Manufacture of yoghurt from stored frozen sheep’s milk

• Published in: Food chemistry Vol. 77; no. 4; pp. 413 - 420
• Main Authors: Katsiari, Maria C, Voutsinas, Leandros P, Kondyli, Efthymia
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2002; Elsevier
• Subjects: Biological and medical sciences; Food industries; Frozen storage; Fundamental and applied biological sciences. Psychology; Milk and cheese industries. Ice creams; Sheep’s milk; Yoghurt; Yoghurt; Frozen storage; Sheep’s milk; Microbiological testing; Organoleptic properties; Dairy product; Sensory analysis; Shelf life; Thawing; Yogurt; Physical properties; Freezing; Ewe milk; Warehousing; Quality; Food preservation; Physicochemical properties
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/S0308-8146(01)00367-3

The effects of long-term deep-frozen storage of sheep’s milk on its physicochemical, microbiological and physical stability characteristics, as well as on the corresponding characteristics and the sensory attributes of the yoghurt manufactured from the stored frozen milk after thawing were examined. Bulk whole sheep’s milk, after clarification and pasteurisation (72° C for 15 s), was sampled for analysis and then poured into plastic bags, frozen in a moving-air freezer at −25° C in thin blocks (21 cm long, 21 cm high and 2.7 cm thick) weighing about 1.2 kg, and stored at −20° C for up to 6 months. At 2, 4 and 6 months of storage, samples were removed, thawed and analysed. Moreover, set type yoghurts were manufactured from these samples and examined. The results indicated that there were no significant ( P>0.05) differences between fresh (control) and stored frozen milk samples in pH, acidity, acid degree value, peroxide value, protein sediment, apparent viscosity or coliform counts. The frozen samples had significantly ( P<0.05) lower total bacterial counts than the fresh milk. No significant ( P>0.05) differences in pH, acidity, lactose, appearance and colour, body and texture, flavour, overall acceptability, consistency, apparent viscosity or syneresis were observed between the control milk yoghurt and the yoghurts made from milk stored frozen for up to 6 months.