WO1994014340A1

WO1994014340A1 - Method for producing a precursor to an edible product

Info

Publication number: WO1994014340A1
Application number: PCT/AU1993/000653
Authority: WO
Inventors: Paul Geoffrey Greethead; Susan Lynda Greethead
Original assignee: Jamestown Holdings Pty Ltd
Current assignee: Jamestown Holdings Pty Ltd
Priority date: 1992-12-24
Filing date: 1993-12-14
Publication date: 1994-07-07
Anticipated expiration: 1995-06-24

Abstract

A method for producing a precursor to an edible product which comprises hydrating microporous cereal grain and equilibrating to a moisture content of about 18-80 weight %. The precursor cereal is suitable for producing quick cooking cereal and for producing chilled or frozen food products.

Description

METHOD FOR PRODUCING A PRECURSOR TO AN EDIBLE PRODUCT

Technical Field The present invention relates to processing of microporous cereal to produce a precursor for edible products and in particular relates to a process of preparing quick cooking cereal.

Background Art Cereal grain generally cooks from the outside of the grain, which is the first part of the grain to absorb moisture and is cooked when the centre of the grain becomes gelatinised. Considerable skill is required to prevent the exterior of the grain becoming sticky or overcooked, whilst waiting for the central part of the grain to be cooked.

Milled rice or conventional white rice is normally cooked by boiling in an excess of water, followed by draining before serving or by the absorption method of cooking, which is boiling in sufficient water such that substantially all of the water is absorbed at the end of cooking. The cooking time for both methods ranges from 15 to 20 minutes, depending upon the desired texture of the cooked rice.

Various processes have been developed to overcome or alleviate problems with cooking cereal. These include sequentially carrying out a number of steps selected from cooking, draining, granulating, drying, rolling, freezing, thawing and further drying. These processes tend to be expensive, since a high consumption of energy is involved in the cooking, drying and freezing steps. Moreover, the cooking step causes product loss and can generate objectionable processing effluent. A number of quick cooking rices produced using these methods generally have a poor cooked texture and appearance and can be different from regular cooked milled rice. Australian patent specification 532158 describes an apparatus and a method for producing quick cooking cereal by heat treatment to produce a microporous structure in the cereal grain. The microporous structure permits rapid penetration of water to the centre of the grain, decreasing cooking time and greatly reduces the tendency of the rice to become "sticky" during cooking.

The present invention concerns a method for producing a precursor to an edible product by processing microporous cereal. The present invention is particularly suitable for processing microporous un illed, milled or polished rice.

The present invention also concerns a method for producing quick cooking cereal by further processing of the precursor to produce quick cooking cereal, wherein the cooking time of the cereal is reduced to below 5 to 6 minutes or which offers at least a new and useful alternative.

The cooking of regular rice on an industrial scale for retail or food service production , is a very costly procedure and the manufacturer generally has specialised cooking equipment and water/sewerage treatment plant to handle the cook water. Due to high capital cost, many manufacturers do not have rice cooking equipment and therefore are excluded from processing rice into finished foods products which generally require only re-heating before they are ready to eat. The present invention further concerns a method for producing a chilled or frozen rice product which is ready to eat following re- heating in a conventional manner and which does not require cooking of the rice before chilling or freezing.

Disclosure of the Invention In a first aspect, the present invention provides a method for producing a precursor to an edible product which comprises hydrating microporous cereal grain and equilibrating to a moisture content of about 18-80 weight

In a second aspect, the present invention provides a method for producing quick cooking cereal which comprises heating the precursor cereal prepared according to the first aspect of the present invention such that there is substantial gelatinisation of the cereal.

Preferably, the cereal of the first and second aspects of the present invention is microporous rice.

In a third aspect, the present invention provides a method for producing a chilled or frozen rice containing product, which product when re-heated in a conventional manner is ready to eat, which comprises the step of chilling or freezing precursor rice grain prepared according to the first aspect of the present invention.

The precursor hydrated rice grain according to.,the first aspect of the present invention can be chilled or frozen separately or in combination with other edible products.

In a fourth aspect, the present invention provides quick cooking cereal product produced according to the second aspect of the present invention.

In a fifth aspect, the present invention provides chilled or frozen food product produced according to the third aspect of the present invention.

