The activity of amylolytic and antioxidant enzymes (catalases, peroxidases) during malting of barley grain depending on the grains’ size and the applied phytoregulators

Abstract

Background. Malting, during which the activity of various enzymes significantly increases in the germinating barley grain, is of great importance in the brewing industry. During the germination of barley seeds under standard conditions, the formation of an active complex of enzymes amylases, proteases, cytases, oxidoreductases, dissolving endo-sperm cells and converting reserve substances into soluble compounds. It was found that phytoregulators activate germination processes and enzyme activity. It has been shown that the activity of enzymes in the process of malting also depends on the grains’ size and can be increased with the use of phytoregulators. The purpose of the research is to study the activity of the enzyme complex of barley grain during malting, depending on the size of the grains and the applied phytoregulators epin-extra, zircon and siliplant. Materials and methods. The object of the research is the grain of “Nadezhniy” malting barley harvested in 2017, grown on a leveled agrobackground of the field experimental base of Moscow Research Institute of Agriculture “Nemchinovka”. The soil of the experimental plot is sod-dy-podzolic medium loamy. In the studies, the grain was fractionated according to the thickness of the grains using a set of sieves. The chemical composition of the grain was evaluated by NIR analysis. The activity of amylolytic enzymes, catalases and peroxidases was determined. The catalytic activity of the isoforms of these enzymes at рН = 5.5, 7.0, 8.0 was detected using a phosphate buffer system (1/15 M phosphate buffer). The activity of enzymes in the germinated grain was determined after the removal of sprouts and roots. The effect of phytoregulators on the process of malting barley grain was evaluated after 1-hour soaking of grains in solutions of regulatory preparations produced by ANO “NEST-M” siliplant, epin-extra and zircon. The consumption rate of drugs is 0.1 ml per 1 liter of de-mineralized water. Results and сonclusions. In experiments on grain fractionation of bre-wing barley, depending on the thickness of the grains, it was found that in the dormant grains of a fraction that is finer in grain thickness (2.2–2.5 mm), the content of water-soluble proteins is increased, and in the seedling grain of this fraction, a high activity of acidic, neutral and alkaline α-amylases. At the same time, in the germinated caryopses of the fraction with the largest grain thickness (>3 mm), a high activity of acid β-amylases and catalases, as well as acidic, neutral, and alkaline peroxidases, was noted. The identified features of these grain fractions improved the brewing properties of the grain. When stu-dying the action of enzymes in acidic (pH = 5.5), neutral (pH = 7) and alkaline (pH = 8) environments, it was found that both in resting and germinated barley grains, acid isoen-zymes α- and β-amylases, as well as neutral and alkaline isoenzymes of catalase and pero-xidase. Under the effect of the phytoregulator zircon, the activity of acidic, neutral and alkaline forms of peroxidases in the grain of 7-day-old barley seedlings increased by 43–81 %, and under the action of epin-extra, by 28–60 %.

Keywords

• malting barley
• grains fractionation by their thickness
• chemical composition of grain
• activity of amylases
• catalases
• peroxidases in germinating grain