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The objective of this work was to explore the possibility of improving the antioxidant capacity and application of whey protein (WP) through non-covalent interactions with hesperidin (HES), a citrus polyphenol with nutraceutical activity. The interaction mechanism was elucidated using several spectroscopic methods and molecular docking analysis. The antioxidant capacity of the WP-HES complexes was analyzed and compared to that of the proteins alone. Moreover, the resistance of oil-in-water emulsions formulated using the WP-HES complexes as antioxidant emulsifiers to changes in environmental conditions (pH, ion strength, and oxidant) was evaluated. Our results showed that HES was incorporated into a single hydrophobic cavity in the WP molecule, where it was mainly held by hydrophobic attractive forces. As a result, the microenvironments of the non-polar tyrosine and tryptophan residues in the protein molecules were altered after complexation. Moreover, the α-helix and β-sheet regions in the protein decreased after complexation, while the β-turn and random regions increased. The antioxidant capacity of the WP-HES complexes was greater than that of the proteins alone. Non-radiative energy transfer from WP to HES was detected during complex formation. Compared to WP alone, the WP-HES complexes produced emulsions with smaller mean droplet diameters, exhibited higher pH and salt stability, and had better oxidative stability. The magnitude of these effects increased as the HES concentration was increased. This research would supply valuable information on the nature of the interactions between WP and HES. Moreover, it may lead to the creation of dual-function antioxidant emulsifiers for application in emulsified food products.

In this research, yak butter (YB) microcapsule with different YB addition was successfully prepared by using maltodextrin/whey protein isolate/sodium caseinate as main wall materials. The microstructures, microencapsulation efficiency and possible sacculation mechanism was then analyzed. The in vitro intestinal digested behavior of the microcapsules affected by bile salts was monitored and investigated in details. The results indicated that microcapsules were hollow spheres with entrapped YB located in the wall materials. Higher YB addition resulted in inhomogeneous larger particles with decreased membrane thickness. H-bonding interactions between protein and carbohydrate ensured the integrity of the capsule wall. The in vitro digestion results suggested that the concentration of bile salts had significant impacts on the digestion behavior of microcapsules. The present of bile salts was necessary for pancreatin hydrolysis of wall material. Hydrolysis of pancreatin, emulsification of bile salt and its positive effect for pancreatin hydrolysis all happened during the digestion and affected the digested behavior in the end. This research would provide valuable information for the bioavailability of microcapsule in human gastrointestinal systems. [ABSTRACT FROM AUTHOR]

Abstract: Protein hydrolysates (SH, TH) were prepared from eel head by enzymatic treatment using protease. The eel head hydrolysates were used as a natural food preservative by adding to grass carp surimi at the 10% ranging. We compared the effect of protein hydrolysates of eel head with traditional antifreeze on the denatration, gel strength and contents of the salt soluble protein in grass carp surimi during frozen storage at -20°C for 80 days. The addition of eel head hydrolysate markedly decreased the activation rate of the Ca-ATPase. The contents of the salt soluble protein in the grass carp surimi containing eel head hydrolysates were higher than those without eel head hydrolysates (control).Therefore, the gel strength of grass carp surimi media with eel head hydrolysate lower than the others. The result suggests that eel head hydrolysate could suppress the denaturation of grass carp surimi during frozen storage. [Copyright &y& Elsevier]

In order to study the spoilage-related microbiota of fried and boiled fish cakes, a combination of traditional plating, culture-independent and culture-based methods were used to analyse the fish cake stored at 4 °C. The population diversity was studied by selective agar cultivation, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of DNA directly extracted from fish cake and from bulk cells from plate counting media. No significant difference in spoilage bacteria between fried and boiled fish cakes could be found during storage period. Plate counts on selective agar showed that the major bacterial group was lactic acid bacteria. Flavobacteriaceae, Psychrobacter sp. and Pseudomonas poae were detected during the entire storage period in DGGE profile. The use of culture-independent method highlighted the species that were not detected by plating. In contrast, culture-based analysis detected bacterial species that were not found in DNA extracted directly from sample. This study confirmed that a combination of traditional plating, culture-independent and culture-based approaches could enhance understanding of the populations of spoilage bacteria. [ABSTRACT FROM AUTHOR]