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فى التصنيع الغذانزيماتت ا تطبيقا ئيApplications of Enzymes in Food Industry Prof. Dr. Mohamed Fawz y Ramadan Hassanien Zagazig University, Egypt

تطبيقات الانزيمات فى التصنيع الغذائى

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Page 1: تطبيقات الانزيمات فى التصنيع الغذائى

ئيتطبيقات االنزيمات فى التصنيع الغذاApplications of Enzymes in Food

Industry

Prof. Dr. Mohamed Fawzy Ramadan HassanienZagazig University, Egypt

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-Enzyme-catalyzed reactions in food processing have been used sinceancient times.

-The enzymes are either an integral part of the food or are obtainedfrom microorganisms.

-Addition of enriched or purified enzyme preparations of animal, plantor, especially, microbial origin is a recent practice.

-Most of these enzymes come from microorganisms, which have beengenetically modified in view of their economic production.

-Using additives provide a number of advantages in food processing:-high reaction rate under mild reaction conditions (temperature, pH), and-fast and continuous, readily controlled reaction process with generallymodest operational costs and investment.

-Examples for the application of microbial enzymes in food processingare given in the following table.

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Examples for the use of microbial enzymes in food processing

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1-Technical Enzyme Preparations

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1-Technical Enzyme PreparationsA-Production

-The production of enzymes for technical purposes isdirected to removing the interfering activities whichwould be detrimental to processing and to staying withineconomically acceptable costs.

-Fractionation methods commonly used include:A-Selective enzyme precipitation by changing the ionicstrength and/or pH,B-Adsorption on inorganic gels such as calcium phosphate gel,chromatography on gel columns andC-Ultrafiltration through membranes.

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1-Technical Enzyme PreparationsA-Production

-Ion-exchange chromatography, affinity chromatography andpreparative electrophoresis are relatively expensive techniquesand are seldom used.

-A few temperature-stable enzymes are heat treated to remove theother contaminating and undesired enzyme activities.

-Commercial enzyme preparations are available with definedcatalytic activity.

-The activity is usually adusted by the addition of suitable inertfillers such as salts or carbohydrates.

-The amount of active enzyme is relatively low, e.g.,-proteinase preparations contain 5–10% proteinase,-amylase preparations used for treamtent of flour contain only0.1% pure fungal α-amylase.

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1-Technical Enzyme PreparationsB-Immobilized Enzymes

-Enzymes in solution are usually used only once.

-The repeated use of enzymes fixed to a carrier is more economical.

-The use of enzymes in a continuous process, for example, immobilizedenzymes used in the form of a stationary phase which fills a reactioncolumn where the reaction can be controlled simply by adjustment ofthe flow rate, is the most advanced technique.

-Immobilized enzymes are produced by various methods.

Forms of immobilized enzymes

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B-Immobilized Enzymes

Bound Enzymes

-An enzyme can be bound to a carrier by-covalent chemical linkages,-physical forces such as adsorption,-charge attraction,-H-bond formation and/or-hydrophobic interactions.

-The covalent attachment to a carrier, in this case anactivated matrix, is usually achieved by methodsemployed in peptide and protein chemistry.

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B-Immobilized Enzymes

Bound Enzymes

-First, the matrix is activated.

-In the next step, the enzyme is coupledunder mild conditions to the reactivesite on the matrix, usually by reactionwith a free amino group.

-This is illustrated by using cellulose as amatrix (Figure).

-Another possibility is a process of co-polymerization with suitable monomers.Generally, covalent attachment of theenzyme prevents leaching or “bleeding”.

Enzyme immobilization by covalent binding to a

cellulose matrix

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B-Immobilized Enzymes

Enzyme Entrapment

-An enzyme can be entrapped or enclosed in the cavitiesof a polymer network by polymerization of a monomersuch as acrylamide or N,N-methylene-bis-acrylamide inthe presence of enzyme, and still remain accessible tosubstrate through the network of pores.

-Suitable processes can bring about enzymeencapsulation in a semi-permeable membrane (micro-encapsulation) or confinement in hollow fiber bundles.

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B-Immobilized Enzymes

Cross-linked Enzymes

-Derivatization of enzymes using bi-functional reagent,e.g. glutaraldehyde, can result in cross-linking of theenzyme and, thus, formation of large, catalytically activeinsoluble complexes.

-Such enzyme preparations are relatively unstable forhandling and, therefore, are used mostly for analyticalwork.

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B-Immobilized EnzymesProperties

-The properties of an immobilized enzyme are often affected bythe matrix and the methods used for immobilization.

