Strength and Keeping Quality of Abomasum Rennet and its Influence on Yield and Quality of Halloumi Cheese made from Cow Milk

Abstract: Halloumi cheese was made from cow milk using commercial rennet, and bovine and ovine rennet. But in Ethiopia commercial rennet is expensive and unavailable for smallholder dairy farmers. To solve this problem an experiment was conducted to evaluate strength, quality and suitability of locally available bovine and ovine abomasum rennet for halloumi cheese making in comparison with commercial rennet. The treatments consisted of bovine rennet, ovine rennet and commercial rennet (control) arranged in a completely randomized design (CRD). Rennet was extracted from bovine and ovine abomasa and comparisons were made with commercial rennet. Shelf life and clotting activity of the extracted rennet were determined using Halloumi cheese making. The result of the study indicated that commercial rennet (0.189 ± 0.02) had a higher clotting activity and short clotting time than bovine (0.179 ± 0.02) and ovine (0.023 ± 0.02) rennet. Bovine rennet was active up to nine weeks of storage while ovine rennet was active only up to six weeks of storage after which both types of rennet start losing their clotting activity. A highly significant difference was observed between locally and commercially produced rennet in terms of rennet and curd pH. The use of bovine and ovine rennet in the Halloumi cheese making was acceptable to the sensory panelist and scored more than the average for overall acceptances (Score >3.5). In conclusion, bovine rennet showed better strength and quality compared to ovine rennet and could be used for halloumi cheese making where commercial rennet is not available.   Keywords: Bovine rennet; Clotting activity; Curd strength; Ovine rennet; Shelf life