Process of manufacturing a starch-based food product

A rice or other starch based product is provided which is manufactured from either broken rice or whole rice which is first ground and then pressure-formed into rice-shaped pieces. The pressure formed pieces are then heated by exposing them to saturated steam at a super atmospheric pressure above 0.5 psig in an autoclave for a sufficient time to gelatinize a major portion of the starch. After further processing, the rice pieces can be reconstituted by a consumer for consumption.

In the rice industry, after the rice is harvested and is being prepared for 
processing and packaging, many of the rice kernels are broken or otherwise 
damaged. It has been common practice to separate the good rice kernels 
from the brokens. The brokens are then sold as rice brokens or brewers 
grits which bring substantially lower prices than whole kernel rice. 
Brokens are then used for purposes other than providing consumable rice, 
such as brewing or rice flour. It would be desirable then to provide a 
process for utilizing these brokens to upgrade their value. 
The present invention provides a rice or other starch based product and a 
method of manufacture which can utilize rice brokens and make a rice 
product which is almost identical in appearance and taste of whole kernel 
rice. It has been found that by practicing the present invention, a rice 
product can be provided which is equal to and in some regards better than 
whole kernel rice while still being economical to produce and sell. One 
advantage provided by the present invention is that the final product is 
quick cooking, similar to those products referred to as "instant rice". 
The processing of rice brokens is discussed in U.S. Pat. No. 3,071,471. In 
this patent, rice is first crushed to a size of 1/64 to 3/32 of an inch, 
after which the crushed rice is extruded and cut to form rice-like pieces. 
Prior to extruding, the pieces are steamed apparently to facilitate 
extruding. After extrusion, the formed pieces are dried before packaging. 
The product produced by such a process has attendant problems typical of 
which are: pasty, non-rice texture (poor eating quality), lack of cooking 
or steam-table tolerance and inconvenient preparation, requiring special 
utensils (e.g. "vaporizer") not normally found in a kitchen. 
The present invention so far as it relates to rice provides a rice product 
and a process of manufacture which overcome the problems attendant with 
the use of processes such as that disclosed in the cited patent. The rice 
product unexpectedly has fast cooking properties and steam-table 
tolerance. The process also produces a rice product which has the 
following advantages: rice-like texture which can be controlled to 
simulate any type of rice, e.g. long grain, parboiled or short grain; 
excellent steam-table tolerance equivalent to parboiled, rice; and 
convenient, one-step preparation, add to boiling water and let stand for 
10 minutes. 
The process was designed for utilizing rice brokens and other rice bits 
which heretofore have been sold at substantially reduced prices as they 
were not considered consumable since they were broken. Further, the 
process is adaptable to high, starch-containing blends and other cereal 
grains. However, for the sake of expedience, the term "rice" will be used 
hereinafter and is to be construed to mean rice (long, medium and short 
grain), wheat, corn (both white and yellow), millet, oats, triticale, 
barley, rye, sorghum (milo), and starch-based products such as potatoes 
and cassava, or mixtures of the above etc. 
OBJECT OF THE PRESENT INVENTION 
A principal object of the present invention is to provide a process for 
utilizing rice brokens or whole kernels to produce a rice product of 
higher value without loss of nutrients. Another object of the present 
invention is to provide a rice product which is fast cooking, convenient, 
and tolerant to variations in home preparation. Another object of the 
present invention is to provide a rice product which has good steam-table 
tolerance which will permit being held long periods of time before 
consumption with minimal deleterious effects on the product. A still 
further object of the present invention is to provide a process which is 
straighforward and can utilize exiting manufacturing equipment. 
Other objects and advantages of the present invention will become apparent 
from the following detailed description taken in connection with the 
accompanying drawings wherein are set forth, by way of illustration and 
example, certain embodiments of the present invention. 
DETAILED DESCRIPTION OF INVENTION 
Rice brokens or whole kernel rice or both, are used as a starting material. 
Product color is primarily a result of the color of the starting material. 
The preferred starting material should be cleaned and polished to meet 
standards for U.S. No. 1 grade or rice as identified in USDA standards 
.sctn.68.310, 68.311, 68.312, 68.313. 