Kinetics-As a rule, higher substrate concentrations are required forsaturation of an entrapped enzyme than for a free, native enzyme.

-This is due to a decrease in the concentration gradient which takesplace in the pores of the polymer network. Also, there is anincrease in the “apparent” constant for an enzyme boundcovalently to a matrix carrying an electrostatic charge.

-This is also true when the substrate and the functional groups ofthe matrix carry the same charge. On the other hand, oppositecharges bring about an increase of substrate affinity for the matrix.

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B-Immobilized Enzymes

Properties

pH Optimum

-Negatively charged groups on a carrier matrix shift thepH optimum of the covalently bound enzyme to thealkaline region, whereas positive charges shift the pHoptimum towards lower pH values.

-The change in pH optimum of an immobilized enzymecan amount to one to two pH units in comparison to thatof a free, native enzyme.

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B-Immobilized Enzymes

Properties

Thermal Inactivation

-Unlike native enzymes, theimmobilized forms are oftenmore heat stable (examplefor β-D-glucosidase, Fig.).

-Heat stability and pHoptima changes induced byimmobilization are of greatinterest in the industrialutilization of enzymes.

Thermal stabilities of free and immobilized enzymes.

1 β-D- glucosidase, free, 2 β-D-glucosidase, immobilized

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2-Individual Enzymes

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2-Individual EnzymesA-Oxidoreductases

-Broader applications for the processing industry, besidesthe familiar use of glucose oxidase, are found primarilyfor catalase and lipoxygenase, among the many enzymesof this group.

-A number of oxidoreductases have been suggested orare in the experimental stage of utilization, particularlyfor aroma improvement.

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2-Individual EnzymesA-Oxidoreductases

1-Glucose Oxidase

-The enzyme produced by fungi such as Aspergillus nigerand Penicillium notatum catalyzes glucose oxidation byconsuming oxygen from the air.

-Hence, it is used for the removal of either glucose oroxygen.

-The H2O2 formed in the reaction is occasionally used asan oxidizing agent, but it is usually degraded by catalase.

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2-Individual EnzymesA-Oxidoreductases

Applications of glucose oxidase in food

-Removal of glucose during the production of egg powder using glucoseoxidase prevents the Maillard reaction responsible for dis-coloration ofthe product and deterioration of its whippability.

-Similar use of glucose oxidase for some meat and protein productswould enhance the golden-yellow color rather than the brown color ofpotato chips or French fries which is obtained in the presence of excessglucose.

-Removal of oxygen from a sealed package system results in suppressionof fat oxidation and oxidative degradation of natural pigments. Forexample, the color change of shrimp from pink to yellow is hindered bydipping them into a glucose oxidase/catalase solution.

-The shelf life of citrus fruit juices, beer and wine can be prolonged withsuch enzyme combinations since the oxidative reactions which lead toaroma deterioration are retarded.

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2-Individual EnzymesA-Oxidoreductases

2-Catalase

-The enzyme isolated from microorganisms is important as anauxiliary enzyme for the decomposition of H2O2 :

-Hydrogen peroxide is a by-product in the treatment of food withglucose oxidase.

-It is added to food in some specific canning procedures.

-An example is the pasteurization of milk with H2O2, which isimportant when the thermal process is shut down by technicalproblems.

-Milk, thus, stabilized is also suitable for cheese-making since thesensitive casein system is spared from heat damage. The excessH2O2 is then eliminated by catalase.

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2-Individual EnzymesA-Oxidoreductases

3-Lipoxygenase

-The enzyme is used in the bleaching of flour and theimprovement of the rheological properties of dough(Bakery products).

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2-Individual EnzymesA-Oxidoreductases

4-Aldehyde Dehydrogenase

-During soya processing, volatile degradation compounds (hexanal, etc.)with a “bean-like” aroma are formed because of the enzymatic oxidationof unsaturated fatty acids.

-These defects can be eliminated by the enzymatic oxidation of theresultant aldehydes to carboxylic acids.

-Since the flavor threshold values of these acids are high, the acidsgenerated do not interfere with the aroma improvement process.

-Of the various aldehyde dehydrogenases, the enzyme from beef livermitochondria has a particularly high affinity for n-hexanal. Hence itsutilization in the production of soya milk is recommended.

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2-Individual EnzymesB-Hydrolases

1-Peptidases

-The mixture of proteolytic enzymes used in thefood industry contains primarily endopeptidases.

-These enzymes are isolated from animal organs,higher plants or microorganisms, i.e. from theirfermentation media (Table).

