CA2000753C - Process for producing instantized parboiled rice - Google Patents

Abstract

A process is described to provide an improved instantized parboiled rice that maintains the texture, appearance and flavor characteristics of eating quality parboiled finished rice product.

Description

2C~00753 i Case 3655 CIP-l -A PROCESS FOR PRODUCING INSTANTIZED

2 PARBOIT~n RI~T' 4 TECHNICAL FIFTn This invention relates to a process for producing an 6 improved instantized parboiled rice by incorporating specific amounts of water into long grain milled 8 parboiled rice, reducing the water content over a period of time to obtain a testure having a specific range of a 10 shear press value to provide an instantized product capab'e on rehydration to produce a rice product having 12 the testure, appearance and flavor characteristics of eating quality parboiled rice.

BACKGROUND OF THT` INV~NTION
16 Parboiled rice is preferred over white rice by many consumers for its testure, appearance, flavor, aroma, and 18 recipe tolerance. However, due to the pretreatment of the rice in the paddy form which produces parboiled rice, 20 the grain is rendered longer-cooking than milled white rice. Most parboiled rice of commerce calls for 22 immersion-cooking of at least 20 minutes in boiling water to prepare the parboiled rice to the desired edibility.
24 During the process of converting rough rice to parboiled rice, the paddy is soaked, steamed, dried, and then 26 milled. It appears that the heat treatment involved in 2~007S3 this processing reduces product rehydratability and 2 renders it harder and longer to cook.
Many attempts have been made to produce an 4 instantized parboiled rice having the texture, appearance and flavor characteristics of eating quality parboiled 6 rice but success has not been completely achieved. In U.S. Patent No. 2,720,460 entitled ~Production of 8 Quick-Cooking Rice~ techniques are described for producing instantized rice by hydrating rice grains in 10 stages but did not consider parboiled rice as the starting material. U.S. Patent No. 2,438,939 entitled 12 ~Quick Cooking Rice And Process For Making Same~
describes a milled rice (not parboiled) cooked in boiling 14 water until its starch is substantially gelatinized and its moisture content is raised to about 65-70%, cooled 16 and quick dried by removing moisture from its surface at a rate sufficiently faster than it can diffuse thereto 18 from their interiors at 140C for 10 to 15 minutes.
Another U.S. Patent No. 3,408,202 entitled ~Process For 20 Preparing A Quick-Cooking Rice~ prepares a quick cook rice by soaking parboiled rice in water below its 22 gelatinized temperature 160F to increase its moisture content to 15-50%, steaming the rice to temperatures of 24 180-212F, reimmersing the rice in water below 160F, steamed again and reimmersed again and then dehydrating 26 the cooked rice. This multiple step process is time consuming and complicated. U.S. Patent No. 2,903,360 28 entitled ~Method Of Making Quick-Cooking Cereals From Parboiled Grains~ soaks parboiled rice in water for 2 to 30 5 hours at temperatures between about 50F and 82F to a moisture content between 45 and 55% compared to 32 temperatures between about 130F to 160F to a moisture content between 65% and 77%. The rice is then boiled in 34 water for about 2 to 5 minutes, separating the boiled grains from the boiling water, spraying the grains with cold water to about 130F, squeezing the cooled grains to 2 1/3 to 1/5 their thickness, washing and drying the grains. This multiple step process is also time 4 consuming and complicated. Finally, U.S. Patent No. 4,361,593 entitled ~Process For Preparing Dry 6 Quick-Cooking Parboiled Rice And Product Thereof~
prepares dry parboiled rice by soaking rough rice in 8 water to increase the moisture content to 30 to 45~ by weight without effecting substantial gelatinization, 10 steaming the hydrated rice under conditions effective to partially gelatinize the starch granules, tempering the 12 partially-gelatinized rice at temperaturs below the gelatinization temperature of the starch while 14 maintaining the level of moisture above 20%, drying the rice to a moisture content less than 15% and milling the 16 rice. This process occurs within the hull of the rice.
Other references are known to produce quick-cooking rice 18 but no references are known which describe the process of this invention relating to the production of an 20 instantized parboiled rice which i8 unigue in its operation to provide an outstanding quality product 22 having the testure, appearance and flavor characteristics of eatinq quality parboiled rice finished product.

