With the continuous development of biotechnology, the use of new enzyme preparations to improve the quality of cereal products has become a hot spot of concern at home and abroad. Lipase, as a safe, efficient, pure natural green additive, is widely used in the processing of fermented products such as steamed bread and bread. Lipase acts on endogenous lipids in wheat flour to produce surfactant molecules, such as lysophospholipids and monoglycerides, to improve the quality of products.

Effect of lipase on bread quality

Lipases have been used in the baking industry since 1990 to improve the processing quality of dough. Wang Yusheng et al. showed that lipase can effectively improve the rheological quality of bread flour and improve the hardness and elasticity of bread. Wang Xuedong et al. showed that the addition of lipase to bread flour can significantly improve the tensile properties of bread flour and improve the quality of bread.

The addition of lipase to bread significantly improved the gloss and whiteness of bread, increased the specific volume of bread, and at the same time improved the fluffiness and made the porosity of the bread flesh more uniform.JANSSEN et al. showed that the addition of Lipopan.F increased the level of polar lipids in the dough, which had a positive effect on the stabilization of air bubbles in the dough and increased the volume of bread.

GERITS et al. found that the effect of lipases LipopanF and Lecitase Ultra on bread was consistent with surfactants, both increasing the volume of bread, and the effect of lipases on lipids resulted in a 56% increase in the volume of bread, depending on the type and concentration of the added lipase.

SCHAFFARCZYK et al. studied the effect of lipases Lipopan.FBG and Lipopan.Xtra BG on bread quality. It was found that these two lipases had different degrees of improvement on the texture and volume of bread, and at the same dosage, Lipopan.F BG improved the volume of bread better than Lipopan.Xtra BG, moreover, the dosage of these two enzymes is not the bigger the better on the volume of bread, and there is an optimal amount of these two enzymes to be added. Using the separation and recombination technique, it was demonstrated that during the bread preparation process, these two enzymes acted more on the polar lipids in the flour, thus producing more polar lipid products and improving the bread quality.

A moderate amount of polar lipids increases the stability of the air chambers in the bread and increases the volume of the bread. Polar lipids can combine with gluten proteins and starch to form complexes, and can promote protein aggregation to form a better network structure in the dough, thus improving the texture of bread.

However, the above studies have not addressed the types of polar lipids that play a major role and their mechanism of action. In addition, lipase can hydrolyze lipids into monoglycerides under certain conditions, and monoglycerides complex with starch molecules during starch pasting to increase the pasting temperature, inhibit the swelling of starch granules, weaken the interaction between starch granules and gluten proteins, and also delay the regrowth of branched-chain starch.

Lipase hydrolyzes lipids to produce peroxides after a series of reactions, which can oxidize the sulfur-hydrogen groups in protein molecules, form intramolecular or intermolecular disulfide bonds, and induce protein molecules to polymerize and make protein molecules larger, thus increasing dough gluten and improving the texture of bread. Lipase can change the structure of bread flesh, make the distribution of stomata small and uniform, its reflection effect is better, improve the brightness, so as to achieve the effect of whitening.

The effect of lipase on the quality of steamed bread

At present, the application of lipase to the improvement of steamed bread quality has been reported less, and the research on the improvement mechanism has not yet been reported. Zhang Lei et al. studied the effects of Novozymes lipase from Denmark, DSM lipase from Holland and Sunson lipase from China on the quality of steamed buns, which showed that the right amount of the three enzymes could improve the gluten strength, prolong the stabilizing time, reduce the degree of weakening, increase the elongation and tensile resistance of dough, and improve the rheological properties of dough. The specific volume, color, structure and elasticity of steamed buns are improved to some extent. Moreover, the amount of lipase added is not the bigger the better, and the over-addition will have a negative effect on the steamed buns instead. And it is speculated that the lipase has an improvement effect on the volume and internal structure of steamed bread because the lipase enzyme dissolves the oil and fat components in the dough to generate natural monoglycerides and other emulsified components; the whiteness of steamed bread is improved because under the action of lipase, the original lutein and lutein dissolved in the fat are released, and in contact with the air, the coloring pigment is oxidized and discoloration.

Du Yang et al. studied the effect of lipase (enzyme activity 4000 U/g) on the appearance quality of steamed bread. It was found that the lipase used was sensitive to pH and temperature conditions, and its higher activity was conducive to improving the shape and color of steamed buns under suitable conditions, and the optimal process conditions for lipase whitening steamed buns were optimized.

Li Shouhong et al. studied the application of several single enzyme preparations in the whitening of steamed bread and the effect of compound use and the application of the new lipase Lipopan.Prime in the whitening of steamed bread and the improvement of tissue. It was found that Lipopan.Prime was able to provide good whiteness, volume and organization, and also had a positive effect on dough stability. It was also pointed out that although the whitening effect of traditional lipase is good, it will destroy the organization of buns. The hydrolysis of lipase determines its effect on the quality of steamed bread.

And Fang Xiaobo found that the effect of lipase on the specific volume of steamed bread is not significant, the effect of lipase depends on the endogenous lipids in flour, and the addition of lipase will improve the activity of these endogenous lipids.

In summary, it can be seen that the quality improvement effect of different lipases on steamed buns made of the same kind of flour is not the same, and the quality improvement effect of the same lipase on steamed buns made of different flours is also not the same. It is speculated that the reason may be the different lipid contents in different flours, as well as the different types and proportions of polar and nonpolar lipids in lipids, which led to the different substrates of lipase action, thus producing different types and proportions of hydrolysis products, and thus having different effects on the quality of steamed bread.