Preferably, the microporous rice is rice which has been made microporous by contacting with hot gases at a temperature of about 100-600° C for a short period of time, as described in Australian patent specification 532158, the subject matter of which is incorporated herein by reference. The rapid short duration heating of the rice causes water contained in the rice to be rapidly converted into steam and this renders the product microporous reducing the moisture content to about 2-7%.

According to the present invention, the microporous rice is hydrated with water to bring the moisture content of the rice to between 18-80%, preferably between 18-60% and more preferably to between 20-40% with a typical moisture content of about 30 weight %. Hydrating of the rice is preferably carried out by passing the rice through a water bath and then draining off excess water or by mixing water with the rice to achieve the desired moisture content. If a water bath is used, generally there are about 30 to 40 litres of water to 100kg of rice.

Hydration of the rice can also be conducted in stock or flavour solutions, such as wine and chicken stock, seafood stock, fried rice flavours or the like, so that the rice is fully or partially flavoured during hydration.

The hydrated microporous rice is then allowed to equilibrate, generally for a number of hours so that there is adequate hydrating of the rice grain, the water being preferably evenly distributed from the surface of the grain into the centre of the grain.

The rice can be made microporous in a number of ways, such as described in our Australian patent specification 532158, or by using any one of a variety of heat treatment processes known in the art of cereal treatment. These include production of microporous grain using fluidised bed heat exchanger, radiant heating tunnel, turbulent flow heating oven, rotary oven, suitable intensity of microwave energy, toroidal bed heat treatment where hot gas forms the support medium or by superheating under pressure followed by rapid expansion to atmospheric or lower pressures.

All of the above alternate methods of producing microporous grain can also be used to heat process the precursor grain according to the second aspect of the present invention.

The heating of the hydrated cereal according to the second aspect of the present invention can be carried out by contacting with hot gases at a temperature of about 100-600° C and preferably at about 400°-600° C. The heating is preferably carried out for a period of 10-20 seconds.

The skilled addressee would understand that different cereal grains gelatinise at different temperatures. The skilled addressee would further understand that the temperature at which the hydrated microporous cereal grain is heated to achieve substantial gelatinisation is dependent on volume of through-put through the heating apparatus, and is generally further dependent on the desired finished moisture and the desired texture of the cooked rice. For an out put of about 680kg/hr at approximately 6% moisture content, typically, the heating is carried out at about 510-570° C for approximately 12 seconds. If the temperature at which the cereal grain exit the heating apparatus is at least the same as or higher than the gelatinisation temperature of the cereal, this will ensure that the cereal is substantially gelatinised. Standard methods of gelatinisation determination such as the use of cross polarised light to examine the degree of birefringence present in a sample or staining with iodine and examining under light microscopy, can also be used to determine whether the cereal is substantially gelatinised.

The temperatures mentioned herein are .with reference to atmospheric pressure or normal operating pressure of the heating apparatus.

If the apparatus described in Australian patent specification 532158 is used to produce the microporous rice, then the hydrated and equilibrated rice can be contacted with hot gases by feeding it back into the same apparatus. The rapid short duration heating of the hydrated grain gelatinises most of the starch granules within the grain. The finished moisture content of rice processed in the manner described above typically ranges from 4-20%. The rice can then be dried to any moisture content as required by using any conventional drying method.

The rice produced according to the second aspect of the present invention can be cooked by a variety of cooking techniques in a very short period of time. These techniques range from pouring an excess of boiling water onto the rice and allowing it to stand in the water for 5-6 minutes; boiling in water for 1 minute and holding for 3 to 4 minutes; boiling in water for 2 to 4 minutes and holding for 1 to 2 minutes; or cooking in boiling water for 4 or 5 minutes. Cooking can be achieved by any conventional means such as by stove-top method, microwave cooking or the like.

Quick cooking milled rice produced according to the second aspect of the present invention generally has a density in the range of 0.25g/ml to 0.6g/ml and typically in the range of 0.36g/ml to 0.46g/ml.

Even though the second aspect of the invention has been described with respect to rice, it is to be understood that the second aspect of the present invention is equally applicable to the treatment of other grain such as barley, wheat, rye and the like to produce quick cooking cereal products. The present invention may be used to treat various kinds of rice including brown, long grain, short grain, medium grain, glutinous rice and rice brokens.