The term "rice" will be used hereinafter for simplicity. However, it is to 
be understood that the present invention is applicable to any ground or 
comminuted material so long as it contains starch in a quantity of at 
least about 20% by weight, on a dry basis of starch plus filler, if 
desired, (hereinafter flour), preferably at least about 50% starch and 
more preferably at least about 70% starch. The filler can be any 
compatible, edible material such as cellulose, protein, bran, gums, or 
combinations thereof, or other ground, edible material or materials mixed 
with the starch to form a mixtures of material hereinafter referred to as 
flour. Starch without filler can also be used as the flour. 
It is preferred in order to obtain the flavor of a starting grain that the 
flour be a majority by weight of the characterizing grain or starch 
product. More preferably more than about 75% and most preferably more than 
about 90% by weight. 
The rice is ground sufficiently to provide ease of extrudability and the 
desired texture. Preferably, it is ground to produce a flour finer than 
150.mu. (ASTM 100 mesh); more preferably finer than 106.mu. (ASTM 140 
mesh); and most preferably finer than 75.mu. (ASTM 200 mesh) as analyzed 
by sifting a 25 gram sample for 3 minutes on an Alpine Model AJS 200 
Air-Jet Sieve. Fine grinding of the rice provides good textural quality, 
i.e. a non-gritty mouthfeel and helps improve down stream processing 
steps. Other grains or materials may not require such fine grinding, 
particularly softer grains such as wheat. An 850.mu. (ASTM 20 mesh) grind 
can be used for wheat. 
Grinding of rice can be accomplished by any suitable grinding process as is 
known in the art, and preferably, grinding is accomplished by impact 
milling followed by air classification to separate the flour from 
oversized material. The oversized material is recycled to the grinder for 
regrinding. Grinding of other grains can be done in a similar manner after 
removal of the desired amount of bran or outer layers. It is also possible 
to select products from commercial milling operations, such as wheat 
flour, samolina, rye flour, corn flour etc. 
After grinding, the flour is hydrated sufficiently to provide good 
pressure-forming characteristics preferably by pressure applied through 
extrusion, molding etc. The flour is hydrated to form a blend of flour and 
water in a suitable manner whereby the blend has a moisture content in the 
range of between about 20% and about 40%, more preferably between about 
27% and 36%, and most preferably in the range of between about 29% and 31% 
by weight of blend. The water is absorbed into the flour particles so that 
the mixture is formable. The hydration can be by any suitable method. 
Preferably, hydration is conducted in a continuous mixer by metering a 
controlled amount of water into a controlled amount of flour. Elevated 
temperatures enhance the forming and stability of the blend in the forming 
step where hydration is a result of starch granules by increased 
temperature. It is preferred that the temperature during hydration be 
between about 120.degree. F. and about 275.degree. F.; more preferable 
between about 140.degree. F. and about 200.degree. F.; and most preferable 
between about 150.degree. F. and about 170.degree. F. Lower temperatures 
can be used for some grains e.g. ambient (70.degree. F.) to 120.degree. F. 
can be used and is particularly useful for wheat hydration. These lower 
temperatures can be used for those grains which have functional protein 
which hydrates to enhance product formation and structure, thus making the 
higher temperatures required for swelling of starch unnecessary and often 
undesirable. Such temperatures, if desired, should be kept below the 
temperature which would result in protein denaturation, reducing its 
desired hydration capacity. 
It is to be understood that the water and flour can be mixed and 
subsequently heated as, for example, in the extruder to simplify the 
hydration step. 
Prior to hydration, processing aids and additives can be added to the flour 
or the blend. For example, substances such as monoglycerides, 
diglycerides, mono/diglycerides, stearic acid, citric acid or titanium 
dioxide can be added to the flour before the water addition to improve the 
properties of the product as, for example, lightness or translucency. 
Also, reducing agents can be added to the water such as sodium bisulfite 
which would help inhibit browning in subsequent processing. Also, 
nutritional additives can be added to the flour or water prior to 
extrusion so that the nutrients are intimately interspersed within the 
rice product. Typical nutrients added to cereal grains include vitamins 
and minerals such as: thiamin, riboflavin, niacin, iron and calcium. 
