Enzymatic Browning

​Browning

By Ana de Lange

Labelling

The sugar has darkened.

How do we call this type of browning?

Drag labels to their correct position on the image

Oxidation

Enzymatic

Caramelization

Non-enzymatic

Maillard

Labelling

Why do avocados darken when exposed to air?

Drag labels to their correct position on the image

Enzymatic browning

Caramelization

Maillard

Oxidation

From ingredients to the end-product...


What elements are needed?

Drag and Drop

In enzymatic browning, the​

Placeholder

and the​

Placeholder

are the substrates. They react and form​

Placeholder

and polymerize to form ​

Placeholder

which are brown.

Drag these tiles and drop them in the correct blank above

phenols

oxygen

quinones

melanins

PPO

enzyme

oxidation

Drag and Drop

The responsible of this transformation (from substrates to product) is the

Placeholder

Drag these tiles and drop them in the correct blank above

PPO

substrate

product

cake

ingredients

melanins

​How to avoid browning?

Match

Strategies

• Blanching

• Strong acidity or alkalinity (extreme pH)

• Chemical inhibitors

• Oxygen Removal

• Freezing

70-90°C denatures the PPO

PPO is most active near neutral pH (5-7)

Ascorbic acid (Vitamin C)

Sulfites

Packing under nitrogen or vacuum

PPO requires mobility to function

• 70-90°C denatures the PPO

• PPO is most active near neutral pH (5-7)

• Ascorbic acid (Vitamin C)

  Sulfites

• Packing under nitrogen or vacuum

• PPO requires mobility to function

Effect of vinegar

Cell Damage Effect

​Vinegar is quite acidic

1. Increase permeability of cell membranes
   This means more phenolic substrates leak out (more fuel for the reaction).

2. At pH 4-5, PPO is still active.

3. Acid promoted pigment formation (not PPO-driven)