Freezing Qualities of Raw Ovine Milk for Further Processing

Abstract

Raw whole ovine (sheep) milk was frozen at −15°C and −27°C and microbiological and physico-chemical properties were evaluated periodically. Total bacteria decreased at a faster rate in milk stored at −15 than at −27°C. Acid degree values for milk stored at −15°C were significantly higher than that stored at _27°C. Samples stored at −15°C exhibited protein destabilization after 6 mo of storage, while those stored at −27°C were stable throughout the 12-mo storage period. Frozen ovine milk was evaluated in several products including cheese, yogurt, and whey protein concentrates. Products produced from milk frozen at −27°C exhibited good sensory and functional characteristics. Ovine whey showed a higher proportion of β-lactoglobulin, about the same proportion of α-lactalbumin and lower proportions of serum albumin and immunoglobulin than bovine whey. Ovine whey protein concentrate showed significantly better foam overrun, foam stability, and gel strength than bovine or caprine whey protein concentrates.