OVINE MILK .2. SEASONAL-CHANGES IN INDEXES OF STABILITY

The stability to heating and to alcohol addition and the renneting beh aviour of ovine milk from a commercial Scottish flock have been studie d over a season. Substantial differences between sheep milk and cow mi lk have been noted in each case. The heat stability of ovine milk exhi bited only modest seasonal change, the majority of which was noted at the end of lactation. In contrast to bovine milk, the natural pH of th e milk fell, with a consequent reduction in its heat-coagulation time. In addition, HCT was negatively correlated with the concentration of non-protein-nitrogen - the reverse of that for bovine milk. Notwithsta nding the differences between ovine and bovine milk, heat stability wa s such that, after pH adjustment, no problems would be anticipated dur ing UHT sterilisation. The alcohol stability-pH profiles of ovine milk changed little over the season and, in marked contrast to bovine milk , did not exhibit a sigmoidal form. No correlation was found between m ilk composition and alcohol stability. An extensive comparison was mad e of the renneting behaviour of ovine and bovine milk. Evidence was pr esented which suggested that both the enzymic and calcium-mediated pha ses of the reaction differed between species, and may be related to di fferences in milk composition.