Food Biochemistry and Food Processing

9 Protein Cross-linking in Food 235

lated with cross-linking of the albumins and globu-
lins and high molecular weight glutenin fractions by
transglutaminase (Gerrard et al. 2001). Subsequent
research suggested that the dominant effect was
attributable to cross-linking of the high molecular
weight glutenins (Gerrard et al. 2002).

FUTURE APPLICATIONS OF
PROTEIN CROSS-LINKING

Although protein cross-linking is often considered
to be detrimental to the quality of food, it is increas-
ingly clear that it can also be used as a tool to
improve food properties. The more we understand
of the chemistry and biochemistry that take place
during processing, the better placed we are to ex-
ploit it—minimizing deleterious reactions and max-
imizing beneficial ones.
Food chemists are faced with the task of under-
standing the vast array of reactions that occur during
the preparation of food. Food often has complex
structures and textures, and through careful manipu-
lation of specific processes that occur during food
preparation, these properties can be enhanced to
generate a highly marketable product (Dickinson
1997). The formation of a structural network within
food is critical for properties such as food texture.
From a biopolymer point of view, this cross-linking
process has been successfully applied in the forma-
tion of protein films, ultimately for use as packag-
ing. Enhancing textural properties, emulsifying and
foaming properties, by protein cross-linking has
been a subject of interest of many working in this
area, as exemplified by the number of studies de-
tailed above.
Cross-linking using chemical reagents remains
challenging, in terms of both controlling the chem-
istry and gaining consumer acceptance. However, as
the extensive recent use of transglutaminase dramat-
ically illustrates, protein cross-linking using en-
zymes has huge potential for the improvement of
traditional products and the creation of new ones.
Transglutaminase itself will no doubt find yet more
application as its precise mode of action becomes
better understood, especially if variants of the en-
zyme with a broader substrate specificity are found.
Whether other enzymes, which cross-link by dif-
ferent mechanisms, can find equal applicability re-
mains open to debate. The thiol exchange enzymes,
such as protein disulfide isomerase, may offer ad-

vantages to food processors if their mechanisms can

be unraveled, and then controlled within a foodstuff.

Other enzymes, such as lysyl oxidase, have not yet

been used, but have potential to improve foods

(Dickinson 1997), especially in the light of recent

work characterizing this class of enzymes (Buffoni

and Ignesti 2000), which may allow their currently

unpredictable effects to be better understood.

ACKNOWLEDGEMENTS

I thank all the postgraduates and postdoctoral fel-

lows who have worked with me on the Maillard

reaction and protein cross-linking of food, in partic-

ular: Dr Siân Fayle, Paula Brown, Dr. Indira Rasiah,

Dr. Susie Meade, Dr. Antonia Miller, and Suhaimi

Yasir.

REFERENCES

Al-Abed Y, Bucala R. 2000 Structure of a synthetic

glucose derived advanced glycation end product that

is immunologically cross-reactive with its naturally

occurring counterparts. Bioconjug. Chem. 11:39–45.

Amadori M 1931. Atti R Acad Naz Lincei Mem Cl Sci

Fis Mat Nat 13:72.

Ames JM. 1992. The Maillard reaction in foods. In:

BJF Hudson, editor, Biochemistry of Food Proteins,

pp. 99–153. Elsevier Applied Science.

An HJ, et al. 1996. Roles of endogeneous enzymes in

surimi gelation. Trends Food Sci Technol 7:321–

327.

Ando H, et al. 1989. Purification and characteristics of

a novel transglutaminase derived from microorgan-

isms. Agric. Biol. Chem. 53:2613–2617.

Aoki T, Hiidome Y, Kitahata K, Sugimoto Y, Ibrahim

HR, Kato Y. 1999. Improvement of heat stability and

emulsifying activity of ovalbumin by conjugation

with glucuronic acid through the Maillard reaction.

Food Res Intern 32:129–133.

Aoki T, Hiidome Y, Sugimoto Y, Ibrahim HR, Kato Y.

2001. Modification of ovalbumin with oligogalactur-
      onic acids through the Maillard reaction. Food Res
      Intern 34:127–132.
      Benjakul S, Visessanguan W, Chantarasuwan C. 2004a.
      Cross-linking activity of sarcoplasmic fraction from
      bigeye snapper (Priacanthus tayenus)muscle. Food
      Sci Technol37:79–85.
      ———. 2004b. Effect of porcine plasma protein and
      setting on gel properties of surimi produced from