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The composition, functional properties and in vitro antioxidative activity of the peptidic fraction of carotenoproteins from shrimp (Parapenaeus longirostris) by-products generated by enzymatic treatment with Alcalase was evaluated. The peptidic fraction of carotenoproteins (PFCP) contained 80.8 ± 0.21% protein, 2.74 ± 0.3% lipid, 14.4 ± 0.14% ash, 1.13 ± 0.08% chitin and 1.08 ± 0.02 μg total carotenoid/g of sample. The amino acid profile of PFCP showed a high percentage of essential amino acids, such as arginine, lysine, histidine and leucine. Therefore, PFCP had a high nutritional value and could be used as a supplement to poorly balanced dietary proteins. PFCP showed an excellent solubility and possessed interfacial properties, which were governed by their concentrations. The antioxidant activities of PFCP at different concentrations were evaluated using various in vitro antioxidant assays, including the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method, reducing power, chelating effects assay and β-carotene bleaching. The antioxidant activity of PFCP, based on their protection of supercoiled DNA strand from scission by peroxyl and hydroxyl radicals into the nicked circular form was also investigated. Results from this study suggest that the peptidic fraction of carotenoproteins is a good source of natural antioxidants and peptides with interesting functionalities.

SummaryThis work investigates how the treatment of thawed deepwater pink shrimp (Parapenaeus longirostris) with several melanosis-inhibiting formulations, affects the quality of the shrimp during chilled storage. Formulations were as follows: a formulation containing 4-hexylresorcinol (0.1 and 0.05%), in combination with organic acids and chelating agents, a commercial formula based on sulphites, and a mixture of gluconic acid and commercial sulphites. No noticeable differences were observed for both trimethylamine and total volatile bases during chilled storage. pH evolution was irrespective of the treatment condition. Microbial load enlarged after the sixth day of chilled storage. Higher total bacteria counts were associated with the control and sulphite treatment conditions, while lactic acid bacteria growth seemed to be favoured under formulations based on 4-hexylresorcinol. The appearance of melanosis occurred more rapidly in control shrimp or in shrimp treated with commercial sulphites. 4-hexylresorcinol formulations preserved the quality of thawed shrimp and could replace traditional sulphites.Keywords Chilled storage, freezing, 4-hexylresorcinol based on formulations, spoilage, sulphites, thawed shrimp. IntroductionSulphites are the most common and effective additives used to prevent melanosis in crustaceans. However, a search for alternative compounds was initiated, after the use of sulphites was found to be related to allergic and asthmatic reactions in some consumers (Taylor & Bush, 1987;McEvily et al., 1991).In the last decade, several studies found evidence that 4-hexylresorcinol may be a good alternative to traditional sulphites. The effectiveness of 4-hexylresorcinol as a melanosis-inhibiting chemical has been demonstrated both in laboratory and on board experiments (McEvily et al., 1991;Otwell et al., 1992;Montero et al., 2001;Martı´nez-Alvarez et al., 2005b). Recently, Montero et al. (2004) reported that deepwater pink shrimp (Parapenaeus longirostris) were highly sensitive to melanosis, and that there was an increase in the inhibition of melanosis after the shrimp were treated with increasing concentrations of 4-hexylresorcinol. These investigators found that a concentration of 0.25% 4-hexylresorcinol was effective at extending the shelf life of this species for 1 week.Frozen crustaceans frequently originate from locations that are a great distance from the countries where they are sold. According to the demands of consumers from Mediterranean countries, frozen crustaceans are usually thawed and commerced as fresh-like crustaceans, or alternatively, as frozen crustaceans, to be used as raw materials and further processed. The phenomena related to spoilage during frozen storage, although not interrupted, are slowed. Given this fact, and bearing in mind that melanosis and spoilage will continue in defrosted shrimp, it would be interesting to test additives with concentrations containing lower doses of 4-hexylresorcinol. To our knowledge, there is no information concerning the role of 4-hexylresor...

International audienceBACKGROUND: Numerous studies have demonstrated that in vitro controlled enzymatic hydrolysis of fish and shellfish proteins leads to bioactive peptides. Ultrafiltration (UF) and/or nanofiltration (NF) can be used to refine hydrolysates and also to fractionate them in order to obtain a peptide population enriched in selected sizes. This study was designed to highlight the impact of controlled UF and NF on the stability of biological activities of an industrial fish protein hydrolysate (FPH) and to understand whether fractionation could improve its content in bioactive peptides. RESULTS: The starting fish protein hydrolysate exhibited a balanced amino acid composition, a reproducible molecular weight (MW) profile, and a low sodium chloride content, allowing the study of its biological activity. Successive fractionation on UF and NF membranes allowed concentration of peptides of selected sizes, without, however, carrying out sharp separations, some MW classes being found in several fractions. Peptides containing Pro, Hyp, Asp and Glu were concentrated in the UF and NF retentates compared to the unfractionated hydrolysate and UF permeate, respectively. Gastrin/cholecystokinin-like peptides were present in the starting FPH, UF and NF fractions, but fractionation did not increase their concentration. In contrast, quantification of calcitonin gene-related peptide (CGRP)-like peptides demonstrated an increase in CGRP-like activities in the UF permeate, relative to the starting FPH. The starting hydrolysate also showed a potent antioxidant and radical scavenging activity, and a moderate angiotensin-converting enzyme (ACE)-1 inhibitory activity, which were not increased by UF and NF fractionation. CONCLUSION: Fractionation of an FPH using membrane separation, with a molecular weight cut-off adapted to the peptide composition, may provide an effective means to concentrate CGRP-like peptides and peptides enriched in selected amino acids. The peptide size distribution observed after UF and NF fractionation demonstrates that it is misleading to characterize the fractions obtained by membrane filtration according to the MW cut-off of the membrane only, as is currently done in the literature. Copyright © 2010 Society of Chemical Industr