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β-Lactoglobulin (β-LG) is recognized as the major milk allergen. In this study, the effects of transglutaminase (TGase) and glucosamine (GlcN)-catalyzed glycosylation and glycation on the conformational structure and allergenicity of β-LG were investigated. The formations of cross-linked peptides were demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and GlcN-conjugated modification was identified using matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Structural analysis revealed that glycosylation and glycation of β-LG induced unfolding of the primary protein structure followed by a loss of the secondary structure. As revealed by circular dichroism (CD) spectroscopy, glycosylated β-LG exhibited the highest increase in the β-sheets from 32.6% to 40.4% (25 °C) and 44.2% (37 °C), and the percentage of α-helices decreased from 17.7% to 14.4% (25 °C) and 12.3% (37 °C), respectively. The tertiary and quaternary structures of β-LG also changed significantly during glycosylation and glycation, along with reduced free amino groups and variation in surface hydrophobicity. Immunoblotting and indirect enzyme-linked immuno sorbent assay (ELISA) analyses demonstrated that the lowest IgG- and IgE-binding capacities of β-LG were obtained following glycosylation at 37 °C, which were 52.7% and 56.3% lower than that of the native protein, respectively. The reduction in the antigenicity and potential allergenicity of glycosylated β-LG was more pronounced compared to TGase treated- and glycated β-LG, which correlated well with the structural changes. These results suggest that TGase-catalyzed glycosylation has more potential compared to glycation for mitigating the allergenic potential of milk products.

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These results indicate that brown seaweed polyphenols and α-tocopherol can be used to prevent oxidative reactions and thus maintain the structure of the gel formed by fish mince during frozen storage. © 2016 Society of Chemical Industry.

Summary The quality loss in fish during freeze–thaw cycles is considered one of the major issues caused mainly by temperature fluctuations during cold storage. The present work is aimed to illustrate the effects of brown algal phlorotannins (BAP) and ascorbic acid (AA) on physiochemical properties of minced snapper muscle through different freeze–thaw cycles. Both AA and BAP could retard lipid and protein oxidation, respectively, and synergistically. The Ca2+‐ATPase activity can be protected with the addition of antioxidants. The addition of 0.1% (w/w) AP showed 22.6% higher activity as compared with other groups especially during three freeze–thaw cycles. Cooking loss was efficiently inhibited and 0.1% AA + 0.3% BAP group showed 25.5% lower than control. Antioxidant is also helpful to maintain gel‐forming ability of minced snapper and 0.1% AA + 0.1% BAP group showed the best. These results revealed that both AA and BAP could prevent minced fish by inhibiting the protein denaturation during freeze–thaw cycles.