enzymatic browning

ENZYMATIC BROWNING

Prepared by:

Annabelle D. Anonuevo

BSFT-III

BROWNING

-A process of food to become brown

Browning Reactions in Foods:

-Some foods are naturally brown-Some foods are expected to be brown-Some foods are expected not to be brown

BROWNING CAN BE BENEFICIAL:

-Cooking meat-Bread crust-Coffee-Chocolate-Tea- Color and flavour or dried fruit ( figs and raisins)

CAN BE DETRIMENTAL:

-Fresh fruits and vegetables

-Seafood such as shrimp

- Food quality and nutritional content

3 MAJOR TYPES OF BROWNING IN FOODS:

1.Enzymatic Browning

2.Caramelization

3.Maillard Reaction (Non-Enzymatic Browning)

ENZYMATIC BROWNINGIs responsible for the discoloration of many fruits and vegetables

CARAMELIZATIONIt occurs when a carbohydrates or sugar are heated by means of isomerization and polymerization process

MAILLARD REACTIONA complex series of reaction between amino acids and reducing sugars at increased temperature

ENZYMATIC BROWNING

-Its a chemical process occurs only with the help of enzyme polyphenol oxidase.

- It losses quality and totally affects post-harvest storage

- But essentialfor the color and taste of tea and coffee production

POLYPHENOLS

-Is called phenolic compound

-Chemical substances responsible for browning of fruits and vegetables

- an aromatic compound

- Acts as anti-oxidant in plants

POLYPHENOLSWhen an apple is cut, exposing it flesh to the air, the freshly white colour of the apple tend to turn brown.

Phenol become phenolic compound when the attachment of benzene ring with one or more hydroxyl (OH) group found in phenol take place.

POLYPHENOLOXIDASE

-A group of enzymes found mostly in plants

-It contains copper (metal ion) at their active site that enables them to oxidize the phenolic group of an aromatic compound to a reaction group.

-It is able to catalyze the transformation of aromatic compounds that have two adjacent phenolic groups on them.

QUINONE

-Is the reactive oxygen molecules bound to a carbon atom by two double bonds.- Copper containing enzymes oxidize the phenolic groups to reactive oxygen molecules which continue reacting with each other and form brown pigments.

MELANIN

-It is browning causes deterioration of fruits and vegetables and resulting large economic losses.-Insoluble polymers has browning effects because of the PPO catalyzes, and converts phenols to produce quinone which undergone polymerization

AFTER ENZYMATIC BROWNING

PHENOLIC COMPOUND

OXYGEN

PPO ENZYMATIC BROWNING

OXIDATION

Phenolic compounds found in plants, support by the PPO when expose to oxidant, can cause oxidation, accelerates the reaction causing rapid oxidation of phenolic compounds and may result to browning.

PREVENTION OF ENZYMATIC BROWNING

XTo avoid this..

Immersed the sliced apple in water so that oxygen will not come in contact with the PPO enzyme

PREVENTION OF ENZYMATIC BROWNING

After 10 minutes…

PREVENTION OF ENZYMATIC BROWNING

Lemon juices contain vitamin C which is an antioxidant and it prevents oxidation.

PREVENTION OF ENZYMATIC BROWNING

•Blanching

enzyme effect inactivation temp.° C

Lipolityc acyl hydrolase

rancidity ~ 75

Lipoxygenase rancidity ~ 80

Polyphenoloxidase

browning ~100

Peroxidase deterioration

~135

PREVENTION OF ENZYMATIC BROWNING

Types of blanching:

a. Blanching in steam/boiling water

b. Microwave blanching

PREVENTION OF ENZYMATIC BROWNING

•Refrigeration•Freezing•Change pH•Irradiation•High Pressure Treatment

PREVENTION OF ENZYMATIC BROWNING

•DehydrationDehydratation is caused by the removing

water molecules from the product.

Common methods for dehydration are:

• Freezing-drying when moisture is removed by sublimation.• Lowering water activity by adding water-binding chemicals.

PREVENTION OF ENZYMATIC BROWNING•Ultrafiltration

Ultrafiltration is a membrane separation process, driven by a pressure gradient. The membrane separates liquid components according to their size and structure.

•Utrasonication

Ultrasonication is an advanced method to inactivate enzymes. Ultrasonic sound waves are able to destroy large molecules by liberating highly reactive radicals from water.

PREVENTION OF ENZYMATIC BROWNING

•Addition of Inhibitors

Inhibitions can act in three ways:

1.Inactivation towards the enzyme.2.Inactivation towards substrate.3.Inactivation towards the product.

PREVENTION OF ENZYMATIC BROWNING

Category Example of inhibitor

Mode of action

Reducing agents

sulphiting agentsascorbic acid and analogscysteineglutathione

removal of oxygen

Chelating agents

phosphates EDTA organic acids

removal of metals (most PPO enzymes contain metal atoms)

Acidulants citric acid phosphoric acid

reducing pH

Enzyme inhibitors

aromatic carboxylic acidspeptidessubstituted resorcinols

react with enzymes

Inhibitors of Enzymatic Browning