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