comparison the effect of thyme, onion and ziziphora clinopodiodes extracts on shelf-life of rainbow trout (oncorhynchus mykiss)

nowadays, using natural preservatives than synthetic ones is increasing. the present study was aimed to compare the effect of thyme (zataria multiflora boiss), onion (allium cepa) and ziziphora clinopodioides extracts on shelf-life extending of rainbow trout (oncorhynchus mykiss) salted, vacuum packaged fillet, kept at 4°c. for this purpose fish filets were kept in 4 treatment: salted in brine 10% and vacuum packaged (v), v treatment with 1% thyme extract (t), v treatment with 1% ziziphora clinopodioides extract (z) and v treatment with 4% onion treatment (o) during 20 days at 4°c and were assessed by the changes of free fatty acid (ffa), tiobarbitoric acid (tba), total volatile nitrogenic basic (tvb-n), total microbial viable count (tvc) and sensory assessments in 3 days ferequencies. in general the results showed that the value of ffa, tvb-n, tba indices and tvc in investigated treatments was v> o> z ≤ t during storage period (p<0.05 and 0.01). according to the chemical and microbial standards and sensory assessments, the t treatment for 6 days, z about 6 days and o for 3 days extended the shelf-life of rainbow trout fillets at 4°c rather than v treatments. regarded to the results of this study, among three studied extracts, the thyme extract has a more efficiency for shelf-life improving of color, odor, texture and total acceptability of this fish.