The effects of partial replacement of fish meal by vegetable protein sources in the diet of rainbow trout (Onchorynchus mykiss) on post mortem spoilage of fillets

Effect of High Hydrostatic Pressure on the Metabolite Profile of Striped Prawn (Melicertus kerathurus) during Chilled Storage

A variety of metabolites contribute to the freshness and taste characteristics of seafood. This study investigated the effects of high hydrostatic pressure (HHP; 400, 500, and 600 MPa) for 10 min) on the metabolome of striped prawn during chilled storage, in relation to microorganisms' development. All treated samples showed lower viable counts throughout storage compared to the untreated counterparts. The limit of acceptability from a microbiological point of view was extended from 9 to as many as 35 days by 600 MPa treatment. Metabolites were quantified by ¹H-NMR through a targeted-untargeted metabolomic approach. Molecules linked to nucleotides' degradation and amines' anabolism suggested an overall freshness improvement granted by HHP. Notably, putrescine and cadaverine were detected only in untreated prawn samples, suggesting the inactivation of degradative enzymes by HHP. The concentration of molecules that influence umami perception was significantly elevated by HHP, while in untreated samples, the concentration of molecules contributing to a sour taste gradually increased during storage. As metabolomics was applied in its untargeted form, it allowed us to follow the overall set of metabolites related to HHP processing and storage, thus providing novel insights into the freshness and taste quality of striped prawn as affected by high hydrostatic pressure.

Determination of nucleotide and enzyme degradation in haddock (Melanogrammus aeglefinus) and herring (Clupea harengus) after high pressure processing

Background

The degradation of nucleotides and their enzymes had been widely used to evaluate fish freshness. Immediately after fish death, adenosine triphosphate (ATP) degrades into inosine-5-monophosphate (IMP) via adenosine-5-diphosphate (ADP) and adenosine-5-monophosphate (AMP). IMP degradation continues to produce inosine (ino) and hypoxanthine (Hx) and further deteriorates the fish by producing xanthine and uric acid. The dephosphorylation of IMP to Ino is carried out by the enzyme 5′-nucleotidase (5′-NT), whereas the degradation of Ino to Hx is carried out by the enzyme nucleoside phosphorylase (NP). This study assesses the application of high pressure processing (HPP) in two species of fishes; haddock (Melanogrammus aeglefinus) and herring (Clupea harengus) as a means to extend the shelf-life by slowing down the rate of nucleotides degradation.

Methods

Haddock (Melanogrammus aeglefinus) and herring (Clupea harengus) fillets were subjected to HPP at 200, 250 and 300 MPa for 1 and 3 min before being stored for 14 days. In addition, 5′-NT and NP enzyme activities were determined on both fish species that were subjected to 100–600 MPa for 1 and 3 min.

Results

Adenosine triphosphate, ADP and AMP in both haddock and herring were lower at higher pressure levels. Inosine (Ino) increased (p < 0.05) after treatment at higher pressures in both species. Hx in herring decreased significantly (p < 0.05) at higher pressures but not in haddock. K values are the ratio of Ino and Hx to all nucleotides. K values in haddock were not significantly (p > 0.05) affected by the pressure treatment. H values are ratio of Hx to the sum of IMP, Ino and Hx. H values in haddock were significantly decreased (p < 0.05) with increasing pressure level. F values are ratio of IMP to the sum of IMP, Ino and Hx. F values showed no significant effects (p > 0.05) after pressure treatment. Furthermore, K values in control herring were significantly higher (p < 0.05) than those of the pressure-treated samples. H values in herring decreased significantly (p < 0.05) with increasing pressure level. F values in herring showed no significant effects (p > 0.05) after pressure treatment. Pressure treatment brought a significant decrease (p < 0.05) in protein content in both haddock and herring. 5′-NT activity was 20–35 fold higher compared to NP activity in haddock and 15–44 fold higher than NP activity in herring. 5′-NT and NP activities decreased significantly with increasing pressure level in both species.

