Enzymatic browning

This arises by the oxidation of polyphenols to o-quinones by enzymes such as polyphenol oxidase (PPO) and peroxidase (Fig. 1.23). A day-to-day example

Polyphenol

Polyphenol

Polyphenol oxidase

h2o h2o2

Fig. 1.23 Polyphenol oxidation.

Polyphenol oxidase

Polymerisation

Quinone

Polymerisation

Melanin

Quinone h2o

2H2O

Maltol

Isomaltol

Isomaltol

Fig. 1.24 Some flavour compounds produced in caramélisation reactions.

would be the browning of sliced apple. In other foods, the reaction is wanted, for example, in the readying of prunes, dates and tea for the marketplace.

Whereas heating boosts non-enzymatic browning, the converse applies to enzymatic browning, as the heat inactivates enzymes. The alternative strategies to avoid the reaction are to lower the levels of polyphenols (the agent polyvinylpolypyrrolidone (PVPP) achieves this) or to exclude oxygen.

Brew Your Own Beer

Brew Your Own Beer

Discover How To Become Your Own Brew Master, With Brew Your Own Beer. It takes more than a recipe to make a great beer. Just using the right ingredients doesn't mean your beer will taste like it was meant to. Most of the time it’s the way a beer is made and served that makes it either an exceptional beer or one that gets dumped into the nearest flower pot.

Get My Free Ebook


Post a comment