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Abstract
The growing interest in minimal processing of foods due to its mild effects on product quality and taste, has led to an increase in the research on novel techniques for food processing. One of these emerging techniques is atmospheric cold plasma (ACP) processing. It can be used to decontaminate food, inactivate enzymes and modify its structure to enhance its appearance and flavor. ACP processing has drawn interest of scientists because of its lower energy consumption, short processing times and low operational cost than that of traditional technologies. The plasma components generated by N2-O2 or N2 and other gases have oxidizing potential to break down the peptide bonds, oxidize amino acids and impact the higher order structures of proteins. Controlled aggregation of milk proteins is known to be key in optimizing their functionality in a food product. Evaluation of the effect of ACP treatment time and type of feed gas on the physico-chemical properties, particle size of skim milk and molecular weight and structure of milk proteins showed denaturation of proteins and the formation of protein aggregates. Further evaluation of the extent of whey protein denaturation caused by ACP and its effect on whey protein distribution in milk showed that the treatment changed the ratio of native β-lactoglobulin and native ⍺-lactalbumin present in milk serum. Furthermore, the protein-protein interactions present in the plasma-induced aggregates showed a change in the content of disulphide and hydrogen onds. ACP treatment also decreased the allergenicity of major milk proteins, viz. casein, β-lactoglobulin and ⍺-lactalbumin. Due to the covalent interactions in the gelling mechanism of proteins, the effect of ACP treatment on the sulfhydryl content and flow properties of skim milk and acid gelling behavior of skim milk was also evaluated. ACP treatment caused an overall decrease in the free sulfhydryl group content of skim milk. Viscosity of milk increased with time, but it still exhibited Newtonian behavior. N2O2 plasma treatment had a significant effect on the final storage modulus, color and firmness of acid milk gels. The acid gels made from milk treated with N2 plasma suffered lesser syneresis than that by N2O2 plasma.