The effect of slaughtered and primary processing methods on Rigor mortis, quality parameters, bacterial and shelf-life on Caspian kutum (Rutilus kutum) during stored in ice

The Caspian kutum is a economic precious species in Caspian sea. It is very important to maintane the nutrition value with increasing of shelf-life until marketing. Determining the best method of slaughtered in this species and proper marketing of fish with acceptable freshness in the consumer market are the main aims of this study. 4 treatments including fish with rapid death (due to branch cut) with visceral emptying (treatment 1), rapid death without visceral emptying (treatment 2), common death with visceral emptying (treatment 3) and common death without visceral emptying (Control treatment, 4) all  stored in ice. and from phase 0 to 16 days were evaluated for freshness by performing qualitative tests. The results showed that the fish entered the rigor mortis stage at a later time in emptying the visceral and rapid death method and left later than other treatments. Also, the amount of TVN-N in this treatment reached an acceptable level of 19.26 mg / 100 g by day 8 and the amount of TBArs reached 1.5 mEq of malon dialdehyde/1000 g, the pH of the treatments from 5.75 to 5.76 were variable. The most total bacterial count was observed in control treatment (6.6 log cfu/g). Primary processing in post harvest is effective on quality parameters. In terms of freshness evaluation in the (treatment 1) until the 8th day was acceptable in all quality indicators, but other treatments before that were spoiling and exceeded the acceptable level.