Discussion

High pressure processing effectively slows down the conversion of Ino to Hx, delaying the undesirable flavour that develops in spoiling fish. The autolytic conversion of IMP to Ino by endogenous 5′-NT predominates in the earliest stages of storage is an autolytic process. However, both bacterial and endogenous NP enzymes are probably responsible for the gradual accumulation of Hx in fish. K values are recommended as a useful measurement of fish freshness.

Impact of Diets Containing Plant Raw Materials as Fish Meal and Fish Oil Replacement on Rainbow Trout (Oncorhynchus mykiss), Gilthead Sea Bream (Sparus aurata), and Common Carp (Cyprinus carpio) Freshness

The present study aimed to evaluate whether the total or high substitution of fish meal (FM) and fish oil (FO) by sustainable plant raw materials (plant meal and oils) in long-term feeding for rainbow trout, gilthead sea bream, and common carp can result in spoilage alterations during ice storage. These three species were fed throughout their whole rearing cycle with plant-based diets and compared to counterparts that received FM/FO-based diets or commercial-like diets. Sensory QIM schemes adopted for these species and ATP breakdown products (K-value and components) were used to evaluate the freshness. Sensory acceptability of 14, 15, and 12 days was found for rainbow trout, gilthead sea bream, and common carp, respectively. This corresponded to K-values of approximately 80%, 35%, and 65% for rainbow trout, gilthead sea bream, and common carp, respectively. No major effect of dietary history on postmortem shelf life was shown for gilthead sea bream and common carp; neither sensory-perceived nor chemical freshness showed diet-related differences. Rainbow trout fed with the plant-based diet exhibited slightly worse sensory freshness than fish fed with FM/FO-based diets, at the end of shelf life. These findings imply that FM and FO can be successfully substituted without major impacts on shelf life of fish.

Effects of Fish-Derived Biological Preservatives on Cold Storage of Grass Carp ( Ctenopharyngodon idellus ) Fillets

Two kinds of fish-derived natural antimicrobial substances, protamine and catfish ( Clarias fuscus ) epidermal mucus extract (CEME), were evaluated for their effect on the quality of grass carp fillets. Fillets were atmosphere packaged in cast polypropylene bags and were stored at 4°C in a low-temperature incubator without light. Solutions (0.5%, wt/vol) of CEME and protamine were used for dip pretreatment, respectively. Bacteriological (aerobic plate count, Shewanella putrefaciens , Pseudomonas fluorescens ) and physicochemical (pH, total volatile basic nitrogen, K value, surface color, texture profiles, water distribution) parameters and volatile odor compounds were measured on days 0, 3, 6, 9, 12, and 15. The results indicated that CEME and protamine could improve all bacteriological and physicochemical indexes, except water distribution within muscle. In comparison, CEME had a more inhibitory effect, as determined by the aerobic plate count, and was more effective in inhibiting the growth of P. fluorescens ; however, protamine was more effective in preventing the production of sulfur-organic (H₂S) group substances. Protamine was more effective in inhibiting the growth of S. putrefaciens . This research suggests that protamine and CEME have the potential to improve the quality and extend the shelf life of grass carp fillets.

Determination of digestible and metabolizable energy of fishmeal and soybean meal in rainbow trout with two different sizes (Oncorhynchus mykiss)

The present research carried out to measure digestible (DE) and Metabolizable Energy (ME) for fishmeal and soybean meal in rainbow trout with two different sizes (120 and 220 g mean body weights). DE and ME are evaluation systems for feedstuffs and also, necessary for diet formulation. The fishes were maintained in metabolic chamber with single ingredient assay of feeding and chromic oxide (Cr2O3) was used as an external marker using total fecal collection method. Gross energy and chromic oxide values measured in feces, fishmeal and soybean meal. The results indicated that DE offishmeal was 3700 and 3591 kcal kg(-1) in 120 and 220 g body weight rainbow trout, respectively. Soybean meal had 3004 and 2889 kcal kg(-1) respectively. Calculated ME from DE were 3204 and 3110 kcal kg(-1) for fishmeal and 2601 and 2502 kcal kg(-1) for soybean meal in 120 and 220 g rainbow trout, respectively. The results showed that rainbow trout can utilize fishmeal more efficiently than soybean meal.