Evaluation of some physico-chemical properties of restructured trout and hake mince during cold gelation and chilled storage

Valorization of recurrently discarded fish species in trawler fisheries in North-West Spain

The progressive elimination of fish discards established by the European Union Council in 2013 has stimulated the valorization of flesh from discarded high-quality species with good protein functional properties but which frequently have excessive fish-bones, fat, strange flavours, soft texture, etc. The present study therefore focuses on valorization of the extracted muscle (minced muscle), from several fish species frequently discarded in north-western Spanish fisheries (Atlantic Ocean): Blue whiting (Micromesistius poutassou), Mackerel (Scomber scombrus), Red scorpionfish (Scorpaena scrofa), Pouting (Trisoreptus luscus) and Gurnard (Trigla spp.). Valorization of these discarded fish resources is a key objective for the survival of the fishery sector in this area. In this regard present study was planned to examine the behaviour of the mince during 6 months of frozen storage by means of physicochemical and sensory analyses, and to test consumer acceptance of three technologically different products (burgers, nuggets and structured fingers) prepared with fish mince from different species. Results indicated that protein aggregation started at the outset of frozen storage but progressed very slowly, with the exception of non-washed blue whiting and red scorpionfish minces. Moreover, during frozen storage lipid oxidation increased in all samples; the increase was with two objectives highest in minced mackerel, a fatty fish, but no rancid flavour was detected. All mince samples presented acceptable physicochemical properties and good sensory acceptability after 6 months of frozen storage. Acceptability of final products made with these minces was high in all cases. Burgers were more acceptable for consumers aged over 40 and fingers and nuggets more for younger people.

Effects of microbial transglutaminase, fibrimex and alginate on physicochemical properties of cooked ground meat with reduced salt level

Effects of microbial transglutaminase (MTGase), fibrin/thrombin combination (fibrimex), alginate or combination of these binding agents on physicochemical parameters of cooked ground beef with reduced salt level were investigated. Seventeen treatments included three control (no binding agent) groups incorporated with varying concentrations of salt (0.5, 1, 2%, w/w) and fourteen treatment groups produced with MTGase or fibrimex or alginate or their combinations at 0.5 or 1% salt levels. The samples were analyzed for cooking loss (CL), pH, color, moisture, fat, protein, ash, salt, texture and TBARS. The results indicated that the use of MTGase or fibrimex or MTGase/fibrimex combination had significant effect on preventing textural deterioration caused by salt reduction. Even though the use of MTGase resulted in higher CL values, formulation of ground beef with fibrimex or alginate or MTGase/fibrimex/alginate combinations reduced CL when compared with the control groups. The use of fibrimex in ground beef resulted in a decrease in TBARS, lightness, redness and pH values. However, the use of alginate caused an increase in pH, lightness and redness values of ground beef. Based on the present study, the use of fibrimex or a combination of fibrimex with MTGase in the product formulation can be an effective strategy to reduce cooking loss, to improve or maintain the textural properties and to extend shelf life of cooked ground beef with reduced salt level.

New Alternatives in Seafood Restructured Products

A general overview, focusing on new trends in the different techniques used in restructured seafood product processing has been described in this work. Heat-induced gelation has been more widely studied in scientific literature than cold gelation technology. This latter technology includes the use of hydrocolloids (alginates and glucomannan) or enzymes (microbial transglutaminase) for making both raw and cooked restructured products. In restructuration processes, fortification processing with some functional ingredients is studied, giving as a result extra value to the products as well as increasing the variety of new seafood products. The process of alleviating heavy metals and organic pollutants from the raw material used has also been reviewed in the present paper.

Suppression of the formation of biogenic amines in mackerel mince by microbial transglutaminase

BACKGROUND

Microbial transglutaminase (MTGase) is an enzyme utilized in the food industry in many areas. In this study, the suppression effect of MTGase at various levels (0, 2, 5, 10 g kg(-1)) on the formation of biogenic amines in mackerel was determined during refrigerated storage of 8 days.

RESULTS

Mince added with 2 g kg(-1) MTGase showed the lowest formation of putrescine, cadaverine and tyramine throughout the storage. Histamine exceeded the consumable limit (500 mg kg(-1) ) after the 4th day, except for that containing 2 g kg(-1) MTGase. The formation of total volatile basic nitrogen and total free amino acid content were retarded and the pH value was unaltered by addition of MTGase. With increasing MTGase levels, the growth of total psychrophilic bacteria, mould, yeast and coliform bacteria was retarded. The sensory scores of mackerel mince increased as MTGase concentrations increased.

CONCLUSION

MTGase plays a role in maintaining the quality of mackerel mince during refrigerated storage. As a result of the present study, a new use for MTGase in the food industry is revealed. It will contribute especially in the field of development of products for consumers with allergic sensitivity.

Effect of transglutaminase on quality characteristics of a value-added product tilapia wastes

The aim of this work was to evaluate the physico-chemical, instrumental color and texture, and sensory qualities of restructured tilapia steaks elaborated with small sized (non-commercial) tilapia fillets and different levels of microbial transglutaminase (MTG). Four concentrations of MTG were used: CON (0 % MTG), T1 (0.1 % MTG), T2 (0.5 % MTG), and T3 (0.8 % MTG). In addition, bacterial content and pH shifts were also evaluated during 90 days of frozen storage. The different levels of MTG did not affect (P > 0.05) either the proximate composition of the restructured tilapia steaks or the bacterial growth during the frozen storage. MTG improved (P < 0.05) cooking yield and instrumental hardness and chewiness as well as sensory (salty taste, succulence and tenderness) attributes; strongly contributing to greater overall acceptance. Therefore, restructured tilapia steaks manufactured with MTG are potentially valued-added products with good consumer acceptance and better purchase-intention than steaks formulated with 0 % MTG.

Comparative study on protein cross-linking and gel enhancing effect of microbial transglutaminase on surimi from different fish

BACKGROUND

Microbial transglutaminase (MTGase) has been used to increase the gel strength of surimi. Nevertheless, its effectiveness varies with fish species. The aim of this study was to elucidate the effect of MTGase at different levels on protein cross-linking and gel property of surimi from threadfin bream, Indian mackerel and sardine in the presence and absence of endogenous transglutaminase.

RESULT

Breaking force of all surimi gels increased as MTGase levels (0-0.6 U g⁻¹) increased except for threadfin bream surimi gel, where the breaking force decreased at 0.6 U g⁻¹ (P < 0.05). In the presence of EDTA, the gel strengthening effect was lower, suggesting the combined effect of endogenous transglutaminase with MTGase. With the addition of MTGase, the gel with the highest increase in breaking force showed highest decrease in myosin heavy chain. When cross-linking activity of MTGase on natural actomyosin (NAM) was determined, the highest decreasing rate in ε-amino group content with the concomitant increased formation of cross-linked proteins was found in NAM from threadfin bream. The reactivity of muscle proteins toward MTGase-induced cross-linking was in agreement with surimi gel strengthening.

CONCLUSION

The composition and properties of muscle proteins of varying fish species more likely determined protein cross-linking induced by MTGase, thereby affecting their gel properties.