Food Biochemistry and Food Processing (2 edition)

BLBS102-c10 BLBS102-Simpson March 21, 2012 13:7 Trim: 276mm X 219mm Printer Name: Yet to Come

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Protein Cross-linking in Food – Structure,

Applications, Implications for Health and

Food Safety

Juliet A. Gerrard and Justine R. Cottam

Introduction

Protein Cross-Links in Food

Disulfide Cross-links

Cross-links Derived from Dehydroprotein

Cross-links Derived from Tyrosine

Cross-links Derived from the Maillard Reaction

Age Protein Cross-Links Isolated to Date in Food

Health and food safety aspects of MRPs

Melanoidins

Maillard-Related Cross-Links

Cross-links Formed via Transglutaminase Catalysis

Other Isopeptide Bonds

Manipulating Protein Cross-Linking During Food Processing

Chemical Methods

Enzymatic Methods

Transglutaminase

Future Applications of Protein Cross-Linking

Acknowledgements

References

Abstract:The capacity of proteins to cross-link with each other has

important implications for food quality. Protein cross-linking can

influence food texture and appearance, or permit the incorporation

of useful nutrients such as essential amino acids or essential oils in

foods to accrue crucial benefits. Protein cross-linking in foods may

be achieved by enzymatic means with transglutaminase or with

cross-linking agents like glutaraldehyde. This chapter discusses the

different cross-linking effects and how they may be exploited by

food processor.

INTRODUCTION

Protein cross-links play an important role in determining the

functional properties of food proteins. Manipulation of the num-

ber and nature of protein cross-links during food processing

offers a means by which the food industry can manipulate the

functional properties of food, often without damaging the nutri-

tional quality. This chapter updates the chapter in the previous

edition of this book and discusses advances in our understand-

ing of protein cross-linking over the last two decades, as well as

examining current and future applications of this chemistry in

food processing and its implications for health and food safety.

It draws on, and updates, two reviews in this area (Gerrard 2002,

Miller and Gerrard, 2005) in addition to earlier reviews on this

subject (Matheis and Whitaker 1987, Feeney and Whitaker 1988,

Singh 1991).

The elusive relationship between the structure and the func-

tion of proteins presents a particular challenge for the food tech-

nologist. Food proteins are often denatured during processing,

so there is a need to understand the protein both as a biolog-

ical entity with a predetermined function and as a randomly

coiled biopolymer. To understand and manipulate food proteins

requires a knowledge of both protein biochemistry and poly-

mer science. If the protein undergoes chemical reaction during

processing, both the ‘natural’ function of the molecule and the

properties of the denatured polymeric state may be influenced.

One type of chemical reaction that has major consequences for

protein function in either their native or denatured states is pro-

tein cross-linking. It is, therefore, no surprise that protein cross-

linking can have profound effects on the functional properties

of food proteins.

This chapter sets out to define the different types of protein

cross-links that can occur in food, before and after processing,

and the consequences of these cross-links for the functional and

nutritional properties of the foodstuff. Methods that have been

employed to introduce cross-links into food deliberately are then

reviewed, and future prospects for the use of this chemistry

for the manipulation of food during processing are surveyed,

including a consideration of health and food safety aspects.

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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