EFFECTS OF USING ROSEMARY EXTRACT AND ONION JUICE ON OXIDATIVE STABILITY OF SARDINE (SARDINA PILCHARDUS) MINCE

Sardine (Sardina pilchardus) mince was treated with rosemary extract (RE – 300 ppm) and onion juice (OJ – 1 mL/100 g) then stored at ?20C for 5 months. Proximate composition, thiobarbutiric acid (TBA), free fatty acids (FFA) and peroxide value (PV) were determined on 0 and 15 days and 1, 2, 3, 4 and 5 months of storage. Fatty acid composition was also determined on 0 and 5 months of frozen storage. TBA, PV and FFA levels increased on all experimental groups due to the lipid oxidation. RE showed antioxidative effect on sardine mince during frozen storage as indicated by TBA, PV and FFA levels. Oxidation was delayed for 3 months by OJ treatment. At the end of 5 months’ storage, the TBA values in OJ treatment and control (C) treatment were out of consumable limits. After frozen storage of 5 months polyunsaturated fatty acid level decreased and saturated fatty acid level increased in the control treatment. No significant change was observed in fatty acid composition in samples of RE and OJ treatments.     

The use of transglutaminase in dairy products

Modification of proteins by enzymes such as transglutaminase (TG) has recently become of great interest to food scientists. TG (EC 2.3.2.13) catalyses the post-translational modification of proteins by transamidation of available glutamine residues by the formation of covalent cross-links between glutamine and lysine residues in proteins. It is suggested that TG is a useful tool for the production of dairy products. In this review, properties of TG and its possible use in the manufacture of dairy products are discussed. Aspects covered include reactions catalysed by the enzyme and properties of modified proteins of selected milk proteins and products.