Alkaline phosphatase as an indicator for the heat treatment of the milk for cheesemaking
Summary
The aim of this diploma thesis was to summarize current knowledge about the evaluation of alkaline phosphatase activity as an indicator of heat treatment of milk for production of dairy products in theoretical part. In experimental part were comparised 2 methods for this enzyme activity determination, the original according to ČSN EN ISO 11816-2 (2003), using pasteurized milk as an extracting agent, and ISO 11816-2/IDF 155-2 (2010), using extraction buffer. For comparison were used 110 cheese samples, 8 quarg products, 49 fresh cheese products, 9 spiced fresh cheese products, 7 white-brined cheese products, 7 Penicillium sp. flora cheese products, 5 coryneform flora cheese products and 25 semi-hard and hard cheese products.
Alkaline phosphatase (EC 3.1.3.1) is a hydrolase cleaving phosphate groups at the 5th and 3rdposition of many molecules including especially nucleotides and proteins. The enzyme has a pH optimum in the alkaline range (pH 10), their cofactors are ions Zn2+and inhibitors Cu2+. Dairy alkaline phosphatase derived from mammary epithelium and other cellular residua in milk. In this medium is the enzyme localized on the membrane of fat globules. Their amount depends on the stage of lactation (the highest concentration is in colostrum) and animal health (their concentration increases when disease, especially mastitis, starts). Due to its specific thermostability is alkaline phosphatase used for proof of milk and milk products pasteurization.
In the experimental part of the diploma thesis was found that the recommended substitution of pasteurized milk for buffer improves enzyme extraction process from cheese matrix and so enhances method sensitivity (p > 0.05). Method unsuitability for Penicillium sp. flora cheese (especially for blue-veined ones) was also confirmed (p > 0.05). This unsuitability could be explained by content of microbial alkaline phosphatase. For the same reason might not be this method suitable also for coryneform flora cheese. On the contrary, this analysis is suitable (p > 0.05) for white-brined cheese. For spiced fresh cheese were the results in terms of evaluation suitability ambiguous. Based on the obtained data was also confirmed the suitability of proposed limit (10 mU/g) for residual enzyme activity in products from pasteurized milk.
| Identifer | oai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:258415 |
| Date | January 2016 |
| Creators | Malínská, Hana |
| Contributors | Potůčková, Miroslava, Lidmila, Lidmila |
| Publisher | Česká zemědělská univerzita v Praze |
| Source Sets | Czech ETDs |
| Language | Czech |
| Detected Language | English |
| Type | info:eu-repo/semantics/masterThesis |
| Rights | info:eu-repo/semantics/restrictedAccess |
Page generated in 0.0016 seconds