SUMM~RY OF T~ I..v~ ION
26 The present invention provideæ a process for making an improved instantized parboiled rice which comprises 28 incorporating about 68 to about 78% of water into long grain milled parboiled rice which has been substantially 30 gela~inized. The resulting product is carefully dried to reduce the water content of the rice to about 6 to about 32 14% over a period of time to obtain a rice having a testure with a shear press value in the range from about 34 60 to below 85 lbs/force, preferably about 64 to about 74 lbs/force, and having a 4~ to 7~ minute stand when an 2~0075:~

equal volume of rice is combined with an equal volume of 2 boiling water to produce an instantized eating quality finished rice product.

D~TAIT~n DF~CRIPTION OF THE INVFNTION
6 The starting rice material for this invention is a parboiled rice typically prepared by soaking rough rice 8 paddy (unmilled rice, substantially as it comes from the field) in cold, warm or hot water for a substantial 10 period of time, until the rice kernels have increased their moisture content, generally to at least above 20%;
12 steaming the rice, generally at super-atmospheric pressure to substantially gelatinize at least 85% and up 14 to 95 to 100% of the starch and the rice is dried and milled. This procedure ensures separateness of grain but 16 it is well known that parboiled rice requires increased cooking time to fully rehydrate the dry parboiled rice to 18 achieve a cooked product.
By this invention, long grain milled parboiled rice 20 substantially gelatinized, is esposed to water at temperatures from about 160F to 212F and higher by 22 soaking, immersion, steaming and the like for a period of time to increase the water content of the rice to about 24 68 to about 78% by weight, preferably about 72 to about 76%, of the total parboiled rice. When the water content 26 of the parboiled rice is achieved, the product is dehydrated using drying temperatures in the range from 28 about 260F to about 325F, preferably from about 260F
to about 305F over a period of time such as 30 to 30 50 mlnutes, preferably 44 to 48 minutes to reduce the water content of the rice to about 6 to about 14% by 32 weight, preferably about 7% to about 11%, to produce a rice having a testure with a shear press value in the 34 range from about 60 to below 85 lbs/force, preferably about 84 to about 74 lbs/force. This rice will have a 4 - 200075~

to 7~ minute stand preferably 5 minute stand which means 2 that when an equal volume of rice is combined with an equal volume of boiling water, the product produced is an 4 instantized eating quality finished parboiled rice product.

6 The ~long grain rice~ as used herein and known in the art, is defined as a rice which is long and slender in 8 shape, as much as 4 to 5 times as long as it is wide.
When cooked, the grains tend to separate and are light 10 and fluffy.
The drying procedure used to dehydrate the high water 12 containing rice is a long drying procedure when compared to the quick drying dehydrating procedure of regular 14 milled rice (not parboiled) normally taking 10 to 15 minutes.
16 The so called ~long drying~ technique of this invention is conducted to achieve specific testure with a 18 specific shear press value as described above.
U.S. Patent No. 2,972,884 issued February 28, 1961 20 describe a tenderness testing apparatus for food products. The apparatus and test has become known as 22 ~shear press~. This test involves the use of a standardized container and cell within which a suitable 24 quantity of product such as rice is placed and the product is penetrated by a multiple bladed ram. The ram 26 as it i8 passing through the material, operates to shear the individual particles or fibers. The force necessary 28 to produce penetration is considered a measure of the tenderness of the product. Under carefully controlled 30 cond~tion~, the numerical value of force or thrust for a given product has been found to have a good correlation 32 with tenderness. In the operation of the shear press test, especially for rice kernels, the rate at which the 34 blade assembly of the ram is driven through the cell bos is an important parameter which must be controlled if the -end result is to be accurate and reproducible. The force 2 applying mechanism used in this test is a hydraulic system operated under precise conditions.
4 The shear press value of the dehydrated long grain parboiled rice product is determined on an Allo-Kramer 6 Shear Press Model SP12 equipped with FTA-300 force transducer and a TG-4 (Food Technology Corp.) digital 8 testure gauge, as described in the accompanying drawing as follows: A hydraulic cyclinder 10 with a power 10 ram 11, containing a force transducer 12 and a blade assembly containing 10 equally placed blades attached as 12 vertical blades 14 is used which contact and completely penetrate the rice sample in the cell bos 15. The force 14 transducer 12 is connected to a digital testure gauge 13 to measure the force produced. A directional control 16 value 17 is set to activate the power ram 11 in the hydraulic cyclinder 10. A ram speed control value 16, 18 controls the speed of the power ram 11. A hydraulic pump and reservoir 18 is activated by the pump switch 19 to 20 supply the pressure to the hydraulic cyclinder 10. The pressure is read on the pressure guage 20 and can be 22 controlled by a pressure relief value 21.
The testure of the rice product is measured by the 24 shear press model in the following manner: The rice product, 131.1 grams, is covered by an egual volume of 26 boiling water (212F) with stirring. After 5 minutes of standing the water is drained for 30 seconds while the 28 blade assembly is mounted on the shear press and locked into position. The cell bos, cover and blades are 30 immersed in 75-85F water until required for use. AT the end of the drain period, the rice product is placed into 32 the cell bos and leveled without compressing the product. The cover is placed on the cell bos and 34 inserted into position under the blade assembly. The hydraulic pump is turned on and the direction control Z~00753 value is placed in the down position and the stroke time 2 of the power ram is 2 minutes, 30 seconds _10 seconds.
The digital testure guage, periodically standardized to 4 obtain the accurate reading, is read in terms of pounds/
force.
6 The cell bos is of sufficient size to hold 131 grams of rice which has been covered with an equal volume of 8 boiling water and after 5 minutes of standing, the water is drained for 30 seconds. After draining, the rice 10 product is placed into the cell bos and leveled without compressing the product. The cell bos or shear cell is 12 formed in three parts, a top plate, a bottom plate and a hollow body portion. The top and bottom plates are 14 slotted for receiving the 10 egually spaced blades passing through the rice being tested. The cell bos has 16 dimensions of 6.6 cm s 6.5 cm s 6.3 cm (volume =270.3 cm3) and made out a suitable material such as 18 stainless steel, mild steel or the like. The cell bos has guide slots on the upper and bottom sides of the cell 20 bos to receive the fingers or blades of the ram and esact alignment of the blade slots is essential so the blades 22 will pass through and penetrate the rice product.
The ollowing Esamples demonstrate the invention in 24 greater detail. It is understood that these Esamples are furnished only by way of illustration and not limitation.

