Fruits and vegetables GapFill

When you’re peeling or cutting vegetables, their surface and insides become exposed to air. Oxygen in the air then reacts with the vegetables in an  denaturationemulsificationoxidationoxygenation reaction. Enyzmic browning is an example of this reaction, and occurs when you destroy the structure of plant  cell membranesvacuolescell wallsfibre, causing the cells’ contents to spill out. The enzyme in the cells’ juices, called  lactasepolyphenol oxidasepolymorphic oxidasepolyphenol hydrolase, reacts with oxygen in the air, and damages substances in plant tissues, causing them to brown. This is negative to the plants’ nutritional value, but on the other hand, helps obtain the desired flavour of products such as  breadblack teaorangesgreen tea, coffee or chocolate. The process is widely present in a number of vegetables and fruits.

Enzymic browning can be slowed down or stopped by:

•  increasingdecreasingdevelopingraising the temperature, because the enzymes work more slowly at low temperatures
• using high heat, such as when  chillingfreezingthawingblanching, because it deactivates the enzymes in food
• adding acid, e.g. lemon juice, as it  enhancesfoamscoagulatesdenatures the enyzmes
• removing  carbon dioxidecarbon monoxidehydrogenoxygen, because the process cannot occur without this gas.