Cereals processing technology

152 Cereals processing technology
matrix to provide support and the desirable chewy texture versus sufficient pore
space to allow rapid starch hydration and swelling. Control of the number and
size of the pores is critical. The number of pores can be influenced by chemical
leavening, fermentation or modification of pores. Addition of chemical
leaveners takes place in two stages. The leavening agent is dissolved in the
water initially being added to the flour while an acid compound is added at the
final stages of mixing to limit gas bubble production. The gluten matrix in wheat
dough stabilizes bubble nuclei but any change in size must happen before starch
gelatinization (80ºC) occurs and sets the noodle’s internal structure. Temperature
gradients are formed from the exterior noodle surface to the interior during
steaming. Existing bubble nuclei will expand in the hotter outer portion and
form pores when they break the surface.
Subsequent drying through controlled conditions allows rapid expansion of
bubbles located within the interior of the noodle, which had not previously
reached the starch gelatinization temperature, thus increasing the noodle’s
porosity. There is minimal expansion of the noodle during the steaming stage
and is confined primarily to the drying stage. Noodle expansion is a function of
the mixing moisture, drying procedure and temperature, the degree of gluten
development, noodle surface hardness and stresses imparted on the noodle
during sheeting and cutting. 23 The final texture of the expanded instant noodle is
determined by the number and size of the noodle pores after rehydration.
Chilled and frozen noodles
Frozen noodle technology has been applied to both Udon and Chinese-style
noodles. The key marketing feature for both these products is that the noodle
has already been optimally cooked thus requiring only a rapid defrosting or
heating, 30 sec, to return to its optimal texture. Chilled noodle production has
reached ¥400 billion annually while frozen noodles have achieved annual sales
of ¥70 billion. Although they are primarily sold to restaurants, they are making
inroads to supermarket and convenience stores. 23 The reduction in cooking
time by vacuum mixing and additional water decreases the amount of material
loss during rehydration and limits stickiness. The increased swelling of the
starch subsequently limits the starch’s retrogradation rate thus extending the
noodle shelf-life. Water absorption levels used during mixing, noodle aging,
cooking time and cooling water temperature all influence the texture of the
final noodle.
Boiled noodles are rinsed or immersed in 5ºC water and immediately
packaged and refrigerated at 4–10ºC if they are being sold as chilled noodles. In
the production of frozen noodles more than 30 min are required to freeze
noodles at 40ºC using either a combination of air blast or contact freezer. 5 A
critical feature to the frozen noodles is the idea that they have been cooked to
their optimum state before flash freezing. Immersion of the frozen noodle in
boiling water for 20–60 sec then returns the noodle to optimum condition,
particularly in terms of their textural attributes. A moisture gradient is developed
with the surface having absorbed 80 percent of its water, while the core 50