Food Biochemistry and Food Processing (2 edition)

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Browning Reactions


Marta Corzo-Mart ́ınez, Nieves Corzo, Mar Villamiel, and M Dolores del Castillo


Introduction
Enzymatic Browning
Properties of PPO
Substrates
Control of Browning
Nonenzymatic Browning
The Maillard Reaction
Factors Affecting Maillard Reaction
Study of Maillard Reaction in Foods
Control of the Maillard Reaction in Foods
Caramelization
Ascorbic Acid Browning
Pathway of Ascorbic Acid Browning
Control of Ascorbic Acid Browning
Lipid Browning
Protein-Oxidized Fatty Acid Reactions
Nonenzymatic Browning of Aminophospholipids
References

Abstract:Browning is one of the most important reactions tak-
ing place during food processing and storage. Both, enzymatic and
nonenzymatic browning can affect the quality of food in either
positive or negative ways, depending on the type of food. Special
attention has been paid in this chapter to chemistry of the reaction.
During enzymatic browning, phenolic compounds are oxidized to
quinones by polyphenol oxidase, this reaction being of particu-
lar importance in fruits, vegetables, and seafoods. Nonenzymatic
browning is referred to as the Maillard reaction (MR), when it takes
place between free amino groups from amino acids, peptides, or
proteins and the carbonyl group of reducing sugars. Ascorbic acid,
its oxidation products and oxidized lipids can also reactviaMR.
It has been also described that aminophospholipids and reducing
carbohydrates can interact by MR. Food browning can be also due
to degradation of carbohydrates also called caramelization reaction
and it is hereby discussed.

INTRODUCTION


Browning reactions are some of the most important phenomena
occurring in food during processing and storage. They represent
an interesting research for the implications in food stability and
technology as well as in nutrition and health. The major groups
of reactions leading to browning are enzymatic phenol oxidation
and so-called nonenzymatic browning (Manzocco et al. 2001).

ENZYMATIC BROWNING


Enzymatic browning is one of the most important color reactions
that affect fruits, vegetables, and seafood. It is catalyzed by the
enzyme polyphenol oxidase (PPO; 1,2 benzenediol; oxygen oxi-
doreductase, EC 1.10.3.1), which is also referred to as phenolox-
idase, phenolase, monophenol oxidase, diphenol oxidase (DPO),
and tyrosinase. Phenoloxidase enzymes (PPOs) catalyze the ox-
idation of phenolic constituents to quinones, which finally poly-
merize to colored melanins (Marshall et al. 2000). Significant ad-
vances have been made on biochemistry, molecular biology, and
genetics of PPO (Yoruk and Marshall 2003, Queiroz et al. 2008).
Enzymatic browning reactions may affect fruits, vegetables,
and seafood in either positive or negative ways. These reactions,
for instance, may contribute to the overall acceptability of foods
such as tea, coffee, cocoa, and dried fruits (raisins, prunes, dates,
and figs). Products of enzymatic browning play key physiologi-
cal roles. Melanins, produced as a consequence of PPO activity,
may exhibit antibacterial, antifungal, anticancer, and antioxidant
properties. PPOs impart remarkable physiological functions for
the development of aquatic organisms, such as wound healing
and hardening of the shell (sclerotization), after molting in
insects and in crustaceans such as shrimp and lobster. The
mechanism of wound healing in aquatic organisms is similar to

Food Biochemistry and Food Processing, Second Edition. Edited by Benjamin K. Simpson, Leo M.L. Nollet, Fidel Toldr ́a, Soottawat Benjakul, Gopinadhan Paliyath and Y.H. Hui.
©C2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc.

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