Effect of Thermal Treatment on the Physicochemical Properties of Emulsion Stabilized by Gelatin from Black Tilapia (Oreochromis mossambicus) Skin

Effect of heat treatment on the physical stability, interfacial composition and protein-lipid co-oxidation of whey protein isolate-stabilised O/W emulsions

This work aimed to investigate the effects of heat treatments at different temperatures (60, 70 and 90 °C, expressed as HT-60, HT-70 and HT-90) on interfacial composition and protein-lipid co-oxidation in whey protein isolate (WPI)-stabilised O/W emulsions during storage. Compared with control group, all heated emulsions exhibited weaker physical stability over 10 days of storage, which verified by the increased droplet size, as well as decreased adsorbed protein levels and absolute ζ-potential values. Moreover, proteins recovered from the HT-90 emulsion showed the highest fluorescence intensity and red-shift of the maximum emission wavelength, indicating partial unfolding of the protein structure. Meanwhile, severe changes in protein structure were also observed in the HT-70 and HT-90 emulsions, which clearly verified by the degradation of bovine serum albumin, α-lactalbumin and β-lactoglobulin. Furthermore, HT-70 and HT-90 emulsions showed lower levels of lipid hydroperoxides and thiobarbituric acid reactive substances. In contrast, the recovered proteins were subject to severe oxidative stress as indicated by carbonyl and N'-formyl-L-kynurenine. Hierarchical cluster and correlation analysis implied that the process of protein-lipid co-oxidation is inevitable, but it can be retarded by heat treatment. Our results clearly revealed the relevance among heat treatment, interfacial adsorption property, and the protein-lipid co-oxidation of O/W emulsions.

Comparison of Oxidative and Physical Stabilities of Conjugated Linoleic Acid Emulsions Stabilized by Glycosylated Whey Protein Hydrolysates via Two Pathways

The objective of the research was to analyze and compare the oxidative and physical stabilities of conjugated linoleic acid (CLA) emulsions stabilized by two glycosylated hydrolysates (GPP-A and GPP-B) that were formed via two different pathways. This study showed that GPP-A exhibited higher browning intensity and DPPH radical scavenging ability in comparison with GPP-B. Moreover, the CLA emulsion formed by GPP-A exhibited a lower creaming index, average particle size, primary and secondary oxidative products, in comparison with GPP-B-loaded emulsion. However, the GPP-A-loaded emulsion showed a higher absolute potential and fraction of interfacial adsorption than that of the CLA emulsion formed by GPP-B. Therefore, the CLA emulsion formed by GPP-A exhibited stronger stabilities in comparison with the GPP-B-loaded emulsion. These results suggested that GPP-A showed an emulsification-based delivery system for embedding CLA to avoid the loss of biological activities. Additionally, the development of CLA emulsions could exert its physiological functions and prevent its oxidation.

Characterization and Cell Viability of Probiotic/Prebiotics Film Based on Duck Feet Gelatin: A Novel Poultry Gelatin as a Suitable Matrix for Probiotics

The probiotic viability, physicochemical, mechanical, barrier, and microstructure properties of synbiotic edible films (SEFs) based on duck feet gelatin (DFG) were evaluated. Four synbiotic systems were obtained by mixing four types of prebiotics, namely, dextrin, polydextrose, gum Arabic, and sago starch, with DFG to immobilize of probiotic (Lactobacillus casei ATCC). The ability of DFG to create a suitable matrix to increase probiotic viability was compared with those of other commercial gelatins in a preliminary evaluation. The DFG showed proper probiotic viability compared with other gelatins. The addition of prebiotics reduced the transparency of SEFs and increased color differentiation, uniformity, and complete coverage of probiotic cells. The estimated shelf-life of surviving bacteria in the SEFs stored at 4 and 25 °C showed that gum arabic showed the best performance and enhanced the viability of L. casei by 42% and 45%, respectively. Dextrin, polydextrose, and sago starch enhanced the viability of L. casei at 4 and 25 °C by 26% and 35%, 26% and 5%, and 20% and 5%, respectively. The prebiotics improved the physicochemical, mechanical, and barrier properties of all SEFs, except polydextrose film. The viability of L. casei can be increased with the proper selection of gelatin and prebiotics.