Ricota: qualidade microbiológica e uso de especiarias no controle de Staphylococcus aureus

Abstract

Ricotta is a soft non-matured cheese, elaborated from whey or from a whey and pasteurized whole or skimmed bovine milk mixture. It is considered one of the products that presents the best conditions for microorganism development, which is due its intrinsic characteristics, such as high water activity and nutrient availability. Furthermore, for being highly manipulated during production, it is prone to countless sources of contamination when appropriate hygienic-sanitary practices are not adopted. This study was conducted in two parts. The first aimed to evaluate the microbiological quality of ricottas marketed in Lavras, Minas Gerais, Brazil. The second consisted of researching the antibacterial effect of Origanum vulgare and Salvia officinalis on the control of Staphylococcus aureus and enterotoxin A production in creamy ricotta and the sensorial acceptance of the ricottas elaborated with different concentrations of spices. Of the 28 samples analyzed in the first stage of this study, 67.85% presented counts above the RDC No. 12 norms, of January 2, 2001, of the National Agency of Sanitary Surveillance for thermotolerant coliforms and 42.85% were above the standard for coagulase-positive staphylococci. All of the samples presented an absence of Salmonella sp. and Listeria monocytogenes. Based on these results, we concluded that the microbiological quality of the available ricottas is, in the majority, inappropriate, which requires, besides the adoption of good production practices, the development of alternative bacterial controls. For the study of the antibacterial activity of O. vulgare and S. officinalis in ricotta the target microorganism was S. aureus, using a Central Composite Rotational Design with three variables. Five temperature levels were selected (7.3-20.7 ºC), concentration of O. vulgare (0 - 3.4% m/m) and concentration of S. officinalis (0 - 3.4% m/m). S. aureus, previously inoculated in the samples was quantified after 12, 24, 120 and 240 hours and the results appraised by the response surface methodology (RSM). Enterotoxin A was analyzed after 24, 120 and 240 hours. Finally, ricottas containing different concentrations of spices were elaborated and appraised sensory by the acceptance test. By the RSM it was observed that the spices inhibited S. aureus growth in ricotta, with different standards depending on the concentration and temperature. In some samples the enterotoxin A was not detected. As for the sensorial aspects, there was higher preference for the ricottas with low spice concentrations. This aspect of the study proves that the spices are potential natural antibacterials in the control of S. aureus in ricotta.