Abstract
Milk pasteurization is a critical issue in the dairy industry, and failures in this process can affect final product safety. Scharer's enzymatic method is still traditionally used to verify pasteurization efficiency compliance, and it is based on screening for residual alkaline phosphatase in milk. Although several methods are used to quantify enzymatic activity to assess milk pasteurization efficiency, there is a small amount of published data regarding the use of these methods to quantify alkaline phosphatase in cheese. In this study, the Scharer's modified method was used to determine the levels of residual alkaline phosphatase in standard minas cheese, before and after 20 days of ripening. The cheeses were made using raw or pasteurized milk with the addition of different concentrations of raw milk (0; 0.05%; 0.10%; 0.20%; and 0.50%). In the fresh cheese samples, the method showed a sensitivity of only 0.50% with the addition of raw milk to the pasteurized milk used to make cheese. In addition, levels of up 0.20% of raw milk in pasteurized milk, the concentrations of phenol was inferior to 1μg phenol/g of dairy product which is the preconized indicator value for adequate pasteurization.
Highlights
Cheeses produced with raw milk may present a threat to public health, mainly due to the possibility of disease outbreaks (Zottola and Smith, 1993)
The following treatment structure was applied: treatment 1; treatment 2, 3, 4, and 5, cheese made from pasteurized milk, added of raw milk at concentrations of, respectively, 0.05%, 0.10%, 0.20%, and 0.50%; and treatment 6
For all the batches in the experiment, alkaline phosphatase activity was detected in the raw milk used for cheese making, and was inactivated after pasteurization
Summary
Cheeses produced with raw milk may present a threat to public health, mainly due to the possibility of disease outbreaks (Zottola and Smith, 1993). Cheese may be manufactured with raw milk, since a 60-day ripening time is observed before consumption. This would be the minimum required time to inactivate pathogenic microorganisms by physicochemical modifications (Kleyn and Goodman, 1977; Abedini et al, 2007). It is important to verify compliance with pasteurization conditions using qualitative and quantitative methods, among them, the determination of alkaline phosphatase (ALP) activity. Alkaline phosphatase (EC 3.1.3.1) is a membrane-bound glycoprotein with sialic acid as sugar moiety. It is a phospho-monoesterase enzyme which catalyzes the hydrolysis of monoesters of phosphoric acid (at alkaline pH), yielding phosphate and the corresponding alcohol. The abundance in nature and importance of this enzyme in biological systems has made ALP activity assessments one of the most commonly performed enzymatic tests (Miggiano et al, 1983; Rankin et al, 2010)
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