Cereals processing technology

100 Cereals processing technology
consistency, cup and standing types give consistent quality in the finished dish
because no real cooking is involved, whereas the others may vary, especially
simmering and sauté/simmering types.
5.6.3 Quick-cooking processes
Many quick-cooking rice products and processes have been developed and
patented during the past decades. Among the processes and products developed,
the following are the commercially useful quick-cooking processes.
• Soak-boil-steam-dry method: Raw milled long-grain white rice is soaked in
water to 30% moisture and cooked in boiling water to 50–60% moisture, with
or without steam. The product is further boiled or steamed to increase the
moisture to 70% and then dehydrated to 8–14% moisture to maintain a
porous structure.
• Expanded and pregelatinization method: Rice is soaked, boiled, steamed, or
pressure-cooked to gelatinize the grain thoroughly, dried at a low temperature
to yield fairly dense glassy grains, and then expanded or puffed at a
temperature to produce the desired porous structure in the product.
• Rolling or ‘bumping’ method: Rice is pregelatinized as described in the
previous section, rolled, or ‘bumped’ to flatten the grains and dried to a
relatively hard glassy product.
• Dry heat treatment method: Rice is exposed to a blast of hot air at 65–82ºC
for 10–30 min, or at 272ºC for 18 sec, to dextranize, fissure, or expand the
grains. No boiling or steaming is applied.
• The freeze-thaw-drying process: Rice is precooked and then frozen, thawed,
and dried. The procedure combines the hydration and gelatinization steps, in
addition to the critical steps of freezing and thawing before drying.
5.7 Canned and frozen rice
Various methods have been used for making canned rice more acceptable. These
fall into two categories: wet pack and dry pack. A product in which there is an
excess of liquid, such as in soup media, is termed wet pack. The rice is
precooked or blanched sufficiently to promote buoyancy in the product. The
washing process removes excess surface starch. The rice is put into cans together
with the sauce. The cans are sealed under vacuum and then retorted to sterilize
the product. A commercial process has been evaluated for canned white rice
packed in 301 411 cans with a fill weight of 340 g rice (55–60% moisture) for
each can. The initial temperature is 40ºC, and the come up time 10–15 min. The
recommended processing time at 118.3ºC is 55 min. The equivalent sterilization
value at 121ºC is 13.3 min.