Application of plasma-activated water in the food industry: A review of recent research developments.

Plasma-activated water (PAW) is liquid treated with plasma. This liquid develops a higher oxygen reduction potential, a lower pH, and conductivity due to the delivery of reactive species from plasma to water. In this article, we review the antimicrobial activity and other applications of PAW in various food products. We discuss the effects of PAW treatment parameters on microbial inactivation efficiency as well as the underlying mechanisms, pesticide dissipation and its degradation pathway, meat curing and strategies to improve the nitrite amount in PAW, enhancement of food functional characteristics, and seed germination and plant growth. Additionally, we highlight the effects of PAW on food quality attributes. We further introduce the synergistic interaction of PAW with other technologies. Finally, we provide an overview of future challenges that must be resolved in the application of PAW in the food industry.

Kinetic, spectroscopic, and molecular docking studies on the inhibition of membrane-bound polyphenol oxidase from Granny Smith apples (Malus domestica Borkh.).

We investigated the inhibitory effect and binding mechanism of four selected compounds (ascorbic acid, l-cysteine, glutathione, and citric acid) on membrane-bound polyphenol oxidases (mPPO) using spectroscopic and molecular docking techniques. Kinetic analysis demonstrated that these inhibitors reversibly inhibited the mPPO activity. Fluorescence spectroscopy revealed that the intrinsic fluorescence intensity of mPPO was quenched by inhibitors with a single class of the inhibition site on mPPO. Amino acid residues His 180, His 201, His 366, Cys 184, Glu 328, and Asn 333 were the important binding sites in the active center. These sites were identified using molecular docking techniques. Our findings suggested that the inhibitors were allosterically bound to the active center of mPPO through hydrogen bonds and ion contacts. This study provides new insights into the active site residues responsible for catalyzing mPPO and provides applicable information about the design of mPPO inhibitors.

Comparison of biochemical properties of membrane-bound and soluble polyphenol oxidase from Granny Smith apple (Malus × domestica Borkh.).

Polyphenol oxidase from Granny Smith apples was purified and characterized in both its soluble form (sPPO) and its membrane-bound form (mPPO). Both forms were purified by temperature-induced phase partitioning, precipitation with ammonium sulfate, and ion exchange chromatography. The specific activity of mPPO was 19.17 times that of sPPO. The optimum pH and temperature for both forms were 7.0 and 35 °C when catechol was the substrate. The Michaelis constant and maximum reaction rate for sPPO were 34.1 mM and 500 U/mL/min, whereas those for mPPO were 53 mM and 10,000 U/mL/min, respectively. The enzymes exhibited diphenolase activity, and their affinity was highest for catechol (sPPO) and 4-methylcatechol (mPPO). Inhibitors of sPPO and mPPO included ascorbic acid, glutathione, and l-cysteine. However, ethylenediaminetetraacetic acid increased the activity of mPPO. Purified sPPO was dimeric with a molecular weight of 31 kDa, whereas mPPO was monomeric with an estimated molecular weight of 65 kDa.