Riboflavin and calcium are not presently added to enriched rice because 
they detract from its appearance. Furthermore, the washing step commonly 
used in rice preparation removes a large amount of the enrichment. This 
invention overcomes both of these shortcomings. 
After hydration, the blend is pressure-formed into integral particles of a 
desired shape. Extrusion or other types of molding can be used. Extrusion 
is preferred to form discrete segments, particles, or granules which can 
be made to resemble whole kernel product. It is preferred that the 
extrusion be done in a screw extruder which provides good blend mixing. 
Extrusion pressure preferably is in the range of between about 400 psi and 
about 1800 psi; preferably in the range of between about 600 psi and 1200 
psi; and most preferably in the range of between about 900 psi and 1100 
psi. 
The blend can be heated to help hydration. This can be done during the 
hydration step and/or in the extruder. The temperature of the water/flour 
mixture in the extruder should be in the range of between about 
130.degree. F. and about 200.degree. F.; preferably between about 
140.degree. F. and about 180.degree. F.; and most preferably between about 
155.degree. F. and about 170.degree. F. Lower temperatures can be used for 
some grains as in the initial above described hydration. 
The pressurized flour/water mixture can be extruded through a die plate and 
cut upon exiting from openings in the die plate. For forming rice shaped 
pieces it is preferred that the die openings be oblong, i.e. the minor 
axis of the grains are in the direction of extrusion. This has been found 
to form a more whole kernel appearing product. 
The rice shaped products have been formed using a standard DeMaCo S-25 
laboratory extruder with a 440 c stainless steel die plate containing 18 
die holes. The inserts are made of Delrin A/F. Each orifice has a major 
axis dimension of 0.281" and a minor axis of 0.063". Orifice lengths and 
entrance geometry are varied to equalize linear flow rates at each 
position on the die face to produce a uniform piece size. The piece cutter 
is a high speed rotary knife adjusted to cut each piece approximately 
0.063" long. The piece length at each orifice can be changed by die 
geometry to simulate the natural variation in grain size. Other die sizes 
and shapes can be used depending on the desired end product. Pasta making 
equipment can be used to produce a variety of pasta type products. Also, 
product can be made in larger sizes and different shapes. 
The blend in the extruder is treated as a pseudo plastic fluid with a flow 
consistency between 3 and 8 lb in.sup.2 /min.; more preferably between 4 
to 7.5 lb in.sup.2 /min.; and most preferably between 5.8 to 7.5 lb 
in.sup.2 /min. The extrusion rate is important and will be determined by 
flow consistency of the blend and the extruder design, operating 
conditions, and die geometry. 
After forming into granules or other suitable particles, processing aids 
can be applied to the granules to help downstream processing steps. For 
example, the formed granules can be coated with an emulsifier such as a 
distilled mono/diglyceride to decrease surface stickiness and enhance 
texture. Such emulsifiers can be applied in a quantity in the range of 
between about 0.025% and about 0.2% by weight of final product by spraying 
a dilute dispersion of distilled mono/diglyceride in water onto the formed 
granules. The emulsifier, such as a mono/diglyceride, can complex with a 
starch during subsequent processing steps to help reduce stickiness etc. 
Other processing aids, such as edible oils, lecithin, or emulifiers can be 
used as is desired. 
The formed granules are then subjected to a heating step. Heating is 
conducted under conditions to substantially, and preferably, to completely 
and uniformly gelatinize the starch in the granules with minimal or no 
degradation of the starch. Puffing in rice should be avoided. Preferably, 
the heating step is conducted such that there will be minimal or no 
moisture loss from the granules to give the desired density and 
compactness. The formed granules have moisture content within the ranges 
as described above for the hydrated flour. The heating step molds the 
structure of the formed granules and, if used, can react applied 
emulsifier with the starch. 
