Changes in gel forming ability and protein solubility of pangasius (Pangasianodon hypophthalmus) muscle at different rigor stages during storage at room temperature (28 to 32°C) and in ice

Abstract

Gel forming ability of fish muscle is greatly influenced by the storage temperature and rigor stages.
The present study was carried out to assess the changes in gel forming ability and protein solubility of
pangasius (Pangasianodon hypophthalmus) muscle stored at room temperature (28 to 32°C) and in ice. Rigormortis in fish sample kept at room temperature (RT) and in ice started 1hr after death. The rigor-index
reached a maximum 73.33% within 7 hrs after death at RT and a maximum 87.09% within 4 hrs in ice
storage. At pre-rigor stage, the breaking force (BF) was 646.00 (±2.08g) which decreased to 266.67
(±3.53g) at post rigor stage at RT and from 660.33 (±1.45g) to 420.67 (±1.45g) in ice in one step stage. At
RT, grade of folding test (FT) decreased from “AA” to “A” and score of teeth cutting test (TCT) from 8 to
4. In ice also grade of FT and score of TCT decreased. Similarly, in two-step heating gels, BF decreased
from 994.33 (±2.33g) to 403.00 (±1.15g) at post rigor stage at RT and 995.33 (±1.45g) to 552.67
(±3.71g) in ice. Immediately after catch myofibrillar protein solubility was 86% which declined below 30%
after 24h of storage at RT and below 30%after 28 h of storage in ice. The study concludes that the rigor
period of pangasius may be extended up to 18 h by storing the fish in ice while at RT this period is only about
5 h, which might contribute to slow down the gel degradation process.