ranging from 30 to 33 days, which is a much shorter ripening period that can still reach acceptable microbiological levels than those required by Normative Instruction SEAGRI N° 7 [ 63 ]. It is important to highlight that Ströher et al [ 49 ] demonstrated that the refrigerated temperature (5 °C) determined by IN 7/2014 is not adequate for ripening this type of cheese.…”