Quinoa protein Pickering emulsion improves the freeze-thaw stability of myofibrillar protein gel: Maintaining protein composition, structure, conformation and digestibility and slowing down protein oxidation.

In this work, the effects of quinoa protein Pickering emulsion (QPPE) on protein oxidation, structure and gastrointestinal digestion property of myofibrillar protein gels (MPGs) after freeze-thaw (F-T) cycles are revealed. SDS-PAGE results indicated that 5.0 %-10.0 % QPPE addition slowed down the protein degradation. Meanwhile, 5.0 %-7.5 % QPPE maintained the stability of the protein secondary and tertiary structure of MPGs after F-T cycles. The sulfhydryl group, disulfide bond and dityrosine content increased with QPPE supplementation. The conformations of disulfide bond changed from g-g-t and t-g-t to g-g-g after F-T cycles, and 5.0 %-7.5 % QPPE stabilized the changes of t-g-t conformation. Furthermore, the increase of dityrosine content after F-T cycles was significantly reduced with 7.5 % QPPE addition, indicating its effect to slow down protein oxidation of MPGs. In addition, MPGs with 5.0 % and 7.5 % QPPE showed noticeably higher zeta potential values than other groups, indicating the enhanced electrostatic repulsion and weakened aggregation caused by F-T damage. This work showed that 7.5 % QPPE improved the F-T stability of MPGs and reduced the protein denaturation and oxidation caused by F-T treatments, exerting no side effect on the digestion property of MPGs. QPPE can be used as a green and effective antifreeze in meat industry.

Quinoa protein Pickering emulsion: A promising cryoprotectant to enhance the freeze-thaw stability of fish myofibril gels.

In this work, the effects of different QPE addition on the freeze-thaw (F-T) stability of fish myofibrillar protein (MP) gels were revealed. During freezing process, QPE decreased the freezing point of MP gels and shortened the time to pass through the maximum-ice-crystal-formation zone. The occurrence of thermal hysteresis effect led to the formation of small ice crystals and alleviated the damage to MP gel network. The incorporation of 7.5% QPE also reduced the free water amount to 19.23% and improved the water holding capacity of MP gels. Furthermore, the incorporation of QPE decreased the carbonyl content of MP gels after F-T cycles and delayed the protein oxidation. Meanwhile, QPE addition maintained the stability of the tertiary structure of MP gels via stabilizing the microenvironment of tyrosine and tryptophan. Overall, QPE shows the potential as a new cryoprotectant to improve the F-T stability of MP gel products.

Effects of quinoa protein Pickering emulsion on the properties, structure and intermolecular interactions of myofibrillar protein gel.

The effects of quinoa protein Pickering emulsion (QPE) on the gel properties, protein structure and intermolecular interactions of myofibrillar protein (MP) gels were studied. Compared with the MP gels without QPE, the MP gels with 5.0%-7.5% added QPE showed significant increasing trends in storage modulus (G'), whiteness, gel strength and water holding capacity (WHC). The content of disulfide bonds in the gel increased with the addition of QPE and the disulfide bond conformation changed from gauche-gauche-gauche to gauche-gauche-trans. Moreover, the increase of hydrogen bonds after QPE addition confirmed the transformation from α-helix to ß-sheet, as ß-sheet structure was stabilized by interchain hydrogen bonds. The added QPE also enhanced the hydrophobic interaction and electrostatic interaction of MP gels. To conclude, the addition of 5.0%-7.5% QPE improved the intermolecular interactions and the structure stability of MP gels, and enhanced the gelation and WHC of MP gels.