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Peptidases (proteinases) utilized in food processing

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2-Individual EnzymesB-Hydrolases

1-Peptidases

-Examples of Peptidases utilization are as follows:

-Proteinases are added to wheat flour in the productionof some bakery products to modify rheological propertiesof dough and, thus, the firmness of the end-product.

-During such dough treatment, the firm or hard wheatgluten is partially hydrolyzed to a soft-type gluten.

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2-Individual EnzymesB-Hydrolases

1-Peptidases (Examples of their utilization)

-In the dairy industry the formation of casein curd is achieved withchymosin or rennin.

-Casein is also precipitated through the action of other proteinases by amechanism which involves secondary proteolytic activity resulting indiminished curd yields and lower curd strength.

-Rennin is essentially free of other undesirable proteinases and is,therefore, especially suitable for cheese-making.

-However, there is a shortage of rennin since it has to be isolated fromthe stomach of a calf. However, it is now possible to produce thisenzyme using genetically engineered microorganism.-Proteinases from Mucor miehei, M. pusillus and Endothia parasitica area suitable replacement for rennin.

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2-Individual EnzymesB-Hydrolases

1-Peptidases (Examples of their utilization)

-Plant proteinases and also those of microorganisms areutilized for ripening and tenderizing meat.

-The practical problem to be solved is how to achieveuniform distribution of the enzymes in muscle tissue!!.

-An optional method appears to be injection of theproteinase into the blood stream immediately beforeslaughter, or re-hydration of the freeze-dried meat inenzyme solutions.

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2-Individual EnzymesB-Hydrolases

1-Peptidases (Examples of their utilization)-Cold turbidity in beer is associated with protein sedimentation.

-This can be eliminated by hydrolysis of protein using plant proteinases.Utilization of papain was suggested by Wallerstein in 1911.

-Production of complete or partial protein hydrolysates by enzymatic methods isanother example of an industrial use of proteinases. This is used in theliquefaction of fish proteins to make products with goodflavors.

-One of the concerns in the enzymatic hydrolysis of proteins is to avoid therelease of bitter-tasting peptides and/or amino acids.

-Their occurrence in the majority of proteins treated (an exception is collagen)must be expected when the molecular weight of the peptide fragments fallsbelow 6000.

-Bitter-tasting peptides, e.g., those which are formed in the ripening of cheese,can be converted to a hydrolyzate which is no longer bitter by adding a mixtureof endo- and exo-peptidases from Latobacilli.

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2-Individual EnzymesB-Hydrolases

2-α- and β-Amylases

-Amylases are either produced by bacteria oryeasts or they belong to the components of maltpreparations.

-α-Amylases added to the wort in beer productionprocess accelerate starch degradation.

-These enzymes are also used in the bakingindustry.

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2-Individual EnzymesB-Hydrolases

2-α- and β-Amylases

-The high temperature-resistant bacterial amylases,particularly those of Bac.Licheniformis are of interestfor the hydrolysis of cornstarch (gelatinization at 105-110 ◦C).

-The hydrolysis rate of theseenzymes can be enhancedfurther by adding Ca2+ ions.

The activity of α-amylase as influenced by temperature

1 α-amylase from Bacillus subtilis, 2 from Bacillus licheniformis

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2-Individual EnzymesB-Hydrolases

3- Glucan-1,4-α-D-Glucosidase (Glucoamylase)

-Glucoamylase cleaves β-D-glucose units from the non-reducingend of an 1,4-α-D-glucan.

-The α-1,6-branching bond present in amylopectin is cleaved at arate about 30 times slower than the α-1,4-linkages found instraight chains.

-The enzyme preparation is produced from bacterial and fungalcultures.

-The removal of transglucosidase enzymes which catalyze, forexample, the transfer of glucose to maltose, thus lowering theyield of glucose in the starch saccharification process, is importantin the production of glucoamylase.

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2-Individual EnzymesB-Hydrolases

3- Glucoamylase

-The starch saccharificationprocess is illustrated in Figure.

-In a purely enzymatic process(left side of the figure), theswelling and gelatinization andliquefaction of starch can occur ina single step using heat-stablebacterial α-amylase.

-The action of amylases yieldsstarch syrup which is a mixture ofglucose, maltose and dextrins. Enzymatic starch degradation

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2-Individual EnzymesB-Hydrolases

4- Pullulanase (Isoamylase)

-Isoamylase is utilized in the brewingprocess and in starch hydrolysis.

-In combination with β-amylase, it ispossible to produce a starch syrup with ahigh maltose content.

