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Non-Enzymatic Browning in Cookies,
Crackers and Breakfast Cereals
A.C. Soria and M. Villamiel
Introduction
Non-Enzymatic Browning Indicators
Available Lysine
Furosine
Hydroxymethylfurfural and Furfural
Colour
Fluorescence
Acrylamide
Maltulose
ReferencesAbstract:In this chapter, the authors have attempted to collect
the main studies carried out up to 2010 on the most investigated
quality indicators in cookies, crackers and breakfast cereals. These
cereal-based foods, mainly consumed for breakfast, constitute a very
important source of energy, particularly in the case of children. For
this reason, their processing (baking or extrusion cooking) should be
carefully carried out in order to keep their quality. One of the main
reactions that takes place during the processing of these cereal-based
foods is non-enzymatic browning including Maillard reaction and
caramelisation, which might contribute to the development of colour
and fluorescence. In this sense, the evaluation of chemical indicators
such as available lysine, furosine, hydroxymethylfurfural, furfural,
acrylamide and maltulose might afford important information on the
processing and storage conditions to which cereal-based products
have been submitted.INTRODUCTION
Cereal-based products such as cookies, crackers and breakfast
cereals represent a predominant source of energy in the human
diet, especially for children consuming cereal derivatives for
breakfast meals.
Cookies, crackers and breakfast cereals can be manufactured
by means of traditional processes or by extrusion cooking. In
general, during conventional treatment of flour products (usu-ally, temperatures higher than 200◦C for several minutes), more
intense processing conditions are applied as compared to those
used in the extrusion process (Gonzalez-Gal ́ an et al. 1991, ́
Manzaneque Ramos 1994, Huang 1998).
Extrusion cooking is a well-established industrial technology
with a number of food applications since, in addition to the
usual benefits of heat processing, extrusion has the possibility of
changing the functional properties of food ingredients and/or
of texturising them (Cheftel 1986). In the extruder, the mixture
of ingredients is subjected to intense mechanical shear through
the action of one or two rotating screws. The cooking can occur
at high temperatures (up to 250◦C), relatively short residence
times (1–2 minutes), high pressures (up to 25 MPa), intense shear
forces (100 rpm) and low moisture conditions (below 30%). In
addition to the cooking step, cookies, crackers and breakfast
cereals manufacture involves toasting and/or drying operations
(Cheftel 1986, Camire and Belbez 1996, Manley 2000).
During these technological treatments, due to the elevated
temperatures and low moisture conditions used, different chemi-
cal reactions such as the non-enzymatic browning can take place.
Non-enzymatic browning includes Maillard reaction (MR) and
caramelisation. The products resulting from both reactions de-
pend on food composition, temperature, water activity and pH,
and can occur simultaneously (Zanoni et al. 1995).
As it is known, MR occurs between reducing sugars such as
glucose, fructose, lactose or maltose, and free amino groups of
amino acids or proteins (usually theε-amino group of lysine).
The MR is favoured in foods with high protein and reducing
carbohydrate content at intermediate moisture content, temper-
atures above 50◦C and a pH in the range from 4 to 7. Carameli-
sation depends on direct degradation of carbohydrates due to
heat and it needs more drastic conditions than those of the MR.
Thus, at temperatures higher than 120◦C, pH lower than 3 or
higher than 9 and very low moisture content, caramelisation is
favoured (Kroh 1994).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.584