Chemistry Reference
In-Depth Information
II.3.2.1.
Colour and Flavour
A typical reddish-brown colour and caramel-like flavour are major
sensory attributes of DL that impact on consumer acceptability of the pro-
duct. Colour, as well as typical texture, correlates positively with the overall
acceptance of DL (Garitta et al., 2004; Ares et al., 2006). However, an
excessively dark brown colour can lead to product rejection (Garitta et al.,
2004).
The negative changes in the level of a desirable attribute, like colour,
may be due to the composition of DL or time of storage. The techniques most
frequently adopted in industry to avoid texture defects (sandiness) involve
higher amounts of reducing sugars in the system. Hydrolysis of lactose with
-galactosidase leads to the liberation of two molecules of reducing sugars
(glucose and galactose) from each molecule of lactose.
On the other hand, if part of the sucrose is replaced by glucose, the
Maillard reaction is favoured and the colour of the product may become
too dark. In addition, some studies on colour formation in casein-sugar
systems have shown that when glucose is present, the Maillard reaction
is faster (Morales and van Boekel, 1998) although variable results have
been reported using different indices of non-enzymatic browning, such as
fluorescence accumulation (Morales and van Boekel, 1997; Rozycki
et al., 2007). An alternative method to avoid the excessive darkening of
DL is to reduce the proportion of glucose or add the glucose syrup later
during
manufacture,
after
the
solid
content
of
DL
reaches
55-60%
(Zalazar, 2003).
A high pH of DL after neutralization (pH
>
7.50) may also cause too
dark a colour in the product due to the catalytic effect of alkaline conditions
on the Maillard reaction and brown product formation (O' Brien, 1997;
Rozycki and Pauletti, 2002; see Chapter 7).
Finally, DL can darken during storage due to continuing of non-enzy-
matic browning in the finished product at room temperature. However,
acceptability tests have shown that the colour changes during storage for
the usual period (up to 180 days) are not determinants for product rejection
by the consumers (Garitta et al., 2004).
II.3.2.2.
Nutritional Value
The impact of lactose on the nutritional properties of DL may be
evaluated from two different points of view, the principal of which is the
loss in nutritive value by damaging essential amino acids by Maillard reac-
tions. The second aspect is the nutritional concern for lactose-intolerant
people, as DL is rich in lactose.
