Evaluation of sensory and biochemical changes in freshwater catfish stored under vacuum and different modified atmospheres.

The present study was carried out to compare the influence of six different packaging atmospheres (air, vacuum and MAPs including 5% O2 + 40% CO2 + 55% N2, 5% O2 + 60% CO2 + 35% N2, 5% O2 + 80% CO2 + 15% N2 and 100% CO2) on the biochemical and sensory attributes of freshwater catfish fillets stored at 4 °C. Fillets were monitored for biochemical parameters (pH, total volatile bases nitrogen (TVBN), lipid oxidation) and sensory attributes for 21 days. Proximate and fatty acid composition were also determined in fresh fillets. The sensory quality of all fillets was acceptable during the first 13 ± 1 days of storage in air, 16 ± 1 days of storage in vacuum and MAP1, 18 ± 1 days of storage in MAP2 and 20 ± 1 days of storage in MAP3. The overall sensory scores for fillets which were packed under 100% CO2 were higher than the acceptable limit at the end of storage. It was found that fillets consisted of 5.71 g lipid per 100 g which is susceptible to oxidation due to the high amount of unsaturated fatty acids (63.86%) versus saturated fatty acids (31.14%). Vacuum packed and 100% CO2 fillets showed the lowest TBARS values while air-stored samples showed the highest TBA values. TVBN increased negligibly during storage in all treatments and never exceeded the acceptability limit (35 mg N per 100 g). It can be concluded that 100% CO2 was the best evaluated atmosphere for storage of catfish fillets at 4 °C with superior biochemical and sensory attributes

Hatchery and growth performance of two trout pure breeds, <i>Salvelinus alpinus</i> and <i>Salmo trutta fario</i>, and their hybrid

An allelic cross between Salmo trutta fario and Salvelinus alpinus was carried out under controlled hatchery conditions. Survival,to the eyed stage was significantly lower for the hybrid than for both purebreds. There were significant differences in survival in the eyed and yolk sac stages and from fertilization to the first feeding (p0.05). The hybrid did not display heterosis with respect to any hatchery property. During the first 45 days of nursing, there were significant differences between the purebreds and the hybrid in terms of weight gain, survival, feed conversion ratio and specific growth rate (p0.05). The hybrid was slightly heterotic (+1.69) with respect to survival however no heterosis was observed in any other property to the first feeding stage

Inhibitory effects of ammonia and urea on gill carbonic anhydrase enzyme activity of rainbow trout (Oncorhynchus mykiss)

The effects of ammonia and urea on branchial carbonic anhydrase (CA) enzyme which plays a key role in ionoregulation, osmoregulation and acid-base balance of rainbow trout (Oncorhynchus mykiss) were investigated. CA activity of the control group for ammonia and urea was determined as 1285.7 +/- 67.9 and 1261.7 +/- 60.8 EU/mg protein, respectively. The CA enzyme activities of the other groups were measured at 1, 2 and 3 h after ammonia and urea applications. The corresponding activities of ammonia were 774.9 +/- 68.8, 732.1 +/- 48.6 and 768.1 +/- 59.5 EU/mg protein, respectively and that of urea were 769.3 +/- 58.9, 638.2 +/- 147.7 and 1108.1 +/- 61.1 EU/mg protein, respectively. The differences between the initial CA activities for the controls was not significantly (P > 0.01). The CA activities were significantly (P < 0.01) inhibited both in ammonia and urea group. However, the ammonia inhibited more than urea since there was significant differences between final values of gill CA activities. (C) 2004 Elsevier B.V.. All rights reserved

Effect of chitosan coating on chemical and microbiological properties of Atlantic bonito (Sarda sarda) fillets

Chemical [(pH, total volatile base nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS)] and microbial (psychrotrophic, mesophilic aerobic bacteria and Enterobacteriacae counts) changes in Atlantic bonito (Sarda sarda) fillets coated with chitosan solution (2%, w/v) or packaged with vacuum or modified atmosphere (100% CO2), or air were determined during storage at 4 +/- 1 degrees C for 12 days. Chitosan coating did not significantly affect pH and TVB-N values. TBARS value increased rapidly after 3 days in chitosan groups. Chitosan group showed generally lower bacterial counts than the control group during storage. However, modified atmosphere packing demonstrated better inhibition than chitosan treatment or vacuum packing