Fruit juice drinks have become an increasingly important part of people's diet.
Since the 90s of the 20th century, China has introduced a number of fruit juice production lines from abroad, and the output and quality have been greatly improved, and the representative fruit juice drinks are almond milk, coconut water, mango juice, kiwi juice, fruit tea, etc.
In 2022, the output of apples will reach 47.57 million tons, citrus will reach 60 million tons, and kiwifruit will reach 38 million tons, and the juice industry has great potential.
There are many ways to classify fruit juice drinks, some according to the form of the drink, and some according to the content of the original fruit juice they contain.
Raw fruit juice: Juice obtained directly from fresh fruit by mechanical method. The nutritional value of raw fruit juice is high.
Fruit juice concentrate: The raw juice is evaporated or frozen to remove part of the natural water, and its concentration is increased by more than 2 times.
Fruit juice drinks in the form of pulp or fruit pieces: It is made from the pulp or pulp particles of natural fruits with fruit juice or other auxiliary materials.
Carbonated fruit drinks: Contains carbon dioxide, fruit juice, acid, flavor, coloring and preservatives, raw fruit juice content" 25%。
Non-carbonated fruit drinks: It does not contain carbon dioxide, and the other ingredients are the same as carbonated fruit juice drinks, and the content of raw fruit juice is 10%.
Mixed fruit drinks: A mixture of several fruit juices, such as orange juice mixed with mango juice, lemon juice or carrot juice.
Application of enzymes in the juice industry
Take apple juice, for example, which has been processed for more than 100 years. The production of apple juice first began in Switzerland, Europe.
In the second half of the 18th century, apple juice was also produced in Germany, France, Austria and the United States. Due to the limitations of the technical conditions at that time, the production equipment of the processing plant was poor, the product quality was low, and the shelf life was short.
In 1930, engineers in the United States and Germany first used pectinase to clarify kernel fruit juices. It was not until the early 70s of the 20th century that there were reports of pectinase treatment of apple pulp, thus opening up a new era of industrial-scale production of apple juice.
Today, the process of producing apple juice by the enzymatic pectinal method has developed into a mature process.
Pectin is a polymer polysaccharide compound ubiquitous in plants, located in the mesocolloidal layer of the cell wall of adjacent cells, and plays a role in uniting cells together.
Pectin is a macromolecule that is a network structure composed of various different sugar molecules cross-linked together.
There are 3 states of pectin present in plants
Protopectin
Methylated polygalacturonide chains bound to cellulose and hemicellulose, which only exist in the cell wall, are insoluble in water, and are hydrolyzed to form glue. In general, enzymes do not act on this part.
Pectin
Polygalacturonide chains methylated and neutralized with varying degrees of carboxyl groups are present in plant juices.
Pectic acid
Slightly soluble in water, it is a completely free polygalacturonoside chain of carboxyl groups, and insoluble precipitates are formed when exposed to calcium. This is a very important property of pectic acid, and foods such as jams, jellies and so on are produced using this property. However, in juice processing, this feature is of little use.
Pectinase is a general term, in fact, it has 3 types that catalyze 3 different reactions. Usually pectinase comes from molds.
Pectin esterase
Catalyzes the removal of methyl ester groups from pectin to generate polygalacturonide chains and methanol.
Polygalacturonidase
It is customary to hydrolyze the enzymes that can hydrolyze polygalacturonididic bonds collectively as polygalacturonidase, and its substrate is the product of pectinesterase, so these two enzymes are often used in combination in industry.
Pectin lyase
Pectin lyase does not require the help of pectin esterase and can act directly on methylated pectin.
According to the different processing objects and processing technology, in the juice processing, different pectinases or different pectinase ratios can be flexibly selected to meet the specific production needs.
Clarification of apple juice production process:
Apple pre-treatment
Including three aspects: sorting, washing and crushing of apples. Sorting involves picking out rotten fruits and apples that are not suitable for processing, and removing sand and stones, grass and other debris.
Juicing
That is, the broken apples are directly entered into the juice pressing system for solid-liquid separation without other treatment, which is a common method used in the apple juice processing industry.
Fruit pulp treatment
After the juicing process, the pulp is obtained, and the pulp needs to be juiced again to get the juice.
In this step, pectinase is added to increase the juice yield. After the above juice extraction process, the original pectin between apple cells has been partially hydrolyzed, the structure of the pulp is still maintained to a certain extent, after pectinase treatment, the degradation of fruit cells reaches complete liquefaction, and the flowing juice can be obtained without pressing, and the juice yield is as high as 90%, which greatly saves costs.