Food Enzymes

8/3/2019 Food Enzymes

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FOOD ENZYMES

Complex, globular protein catalysts,accelerate chemical reaction rates by

factors of 1012-1020 at temperature ofaround 370C and unchanged at the

end of reaction


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Food Enzyme

Most remarkable and highly specialized

proteins

show extraordinary catalytic power high degree of specificity for their substrates


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Death animals cells meats,

Senescence of plants cells fruits andvegetables

Disruption of cells in processing

enzyme activity uncontrolled towardscatabolism

Success of Food Scientist has in regulating enzymicactivity has marked effect on quality andquantity of foods available


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CLASSIFICATION OF ENZYMES

- Named after substrate, substance uponwhich enzymes act.

Substrate Enzyme

urea urease

maltose maltase

amylose amylase

lipid lipase


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- Common name (exception)

pepsin papain

trypsin bromelain

- Grouping according to the type of reaction

which they control (most useful)

Oxidases

Hydrolases


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Nomenclature of Enzymes

Classify each enzyme by a code of four

Numerals.

First numberallocates the enzyme to one ofthe six main groups:-

1) OxidoreductasesOxidationReduction reaction

2) TransferaseGroup transfer reaction

3) HydrolasesHydrolytic reaction


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4) Lysesinvolved in the addition of groups to orfrom a double bond

5) Isomerases- transfer groups within a molecule

to yield a new isomeric form

6) Ligasescombining of 2 molecules withsimultaneous splitting of energy

rich phosphate bonds (synthetases)form carbon to carbon, carbon to sulfur, carbon to oxygen, or carbon to nitrogen chemical

bonds via condensation type reactions coupled to ATP


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Second numberSub-group denotes thechemical nature of the bonds or grouping ofsubstrate attacked by enzymes

e.g Hydrolases that split groups of esters

3.1

3.2Include all glycosidases


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Third numberSub-sub-group explain the

reaction in greater detail. Bond specificity.

e.g Oxido-reductases which attack carbinol groups1.1.1 and which NAD/NADP as hydrogen acceptor

Fourth numberIn the sub-subgroups all

known enzymes are numbered in order.

e.g Acetyl-CoA-hydrolase (thiolesterhydrolase)

EC 3.1.2.1

EC 3.1.1.3 Pancreatic lipase


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HYDROLASES

Important

Catalyse hydrolytic cleavage of molecular

bonds. Divided according to types of bond attack.

3.1 Ester bond3.2 Glycosidic bonds

3.3 Peptide bonds


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LIPOLYTIC ENZYME

LipaseHydrolyze ester lingkages of emulsified

triacyglycerol at an oil/water interface.

Found in plants, animal, microorganisms

Triacylglycerol Diacylglycerol (1,2 or 2,3)

Fatty acid 2-Monoacylglycerol

Fatty acids produced can lead to desirable or

undesirable flavors.


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1. OXIDOREDUCTASES

Transfer of electron in oxidation and reductionprocess

o Phenoloxidases (Cu2+)o Ascorbic Acid Oxidase (Cu2+)

Browning reaction in juices

lemon/ grape fruit concentrates)


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ENYZMIC BROWNING IN FOODS

Browning reaction in foods

Maillard

Caramelization

Ascorbic Acid Oxidation

Phenolase browning-Oxidoreductases


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Ascorbic Acid Oxidase

L-ascordic acid

2,3-diketo-L-gulonic acidDecomposition

Product

(furfural)

PolymerizationBrown Pigments

Dehydroascorbic

Acid + H2O

O2


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EnzymeCatalyzed Oxidative Browning

Commercial significance especiallyin fruits and vegetables.

apple, banana, potatoes, celery etc.

EnzymePhenolase withCu2+

prostheticgroup widely distributed

Phenol Hydroxylase or Cresolaseactivity (hydroxylation)

Polyphenol oxidase (PPO) orCatecholase

(oxidation)


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Catalyzed faster


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Characteristic of Phenolases

o Active at pH range 5-7o Below pH 3.0, irreversibly inactivated

o Reagents capable of complexing withCu2+

will inhibit enzyme activity

Methods to inhibit enzymic browning

o Elimination of one or more essential

components:--O2, enzyme,Cu

2+ Substrate (vacumization,brine/syrup)


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o Heat treatments

o Sulfur dioxide / sulfites

o Addition of acidulentscitric, malic, phosphoric

Phenolaseinduced browning is a major

contributor to the desirable color of some

foodscider, tea, cocoa

Also contribute to colors of raisins, prunes,

dates

reducing agent

Inhibitor


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LIPOXYGENASE

o Widely distributed in legumes (soy bean, cerealsand fruits)

o Require Feo Substrate Fatty acid

o Oxygenate polyusaturated fatty acid containing

cis, cis1,4 Pentadiene double bond


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o Stereo specific

H H H HCH3-(CH2)4-C=C-CH2-C=C-(CH2)7-COOH+O2

Hydroperoxides can have detrimental effects on color,

flavor, texture and nutritive properties of foods.

Linoleic Acid

decomposition

9-Hydroperoxide 13-hydroperoxides

rancid


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Undersirable effects

Destruction ofChlorophyll,Carotenes

Development of Oxidative flavor, aromas

Oxidation of Essential Fatty Acids

Damage to Vitamins, Protein


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Desirable Functions

Bleaching of wheat, soybean flour

Formation of disulfide bond in gluten

Dough Improvement by changing rheological

properties of gluten


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QUIZ NO 3Read the passage below and identify at least 4

enzymes (allocate the group) that are responsiblefor each case

Sarah and friends were not happy with the foods served at the

Caf. The cut apples and carambola have turned slightly brownand the peanuts gave off flavour and tasted rancid. In addition,all the drinks were added milk, which are not what they ordered.Angrily, Sarah explained to the waiter that she cannot take milkas she suffers from lactose intolerance.

The friends then continue discussing the sad disturbing story thatwas in the newspaper the day before, which reported the deathof a family of four in a remote kampong near the western coast ofMalaysia. Upon investigation, it was discovered that the cause ofdeath due to hydrogen cyanide that originated from a wildcassava (ubi kayu) that the man brought home for the family.

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Food Enzymes