From: Arnie Skurow <arnie@magnus.acs.ohio-state.edu>
Subject: More on Puffing Rice
Organization: The Ohio State University
Date: Thu, 19 Nov 1992 16:23:12 GMT

As a sequel to my article on Grape Nuts yesterday.....

Under normal means of what most folks have in their kitchens, it is not
within our realm of possibility to puff rice or wheat, or other grains for
that matter, at home.

The description of dropping rice into hot oil, if one uses the whole 
grain rice complete with hull or bran, will give an oily product like 
popcorn and will give inconsistent results.

The production building connected to the Post Toasties building, where I
had my primary responsibilities, was the puffed rice/wheat production
facility.  Puffing rice and wheat is an interesting process.

Years ago, one cereal maker proclaimed that OUR RICE IS SHOT FROM CANNONS, 
and they showed an old style ships cannon shooting put puffed rice.

Well, in the cereal industry, the device is truly a cannon, but it has 
absolutely no appearance to a military device; it is a long metal tube.

The way rice and wheat are puffed by the cereal makers is to place the
whole grain, which is the rice complete with the bran or hull on, into a
high pressure steam vessel.  After a rigidly controlled time and 
temperature process a valve located at the back end of the "cannon" or
puffing tube is opened extremely rapidly, shooting the rice through the
puffing gun.  It's analogous to making popcorn where the pressure of the
corn builds up within the hull and at a certain point of time, pressure
and temperature causes the corn to "explode" into what we eat as
popcorn.

After the rice or wheat is "shot" through the puffing tube, a new batch
of raw rice/wheat is placed into the pressure retort and the process 
begins all over again.

Meanwhile, the puffed rice or wheat, replete with loose hulls, is 
permitted to dry to a packagable moisture content, usually 12 - 13%
moisture, the hulls are separated by an air separation process, the
rice/wheat go on to the packaging line and the hulls go to animal feed
or other bran cereals.

My direct boss was a dual degree genius who earned his fast-track
status with Post/General Foods by designing a continuous puffing 
cannon.  It eliminated the batching of filling a retort, achieving
time/pressure/temperature/shooting requirements and then beginning
over.  He designed and prototyped a continuous (analogous to a 
revolver) system that had multiple chambers that acted as a retort.
At the appropriate time the revolving retort reached the firing 
chamber and that batch was shot through the puffing barrel.  This 
achieved tremendous production levels permitting Post/GF to private
label puffed rice and puffed wheat to many chain stores such as IGA,
Kroger, etc, resulting in considerable profit for the company.

The reason I stated that it is nearly impossibe to to this at home
is because of the extremely high temperature need for superheated,
dry steam, and the very explosive nature of the puffing gun.

The only thing I can relate this to would be to using a pressure
cooker and removing the lid instantly without a cool-down period.
The result can be disastrous as with any steam explosion.

Another way to think about it is as though you put a quart of
popcorn in a vessel, turned up the heat and pressure and every
kernel popping at one time.  The resulting energy output can
be extremely explosive and dangerous.

Arnie Skurow
Organization: Masters student, English, Carnegie Mellon, Pittsburgh, PA