Juice enzymes

Whitaker JR (1984) Pectic substances, pectic enzymes and haze formation in fruit juices. Enzyme Microb Technol 6 341-349... 

Clarification apple juice Enzymic juice extraction... 

Ingallinera, B., Barbagallo, R.N., Spagna, G., Pahneri, R., and Todaro, A. 2005. Effects of thermal treatments on pectinesterase activity determined in blood orange juices. Enzyme Microb. Technol. 

Naranginase Debittering of juice Enzyme immobilized in PVA-cryogel [23]... 

Enzymes may be described a organic catalysts of biological origin. The majority are obtained from the interior of cells, but some are obtained from natural secretions such as the digestive juices and milk. For a full discussion of the nature of enzymes and the mechanism of their reactions the student should consult a work such as Chemistry and Methods of Enzymes, by J. B. Sumner and G. F. Somers (Academic Press, New York), or Enzymes, by M. Dixon and E. C. Webb[(Longman Group Ltd.). The following points should however be noted ... 

The so-called "trypsin," obtainable from pancreatic juice and from fresh extracts of the pancreas, is not a simple enzyme but a mixture of trypsin proper (which hydrolyses proteins to proteoses and peptones) and a series of enzymes which hydrolyse these breakdown products to their constituent amino-acids. The term trypsin," when used below, refers to this mixture. 

Enzyme degradation of leaf protein may occur during emshing and separation from the fiber. The amino acids produced by this enzyme action are soluble in the juice and may be lost unless all of the juice is recovered. 

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). 

Pectic enzymes are inactivated by pasteurization. Citms juices require higher temperatures for enzyme deactivation than for pasteurization. Heat treatment at 85—94°C for 30 s inactivates pectic enzymes (9) and is more than adequate for pasteurization. 

Pectin is a long chain of pectic acid and pectinic acid molecules. Because these acids are sugars, pectin is categorized as a polysaccharide. It is prepared from citrus peels and the remains of apples after they are squeezed for juice. In the plant, pectin is the material that joins the plant cells together. When fungus enzymes break down the pectin in fruit, the fruit gets soft and mushy. 

The body maintains an antioxidant network consisting of vitamins A, C, and E, antioxidant enzymes, and a group of related compounds called coenzyme Q, for which the general formula is shown below. The n represents the number of times that a particular group is repeated it can be 6, 8, or 10. Antioxidants are molecules that are easily oxidized, so they react readily with radicals before the radicals can react with other compounds in the body. Many common foods, such as green leafy vegetables, orange juice, and chocolate, contain antioxidants, as do coffee and tea. 

There are two main classes of proteolytic digestive enzymes (proteases), with different specificities for the amino acids forming the peptide bond to be hydrolyzed. Endopeptidases hydrolyze peptide bonds between specific amino acids throughout the molecule. They are the first enzymes to act, yielding a larger number of smaller fragments, eg, pepsin in the gastric juice and trypsin, chymotrypsin, and elastase secreted into the small intestine by the pancreas. Exopeptidases catalyze the hydrolysis of peptide bonds, one at a time, fi"om the ends of polypeptides. Carboxypeptidases, secreted in the pancreatic juice, release amino acids from rhe free carboxyl terminal, and aminopeptidases, secreted by the intestinal mucosal cells, release amino acids from the amino terminal. Dipeptides, which are not substrates for exopeptidases, are hydrolyzed in the brush border of intestinal mucosal cells by dipeptidases. 

A biochemical catalyst is called an enzyme. Enzymes are specialized proteins that catalyze specific biochemical reactions. Some enzymes are found in extracellular fluids such as saliva and gastric juices, but most are found inside cells. Each type of cell has a different array of enzymes that act together to determine what role the cell plays in the overall biochemistry of the organism. Enzymes are complicated molecules. Biochemists have determined the molecular structures of some enzymes, but the structures of many enzymes are not yet known. 

Amylase enters the blood largely via the lymphatics. An increase in hydrostatic pressure in the pancreatic ducts leads to a fairly prompt rise in the amylase concentration of the blood. Neither an increase in volume flow of pancreatic juice nor stimulation of pancreatic enzyme production will cause an increase in senm enzyme concentration. Elevation of intraductal pressure is the important determinant. Stimulation of flow in the face of obstruction can, however, augment the entry of amylase into the blood, as can disruption of acinar cells and ducts. A functional pancreas must be present for the serum amylase to rise. Serum amylase determination is indicated in acute pancreatitis in patients with acute abdominal pain where the clinical findings are not typical of other diseases such as appendicitis, cholecystitis, peptic ulcer, vascular disease or intestinal obstruction. In acute pancreatitis, the serum amylase starts to rise within a few hours simultaneously with the onset of symptoms and remains elevated for 2 to 3 days after which it returns to normal. The peak level is reached within 24 hours. Absence of increase in serum amylase in first 24 hours after the onset of symptoms is evidence against a diagnosis of acute pancreatitis (76). 

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