Evaluation of factors affecting NaCl content the evolution in ewes milk and of its effect on technological properties

• Published in: Journal of animal science Vol. 94; p. 182
• Main Authors: Serdino, J, Correddu, F, Manca, M G, Nudda, A, Urgeghe, P, Macciotta, N P P
• Format: Journal Article
• Language: English
• Published: Champaign Oxford University Press 01-10-2016
• Subjects: Altitude; Birth; Cheese; Coagulation; Curd; Dairy products; Firmness; Milk; Ovis aries; Physiological effects; Sheep; Sodium chloride; Winter
• ISSN: 0021-8812; 1525-3163

The work was aimed at investigating factors affecting variation of NaCl content in sheep milk and at evaluating its relationships with (MCP) and cheese yield. A total of 2778 individual milk samples were collected from 607 Sarda dairy ewes farmed in 34 flocks. MCP (rennet coagulation time = RCT, curd firming time = k20, curd firmness = a30) were measured by Formagraph. Individual laboratory cheese yield (ILCY) were determined by micro-manufacturing experiments. NaCl content (mg NaCl/100 mL milk) was measured by MilkoScanTM. NaCl content was analyzed with a mixed linear model that included the fixed effects of parity, season of lambing, birth type, altitude, and the random effects of flock-test-date and of the animal. Moreover effects of NaCl on MCP were investigated with a similar model, that included also the fixed effect of NaCl class. Four classes were considered according to the 25th, 50th, 75th and 100th percentiles of the NaCl distribution: A = 57-113.3, B = 113.4-132.9, C = 133-157.8 and D = 157.9-259.6. The average content of NaCl was 137.55 ± 34.44 mg/100 mL, ranging from 57.60 to 259.60. NaCl content increased with days in milk, and it was lowest in secondiparous ewes compared with older parities. The season of lambing influenced NaCl concentration, which was higher in milk of ewes lambing in late winter and early spring (from February to April) compared with ewes lambed in early winter (October and November), with values for December and January being intermediate. Birth type at lambing and altitude of location of flocks did show significant effects on NaCl content. MCP were affected by NaCl concentration. In particular, RCT and k20 tended to increase moving from A to D NaCl classes, whereas a30 exhibited the opposite pattern. ILCY showed the highest value for in the class of the highest content of NaCl. Results of the present study highlight the influence of factors related to the physiological status of the animal on the NaCl variation. The results on milk coagulation properties found in this work seems to suggest a relationship between NaCl and cheese making attitude of sheep milk.