The rising interest in the valorisation of industrial by-products is one of the main reasons why exploring different species and optimizing the extracting conditions of collagen and gelatin has attracted the attention of researchers in the last decade. The most abundant sources of gelatin are pig skin, bovine hide and, pork and cattle bones, however, the industrial use of collagen or gelatin obtained from non-mammalian species is growing in importance. The classical food, photographic, cosmetic and pharmaceutical application of gelatin is based mainly on its gel-forming properties. Recently, and especially in the food industry, an increasing number of new applications have been found for gelatin in products such as emulsifiers, foaming agents, colloid stabilizers, biodegradable film forming materials and micro-encapsulating agents, in line with the growing trend to replace synthetic agents with more natural ones. In the last decade, a large number of studies have dealt with the enzymatic hydrolysis of collagen or gelatin for the production of bioactive peptides. Besides exploring diverse types of bioactivities, of an antimicrobial, antioxidant or antihypertensive nature, studies have also focused on the effect of oral intake in both animal and human models, revealing the excellent absorption and metabolism of Hyp-containing peptides. The present work is a compilation of recent information on collagen and gelatin extraction from new sources, as well as new processing conditions and potential novel or improved applications, many of which are largely based on induced cross-linking, blending with other biopolymers or enzymatic hydrolysis.

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The purpose of this study was to analyze the effect of 10-min continuous pressure and pulsed pressure in two 5-min steps (400 MPa at 7 degrees C) on the microbial flora, total volatile bases, pH, and texture of purified and unpurified oysters. High-pressure treatment reduced the number of all the target microorganisms (total viable count, H2S-producing microorganisms, lactic acid bacteria, Brochothrix thermosphacta, and coliforms), in some cases by around 5-log units. The difference between the counts in the control and the pressurized oysters remained stable throughout 41 days of storage at 2 degrees C. No Salmonella spp. were detected in either the control batch or the pressurized batches during this storage period. Deterioration of the oyster was accompanied by increased total volatile bases, mainly in the nonpressurized samples. The pH was practically constant in the pressurized oysters and fell slightly in unpressurized samples. As for mechanical properties, shear strength values were higher in pressurized than in unpressurized oysters. Step-pulse pressurizing (400 MPa at 7 degrees C in two 5-min pulses) produced no apparent advantages over continuous pressurizing based on any of the indices used.

a b s t r a c tIn order to provide gelatin films with antioxidant capacity, two sulphur-free water-insoluble lignin powders (L 1000 and L 2400 ) were blended with a commercial fish-skin gelatin from warm water species at a rate of 85% gelatin: 15% lignin (w/w) (GeL 1000 and GeL 2400 ), using a mixture of glycerol and sorbitol as plasticizers. The water soluble fractions of GeL 1000 and GeL 2400 films were 39.38 AE 1.73% and 46.52 AE 1.66% respectively, rendering radical scavenging capacity (2,2 0 -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid, ABTS assay)) of 27.82 AE 2.19 and 15.31 AE 0.88 mg vitamin C equivalents/g film, and ferric ion reducing ability (FRAP assay) of 258.97 AE 8.83 and 180.20 AE 5.71 mmol Fe 2þ equivalents/g film, respectively. Dynamic oscillatory test on film-forming solutions and Attenuated Total Reflectance (ATR)-FTIR spectroscopy study on films revealed strong lignin-induced protein conformational changes, producing a noticeable plasticizing effect on composite films, as deduced from the study of mechanical (traction and puncture tests) and thermal properties (Differential Scanning Calorimetry, DSC). The gelatin films lose their typical transparent and colourless appearance by blending with lignin; however, the resulting composite films gained in light barrier properties, which could be of interest in certain food applications for preventing ultraviolet-induced lipid oxidation. Lignin proved to be an efficient antioxidant at non-cytotoxic concentrations, however, no remarkable antimicrobial capacity was found.

A coating made in cold from a blend of a chitosan and a gelatin solution was applied to patties made of chilled cod, and its preservative effect was assessed by colour measurements, rheological measurements (hardness, elasticity, cohesiveness, chewiness, gumminess, and adhesiveness), biochemical determinations (total volatile bases and thiobarbituric acid as measures of rancidity) and microbiological assays (total bacterial counts, luminiscent bacteria, enterobacteria, pseudomonas, lactic acid bacteria, and Staphylococcus aureus). The effect of dry powdered chitosan mixed into the patties was tested as well. The use of chitosan either as a coating or as a powdered ingredient did not affect lightness at the end of the storage period considered but did result in an increase in the value of yellowness. The coating increased patty elasticity, whereas adding powdered chitosan to the patty mixture increased the other rheological parameter values. The findings on the effect of the chitosan on rancidity were not conclusive due to the low values recorded in the cod. However, the coating did prevent spoilage of the cod patties as reflected by a decrease in total volatile basic nitrogen and in the microorganism counts, in particular counts of gram-negative bacteria. In contrast, none of these effects on spoilage were observed when the chitosan was added to the patty mixture in powdered form. Coatings prepared in cold from a blend of gelatin and chitosan offer a promising alternative for preserving fish patties.