Effects of dietary Bacillus subtilis on growth performance and immune responses, in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792)

Four hundred and eighty five rainbow trout (76 ± 6.44 g mean weight) were acclimated to laboratory conditions and then randomly divided into four groups of tanks in triplicate. The first group (Group 1) was fed on a commercial diet (control) without Bacillus subtilis supplementation. The second, third and fourth groups (Group 2, Group 3 and Group 4, respectively) were given a diet supplemented with 1, 5 and 10 g probiotic powder (containing 8×10^7 CFU g^-1 Bacillus subtilis) per kg commercial feed. Growth performance, immune responses and glucose levels were analyzed on days 0, 22 and 44. The results showed that dietary Bacillus subtilis supplementation significantly (p0.05) was observed in weight gain rate (WGR) between the control and group 2. On the effect of dietary Bacillus subtilis on serum lysozyme, it was observed that group 3 and group 4 did not show any significant differences in serum lysozyme activity and serum total antibody on day 44. Results of alternative complement activity, showed significant increase during the experimental days (p<0.05). Results on glucose assay showed that group 3 had the lowest glucose level (13.71 mg/dL) which was not significantly different than that in other groups on day 44. Fish diet supplementation with 5 g probiotic powder (Group 3) is preferable for immune system responses; however, high dose of Bacillus subtilis may be helpful to improve growth performance in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792)

Antimicrobial and antioxidant effects of nisin Z and sodium benzoate in vacuum packed Caspian kutum (Rutilus frisii) fillet stored at 4°C

This study was done to evaluate the antimicrobial and antioxidant effects of nisin Z (0.02 %) and sodium benzoate (1.5 and 2.5 %) in vacuum packed Caspian Kutum (Rutilus frisii) fillet stored at 4°C. Microbial changes [aerobic plate counts (APC), psychrotrophic counts (PTC) and lactic acid bacteria] and chemical indices [peroxide value and total volatile basic nitrogen (TVB-N)] were determined in days 0, 4, 8, 12 and 16. Results showed that PV and TVB-N in control samples (the sample dipped in prechilled distilled water) were deteriorated after 12 days compared to preserved samples which were acceptable after 16 days. Microbial tests indicated that control samples contained APC and PTC bacteria in day 16 more than standard limit, whereas treatment samples were in the acceptable range. In case of lactic acid bacteria, after 16 days, all samples were in the acceptable range. Results of chemical and microbial analysis showed that simultaneous use of nisin Z and sodium benzoate could increase the shelf life of vacuum packed R. frisii

Antibacterial activities of nisin encapsulated in zein and modified atmosphere packaging on rainbow trout (Oncorhynchus mykiss) fillet during chilled storage 4°C

Nisin is a widely used naturally occurring antimicrobial effective against many pathogenic and spoilage microorganisms. It has been proposed that reduced efficacy of nisin in foods can be improved by technologies such as encapsulation to protect it from interferences by food matrix components. This study was carried out to evaluate the microbiological quality of fresh trout slices treated with N1 (nisin 0.15 g/kg) and N2 (nisin 0.25 g/kg), NE1(encapsulated nisin 0.15 g/kg), NE2 (encapsulated nisin 0.25 g/kg ) and were then packaged under Modified Atmosphere Packaging (MAP) (45% CO2, 50% N2, 5% O2) and stored at 4±1 °C for 20 days. The results revealed that nisin in both forms of free and encapsulated was efficient against the proliferation of various categories of spoilage microorganisms including aerobic and psychrotrophic populations and lactic acid bacteria. The shelf life of the treated products was extended by 4–7 days more than that of the control. As a consequence, nisin, in particular encapsulated nisin, might be considered as an effective tool in preventing the quality degradation of the fillet, resulting in an extension of their shelf life

The effects of refining steps on kilka (Clupeonella delicatula) fish oil quality

Kilka fish are known as the main industrial and pelagic species of Iran that are captured abundantly in the southern Caspian Sea. This study was conducted to survey the effectiveness of refinement steps on Kilka (Clupeonella delicatula) crude oil quality and fatty acid profiles. Neutralization, bleaching, winterization and deodorization were performed on crude oil with deodorization done under two different conditions of A: at 180˚C for 120 min and B: at 140˚C for 240 min. During refinement, peroxide value (PV) significantly decreased from 7.66 meq/kg in crude oil to 0.5 in deodorized oil A and to 0.21 in deodorized oil B (p<0.05). Significant reduction in free fatty acids (FFA) was recorded from 0.86% oleic acid in crude oil to 0.15% in deodorized oil A and to 0.33% in deodorized oil B (p<0.05). N-3 fatty acids content and fatty acids composition were determined by GC-FID and n-3 fatty acids content increased from 18.74% in crude oil to 21.58% in deodorized oil A and to 21.75% in deodorized oil B. The red color in oil significantly decreased from 5.4 to 0.4 and 0.5 in deodorized oil A and deodorized oil B, respectively (p<0.05). Results confirm that refinement steps improved oil quality and raised n-3 PUFA concentration and n-3/n-6, properly. Deodorization at 180˚C for 120 minutes (A) was more effective than deodorization at 140˚C for 240 minutes (B) in removing off flavors