Entrapment of natural compounds in spray-dried and heat-dried iota-carrageenan matrices as functional ingredients in surimi gels.

Two drying methods (spray drying and heat drying) were used to entrap various natural compounds within a matrix of iota-carrageenan. The natural compounds were, namely, collagen hydrolysate (CH), pomegranate polyphenolic extract (PP) and shrimp lipid extract (SL). The resulting dry powders were compared in terms of water solubility, entrapment efficiency, hydrodynamic particle properties, ζ potential and antioxidant properties (ABTS radical scavenging capacity, ferric ion reducing power and Folin-reactive substances). Dry powders and plain compounds were incorporated into squid surimi gels, and after in vitro simulated gastrointestinal digestion (sGID), the residual antioxidant and angiotensin-converting enzyme (ACE)-inhibitory activities were evaluated. All powders showed antioxidant properties, electronegative ζ potential and great entrapment efficiency after rehydration (ranging from ∼70 to 97%). The heat-dried powders were composed of microparticles ranging from 177 to 380 µm resulting in low water solubility (21.6-36.1%), while the average particle size and solubility values of spray-dried preparations were 2.9-13.2 µm and >86%, respectively. In contrast to the plain compounds, the addition of any of the microparticle dried preparations allowed obtaining well-conformed surimi gels. The ACE-inhibitory capacity of the surimi gels after sGID was increased by the addition of any of the compounds studied, but to a lesser extent by their entrapment forms (except with the entrapped SL). The antioxidant activities of gels with the entrapped compounds were even lower than those of gels without bioactives in some cases. In conclusion, the addition of dried microparticles did not increase the biological activity as compared to the plain compounds; however, they were beneficial to ensure adequate gel consistency.

Functional aptitude of hake minces with added TMAO-demethylase inhibitors during frozen storage.

The ability of compounds of natural origin (black, white, red, and green tea extracts, phytic acid) to inhibit TMAO-demethylase enzyme was assayed. Black tea and phytic acid exerted the highest inhibiting activities, similar to the already known inhibitor sodium citrate. Hake minces incorporating these three compounds were prepared and stored frozen (150 days, -12 °C). TMAO-demethylase enzyme was partially inhibited (lower enzyme activity, reduction of formaldehyde accumulation). The study of physicochemical properties of the minces (salt-soluble proteins, water holding capacity, structural water associated with myofibrils) pointed to evident protein aggregation and loss of functionality when phytic acid was added, whereas black tea and sodium citrate did not have a negative effect. Consequently, the salt-ground mince with phytic acid showed worse viscoelastic properties than the others. In conclusion, black tea polyphenols and sodium citrate can be used as additives to inhibit TMAO-demethylase enzyme during frozen storage of fish minces.

Recovery, viscoelastic and functional properties of Barbel skin gelatine: investigation of anti-DPP-IV and anti-prolyl endopeptidase activities of generated gelatine polypeptides.

The characteristics and functional properties of gelatine from freshwater fish skin (Barbus callensis) were investigated. The gelatine extraction efficiency was improved by an acid-swelling process in the presence of barbel crude acid protease extract. Barbel skin gelatine (BSG) contained 92.15% protein, 0.31% lipid and 0.72% ash. The amino acid profile of BSG showed a high percentage of imino acids. The electrophoretic profile showed that BSG is mainly composed of α- and ß-components. BSG showed an excellent solubility and possessed interfacial properties, which were governed by the protein concentration. Biological activities of the hydrolysates obtained after digestion of BSG with several commercial proteases were evaluated. The results suggested that these hydrolysates are a good source of natural inhibitors of dipeptidyl peptidase-IV and prolyl endopeptidase and could potentially be used as dietary ingredients in the management of type 2-diabetes and/or neuropathological disorders.