3.3.2.4 Fruit and vegetables GapFill

When you’re peeling or cutting vegetables, you destroy the structure of plant  cellulosecell wallscell membranesfruit, causing the cells’ contents to spill out. The enzyme in the cells’ juices, called  ATP-asepolyphenol hydrolasekinasepolyphenol oxidase, 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  black teabeetrootsgreen teaice cream, coffee or chocolate. The process is widely present in a number of vegetables and fruits.

Enzymatic browning can be slowed down or stopped by:

•  escalatingincreasingdecreasingblanching the temperature, because the enzymes work more slowly at low temperatures
• using high heat, such as when  coolingfreezingblanchingdiminuting, because it deactivates the enzymes in food
• adding acid, e.g. lemon juice, as it  coagulatesshortensdenaturesgelatinises the protein
• removing  nitrogenethyleneoxygenhydrogen, because the process cannot occur without this gas.