It is estimated that 25% to 80% of harvested fruits and vegetables are lost during transportation and storage due to its high perishability. Therefore, they need special care in both postharvest storage and processing. Processing of fruits and vegetables has improved with the production of juices, pulps, purees, jelly, dried fruit, sweets, and jams, which allows uninterrupted consumption, waste reduction, and increased consumption of processed products.
Enzymes are important throughout the life cycle of fruits and vegetables. Enzymes remain active even after harvest and may have undesirable effects on color, texture, taste, smell, and nutritional value. The use of enzymes aids in the processing of fruits and vegetables, acting mainly in the hydrolysis of polysaccharides and facilitating the extraction of intracellular compounds. As the content of these biomolecules differs in each plant in composition and quantity, different enzymes are required for each process. The enzymatic process has advantages compared to the use of chemicals, such as higher specificity, mild reaction conditions, and less waste production. Main enzymes used in fruit and vegetable processing include pectinesterase, pectinase, protopectinase, hemicellulase, α-amylase, glucoamylase, etc.
Pectinases
Pectins include protopectins, pectin acids, and pectic, and represent around 0.5% to 4.0% of the total weight of fresh fruits as well as constituents from 2% to 35% of the middle lamellae, which connects adjacent cells.The pectin can be degraded by pectin lytic enzymes, which may be from vegetable or microbial origin. These enzymes are obtained from fruits and even fermentation of by-products of juice extraction. The pectinesterase (polymethyl galacturonate esterase, PMGE, EC. 3.1.1.11) catalyzes the hydrolysis of methyl ester groups from pectin, releasing methanol and converting pectin in pectane. The addition of pectinase facilitates hydrolysis of carbohydrates that allows better squeezing of fruit, providing increased extraction yield and enhancing the concentration of acids, flavorings, and colorants. Consequently, pectinases play a vital role in the food processing industries, especially in the production of beverages, which are widely used for extraction of oils, syrups, and starches. These enzymes are used for reducing the texture of vegetables in order to facilitate processing. Frequently, combinations of pectinases, cellulases, and hemicellulases, known as macerating enzymes, are employed in juice production, in order to facilitate maceration, liquefaction, and clarification.
Cellulases
Cellulases promote the hydrolysis of cellulose, which is a polysaccharide composed of several glucose units. These enzymes are highly specific biocatalysts that act synergistically to release sugars, of which glucose has major industrial importance due to the possibility of its conversion into ethanol, sweeteners, phytohormones, and organic acids, among others. The main commercial preparations of cellulases are obtained from filamentous fungi. Cellulases are used in the beverage industry for the production of fruit juices and wine processing. They facilitate the extraction of juices and maceration for production of fruit nectars by breaking the cellulose chains that helps hold the liquid in the plant cells. In addition, it breaks unpleasant-tasting compounds, releasing flavoring substances and improving beverage aroma and flavor.
Xylanases (Hemicellulases)
The hemicellulose xylan is the most abundant biopolymer in the world, representing about 30% of the renewable and organic carbon. Hemicellulases (xylanases) are a group of enzymes that degrade hemicellulose polymers. These enzymes are produced by bacteria, fungi, algae, protozoa, nematodes, crustaceans, insects, and plants. Xylanases are used together with cellulases and pectinases for clarification and liquefaction in the fruit and juice industry.
α-Amylases
α-Amylase occurs in plants, mammalian tissues, and microorganisms. Fungi α-amylase is thermosensitive, and it is inactivated at temperatures higher than 70°C. α-Amylases account for about 30% of the enzymes in the world market and are applied in many industrial processes, such as starch saccharification, the textile industry, paper, brewing, baking, detergent, cakes, fruit juices, starch syrups, distilleries, preparation of drugs for stomach problems, and other pharmaceuticals.
The use of enzymes in the food industry has increased significantly, generating more added value to the final product and an increase in production while reducing costs. The enzyme-assisted extraction is also an ecofriendly extraction method for the production of a variety of bioactive molecules, saving processing time and energy, and potentially providing a more reproducible extraction process on the commercial scale which demonstrates its importance for the future markets.
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