Protease is another notable enzyme. Cow milk contains a number of different whey proteins such as lactoglobulin and lactalbumin. The denaturing of these whey proteins, using proteases as catalysts, results in a creamier yogurt product. The denaturing of whey proteins is also essential for cheese production. In addition, proteases reduce allergic properties of cow milk products for infants, which produce healthier milk for them.
Lactease is a glycoside hydrolase enzyme that decomposes lactose into its constituent sugars of galactose and glucose. Lactose intolerant individuals can result from insufficient production of lactase enzyme in the small intestine. Feeding lactose-containing milk to lactose-intolerant individuals can result in discomforts such as: cramps, gas, dehydration, diarrhoea in the digestive tract upon ingestion of milk products, or maybe even death. Lactase provides relief for lactose and tolerant individuals because it can be used commercially to prepare lactose-free products, particularly milk by the process of hydrolysis of the lactase into glucose and galactose. In addition, lactase enzymes can be used in preparation of ice cream to make a creamier, sweeter-tasting product and improving digestibility. Finally, this reduces sandiness due to crystallization of lactose in concentrated preparations. Also, cheese manufactured from hydrolyzed milk ripens more quickly than the cheese manufactured from normal milk.
Another problem presented by lactose is its low solubility. This prevents the use of concentrated whey syrups in many food processes as they have an unpleasant sandy texture and are readily prone to microbiological spoilage. Adding to this problem, the disposal of such waste whey is expensive due to its high biological oxygen demand. These problems may be overcome by hydrolysis of the lactose in whey; the product being about four times as sweet, much more soluble and capable of forming concentrated, microbiologically secure, syrups. Technologically, lactose crystallizes easily which sets limits to certain processes in the dairy industry, and the use of lactase to overcome this problem has not reached its fullest potential because of the associated high costs. Moreover, the main problem associated with discharging large quantities of cheese whey is that it pollutes the environment. But, the discharged whey could be exploited as an alternate cheap source of lactose for the production of lactic acid by fermentation.
In the production of cheese, hydrogen peroxide is a potent oxidizer and toxic to cells. Catalase enzymes are used are used instead of pasteurization, when making certain cheeses such as Swiss, in order to preserve natural milk enzymes that are beneficial to the end product and flavour development of the cheese. Due to pasteurization, these enzymes would be destroyed by the high heat. Therefore, Catalase enzymes are typically added to convert to the hydrogen peroxide to water and molecular oxygen which will enhance final production.
Finally, there are the lipases in the dairy industry. Lipase enzymes are primarily used to break down milk fats and give characteristic flavours to cheeses. The flavours come from the three fatty acids produced when milk fats are hydrolyzed. Hydrolysis of shorter chains of fatty acids is preferable as it results in desirable tastes of many cheeses unlike the hydrolysis of longer chains of fatty acids which could result in soapiness or no flavour at all.
It is notable to mention egg products. Many industrially produced cream products used dried egg powder instead of fresh eggs. The enzymes of lipase and glucose are implemented in order to preserve egg powder and maintain its colour. These enzymes are often produced with the assistance of genetically modified microorganisms. Genetically modified microorganisms result in better yields in simply systems. Several cheese making experiments have been carried out with recombinant chymosin and the general aspects of recombinant chymosin have been dealt with. Since most of the rennet (>90%) added to cheese milk is lost in the whey, immobilization would considerably extend its catalytic life. Several rennets have been immobilized, but their deficiency as milk coagulants has been questioned. So, there is a fairly general support for the view that immobilized enzymes cannot coagulate milk properly, owning to inaccessibility of the peptide bond of K-Casein, and that the apparent coagulating activity of immobilized rennets is due to leaching of the enzyme from the support. Different types of conventional cheeses have been successfully made by using recombinant rennet on an experimental scale. No major differences have been detected between cheeses made with recombinant chymosins or natural enzymes, regarding cheese yield, texture, smell, taste, and ripening.
Cheese ripening is a complex process mediated by biochemical and biophysical changes during which a bland curd is developed into a mature cheese with characteristic flavour, texture, and aroma. The desirable attributes are produced by the partial and gradual breakdown of carbohydrates, lipids, and proteins during ripening, mediated by several agents (i) residual coagulants, (ii) starter bacteria and their enzymes, (iii) nonstarter bacteria and their enzymes, (iv) indigenous milk enzymes, especially proteinases, and (v) secondary inocula with their enzymes. Proteolysis occurs in all the cheese varieties and is a prerequisite for characteristic flavour development that can be regulated by proper use of the above agents. Cheese ripening is essentially an enzymatic process which can be accelerated by augmenting activity of the key enzymes. This has the advantage of initiating more specific action for flavour development compared to use of elevated temperatures that can result in accelerating undesirable nonspecific reactions, and consequently off flavour development. Enzymes may be added to develop specific flavours in cheeses, for example lipase addition for the development of Parmesan or Blue-type cheese flavours. The pathways leading to the formation of flavour compounds are largely unknown, and therefore the use of exogenous enzymes to accelerate ripening is mostly an empirical process.
Moreover, there are Proteolytic enzymes of lactic acid and bacteria in fermented milk products. This system is composed of proteinases which initially cleaves the milk protein to peptides; peptidases which cleave the peoptides to small peptides and amino acids; and transport system responsible for cellular uptake of small peptides and amino acids. Lactic acid bacteria have a complex proteolytic system capable of converting milk casein to the free amino acids and peptides necessary for their growth. These proteinases include extracellular proteinases, endopeptidases, aminopeptidases, tripeptidases, and proline-specific peptidases, which are all serine proteases. Aminopeptidases are important for the development of flavour in fermented milk products, since they are capable of releasing single amino acid residues from oligopeptides formed by extracellular proteinase activity.
Nevertheless, the other minor enzymes having limited applications in dairy processing include: glucose oxidase, catalase, superoxide dismutase, sulphydryl oxidase, lactoperoxidase, and lysozymes. Glucose oxidase and catalase are often used together in selected foods for preservation. Superoxide dismutase is an antioxidant for foods and generates H2O2, but is more effective when catalase is present. Thermally induced generation of volatile sulphydryl groups is thought to be responsible for the cooked off-flavour in ultra high temperature processed milk. Use of sulphydryl oxidase under aseptic conditions can eliminate this defect. The natural inhibitory mechanism in raw milk is due to the presence of low levels of lactoperoxidase, which can be activated by the external addition of traces of H2O2 and thiocyanate.
The societal impacts of some dairy enzymes are that chymosin, a high quality enzyme, is available at an attractive price. This helps assure available of extra cheeses at a reasonable cost. Due to the lipases, there is a wide variety of flavourful, high-quality cheeses.
To sum up, I think that it is amazing that there is a wide variety of alternatives of dairy products as a result of these enzymes that aid the dairy processes. The lactase enzymes can now help individuals enjoy the nutritional benefits and sensory pleasure of dairy products without gastrointestinal side effects by selecting lactose-free or lactose-low dairy products or by providing commercially available lactase to dairy products in the home. It is interesting how these enzymes sustain processes that enable higher yields, more enzyme production; and higher activity, more efficient, affective, dynamic enzymes.
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