FX~MPT.~ 1 28 Raw M~teri~l: Long grain milled parboiled rice substantially gelatinized.
30 - ~arboiled rice is metered into a flume tank at a rate of 750 lbs./hr. The water temperature is 205F, and 32 flume retention time is 15 seconds before the rice enters the front of the steamer (cooker). In the steamer, the 34 rice is cooked on a moving belt by means of topical water addition and steam addition from the top and bottom of - 2(~00753 the steamer belt (atmospheric pressure). The spray water 2 temperature is 195 to 205F at a rate of approsimately 175 pounds per hour and covers the entire rice bed. The 4 rice is cooked to the desired moisture (72-74~) with a retention time of 40 minutes in the 39 foot long, 6 foot 6 wide steamer. At the end of the steamer, the rice is flumed with unheated water (Masimum flume water 8 temp. 100F) to a drain belt. At the drain belt, the rice is spread evenly onto the drain belt and escess 10 surface water is dripped off before rice enters the dryer. The rice is evenly spread onto the dryer belt 12 with a bladed real (fluffer - like a lawn mower real).
Rice entering the drier is appro~imately 3/4 to 1 inch 14 deep on the belt. Retention time in the dryer is 40 minutes with varying temperatures in each of three 16 drying zones: Zone one 290 to 310F, zone two 290 to 310F and zone three at 130 to 145F. The rice esits the 18 dryer with a moisture content of 7 to 11%.

20 FINI~n PRODUCT:
This instanized rice product will have a shear press 22 value of 100 to 105 lbs/force at a 5 minute stand with egual volumes of rice and boiling water. The density of 24 the finished product in the dry form will be in the range of 400 to 475 grams per liter.
26 Thi~ superior rice product after rehydration for 5 minutes, will be smooth with separate kernels (not 28 sticky) and, will have a desirable chewy and rubbery testure. This product is firm and fluffy not mushy or 30 stic~y. The final eating moisture at a 5 minute stand is 67%.

