Piga, Carlo and Urgeghe, Pietro Paolo and Piredda, Giovanni and Scintu, Maria Francesca and Di Salvo, Riccardo and Sanna, Gavino (2013) Thermal inactivation and variability of γ-glutamyltransferase and α-L-fucosidase enzymatic activity in sheep milk. LWT - Food Science and Technology, Vol. 54 (1), p. 152-156. ISSN 0023-6438. Article.
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We present a study of the thermal inactivation and variation of activity of two enzymes in sheep milk: γ-glutamyltransferase and α-L-fucosidase. We find that the thermal treatment of milk causes inactivation of α-L-fucosidase between 57 °C and 68 °C, and γ-glutamyltransferase between 68 °C and 80 °C. In untreated sheep milk, the highest level of enzymatic activity (EA) for these two enzymes is in the pH range 5.5–6.0 and 8.0–8.5, respectively. Skimming treatment causes the loss of 35% of the activity of γ-glutamyltransferase. No differences in the EA were ascribable to the diets evaluated in this study. We observed EAs of α-L-fucosidase and γ-glutamyltransferase over the entire lactation cycle, noting that the EA of the former increased from 81 to 207 U mL−1 (average 159 ± 30 U mL−1) while the EA of the latter from 3.12 to 4.89 U mL−1 (average 3.83 ± 0.34 U mL−1). Relationships between both enzymes and selected milk parameters (lipids, proteins, lactose, urea and somatic cells) are highlighted by Principal Component Analysis.
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