Functional properties of Rohu (Labeo rohita) proteins during iced storage

The effect of iced storage on functional properties viz. solubility, emulsion activity index (EAI), viscosity, foaming, of muscle proteins from fresh water fish Rohu (Labeo rohita) was evaluated. Myofibrillar protein (MFP) solubility showed an increasing trend up to 11 days of storage followed by a decrease. Solubility of sarcoplasmic protein (SPP) showed a decreasing trend through out the storage period. A 44% drop in emulsion activity index (EAI as m2/g) was observed in the case of MFP on storage. MFP showed foam volume stability (FVS) of 94% and a 22% loss in stability was recorded on the 25th day. Viscosity of SPP remained relatively stable through out the duration of study while that of MFP showed an increasing trend during the first week and then decreased. Influence of protein concentration on different functional properties were also studied. The data are discussed in relation to protein conformational changes as indicated by changes in hydrophobicity, and reactive sulphhydryl groups. Reactive sulphhydryl groups increased gradually attaining a maximum on the 6th day and a gradual decline towards the end. Hydrophobicity of myofibrillar fraction showed a decrease till the 11th day and thereafter it increased gradually. K-value was taken as an index of quality which shot-up from 0.2% to 59.80% during the storage of fish in ice.