ExAMpT~ ~
34 Raw Material: Long grain milled parboiled rice substantially gelatinized.

g - Parboiled rice is metered into a flume tank at a rate 2 of 750 lbs./hr. The water temperature is 205F, and flume retention time is 15 seconds before the rice enters 4 the front of the steamer (cooker). In the steamer the rice is cooked on a moving belt by means of topical water 6 addition and steam addition from the top and bottom of the steamer belt (atmospheric pressure). The spray water 8 temperature is 195 to 205F at a rate of approsimately 175 pounds per hour and covers the entire rice bed. The 10 rice is cooked to the desired moisture (72-74%) with a retention time of 40 minutes in the 39 foot long, 6 foot 12 wide steamer. At the end of the steamer, the rice is flumed with unheated water ~Masimum flume water 14 temp. 100F) to a drain belt. At the drain belt, the rice is spread evenly onto the drain belt and escess 16 surface water is dripped off before rice enters the dryer. The rice is evenly spread onto the dryer belt 18 with a bladed real (fluffer - like a lawn mower real).
Rice entering the drier is approsimately 3/4 to 1 inch 20 deep on the belt. Retention time in the dryer is 40 minutes with varying temperatures in each of three 22 drying zones: Zone one 290 to 310F, zone two 290 to 310F and zone three at 130 to 145F. The rice esits the 24 dryer with a moisture content of 7 to 11%.
The process can be altered to give a softer (less 26 firm) finished product that is still an escellent product after a 5 minute stand.
28 By means of a longer retention time in the steamer (45 minutes) the rice contains 76 to 78% moisture. The 30 dryi~g retention time is maintained from 30 to 35 minutes at temperatures in zone 1 at 260 to 285F; zone 2 at 260 32 to 285F and zone 3 at 130 to 140F. The rice esits the dryer at 7 to 11% moisture.

-FINISHED PRODUCT
2 This instantized rice product will have a shear press value of 85 to 90 lbs/force at a 5 minute stand with 4 equal volumes of rice and boiling water. The density of the finished product is slightly less than in Esample l;
6 in the range of 375 to 430 grams pre litre.
This product is still far superior to other instant 8 rice products. It is a softer (less firm) rice compared to Esample 1 product, but still has a firm, chewy, 10 rubbery testure. Separate kernels and fluffy rice are still maintained and there is a slightly higher moisture 12 content after a 5 minute stand (69%).

14 EX~PT~ 3 Raw Material: Long grain milled parboiled rice 16 substantially gelatinized.
- Parboiled rice is metered into a flume tank at a rate 18 of 750 lbs./hr. The water temperature is 205F, and flume retention time is 15 seconds before the rice enters 20 the front of the steamer (cooker). In the steamer the rice is cooked on a moving belt by means of topical water 22 addition and steam addition from the top and bottom of the steamer belt (atmospheric pressure). The spray water 24 temperature is 195 to 205F at a rate of approsimately 175 pounds per hour and covers the entire rice bed. The 26 rice is cooked to the desired moisture (72-74~) with a retention time of 40 minutes in the 39 foot long, 6 foot 28 wide steamer. At the end of the steamer, the rice is flumed with unheated water (Masimum flume water 30 temp. 100F) to a drain belt. At the drain belt, the rice is spread evenly onto the drain belt and escess 32 surface water is dripped off before rice enters the dryer. The rice is evenly spread onto the dryer belt 34 with a bladed real (fluffer - like a lawn mower real).
Rice entering the drier is approsimately 3/4 to 1 inch ZC~00753 _.

deep on the belt. Retention time in the dryer is 2 40 minutes with varying temperatures in each of three drying zones: Zone one 290 to 310F, zone two 290 to 4 310F and zone three at 130 to 145F. The rice esits the dryer with a moisture content of 7 to 11%.
6 The process can be altered to give a very soft rice.
This is achieved by over cooking the parboiled rice in 8 the steamer. A retention time of 50 minutes is used which increases the kernel moisture to 82% will give a 10 shear press value of 75 lbs/force. Therefore the rice is very soft and many kernels are split open. The rice is 12 more sticky and there are less separate kernels. Most of the desired testure characteristics are lost. It is less 14 chewy, less rubbery and somewhat mushy. The eating moisture content at a 5 minute stand is 72%.

