抄録
Enzymes are at the center of the development of plant proteins and foods that use them. Among them, protein-glutaminase deamidates proteins, lowering their isoelectric point and improving their solubility in more acidic conditions. In addition, the intramolecular electrostatic repulsive force generated between the carboxyl groups loosens the higher order structure of the protein, which is thought to expose hydrophobic regions buried within the molecule to the molecular surface. This gives plant proteins excellent functionality as emulsifiers and foaming agents. They are widely used in food processing abroad to improve these food functions.
One of the challenges of vegetable milk replacer is its low protein content compared to cow's milk, but the use of protein-glutaminase in the production process of oat replacer solubilizes the protein and increases the amount of protein transferred to the centrifuge supernatant, improving the dispersibility and dispersion stability. In addition, when the tribological smoothness of protein-glutaminase-treated soy milk was measured as an index to evaluate the mouthfeel, the enzyme-treated soy milk reduced the coefficient of friction of the soy milk, regardless of whether saliva was present or not. This is considered a result that may be associated with improved mouthfeel. Another issue is that vegetable milk substitutes do not disperse when added to hot coffee as coffee milk, resulting in protein aggregation. This is because the isoelectric point of vegetable proteins is weakly acidic to acidic, so they tend to aggregate when added to coffee, which is an acidic beverage. When enzyme-treated almond milk was added to coffee and allowed to stand, protein aggregation was observed in the untreated sample, but not in the enzyme-treated sample, and dispersion was maintained.
Other enzyme applications include the use of starch-related enzymes to control the type and amount of carbohydrates in milk substitutes to adjust the desired (mainly sweet) taste quality. Transglucosidase treatment can impart a full-bodied sweet taste, which may be due to the formation of isomaltooligosaccharides. In addition, glucoamylase treatment can enhance sweetness by producing glucose, β-amylase treatment can impart mild sweetness by producing maltose, and maltotriohydrolase treatment can impart refreshing sweetness by producing maltotriose. Thus, the taste of the vegetable milk substitute can be adjusted according to the product concept. On the other hand, it is difficult to reproduce the unique flavor of plant-based meat substitutes, but by treating them with protease and peptidase, it is possible to impart a flavor and aroma typical of cooked meat. The amino acids in the baked enzyme-treated meat alternatives were quantified, and the amounts of glutamic acid and cysteine were increased. Glutamic acid was thought to contribute to the umami flavor, while cysteine was thought to enhance the savory flavor of the meat through the Maillard reaction. In addition, bean odor is a factor that negatively influences consumer purchasing decisions for plant-based meat substitutes. The entrapment ability of cyclodextrins produced by enzymatic treatment with the cyclodextrin glucanotransferase reduced the volatiles of hexanal, 1-octen-3-ol and benzaldehyde, the major contributors to soy odor, to less than half.