Preferably, the heating step is an autoclaving step wherein the granules 
are exposed to steam at super atmospheric pressure. Preferably, the 
environment is saturated steam in the range of between about 0.5 psig and 
75 psig, more preferably between about 3 psig and 35 psig, and most 
preferably about 5 psig and 20 psig. The time of exposure for heating is 
generally inversely related to the temperature and pressure of the heating 
step, i.e. the higher the temperature or pressure, the lower the required 
time. If the granules are left in too long a period of time, they will 
have a tendency to brown which is a Maillard browning reaction. If left in 
too short of time, the product will become grainy or chalky in texture and 
have poor integrity. It is preferred that the time of heating be in the 
range of between about 1 minutes to 30 minutes; more preferably in the 
range of between about 3 minutes and about 15 minutes; and most preferably 
in the range of between about 4 minutes and 12 minutes. 
The temperature and presssure of saturated steam are directly related (see 
"Thermodynamic Properties of Steam", by Keenan & Keyes, 1936). 
Although not being bound by the following theory it is provided in order to 
better understand the invention. At atmospheric steam pressue (212.degree. 
F.) it is not possible to obtain the desired degree of gelatinization no 
matter how long the product is held, hence this product would have the 
same characteristics as the "short time" product described above. Results 
of excessive pressures are not entirely the same as excessive time. Excess 
pressure causes cell disruption and starch degradation which is 
characterized by stickiness and solubilization. The extent of this problem 
is related to the time at the high pressure, e.g. the logical approach of 
high steam pressure for a very short time can result in a product with a 
sticky, degraded surface and an underprocessed "short time" type of 
center. Such a product might not be undesirable if one wants a sticky 
"Japanese" style rice. 
Preferably the heating is done in an autoclave. When the granules have been 
sufficiently heated to the desired degree of gelatinization of at least 
about 60% preferably at least about 80% and more preferably at least about 
95% (as measured by X-ray diffraction), it is preferred that their 
moisture content be within the ranges as described above for the hydrated 
flour. 
The formed granules can also be heated in a multiple stage process. It has 
been observed that the granules tend to become somewhat sticky during the 
autoclaving step. If this step is preceded by a preheating step with steam 
at sub-atmospheric or atmospheric pressure, the stickiness is 
substantially decreased. The two-stage process also seems to increase the 
tolerance of the product to autoclaving, resulting in a more uniform cook 
in the finished product. The preheating is conducted at a temperature 
above the gelatinization temperature and preferably above about 
180.degree. F. and most preferably at about 212.degree. F. (i.e. at 
atmospheric pressure). This initial heating step is of some benefit 
regardless of the heating time; however, maximum benefit seems to require 
a heating time above about 5 minutes for rice-sized granules. 
While the product is normally dried to produce a shelf stable product after 
the heating step described above, it is also possible to obtain an 
intermediate or full moisture product at this point of the process. 
A full moisture product would be obtained by adding back, after the heating 
step, sufficient water to obtain a normal cooked moisture content of about 
60% by weight (for long grain rice), and freezing or canning the finished 
product. 
Intermediate moisture products are defined as those between the moisture 
content of dry rice and full-moisture rice, or about 15% to about 55% 
moisture by weight. For this purpose, the product should have a water 
activity (A.sub.w) of less than 0.85, be sterilized and aseptically 
packed, or at least pasteurized and refrigerated. The A.sub.w can be kept 
to less than 0.85 either by reducing the final moisture content and/or by 
the addition of A.sub.w controls such as using glycerine to replace part 
of the water in the product formulation. 
Dry product is defined as having an A.sub.w of less than about 0.65. This 
is obtained by drying the granules after the previously-described heating 
step. A.sub.w is normally measured through an equilibrium-testing 
procedure. 
Preferably, the formed granules have a moisture content after drying in the 
range of between about 6% and 16% by weight; more preferably in the range 
of between about 8% and about 14%; and most preferably in the range of 
between about 10% and about 12%. Product can be dried in any suitable 
manner to remove undesired moisture such as in a continuous-heating oven 
and is done at an elevated temperature. Preferably, the drying temperature 
is in the range of between about 150.degree. F. and about 600.degree. F.; 
more preferably in the range of between about 250.degree. F. and about 
450.degree. F.; and most preferably in the range of between about 
300.degree. F. and about 400.degree. F. In the case of wheat pasta the 
drying temperature should be below about 300.degree. F. and preferably 
between about 150.degree. F. and 250.degree. F. The drying time is 
adjusted to obtain the desired product moisture level. The time of drying 
is related to temperature and air flow. The higher the temperature and/or 
air flow, the lower the required time. Typical drying times have been 
between 1 and 5 minutes at higher temperatures. At 150.degree. F. drying 
temperatures can be as long as 3 hours. 