~l~!IPT.F~ 4 18 Raw Material: Long grain milled parboiled rice substantially gelatinized.
20 - Parboiled rice is metered into a flume tank at a rate of 750 lbs./hr. The water temperature is 205F, and 22 flume retention time is 15 seconds before the rice enters the front of the steamer (cooker). In the steamer the 24 rice i8 cooked on a moving belt by means of topical water addition and steam addition from the top and bottom of 26 the steamer belt (atmospheric pressure). The spray water temperature is 195 to 205F at a rate of approsimately 28 175 pounds per hour and covers the entire rice bed. The rice is cooked to the desired moisture (72-74~) with a 30 retention time of 40 minutes in the 39 foot long, 6 foot wide steamer. At the end of the steamer, the rice is 32 flumed with unheated town water (Masimum flume water temp. 100F) to a drain belt. At the drain belt, the 34 rice is spread evenly onto the drain belt and escess surface water is dripped off before rice enters the 2~007S3 dryer. The rice iæ evenly spread onto the dryer belt 2 with a bladed real (fluffer - like a lawn mower real).
Rice entering the drier is approsimately 3~4 to 1 inch 4 deep on the belt. Retention time in the dryer is 40 minutes with varying temperatures in each of three 6 drying zones: Zone one 290 to 310F, zone two 290 to 310F and zone three at 130 to 145F. The rice esits the 8 dryer with a moisture content of 7 to 11%.
The process can be altered to make a very smooth and 10 firm desirable product which is ready in 7~ minutes, but not a S minute stand. The shear press value is 100 12 lbs/force. The rice is cooked in the steamer to a moisture of 72% at a 750 lbs/hr. infeed rate. The drying 14 iS conducted for a much longer time (56 minutes retention time in the dryer) at temperatures in the same ranqe as 16 Esample 2. A slower dryer belt speed is used and the bed depth used is about ~ inch thicker (1~ to 1~ inches 18 thick).
The density is 450 to S00 grams per liter. This 20 product is very smooth when rehydrated. It is firm and rubbery and has separate kernels. This is an e~cellant 22 product when rehydrated for a 7~ minute stand. It i8 too firm and dry in S minutes (65% eating moisture).

P~X~!IPT-P~ S
26 Raw Material: Long grain milled parboiled rice substantially gelatinized.
28 - Parboiled rice is metered into a flume tank at a rate of 780 lbs./hr. The water temperature is 205F, and 30 flume retention time is 15 seconds before the rice enters the front of the steamer (cooker). In the steamer the 32 rice is cooked on a moving belt by means of topical water addition and steam addition from the top and bottom of 34 the steamer belt (atmospheric pressure). The spray water temperature is 195 to 205F at a rate of approsimately r 20~Q753 175 pounds per hour and covers the entire rice bed. The 2 rice is cooked to the desired moisture ~74.5%) with a retention time of 45 minutes in the 39 foot long, 6 foot 4 wide steamer. At the end of the steamer, the rice is flumed with unheated town water (Masimum flume water 6 temp. 100F) to a drain belt. At the drain belt, the rice is spread evenly onto the drain belt and excess 8 surface water is dripped off before rice enters the dryer. The rice is evenly spread onto the dryer belt 10 with a bladed real (fluffer - like a lawn mower real).
Rice entering the drier is approximately 3/4 to 1 inch 12 deep on the belt. Retention time in the dryer is 40 minutes with varying temperatures in each of three 14 drying zones: Zone one 304F, zone two 262F and zone three at 144F. The rice exits the dryer with a moisture 16 content of 7 to 11%.

This instantized rice product will have a shear press 20 value of 60 to 69 lbs/force at a 5 minute stand with equal volumes of rice and boiling water.
22 This product is still superior to other instant rice products. It is a softer (less firm) rice compared to 24 Esample 1 product, but still has a firm, chewy, rubbery testure. Separate kernels and fluffy rice are still 26 maintained and there is a slightly higher moisture content after a 5 minute stand (69%).

Claims (7)

1. A process for producing an improved instantized parboiled rice which comprises incorporating about 68 to about 78% weight percent water into long grain milled parboiled rice in which the starch has been substantially gelatinized, drying said water-containing rice at temperatures from about 260°F to about 325°F to reduce the water content of said rice to about 6 to about 14%
over a period of time to obtain rice having a texture with a shear press value in the range from about 60 to below 85 lbs/force and having about a 4 to about 7 minute stand recipe when an equal volume of rice is combined with an equal volume of boiling water to produce an instantized eating quality parboiled finished rice product.

2. The process of claim 1 wherein the water incorporated into the long grain milled parboiled cell ranges from about 72 to about 76% weight percent.

3. The process of claim 1 wherein the water content of the long grain milled parboiled rice is reduced to about 7 to about 11 weight percent.

4. The process of claim 1 wherein said drying temperatures of said water-containing long grain milled parboiled rice are from about 260°F to about 305°F.

5. The process of claim 1 wherein the drying time ranges from about 40 to about 50 minutes.

6. The process of claim 1 wherein the shear press value ranges from about 64 to about 74 pounds per force.

7. The process of claim 1 wherein the instantized parboiled rice product has a 5 minute stand.