Enzymes juice clarification

Juice solids have a critical effect not only on wine quality (discussed under juice clarification) but also on yeast activity. A juice that is too clean, from excessive pectic enzyme treatment, filtration, or centrifuging, may have difficulty completing fermentation. Groat and Ough (24) and others have reported that juice solids levels below 0.1 to 0.5 percent resulted in slower fermentations. Levels of 0.5-2.5 percent solids are used commonly in the North Coast. 

Clarification apple juice Enzymic juice extraction... 

Such applications appear to be more attractive for the use of bioreactors than traditional uses of endopeptidases for chillproofing beer, juice clarification, and curd formation in cheesemaking which currently use well established soluble enzyme processes. In the case of curd formation, hydrolysis of micellar k-casein by immobilized chymosin is questionable (56). 

The enzymes used for juice clarification are almost exclusively pec-tolytic. The reasons for the clarification effect are as follows. Pectin stabilizes the suspended solids in the juice. Through addition of the enzyme, the pectin is converted to a dissolved form and broken down. This is associated with a significant decrease in viscosity. In addition, pectins that have been made soluble act as protective colloids for many of the suspended particles. As soon as the protective effect of pectin is lost, these suspended particles coagulate and are precipitated. A significant decrease in viscosity is accompanied by a significant increase in filtration performance. 

Okada et at 189) reported an unknown enzyme from Aspergillus niger which was not a polygalacturonase nor a pectinesterase but which was a potent clarifier of citrus juices. This factor had no effect by itself, but it strongly accelerated juice clarification when added with polygalacturonase. In subsequent papers 190, 191) the enzyme was reported purified and found to be a hemicellulase. 

Amino acid production by fermentation started around 1960 in Japan. Initially glutamic acid was the main product. It was sold as sodium salt, monosodium glutamate (MSG), a flavor enhancer on oriental cuisine. Other amino acids soon followed. They are used in food and feed to increase the efficiency of low protein substrates. Microbiologically produced enzymes were introduced around 1970. They are used in grain processing, sugar production, fruit juice clarification, and as detergent additives (Table 9.1). 

Clarifying agents or flocculants are used to eliminate turbidity or suspend particles from liquids, e.g., chill haze in beer, precipitates in fruit juices and wines, and haze in oils. Often, they provide a nucleation site for suspended fines. Examples of clarifying agents are lime in sugar juice clarification, pectic enzymes to break down pectins in fruit juices, and gelatin for clarification of fruit juices. 

The addition of pectic and cellulolytic enzymes to aid juice clarification and increase yield has been a relatively common industrial practice for several years (1-3). The enzymes are used to free more juice by cell lysis and to increase filtration efficiency by viscosity reduction. 

In recent years, developing technology has led to the use of ultrafiltration and microfiltration membranes for juice clarification (1,4-13). The use of membranes has several advantages. Lower labor costs may be possible due to automation possibilities of membrane filtration (8). Filter aids such as diatomaceous earth (DE) aren t needed (9) so that product that would have been discarded with DE is saved, and DE acquisition and disposal costs are eliminated. Enzymes may be rejected by ultrafiltration membranes (4,12) causing the ultrafiltration equipment to act as an enzyme reactor (12), although some odor-active volatiles may be retained, resulting in some loss or change in flavor (8). 

Fruit juice clarification by pectinases and cellulases is another interesting application. In the conventional process after the enzymatic reaction in the pulp treatment step takes place, filtration over diatomaceous earth follows. This filtration-type process produces a lot of solid waste, and results in costly enzyme loss. MBR are appropriate for such application either for enzyme recovery and recycle or in the form of a more compact CMR type system, with the biocatalyst immobilized on the membrane itself [4.58]. 

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. 

CLEAs are made by the traditional protein methods of precipitation (e.g., solvents, salting out, etc.), but not full purification is required.The main features of CLEAs are the combination of easy procedures, low cost of protein processing, and robustness of the biocatalyst, which is required for the development of a biocatalyzed industrial process. This strategy has been demonstrated useful for multimeric enzymes. An interesting approach is to develop an enzymatic cascade based on many steps, i.e.,multienzymatic biotransformation process in just single CLEAs, or in noncascade type, which are named as combi-CLEAs. The vast potential of CLEAs at industrial level allows to explore this technolc for many appHcations in the food industries such as vinification, or citric juice clarification, or for medical purposes Hke scar debriding or cystic fibrosis appHcations. ... 

Enzymes are used also in fruit juice manufacturing. Addition of pectinase, xylanase, and ceUulase improve the liberation of the juice from the pulp. Pectinases and amylases are used in juice clarification. Similarly enzymes are widely used in wine production to obtain a better extraction of the necessary components, and thus improving the yield. Enzymes hydrolyze the high molecular weight substances like pectin. 

The covalent coupling of polygalacturonase, a pectinolytic enzyme of practical interest for fruit juice clarification, has been investigated using a number of matrices and detailed studies have been made of the efficiency of the coupling reactions and the characteristics of the resulting preparations. ... 

Pectic enzymes (usually representing a mixture of various enzymes) are manufactured and used on a large scale , the major applications being in fruit juice clarification, as an aid in wine manufacture, and in other instances where a partial or complete destruction of the naturally occurring pectic substances is desirable. 

Other applications of ultrafiltration are scattered. Not surprisingly there is a growing market in microelectronics, where smaller and smaller integrated circuits require purer and purer water. There is also a market in pyrogen removal for pharmaceuticals. Ultrafiltration is used to sterilize beer without heating and hence to produce draft beer in cans. Enzyme recovery, gelatin concentration, and juice clarification are possible, but their success depends on specific situations. 

Use of ultrafiltration (UF) membranes is becoming increasingly popular for clarification of apple juice. AH particulate matter and cloud is removed, but enzymes pass through the membrane as part of the clarified juice. Thus pasteurization before UF treatment to inactivate enzymes prevents haze formation from enzymatic activity. Retention of flavor volatiles is lower than that using a rack-and-frame press, but higher than that using rotary vacuum precoat-filtration (21). 

Pectin degradation requires fee combined action of various enzymatic activities. However, evaluation of fee contribution of individual pectinases in Suit juice extraction and clarification is rather complicated. Most commercial pectinolytic enzyme preparations are produced by fermentation wife filamentous fungi, mostly strains belonging to fee genus Aspergillus,. plication studies with mixtures of isolat enzymes obtained by fermentation or by means of fractionation of commercial enzyme preparations can be used to assess the importance of fee various individual enzymes. Subsequently, molecular biology and fermentation technology can be used to enhance specific desirable enzymatic activities. 

Rhamnogalacturonase may be useful in the prevention of haze formation in apple Juice concentrates. In combination with other enzymes it mi t improve liquefaction, resulting in increase juice yield and clarification. 

---