Piga, Carlo (2008) Messa a punto e validazione di metodologie analitiche impieganti marker enzimatici endogeni per l'individuazione di blandi trattamenti termici su prodotti del comparto lattiero-caseario. Studi e applicazione sul latte e formaggi ovini sardi. Doctoral Thesis.
As thermal treatments represent one of the main factors affecting properties of milk, a significant attention has been paid in the past in the assessment of analytical methods devoted to identify thermal treatments of dairy products. Among all bovine milk constituents some highly-thermolable endogenous enzymes (i.e. α-L-fucosidase and γ-glutamyltransferase) seems to have all necessaries characteristics to become appropriates markers of soft heat treatment. The lack of analytical methods capable to measure their activity in sheep’s milk and the absence of data attesting their characterization in this matrix are hampering factors towards the protection of typical PDO raw or thermized sheep’s milk made dairy products. In order to overcome the problem this study proposes the development and fully validation of two analytical procedures (i.e. by means UV-VIS spectrophotometry and a RP-HPLC methods) for the determination of both enzymes activities in sheep milk and cheese, whereas the characterization of both enzymes consist of the assessment of their thermal inactivation and the evaluation of enzymatic activity in relation to chemical-physical and zootechnical parameters in Sardinian sheep’s milk. Both methods are characterized by good analytical performance. α-L-fucosidase and γ-glutamyltransferase showed a thermal inactivation in a time/temperature range characteristic of thermization and pasteurization treatment respectively. Both enzymes activities showed a seasonal variability while seems to be not significantly influenced from alimentation parameters. Finally through a chemometrics approach a correlation was highlighted between both enzymes activities and gross milk constituents (fat, protein and lactose).
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