Rancidity development of refrigerated rainbow trout (Oncorhynchus mykiss) fillets: comparative effects of in vivo and in vitro lycopene.

BACKGROUND: The problem of lipid oxidation in fish during storage is well known and is related to both temperature and storage time. Antioxidants could have a main role in limiting the deteriorative effects of lipid oxidation in fish. The present study aimed to investigate the effect of dietary supplement against postmortem addition of lycopene on the deterioration of trout fillets during storage at 4 ± 1 °C for 12 days. RESULTS: At the end of the feeding trial, no significant differences were observed with respect to the fatty acid composition of different dietary groups. However, a strong positive correlation (r = 0.96) was observed between fillet and diet lycopene levels. Lower indices of lipid oxidation (peroxide value and thiobarbituric acid) and lipid hydrolysis (free fatty acids) were observed in fillets that received lycopene (P < 0.05). Although exogenous lycopene was more effective (P < 0.05) than endogenous lycopene in delaying lipid oxidation, the fatty acid composition of fillets that received dietary lycopene supplement showed a higher stability (P < 0.05) during refrigeration storage. CONCLUSION: Accordingly, based on the time of appearance of off-odors and discoloration in fish fillets, exogenous lycopene, especially at higher levels, was more effective in terms of quality parameters. © 2017 Society of Chemical Industry.

A Comprehensive Approach to Assess Feathermeal as an Alternative Protein Source in Aquafeed.

The effect of partially replacing fishmeal in aquafeed with feathermeal (FTH) at three levels (0%: FTH0, 8%: FTH8, 24%: FTH24) and two extrusion temperatures (100 and 130 °C) was evaluated in rainbow trout (Oncorhynchus mykiss) with respect to growth performance, metabolism response, and oxidative status of the feed proteins. Multivariate data analyses revealed that FTH24 correlated positively with high levels of oxidation products, amino acids (AA) racemization, glucogenic AAs level in liver, feed intake (FI), specific growth rate (SGR), and feed conversion ratio (FCR); and low AAs digestibility. Both FI and SGR were significantly increased when 8 and 24% feathermeal was included in the feed extruded at 100 °C, while there was a negative effect on FCR in fish fed FTH24. In conclusion, higher oxidation levels in FTH24 may give rise to metabolic alterations while lower levels of FTH may be considered as fishmeal substitute in aquafeed for rainbow trout.

Chitosan coating incorporated with the lactoperoxidase system: an active edible coating for fish preservation.

BACKGROUND: As a result of consumers' concerns about chemicals there is a particular interest in the food industry to use natural bio-preservatives such as antimicrobial enzymes for antimicrobial packaging. Based on the antimicrobial activity of the lactoperoxidase system (LPOS), the present study evaluated the coating effect of LPOS incorporated into chitosan solution (CH) on the quality and shelf life extension of rainbow trout during refrigerated storage (4 ± 1 °C), for a period of 16 days. RESULTS: The results indicated that samples of the CH+LPOS group had significantly lower numbers of Shewanella putrefaciens, Pseudomonas fluorescens, and psychrotrophic and mesophilic bacteria than did the CH and control group during the entire storage period. Total volatile basic nitrogen (TVB-N) levels for the CH+LPOS samples (22.07 mg 100 g(-1)) did not exceed the limit of consumption (30-35 mg N 100 g(-1)), while the CH (31.03 mg 100 g(-1) ) and control groups (37.78 mg 100 g(-1) ) reached this level at days 12 and 16, respectively. Thiobarbituric acid values of the CH and CH+LPOS samples, ranged between 0.49 and 0.51 on day 0 and 4.59-4.66 mg kg(-1) on day 16, were significantly lower (P < 0.05) than the corresponding values of the control samples (0.47 on day 0 to 4.78 mg kg(-1) on day 16 of storage) during the chilled storage period. CONCLUSION: The coating treatments (CH and CH+LPOS) extended the shelf life of trout fillets by at least 4 days as compared to the control samples, so that they showed moderate to high acceptability in all investigated sensory attributes even on the 16th day of storage.

Microbiological properties and biogenic amines of whole pike-perch (Sander lucioperca, linnaeus 1758): a perspective on fish safety during postharvest handling practices and frozen storage.

The biogenic amines (tyramine, histamine, cadaverine, and puterscine) and microbiological properties (mesophilic, psychrotrophic, and Pseudomonas spp.) of whole pike-perch (Sander lucioperca) was investigated during 2 d prestorage icing and 90 d frozen storage (-24 °C). At the end of ice storage, a noticeable increase only was found for puterscine level (P < 0.05), and microbial loads of fish increased in comparison with fresh fish (P < 0.05). During the frozen storage, as time passed, a continuous increase of biogenic amines and decrease of bacterial load (except for Pseudomonas spp. at the last 30 d) was detected (P < 0.05). The total contents of biogenic amines ranged from 6.24 to 91.76 µg/g during the investigated period. Puterscine was the major amine detected in pike-perch and its concentration varied between 1.75 and 56.95 µg/g; due to a more step-wise increase it was a good quality indicator. At the end of storage, all of the obtained values are below the tolerable maximum amounts based on available regulations. Based on biogenic amines content and microbial load, it could be concluded that pike-perch can be consumed without any health risks after 2 d icing condition and 90 d frozen storage.

Improvement of lipid stability of refrigerated rainbow trout (Oncorhynchus mykiss) fillets by pre-storage α-tocopherol acetate dipping treatment.

One of the simplest methods for short-term handling and storage of fish is the refrigeration in combination with dip treatments. This study was conducted to determine the effect of pre-storage α-tocopherol acetate dipping treatments on lipid stability of refrigerated rainbow trout fillets. Trout fillets were dipped in α-tocopherol acetate solutions (200 and 500 mg kg(-1) flesh) and subsequently stored in a refrigerator at 4 ˚C for 12 days. Control samples received no α-tocopherol acetate during dip treatment. At the end of 0, 3, 6, 9 and 12 days of storage, lipid damage analysis of trout fillets was performed. A continuous notable increase (p < 0.05) in peroxide value (PV), thiobarbituric acid (TBA) and free fatty acid (FFA) was observed for all samples throughout the storage period. Although throughout the storage period the lipid hydrolysis (FFA) of fish fillets was not affected by α-tocopherol acetate solutions, successful (p < 0.05) inhibition of lipid oxidation (PV and TBA) in refrigerated trout fillets was possible with dip treatment in α-tocopherol acetate solutions (200 and 500 mg kg(-1) flesh). There was no significant (p > 0.05) effect of increasing α-tocopherol acetate concentration on the lipid deterioration of fish fillets. These results indicated that α-tocopherol acetate especially at lower level (200 mg kg(-1) flesh) was very effective in retarding the lipid oxidation.