Effects of storage time on compositional, micro-structural, rheological and sensory properties of low fat Iranian UF-Feta cheese fortified with fish oil or fish oil powder.

The fish oil (FO), and fish oil powder (FOP) at 10 % of recommended daily intake (RDI) were used to make two types of fortified feta cheeses. The physicochemical, rheological and sensory properties of ripened samples at 0, 30, and 60th days of cold store (5 °C) showed that the FO samples had a faster pH reduction, higher MSNF (milk solid non-fat) increase (p < 0.05) and more pores formation. Storage (G') and loss (G") moduli for both samples decreased until the 30th day of cold storage and then increased until the end of the storage time but both of them were higher for FOP samples. The index of secondary lipid oxidation or thiobarbituric acid reactive substances (TBARS) of FO was lower than FOP samples. Although the polyunsaturated fatty acids of both samples were much higher than common feta cheese, their degradation in FO was less than FOP samples after storage. The sensory scores of FO were significantly higher than FOP sample (P < 0.05), and it obtained up to 70 % of overall acceptability after 30 and 60 days storage for its better hardness, texture and flavor.