With the continuous improvement of people’s living standards, natural, high juice content of the beverage has become a new trend in the development of the industry.

Fruits are rich in cellulose and not easy to hydrolyze, and its crystalline rigid structure increases the difficulty of juice processing. Cellulose is easy to be hydrolyzed by specific cellulase, so the study of cellulase has become a hot spot in beverage production.

Cellulase from Aspergillus niger (hemicellulase) and cellobiase; cellulase from Aspergillus niger, Trichoderma reesei (Trichoderma reesei), Trichoderma viride (Trichoderma viride) and so on. Cellulase is allowed to be used in GB 2760-2014. As people’s expectation of food safety is getting higher and higher, cellulase has great advantages in food processing with high safety.

Structure of cellulase

Cellulase is a complex enzyme system composed of a variety of hydrolytic enzymes, mainly composed of glucose endonuclease, glucose exonuclease, β-glucosidase 3 kinds of enzymes (see Table 1). The degradation of cellulose molecules into glucose requires the joint action of the three enzymes.

Cellulase in the application of fruit juice drinks

2.1 Application in citrus juice production
Due to the sweet and sour taste of citrus, rich in vitamin C, folic acid and potassium, has an important role in human health. However, citrus vesicles are rich in cellulose and bitter glycosides, simple direct juicing technology can not meet the quality requirements of citrus juice, the use of cellulase hydrolysis of citrus vesicles in the cellulose can be obtained complete citrus vesicles, the production of pollution is far less than the traditional production process.

Baker study showed that the adhesion between citrus peel and pulp is related to pectin, cellulose and hemicellulose.

Ben-Shalom use cellulase to hydrolyze the citrus endocarp in the sac coat part of the citrus juice, citrus juice yield is high and maintain the original taste and quality of citrus.

2.2 Application in strawberry juice production
Strawberry is rich in many kinds of natural nutrients and has a sweet and sour taste, which is very popular among people. However, the structure of strawberry is soft, and the viscosity of strawberry pulp after crushing is too big and the pulp residue is not easy to be separated, resulting in a very low yield of strawberry juice.

Generally, pectinase is used to pre-treat the raw material, but the domestic pectinase is a single enzyme, which is mainly used for degumming and clarification of fruit juice, and cannot fully release a large amount of nutritive soluble substances in the pulp, which greatly affects the nutritional value of strawberry juice.

Compared with the traditional production process, the cellulase enzyme produced by Green Xylinum strain YV95os by Wan Riyu et al. increased the juice yield by 9.2%, shortened the pressing time by 15 min, and improved the production efficiency of strawberry juice.

In order to reduce the polymerization and crystallinity of cellulose in strawberry juice, increase the accessibility of cellulose, and improve the reactivity of cellulose, the juice can be pretreated by ultrasonication or esterification.

2.3 Application in the production of mango juice
Mango is rich in a variety of nutrients, and sweet and delicious is one of the world’s top five fruits, known as the king of tropical fruits. However, mango harvest period is short, high water content, fresh fruit is very easy to rot and deteriorate. Mango juice is the main product form of mango deep processing. Because mango is rich in edible fiber and pectin, resulting in pulp viscosity, juice yield is not high; cellulase and pectinase hydrolysis of cellulose and pectin in the pulp reduces the viscosity of the pulp and improves the juice yield.

Sreenath et al. studied the effect of cellulase and pectinase on reducing the viscosity of mango pulp, and found that the Danish Ultrazym100 has the best effect on reducing the viscosity of mango pulp, which can reduce the viscosity by 82%, and pectinase and cellulase can increase the juice yield by 8% to 10% when used simultaneously.

Li Changbao, etc. “Ivory” mango as raw materials, cellulase and pectinase pulp treatment, when the pectinase addition of 0.01%, cellulase addition of 0.007%, the highest juice yield of mango can reach 71.15%.

2.4 Application of pineapple juice production
Pineapple is juicy, sweet and sour, rich in a variety of nutrients loved by consumers. However, pineapple production is seasonal, the harvest period is more concentrated, the water content is high, the respiratory strength is large, and it is easy to rot and deteriorate during storage and transportation.

Pineapple juice processing is an important production method of pineapple deep processing. However, the existing pineapple juice processing can not get clarified pineapple juice. The main substances that cause turbidity in pineapple juice are cellulose and pectin. Chen Yu et al. studied the effect of pectinase and cellulase on pineapple juice clarification, untreated pineapple juice at 20 ℃ when the light transmittance of 40%, at 30 ℃ under the condition of using 8.84 U/100 mL pectinase, 42.13 U/100 mL cellulase treatment of pineapple juice for 40 min can be obtained with a light transmittance of 87% of the juice.

2.5 Application in the production of beef heart persimmon juice
Niushin persimmon fruit is rich in polysaccharides, cellulose, organic acids and minerals and essential amino acids, has a high food value and medicinal value.

But persimmon fruit is rich in cellulose and polysaccharides, pulp viscosity. Industrial juicing machinery extrusion pulp juice rate is low, poor product quality. The use of cellulase treatment of persimmon fruit pulp, can greatly reduce the cellulose content in the pulp, so that the pulp viscosity is reduced.

Wang Jun et al. used Shaanxi cow heart persimmon as raw material at 50 ℃ under the condition of 0.20% pectinase and 0.03% cellulase on the cow heart persimmon pulp treatment 5h juice rate of 74.9%.

Prospect

In food processing, the use of cellulase pretreatment of fruit raw materials to produce fruit juice drinks compared with the traditional fruit beverage processing not only reduces the loss of fruit nutrients, improves the taste, is more conducive to digestion and absorption, saves the processing time and cost, and reduces environmental pollution, etc. At the same time, the cellulase pretreatment of fruit pulp with 0.03% cellulase and 0.20% pectinase at 50 ℃ yielded 74.9% juice.

At the same time, the use of cellulase is not only used in the deep processing of fruits, but also used in fermentation, brewing and new energy development research. And the use of cellulase to recycle cellulose waste into treasure is one of the future development directions to open up the source of raw materials for the food industry.

At present, cellulase has been widely used in various industries, including food. The biggest bottleneck in the production of cellulase is the optimization of enzyme-producing conditions of strains and the low enzyme activity and poor acid and alkali resistance in industrial production.

The use of mutation breeding combined with genetic engineering and other means is expected to gradually solve such problems. And explore a variety of microbial synergism to degrade cellulose, targeted selection of enzyme species and compound enzyme to improve product quality is also a trend in the development of cellulose degrading bacterial agents.