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Gelatin was extracted from fish scales in this work, in an attempt to valorise abundant and available fishery by-products as an approach towards a more circular economy. With this strategy in mind, fish scale gelatin was used to prepare active films. In this regard, the development of advanced materials from gelatin involves its modification to enhance functional properties, particularly barrier properties, to achieve the requirements for specific value-added purposes, such as food or pharmaceutical/biomedical applications. The improvement of those functional properties can be achieved by means of chemical cross-linking processes. In this context, non-enzymatic reactions were carried out with the addition of fructose and ascorbic acid into gelatin film forming formulations, and cross-linking was induced by a heat-treatment. These cross-linking reactions resulted in higher barrier features, especially for those films prepared with ascorbic acid.

The aim of this work was to assess the effect of fish gelatin−citric acid nucleophilic substitution and agar−citric acid esterification reactions on the properties of agar/fish gelatin films. Since temperature is an important cross-linking parameter, films were treated at 90 °C and 105 °C and film properties were compared to those of non-cured films. It was observed that temperature favored the aforementioned reactions, which induced physical and morphological changes. In this regard, darker films with a rougher surface were obtained for the films with a higher cross-linking degree. While mechanical properties were slightly modified, the barrier properties were enhanced due to the reactions that occurred. Therefore, these agar/fish gelatin films cross-linked through two different reactions can be considered to be promising materials as active films for different purposes, such as active packaging or pharmaceutical applications.

Catfish (Pangasius hypophthalmus) is one of the main seafood products of Vietnam with a large amount of over 1.3 million tons in 2018. However, after the processing, large amount of the harvested catfish is considered as by-products. In this study, catfish by-products have been used to produce three bioactive components, including fish protein hydrolysate (FPH), hydroxyapatite (HA) and lipid fraction by an enzymatic method. The fish by-products were hydrolyzed by using an Alcalase-substrate ratio of 0.4% (v/w) at 60 °C and natural pH for 9 h with a water-raw material ratio of 1:1 (mL/g). The results show that the protein hydrolysate has degree of hydrolysis (DH) of over 30%, nitrogen recovery (NR) of over 80% and contained a large amount of essential amino acids. HA particles have a size of 50–70 nm with high porosity and quite uniformity, suggesting its potential applications such as bone scaffold or regenerative materials. The lipid fraction has high vitamin A content with a small amount of fatty acids (ca. 90 mg/g) that can be refined for further food applications. This recovery method is simple, environmentally-friendly and can be scale-up easily. In addition, the cheap fish by-products were processed to give value-added products as well as reduce the undesirable environmental impact. [ABSTRACT FROM AUTHOR]

Experimental results proved that the development of Colletotrichum capsici B4 is extremely sensitive to water-soluble chitosan (WSC) and inhibitory effects increase with increasing concentrations of WSC. In the in vitro test, the results showed that the entire prevention of conidial germination and mycelial diameter development are recognized in a potato dextrose agar medium containing 0.4% and 0.8% WSC, respectively. WSC was more efficient in a potato dextrose broth where it absolutely prevented the mycelial development of C. capsici B4 at a concentration of 0.32%. WSC treatments considerably decreased disease prevalence and the lesion diameter of anthracnose disease on chilli pepper fruits in the in vivo experiments. Experiments in biochemistry indicated that the activities of the key defense-related enzymes in peel, consisting of chitinase, β-1,3-glucanase and total phenolic content, were increased by both C. capsici B4 infection and C. capsici B4 treatment, and was further treated with a 0.5% WSC concentration. Practical applications From the present studies we conclude that water-soluble chitosan (WSC) can directly inhibit the development of C. capsici B4 isolated from infected chili pepper fruits showing typical symptoms of anthracnose in in vitro and effectively control anthracnose in chili pepper fruit in in vivo with concentration-dependent antifungal effects. These findings suggest that WSC may be recognized as a feasible effective alternative to artificial fungicides for postharvest disease control of chili pepper fruits. [ABSTRACT FROM AUTHOR]

Aquaculture is currently one of the most rapidly growing production sectors in Vietnam. This publication describes the concentrations of heavy metals in the farming environment and some aquaculture species in the Khanh Hoa Province in Vietnam. The concentration of total As in the sediments ranged from 0.07 to 0.64 mg/kg, whereas the concentration of Hg varied from <0.0005 to 0.56 mg/kg. The corresponding concentration span for Cd and Pb, were 0.001–0.069 and 0.016–0.078 mg/kg, respectively. The concentrations of As in the aquaculture organisms spanned from 0.14 to 1.03 mg/kg. For Hg the concentrations varied from 0.1 to 0.45 mg/kg, for Cd from 0.02 to 0.10 mg/kg and for Pb from 0.07 to 0.37 mg/kg. [ABSTRACT FROM AUTHOR]

Biological hydroxyapatite (HA) can be obtained from fish bones. However, various fish species will provide HAs with different morphologies, porosities and purities. In this study, the properties of HAs prepared from four different fish bones, including catfish (Pangasius hypophthalmus), tilapia (Oreochoromis sp.), seabass (Lates calcarifer), and yellowfin tuna (Thunnus albacares), were characterized and compared. By using the same treatment conditions with a calcinating temperature of 700 °C for 2 h, HA prepared from seabass (Lates calcarifer) bones showed the most uniform and smallest size of ca. 50–70 nm. The HA powder obtained from tilapia (Oreochoromis sp.) bones presented the highest specific surface area of 32.83 m2 g−1. All HA products had a similar polycrystalline property and the Ca/P ratio of about 1.80. These findings are particularly useful to consider for further production and applications of HA powders prepared from fish bones. [ABSTRACT FROM AUTHOR]