Food Biochemistry and Food Processing (2 edition)

BLBS102-c04 BLBS102-Simpson March 21, 2012 11:59 Trim: 276mm X 219mm Printer Name: Yet to Come

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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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