Industrial enzymes fruit juice industry

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

Previous chapters in this volume have been concerned with chemical reaction engineering and refer to reactions typical of those commonplace in the chemical process industries. There is another class of reactions, often not thought of as being widely employed in industrial processes, but which are finding increasing application, particularly in the production of fine chemicals. These are biochemical reactions, which are characterised by their use of enzymes or whole cells (mainly micro-organisms) to carry out specific conversions. The exploitation of such reactions by man is by no means a recent development—the fermentation of fruit juices to make alcohol and its subsequent oxidation to vinegar are both examples of biochemical reactions which have been used since antiquity. 

Pectinex Ultra SP-L is a commercial enzyme preparation from Aspergillus acu-leatus that is used in the food industry for reducing viscosity in fruit juice processing. It contains different pectinolytic and cellulolytic enzymes [29]. In addition, the existence of fructosyltransferase activity in Pectinex Ultra SP-L has been reported by several authors [30-32]. In recent years, we have investigated the purification, characterization, and application of the fructosyltransferase from A. aadeatus contained in this commercial preparation [33]. 

Microcrystalline chitin has been used as a thickening/gelling agent in the binding, stabilizing, and texturing of food [58]. Chitin is widely used to immobilize enzymes and whole cells enzyme immobilization has applications in the food industry, such as clarification of fruit juices and... 

In order to produce clear juice the cloudy product is treated with pectolytic enzymes to degrade the pectic substances which are responsible for the cloud stability of the cloudy juice. The treatment time depends on the activity of the enzymes and the temperature respectively. Several years ago the industry had no enzymes which were able to work in very acid juice environments (e.g. lemon juice). However, in the meantime new types were developed which are capable of treating acid juices satisfactorily. Some fruit juices contain substances which cannot be removed with pectolytic enzymes and which require other specific enzymatic products to eliminate turbidity, e.g. starch in apple juice requires a suitable amylase. 

The system described is an example of the use of a biocatalyst for the flavor enrichment of beverages that could be employed in industry. Such a continuous process will be of great interest in oenology and in fruit juices industry. Because, the use of exogenous enzyme preparations makes it possible to overcome the problem of the insufficient aroma content of some wines and fruit juices while remaining its natural characteristics. 

The immobilization of a 13-glucosidase provides a biocatalyst of potential interest to produce release of volatiles in fruit juice and wine. The advantage of using immobilized enzymes over traditional batchwise treatment for industrial process is primarily due to a better control of the enzymatic process. The other advantages include the possibility of the repeated use of the biocatalyst and the feasibility of a continuous process. 

Enzymes could also be used to modify insoluble biopolymers and this is very important to the food industry. Examples include pectinase use in fruit juice and nectar production, food (e.g., fish, meat, and plant) protein hydrolyses, the production of yeast hydrolysates, the hydrolysis and recovery of proteins from by-product sludges, the recovery of meat scraps from bones... 

Enzymes are protein catalysts of high molecular weight, which are produced not only by plants and animals but also mainly by microorganisms as a result of fermentation processes. Enzymes fall into two categories (1) bulk industrial enzymes, which mainly include proteases for detergents, amylases for textile desizing and starch hydrolysis, pectin-ases for fruit-juice clarification, and proteases for the leather industry (Table 48.1) and (2) analytical enzymes. 

Chitin was used also to immobilize enzymes and whole cells. Enzyme immobilization was used for applications in food industries such as clarification of fruit juices and processing of milk with a- and p-amylases and invertase fixed on chitin [89]. Chitin is also used for the treatment of environmental pollutants [90,91], or in biosensors [92,93]. 

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