The impact of heat treatment conditions on the stability of selected biochemical parameters of small ruminant's milk in Armenia

Abstract

Background: There is a growing need to precisely identify key biological markers to assess the pasteurization of milk from small ruminants accurately. In the case of milk from cattle, such indicators have been specified, whereas for small ruminants, they have not; therefore, this is an area that requires further research.

Objective: The research aimed to assess the stability of the biochemical parameters of goat and sheep milk pasteurized under two different sets of conditions. The overall goal was to precisely determine the key biochemical markers for accurate pasteurization of milk from small ruminants to produce safe, functional food for consumption.

Materials and Methods: Alkaline phosphatase (ALP), lactoperoxidase (LP), and furosine (FRS) were measured photometrically on a CDR FoodLab Analyzer. γ-glutamyl transferase (GGT), lysozyme, and lactoferrin (LF) levels were
determined spectrophotometrically, while casein, lactose, and fat levels were measured using a milk analyzer. The milk heat treatment conditions were 72 °C for 30 seconds and 82 °C for 15 seconds.

Results: Heat treatment decreased ALP, LP, and GGT levels in goat and sheep milk at 72 °C/30 sec by 87.2%, 61.3%, and 83.1%, respectively, and by 96.6%, 61.4%, and 64.9%, respectively. In contrast, levels of lysozyme and LF were unaffected by heat treatment. ALP and LF were not detected in goat and sheep milk heat-treated at 82 °C/15 sec, and their absence in both types of milk provides a basis for proposing them as biochemical markers for precise pasteurization. Furosine was reliably generated in goat and sheep milk as the temperature increased. The total casein, fat, and lactose in raw sheep milk exceeded goat milk by 1.7, 1.3, and 1.2 times, respectively, and a similar trend was observed during heat treatment.

Novelty: We propose a species-specific biomarker panel for goat and sheep milk pasteurization—ALP, LP and GGT
suppression with FRS increase, plus LF loss at 82 °C/15 s—validated under 72 °C/30 s and 82 °C/15 s. This fills the gap
beyond cattle-based indicators and enables precise pasteurization for safe, functional dairy and cheese production.

Conclusion: The practical implication of the research is that ALP, LP, LF, and FRS can be considered as biochemical
markers for the accurate pasteurization of goat and sheep milk in RA. This proposal provides a basis for clarifying
indicators for the production of fermented dairy products under UHT conditions.

Keywords: furosine, alkaline phosphatase, small ruminant, proper pasteurization marker