We present a study of the thermal inactivation and variation of activity of two enzymes in sheep milk: gamma-glutamyltransferase and alpha-L-fucosidase. We find that the thermal treatment of milk causes inactivation of alpha-L-fucosidase between 57 degrees C and 68 degrees C, and gamma-glutamyltransferase between 68 degrees C and 80 degrees 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 gamma-glutamyltransferase. No differences in the EA were ascribable to the diets evaluated in this study. We observed EAs of alpha-L-fucosidase and gamma-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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|Titolo:||Thermal inactivation and variability of gamma-glutamyltransferase and alpha-L-fucosidase enzymatic activity in sheep milk|
|Autori interni:||SANNA, Gavino|
|Data di pubblicazione:||2013|
|Rivista:||LEBENSMITTEL-WISSENSCHAFT + TECHNOLOGIE|
|Appare nelle tipologie:||1.1 Articolo in rivista|