Drying provides a formed granule which is easily rehydratable or 
reconstitutable and has a porous structure of good flavor and texture. 
Drying also enhances the stability of the formed granule. 
The drying condition can be adjusted from very high temperatures which puff 
the granules, to intermediate temperatures which neither puff nor shrink 
the granule, but provide a porous structure resulting from moisture loss, 
to low temperatures which allow the granule to shrink and result in a 
hard, non-porous, glassy structure. These differences control the rate of 
rehydration and can affect product texture. 
After drying, the formed granules are cooled. The cooling step can also be 
utilized to stop the drying action. Preferably, the product is cooled to 
room temperature. 
After cooling, the product can be bleached as is known in the art as, for 
example, using chlorine or peroxide. This will provide the desired degree 
of whiteness. Bleaching products is well known in the art as disclosed in 
Cereal Flours and Related Products, F.D.C. Regulations, Part 15. 
The above process can be modified to provide different types of end 
products, for example, rice bran can be added to the flour so that a quick 
cooking brown rice can be provided. Also, other flavors, filler, cereal 
grains or other products can be added prior to the extrusion step to 
provide homogeneous mixture and homogeneous end product. The present 
invention provides formed granules which are very close in appearance to 
the natural-occurring product, are quick cooking and pleasing in flavor. 
Also, surprisingly, it was found that rice product produced in accordance 
with the above disclosure was stable on a steam table for several hours, 
i.e., greater than 4 hours without the product becoming pasty. This could 
be due to the limitation of starch gelatinization by controlling the time 
and temperature or possibly available moisture. Further, by utilization of 
the above-described process, a product can be produced which has all the 
natural components of the natural product, or can have in addition thereto 
additional components which heretofore have not been successfully included 
in rice, other whole cereal grain, and starch-based products. 
The final product is characterized by: uniformity of components, i.e. less 
than about a 2% variation throughout the granules, exclusive of coating or 
other materials added after forming; the starch is the predominant binder 
in those products which have little or no functional protein, i.e. at 
least about 90% of the binding is due to starch; there is little or no 
starch degradation, i.e. there is less than about 5% degraded starch and 
preferably substantially no or no degraded starch; there is greater than 
about 95% gelatinization and preferably substantially complete 
gelatinization; and is a precooked, reconstitutable product.

The following are examples showing the operability of the present 
invention. 
EXAMPLE I 
1000 grams of vacuum-dried riced potato (80% starch on dry basis) was 
ground to a fine flour which was then hydrated to a moisture content of 
about 40%. This blend was extruded in a screw extruder barrel at 
120.degree. F. barrel temperature. The extrudate was cut into rice shaped 
granules. These granules were autoclaved for 3 minutes at 250.degree. F. 
(15 psig), after which they were dried for 1 minute at 400.degree. F. to a 
moisture content of 10% by weight. 
The dried granules were reconstituted by adding 40 grams of product to 1/3 
cup of boiling water and let stand for 10 minutes. The prepared product 
was judged to have good potato flavor and texture and was neither gummy 
nor sticky. 
EXAMPLE II 
Fine-ground rice flour was hydrated to a moisture content of 30% by weight. 
The hydrated flour was extruded in a pasta press which was at a 
temperature of 160.degree. F. The extrudate was cut into rice-sized 
pieces. These pieces were coated with a 4% monoglyceride in water 
dispersion to give a 0.1% level of monoglyceride on the rice pieces. The 
coated rice pieces were divided into three 1000 gm batches. 
These three batches were heated with saturated steam at 212.degree. F. for 
15 minutes, 30 minutes and 60 minutes, respectively. Each of the batches 
was dried at 400.degree. F. for 2 minutes. 