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2-Individual EnzymesB-Hydrolases

5- Endo-1,3(4)-β-D-Glucanase

-In the brewing process, β-glucans frombarley increase wort viscosity and impedefiltration.

-Enzymatic endo-hydrolysis reduces viscosity.

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2-Individual EnzymesB-Hydrolases

6- α-D-Galactosidase

-This and the following enzymes attack the non-reducingends of di-, oligo- and polysaccharides with release ofthe terminal monosaccharide.

-The substrate specificity is revealed by the name of theenzyme, e. g., α-D-galactosidase:

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2-Individual EnzymesB-Hydrolases

6- α-D-Galactosidase

-In the production of sucrose from sugar beets, theenzymatic preparation from Mortiella vinacea hydrolyzesraffinose and, thus, improves the yield of granular sugarin the crystallization step.

-Raffinose in amounts >8% effectively preventscrystallization of sucrose.

-Gas production (flatulence) in the stomach or intestinesproduced by legumes originates from the sugarstachyose. When this tetrasaccharide is cleaved by α-D-galactosidase, gas production from this source could beeliminated.

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2-Individual EnzymesB-Hydrolases

7- β-D-Galactosidase (Lactase)

-Enzyme preparations from fungi (Aspergillus niger) orfrom yeast are used in the dairy industry to hydrolyzelactose.

-Immobilized enzymes are applied to produce milksuitable for people suffering from lactose mal-absorption.

-Milk treated in this way can also be used to makeproducts like skim milk concentrate or ice cream, thusavoiding interference by lactose due to its low solubility.

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2-Individual EnzymesB-Hydrolases

8- β-D-Fructofuranosidase (Invertase)

-Enzyme preparations isolated from specialyeast strains are used for saccharose (sucrose)inversion in the confectionery or candyindustry.

-Invert sugar is more soluble and, because ofthe presence of free fructose, is sweeter thansaccharose.

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2-Individual EnzymesB-Hydrolases

9- α-L-Rhamnosidase

-Some citrus fruit juices and purées (especiallythose of grapes) contain naringin with a verybitter taste.

-Treatment of naringin with combinedpreparations of α-L-rhamnosidase and β-D-glucosidase yields the non-bitter aglyconecompound naringenin.

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2-Individual EnzymesB-Hydrolases

10- Cellulases and Hemicellulases

-The baking quality of rye flour and the shelf life of rye breadcan be improved by partial hydrolysis of the rye pentosans.

-Technical pentosanase preparations are mixtures of β-glycosidases (1,3- and 1,4-β-D-xylanases).

-Solubilization of plant constituents by soaking in an enzymepreparation (maceration) is a mild process.

-Such preparations usually contain exo- and endo-cellulases,α- and β-mannosidases and pectolytic enzymes.

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2-Individual EnzymesB-Hydrolases

10- Cellulases and Hemicellulases

-Examples of the utilization are:-production of fruit and vegetable purées (mashed products),-disintegration of tea leaves, or-production of dehydrated mashed potatoes.

-Some of these enzymes are used to prevent mechanical damageto cell walls during mashing and, thus, to prevent excessiveleaching of gelatinized starch from the cells, which would make thepurée too sticky.

-Glycosidases (cellulases and amylases from Aspergillus niger) incombination with proteinases are recommended for removal ofshells from shrimp. The shells are loosened and then washed off ina stream of water.

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2-Individual EnzymesB-Hydrolases

11-Lysozyme-The cell walls of gram-positive bacteria are formed frompeptidoglycan (murein).

-Peptidoglycan consists of repeating units of the disaccharide N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)connected by β-1,4-glycosidic linkages, a tetrapeptide and apentaglycine peptide bridge. The NAG and NAM residues inpeptidoglycan alternate and form the linear polysaccharide chain.

-Lysozyme solubilizes peptidoglycan by cleaving the 1,4-β-linkagebetween NAG and NAM.

-Combination preparations containing both lysozyme and nisin arerecommended for the preservation of meat preparations, saladdressings and cheese preparations.

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2-Individual EnzymesB-Hydrolases

12- Thioglucosidase

-Proteins from seeds of the mustard family(Brassicaceae), such as rapeseed or brown or blackmustard, contain glucosinolates which can beenzymatically decomposed into pungent mustard oils(esters of isothiocyanic acid).

-The oils are usually isolated by steam distillation.

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2-Individual EnzymesB-Hydrolases

13- Pectolytic Enzymes-Pectinolytic enzymes play an important role in foodprocessing, increasing the yield of fruit and vegetablejuices and the yield of oil from olive fruits.

