BLBS102-c30 BLBS102-Simpson March 21, 2012 13:56 Trim: 276mm X 219mm Printer Name: Yet to Come
588 Part 5: Fruits, Vegetables, and Cerealswas very different, comparison could not be made for the effect
of extrusion.
Hunter ‘L’ values determined for wheat flours, commercial
flaked-toasted, extruded-toasted, and extruded-puffed breakfast
cereals were found to be positively correlated with available
lysine (McAuley et al. 1987). Rufian-Henares et al. (2009) con- ́
cluded that the colour difference (E) obtained from the CIE
Lab parameters L∗,a∗,b∗between toasted and untoasted sam-
ples results in a reliable measurement of the visible colour pro-
duction for the toasting step of different flours usually used for
the formulation of cereal-based products. During industrial bak-
ing of cookies, the effect of time on colour development and
other parameters (volume, structure, weight and crispness) was
studied by Piazza and Masi (1997). The development of crisp-
ness increased with time and was found to be related to the
other physical processes that occur during baking. Gallagher
et al. (2003) observed different colour development in the pro-
duction of a functional low-fat and low-sugar biscuit, depend-
ing upon the quantities of sugar and protein present. Regarding
spaghetti pasta fortified with different levels of Mexican com-
mon bean flour, the difference in colour was associated with the
use of common flour rather than the drying temperature assayed
(Gallegos-Infante et al. 2010).
The manufacture of many breakfast cereals starts with the
cooking of whole cereal grains in a rotary pressure cooker. Dur-
ing this operation, the grains absorb heat and moisture, and
undergo chemical (browning reactions) and physico-chemical
changes as a consequence. The cooking stage is thought to have
a key influence on the properties of the final product, such as
colour, flavour and texture. Horrobin et al. (2003) studied the in-
terior and surface colour development during wheat grain steam-
ing and the results obtained indicated the possible relationship
between the colour development and moisture uptake during the
cooking process. In a study on the effects of oven humidity on
foods (bread, cakes and cookies) baked in gas convection ovens,
Xue et al. (2004) observed that increased oven humidity results
in products with lighter colour and reduced firmness.
As aforementioned, the formation of MR products and in-
tense colour are responsible for the organoleptic properties of
this type of products. Moreover, it is also important to consider
that the brown pigments formed could present some biological
activities. Thus, Bressa et al. (1996) observed a considerable
antioxidant capacity in cookies during the first 20–30 minutes
of cooking (when browning takes place). Whole grain break-
fast cereals have also proved to be an important dietary source
of antioxidants (Miller et al. 2000). Borrelli et al. (2003) stud-
ied in bread and biscuits the formation of coloured compounds
and they examined the antioxidant activity and the potential
cytotoxic effects of the formed products. Summa et al. (2006)
also correlated acrylamide concentration and antioxidant activity
with colour of cookies by means of a three-dimensional model
in which the three coordinates of the CIE colour space were used
as variables.
Bernussi et al. (1998) studied the effect of microwave baking
on the moisture gradient and overall quality of cookies, and they
observed that colour did not differ significantly from that of the
control samples (cookies baked using the traditional process).Broyart et al. (1998) carried out a study on the kinetics of
colour formation during the baking of crackers in a static elec-
trically heated oven. These authors observed that the darkening
step starts when the product temperature reaches a critical value
in the range of 105–115◦C. A kinetic model was developed in
order to predict the lightness variation of the cracker surface
using the product temperature and moisture content variations
during baking. The evolution of lightness appears to follow a
first-order kinetic influenced by these two parameters.
Colour development has also been included, together with
other parameters (temperature, water loss, etc) in a mathematical
model that simulated the functioning of a continuous industrial-
scale biscuit oven (Broyart and Trystram 2003).
The effect of raising agents and sugars on surface colour of
cookies was studied by Gokmen et al. (2008b). ̈
Changes in surface colour, water activity and pH of cookies
were determined to understand the chemical mechanisms re-
sponsible for HMF formation during baking of cookies from
different formulations.FluorescenceDuring the advanced stages of the non-enzymatic browning,
compounds with fluorescence properties are also produced. Sev-
eral analytical methods based on fluorescence measurements
have been used to evaluate the extent of this reaction (Rizkallah
et al. 2008, Tr ́egoat et al. 2009, Calvarro et al. 2009). For in-
stance, the FAST (fluorescence of advanced Maillard products
and soluble tryptophan) method proposed by Birlouez-Aragon
et al. (1998) is based on the fluorescence ratio between MR prod-
ucts and tryptophan determined when excited at 330–350 nm.
This parameter is dependent on heat treatment of the product
and is related to its protein nutritional loss. Thus, this method,
firstly validated on milk samples, has been used in other foods
modified by the MR such as breakfast cereals (Birlouez-Aragon
et al. 2001) and rye bread (Michalska et al. 2008).
Birlouez-Aragon et al. (2001) studied the correlation between
the FAST index, lysine loss and HMF formation during the
manufacture of breakfast cereals by extrusion and in commercial
samples. The FAST index was in good agreement with HMF for-
mation. These authors also found that the relationship between
FAST index and lysine loss indicates that, for severe treatments
inducing lysine blockage higher than 30%, lysine loss is less
rapid than the increase in the FAST index. Thus, the fluorimetric
FAST method appears to be an interesting alternative to eval-
uate the nutritional damage on a great variety of cereal-based
products submitted to heat treatment.
Delgado-Andrade et al. (2006) determined free and total
(free+linked-to-protein backbone) fluorescence intermediate
compounds (FIC) related to MR in commercial breakfast ce-
reals. Levels of free and total FIC were also correlated with
other well-established heat-induced markers of the extent of the
MR or sugar caramelisation during cereal processing, such as
HMF, furfural, GIM and furosine. Data support the usefulness of
FIC measurements as an unspecific but adequate heat-induced
marker of the extent of thermal processing in breakfast cereals,
since statistically significant correlations were found between