75 gms of each dried batch was added to 2/3 cup of boiling water and 
allowed to stand for 10 minutes. All reconstituted product was judged to 
be unacceptable because they were dry, rough and grainy in the mouth, and 
had raw starchy flavor. 
EXAMPLE III 
Rice flour was hydrated and extruded, as in Example II. However, the formed 
pieces were heated in an autoclave with saturated steam at 15 psig, at 
temperature of 250.degree. F. for 5 minutes. 
Upon removal from the autoclave, the rice pieces were loosely matted 
together. The pieces were allowed to cool and were separated. The 
separated pieces were dried at 400.degree. F. for 2 minutes. 
75 gms of pieces were added to 2/3 cup of boiling water and allowed to 
stand for 10 minutes. 
The reconstituted product was judged to have excellent texture and flavor. 
EXAMPLE IV 
Rice flour was hydrated and extruded as in Examples II and III. However, 
the formed pieces were preheated prior to autoclaving. 
The pieces were preheated with atmospheric steam (212.degree. F.) for 10 
minutes. They were then autoclaved at 10 psig (240.degree. F.) for 6 
minutes. The autoclaved product was only slightly adhered together, i.e. 
less than the product of Example III. 
The pieces were then dried at 400.degree. F. for 2 minutes. 
75 gms of product were added to 2/3 cup of boiling water and allowed to 
stand for 10 minutes. The product was judged to have excellent texture and 
flavor. 
EXAMPLE V 
1000 grams of yellow corn flour was hydrated to a moisture content of 32% 
by weight. The hydrated corn flour was extruded in a pasta press which was 
at a temperature of 165.degree. F. The extrudate was in the form of elbow 
macaroni. These elbows were autoclaved at 250.degree. F. for 5 minutes 
after which they were dried for 5 minutes at 275.degree. F. 
The dried "macaroni" was reconstituted by adding the product to boiling 
water and boiling for 15 minutes. The prepared product was judged to have 
a good corn flavor and a firm pasta texture. 
EXAMPLE VI 
White corn meal was ground to a fine flour which was then hydrated to a 
moisture content of 32% by weight. The hydrated white corn flour was 
extruded into macaroni elbows, autoclaved and dried as in Example V. 
The reconstituted "macaroni" was judged to have very good mild flavor and a 
firm texture. 
EXAMPLE VII 
A sample of pearl millet was debranned to remove 20 % bran and yield 80% 
millet. The debranned millet was ground to a fine flour which was then 
hydrated to a 31% moisture. The hydrated flour was extruded in a pasta 
press at a temperature of 160.degree. F. The extrudate was cut into rice 
shaped pieces. These pieces were autoclaved for 8 minutes at 240.degree. 
F., after which they were dried for 2 minutes at 400.degree. F. 
75 grams of the pieces were added to 2/3 cup of boiling water and allowed 
to stand for 10 minutes. 
The reconstituted product was judged to have a strong millet flavor with 
rice like soft texture. 
EXAMPLE VIII 
A sample of soft white wheat second clears flour was hydrated to a moisture 
of 32%. The hydrated flour was extruded in a pasta press which was at a 
temperature of 116.degree. F. The extrudate was in the form of elbow 
macaroni. The elbows were autoclaved for 10 minutes at 240.degree. F., 
after which they were dried for 3 hours at 150.degree. F. 
The dried elbows were reconstituted by adding to boiling water and boiling 
for 9 minutes. The elbows were drained and evaluated. They were judged to 
have good pasta flavor, "al dente" texture and deep yellow color. 
EXAMPLE IX 
A blend of 90% corn starch and 10% yellow corn flour was hydrated to a 
moisture of 32% moisture. The hydrated blend was extruded in a pasta press 
which was at a temperature of 165.degree. F. The extrudate was in the form 
of elbow macaroni. The elbows were autoclaved for 5 minutes at 250.degree. 
F., after which they were dried at 275.degree. F. for 5 minutes. 
The dried elbows were reconstituted by adding to boiling water and boiling 
for 12 minutes. The elbows were drained and evaluated; they were judged to 
have good mild flavor and pasta texture.