-Pectic acid which is liberated by pectin methylesterasesflocculates in the presence of Ca2+ ions. This reaction isresponsible for the undesired “cloud” flocculation incitrus juices.

-After thermal inactivation of the enzyme at about 90 ◦C,this reaction is not observable.

-However, such treatment brings about deterioration ofthe aroma of the juice.

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2-Individual EnzymesB-Hydrolases

13- Pectolytic Enzymes

-Investigations of the pectinesterase of orange peel haveshown that the enzyme activityis affected by competitiveinhibitors: oligogalacturonicacid and pectic acid.

-Thus, the increase in turbidityof citrus juice can be preventedby the addition of suchcompounds.

Pectin esterase (orange) activity as affected by inhibitors

1 Without inhibitor, 2 hepta- and octagalacturonic

acids, 3 pectic acid

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2-Individual EnzymesB-Hydrolases

13- Pectolytic Enzymes

-Pectinolytic enzymes are used for the clarification of fruit andvegetable juices.

-The mechanism of clarification is as follows:-The turbidity causing particles consists of carbohydrates andproteins (35%).-The prototropic groups of these proteins have a positive charge atthe pH of fruit juice (3.5).-Negatively charged pectin molecules form the outer shell of theparticle. Partial pectinolysis exposes the positive core.-Aggregation of the polycations and the polyanions then follows,resulting in flocculation.

-Clarification of juice by gelatin (at pH 3.5 gelatin is positivelycharged) and the inhibition of clarification by alginates which arepolyanions at pH 3.5 support this suggested model.

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2-Individual EnzymesB-Hydrolases

14- Lipases

-Lipase from microbial sources (e.g. Candida lipolytica) isutilized for enhancement of aromas in cheese-making.

-Limited hydrolysis of milk fat is also of interest in theproduction of chocolate milk. It enhances the “milkcharacter” of the flavor.

-Staling of bakery products is retarded by lipase, presumablythrough the release of mono- and di- acylglycerols.

-The defatting of bones, which has to be carried out undermild conditions in the production of gelatin, is facilitated byusing lipase-catalyzed hydrolysis.

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2-Individual EnzymesB-Hydrolases

15- Tannases

-Tannases hydrolyze polyphenolic compounds(tannins):

-For example, preparations from Aspergillusniger prevent the development of turbidityin cold tea extracts.

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2-Individual EnzymesB-Hydrolases

16- Glutaminase

-This enzyme catalyzes the hydrolysis of glutamine.

-It increases the concentration of glutamic acid, which substantiallycontributes to the taste of meat.

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2-Individual EnzymesC- Isomerases

-Of this group of enzymes, glucose isomerse, which isused in the production of starch syrup with a highcontent of fructose, is very important.

-The enzyme used industrially is of microbial origin.

-Since its activity for xylose isomerization is higher thanfor glucose, the enzyme is classified under the name“xylose isomerase” .

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2-Individual EnzymesD- Transferases

-Protein glutamine-γ-glutamyl transferase (trans-glutaminase,TGase) catalyzes the acyl transfer between the carboxyamidegroup of peptide-bound glutamine (acyl donor) and primaryamines (acyl acceptor, I in Formula), e. g., peptide-bound lysine (IIin Formula).-Free acid amides and amino acids also react. Proteins or peptidesare cross linked in this way. If amines are absent, TGase cancatalyze the deamination of glutamine residues in proteins withH2O as the acyl acceptor (III in Formula).

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2-Individual EnzymesD- Transferases

-TGases play an important role in the metabolism of animals andplants.

-For the production of protein gels, the TGase from theactinomycete Streptoverticillum mobaraense is of special interest.

-In contrast to the TGases from mammals, the activity of thisenzyme, which is released in large amounts by the microorganismsinto the nutrient medium, does not depend on Ca2+ .

-This enzyme consists of 331 amino acids (Mr: 37,842) of knownsequence.

-A cysteine residue is probably at the active center. The pHoptimum of TGase activity is between 5 and 8.

-This enzyme can also be used at low temperatures and is rapidlydenatured at 70 ◦C.

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2-Individual EnzymesD- Transferases

-Proteins are cross linked by the formation of (glutamyl)lysineisopeptide bonds. However, the biological availability of lysine isnot appreciably reduced.

-The viscoelastic properties of the resulting protein gels dependnot only on the type of proteins and the catalytic conditions (TGaseconcentration, pH, temperature, time), but also on thepretreatment of the protein, e. g., heat denaturation.

-Possible applications of TGase in the production of food areshown in the following Table.

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Possible applications of transglutaminase