Ishfaq Ahmed et al
The adaptation of proper milling process is very
important to obtain flour of desired properties i.e.
bright color, fine particles, low ash concentration
and damaged starches. Every type of noodles
has their own specific protein range. The milling
procedure must be adopted in such a way as to ensure
proper separation of endosperm and bran, including
tempering as well as break release adjustment in
the mill [26]. Usually, flour containing high protein
concentration is required to develop dried noodles,
while boiled or fresh noodles are made from flour
containing lower protein concentration. However,
high level of protein in dried noodles helps to
keep the noodle texture during drying. Protein
concentration plays vital role in the preparation of
instant noodles, because fat uptake decreases as the
protein concentration increase during the frying
process [27-28]. The natural color pigments in
flour are destroyed by bleaching. Noodle darkening
increases with higher extraction rate of flour. The
high bran level resulted in dark color noodles due to
the greater level of polyphenol oxidases in the bran
layer. Low ash concentrations and low extraction
rate are mostly preferred to develop high quality
noodles with bright and clean appearance [1].
On the other hand, thermal properties such as
gelatinization, pasting and retrogradation impart
significant role in product development. It controls
the rheological properties and determines the
quality of starch based products [29]. Gelatinization
refers to the disruption of molecular order within
the starch granule, thereby leading to irreversible
changes in properties i.e. loss of birefringence,
granular swelling, loss of crystallinity and starch
solubilization. The gelatinization process is
governed by the concentration of starches, types of
granule and amylose and amylopectin concentration.
While retrogradation is the reassociation of
starch chain into an ordered structure after starch
solutions are cooled [30]. Zhou et al.[31]found no
significant difference in onset temperature (T
o
),
while significant difference was noted in peak
temperature (T
p
), gelatinization enthalpy (ΔH)
and conclusion temperature (T
c
) in flour obtained
from three different rice varieties, which were
stored at 4°C and 37 °C for 6 months. Hormdok
and Noomhorm [9] found that rice starch had 67.7,
73.49, 78.75
o
C and 13.21 j/g in case of T
o
, T
p
, T
c
and (ΔH), respectively. Bao et al [32] also observed
similar results regarding rice starch. They concluded
that gelatinization temperature is a critical step, as
it is an indicator of processing and cooking quality.
Gelatinization leads to collapse of double helical
structure and crystallinity, which resulted in crystals
melting at different temperature to form suspensions
of starch mixtures. The variation in morphology
and rigidity of starch granule causes differences
in gelatinization peaks of waxy and indica starch.
Amylose and amylopectin concentration also affect
the gelatinization peak [30]. Tan et al [33] reviewed
that long chain amylopectin might also be a factor
to higher gelatinization temperature of starches.
Therefore, it can be concluded that starch thermal
properties are influenced by various factors like,
variety, starch source, morphology of granules,
amylose, amylopectin concentration etc. Flours
containing high percent crystallinity and amylose
concentration exhibited higher gelatinization
parameters due to the rigid amorphous regions of
starch granule by the association of amylose chains.
This might increase the stability of amorphous
region, thereby leading to higher energy input for
gelatinization process [34].
Starch gel is defined as a continuous network of
solid-liquid phases in which liquid is dispersed in the
solid phase [35]. Hydrogen bond is formed between
amylose molecules as well as with amylopectin
branches of swollen granules. Morphology of
starch gels and its strength is effected by different
factors i.e. starch sources, cultivar or variety of
each source, granule size and shape, moisture
concentration, ratio of amylose to amylopectin,
gelatinization time and temperature and pH [9,
36-38]. Comparatively, the gelling strength of
aged rice flour is superior to flour obtained from
freshly harvested rice grains [39]. Hormdok and
Noomhorm [9] also observed that ageing of rice
flour had increased the gel strength significantly,
as evident from the observed values of 27.38 (flour
from freshly harvested grains) and 33.13 g (aged
rice flour). Huang et al.[40] made mixed gel from
two rice varieties (Japonica and Indica starch),
hydrocolloids (carrageenan and gellan), deionized
water and CaCl
2
. They observed the influence of
rice starch, hydrocolloids and its concentration
on the quality of gel via texture profile analysis. It
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