Applications Of Enzyme Use

Sukhkaran Dhaliwal

AP Biology

Thursday, October 9, 2008

Applications of Enzyme Use 1. Pickling, which is also known as brining or corning is the process of preserving food by anaerobic fermentation in brine, a solution of salt in water, to produce lactic acid, or marinating and storing it in an acid solution; the most common solution being vinegar (acetic acid). Pickling is unique and beneficial because the solution has a pH less than 4.6, which is adequate to kill most bacteria. The food is placed in an edible anti-microbial liquid that inhibits or kills bacteria and other micro-organisms that could spoil food. If the food contains sufficient moisture, a pickling brine may be produced simply by adding dry salt. Natural fermentation at room temperature by lactic acid bacteria produces the required acidity. Unlike canning, pickling doesn’t require that the food be completely sterile before it is sealed. Bacteria, yeasts, and moulds need a food source and water to grow. When food is dehydrated, most of the water is removed which prevents this growth process. Then it can be said that by reducing water activity sufficiently, it can be delay or prevent bacterial growth. Dehydrating also slows down the action of enzymes in food. Enzymes are naturally present in food, causing it to ripen and eventually spoil. Therefore, by slowing down enzyme action, food will last longer. When water is removed, enzyme action is not completely stopped. The removal causes the enzyme to become inactive until it is hydrated again. Canning foods essentially means boiling them then putting it in can (while still boiling or after it has finished). A can be any sealable container. When you boil the food, you are killing the bacteria and causing the enzymes to become inactive. The heating and later cooling forms a vacuum seal, which prevents other microorganisms from contaminating the food once within the can again. The can in which the food is in is sterile and has no bacteria because of it boiled. Once the can is opened, the vacuum seal is broken, allowing bacteria to attack the food. This is why some products give instructions to refrigerate the contents after opening. The principal of freezing food for preservation is based largely on the fact that reducing the temperate of the food lessens the activity of the enzymes to a minimum. The purpose of freezing the food is so the enzymes will not be able to live, which is true in most cases, but some of them may still live, but have almost no activity. The effect is negligible and will therefore cause food to last longer. This method of preservation is still one the most used by people.

2. Making yogurt has many steps involved, but before the milk is inoculated with the bacteria, the milk is cooled to about 40oC after pasteurization and homogenization. During pasteurization, the milk is heated to about 85oC, and then cooled for inoculation. To be named a yogurt, it must be made with the bacterial species Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus. The optimum temperature for these bacterial cultures is approximately 40oC. When the bacteria are added to the milk, it is already at its 1|P a g e

Sukhkaran Dhaliwal

AP Biology

Thursday, October 9, 2008

optimum temperature so yogurt production can occur much faster. During this time, the bacterium metabolizes certain compounds in the milk producing the characteristic yogurt flavor. An important byproduct of this process is lactic acid. The longer the inoculation, the mort tart the yogurt will be due to more lactic acid being created. 3. Rennin is also known as an enzyme called chymosin. In the case of chymosin, the reaction involves the breakdown of casein in milk resulting in clot formation in the presence of calcium ions. This is the basis for the production of many varieties of cheeses. The chief milk protein, casein, is coagulated by the enzyme action of rennet. Coagulation when used in the context of cheese production means separating the whey (liquid) from the curds (solid). The specific linkage between the hydrophobic and hydrophilic group of casein inside would milk would between broken if chymosin causes cleavage of the peptide bond between phenylalanine and methionine in the kappa-casein. The hydrophobic group would unite together and would form a 3D network to trap the aqueous phase of the milk. Due to this, rennin is added to bring about the extensive precipitation and curd formation in the cheese. The temperature of the milk is kept at 35oC because this is the temperature where the ideal amount of whey is separated from the curd. If the temperature is higher, it forces more whey out from the curd. This makes sense because rennin is extracted from the stomach of the calf and the body temperature of a calf is about 37oC. The optimum pH of the enzyme is approximately 3.5. 4. Starch can be converted to glucose syrups by hydrolysis, and the syrups find many applications as sweeteners in foods, such as candy, biscuits, jams and jellies, and pharmaceuticals like cough syrups, tonics, and vitamin preparations. Hydrolysis can be accomplished without enzymes, but this method can generate distasteful flavours and unsightly colours. Enzymatic hydrolysis offers a cleaner and more efficient hydrolysis. In a common process, α-amylase, produced by the bacterium Bacillus licheniformis, hydrolyzes starch to maltose. Then the enzyme glucoamylase, produced by moulds such as Aspergillus and Rhizopus, is added to hydrolyze maltose into individual glucose molecules amylase amylose and amylopectin

glucoamylase (maltase) maltose

B. licheiforms

α- glucose Aspergillis or Rhizopus species

5. Lactose intolerance is the inability to digest and absorb significant amounts of lactose, which is a major sugar that is found in milk. Lactose is made up of two simple sugars called glucose and galactose (both with the chemical formula C6H12O6), which are isomers of each other. After it is breaks down into those two components, it is then absorbed into the bloodstream. Those who cannot break down lactose into its simpler forms are said to be lactose intolerant. For the lactose to be absorbed in the bloodstream, it must be broken down into the glucose and galactose in the small intestine. The enzyme that splits lactose into glucose and galactose is called lactase and is located on the surface of the cells lining the small intestine. Lactose intolerance is caused by reduced or absent activity of lactase that prevents the splitting of lactose. Some of the symptoms of lactose intolerance include nausea, cramps, bloating, gas, 2|P a g e

Sukhkaran Dhaliwal

AP Biology

Thursday, October 9, 2008

and diarrhea. For those react to very small amounts of lactose or have trouble limiting their intake of foods that contain it, the lactase enzyme is available without a prescription to help people digest foods that contain lactose. The tablets can be taken with the first bite of dairy food. Lactase enzyme is also available as a liquid. Adding a few drops of the enzyme makes lactose more digestible for people with lactose intolerance. Lactose-reduced milk and other products are available at most grocery stores. The milk contains all of the nutrients found in regular milk and remains fresh for about the same length of time or longer it is superpasteurized. 6. Dirt commonly found on clothing includes proteins, starch, and lipids. Although it is possible to remove these stains with soaps and detergents, enzymes allow stains to be removed at lower temperatures and will less mechanical agitation in a washing machine. Enzymes are also more effective than nonbiological cleaning agents at removing stains such as blood, grass, milk, and perspiration. The cleaning industry commonly adds proteases and amylases to detergents to help remove protein and carbohydrates stains from clothing and other fabrics. The enzyme protease breaks down protein stains and lipase breaks down fats and oils (lipids). The breakdown of protein and fat molecules is called hydrolysis, which simply means reaction with water. The enzyme catalyzes these hydrolysis reactions, therefore help with the removal of stains. Biological detergents and washing powders use lipases and proteases to break down fat and protein molecules from food stains, which have remained on clothing. The fatty acids, glycerol, and amino acids are removed in the water during the washing process. Also, cellulases are use for color brightening and softening of cotton garments. Enzymes are also used in textiles for the stone washing of denim (in combination with pumice stones), biopolishing and softening of cotton, bleaching, cleanup, and removal of starch from woven materials.

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