The precursor rice which is used in the third aspect of the present invention is rice which has preferably been hydrated to approximately 40-70%. This rice is then chilled or frozen and the chilled or frozen product can be re-heated in a number of conventional ways to provide a fully cooked ready to eat product. The quick cooking rice prepared according to the second aspect of the present invention can also be used to prepare the precursor rice according to the first aspect of the present invention. The precursor rice so produced and chilled or frozen according to the third aspect of the present invention can be re-heated in a number of conventional ways to provide a fully cooked ready to eat product.

The advantage of this type of application is that it allows manufacturers of food products to avoid cooking regular rice at their manufacturing site by allowing the manufacturer to simply hydrate microporous rice. The cooking of regular rice on an industrial scale for retail or food service production is a very costly procedure and the manufacturer generally has specialised cooking equipment and water/sewerage treatment plant to handle the cook water. Due to high capital cost, many manufacturers do not have rice cooking equipment and therefore are excluded from processing rice into finished foods products. According to the present invention, a manufacturer, who wishes to include rice in finished products, requires only a hydrating bath and since most of the water is absorbed by the rice, there is little or no water effluent. By hydrating microporous rice according to the present invention, a manufacturer is able, for example, to mix with or add to the hydrated rice, cooked or raw meats, seafood, vegetables or the like, fill into packs and chill or freeze the mixed or combined product. The hydrated rice can also be chilled or frozen separately and sold in combination with accompanying meat or vegetable packs or sold separately for purchase by the consumer according to need.

The chilled or frozen products in which meat or vegetable has been added to the rice before chilling or freezing or in which the rice is mixed with accompanying meat or vegetable or the combined products can be sold, for example as "frozen mushroom risotto", "frozen wine and seafood paella", "chilled mushroom risotto", "chilled wine and seafood paella" or other new or currently available chilled or frozen food products. These food products can be sold at retail level in microwave containers, 500g flexible packs etc. or in l-2kg packs for food caterers or can be packaged according to need. The consumer can then cook the product directly from the chilled or frozen form in a number of conventional ways, such as microwave, oven, stove-top, boil-in-the-bag, or the like. Foods packs in quantities for caterers can be heated in a bain marie system in a conventional manner. Re-heat times may vary from 2 minutes to 2 hours depending on the type of equipment used and the pack weight and the consumer would follow the instructions of the manufacturer in the usual way.

Specific embodiments of the present invention are illustrated by the following examples. It will be understood, however, that the invention is not confined to the specific limitations set forth in the examples.

Best Modes for Carrying Out the Invention

In the following examples "the furnace" refers to the apparatus disclosed in Australian patent 532158. The rice used is milled, long grain white jasmine rice originating from Thailand. Preparative Example 1

Milled long grain rice was contacted with hot gas from the furnace at a temperature of approximately 450° C for 12 seconds. The initial moisture content prior to treatment was 13 weight %. The treated rice had a moisture content of 6%. The density of the untreated material was 0.82g/ml and this was reduced to 0.42g/ml following treatment.

Preparative Example 2 Milled long grain rice was contacted with hot gas from the furnace at a temperature of approximately 450° C for 12 seconds. The initial moisture content prior to treatment was 13 weight %. The treated rice had a moisture content of 5%. The density of the untreated material was 0.82g/ml and this was reduced to 0.40- 0.42g/ml following treatment.

Preparative Example 3

Pearled barley was contacted with hot gas from the furnace at a temperature of approximately 500° C for 12 seconds. The initial moisture content prior to treatment was 13 weight %. The treated barley had a moisture content of 4%.

The density of the raw untreated pearled barley was 0.75g/ml-0.79g/ml. The bulk density of the processed microporous barley was 0.46g/ml-0.48g/ml.

Example 1

Step 1

The rice produced in preparative example 1 above was hydrated by soaking in a water bath for 5 minutes. The rice was then drained and allowed to equilibrate for 12 hours. After equilibration the average moisture content of the rice was between 30 and 40 weight %. Step 2 .

The hydrated and equilibrated rice was then contacted with hot gas from the furnace at a temperature of approximately 565° C for 12 seconds. (After hydration and equilibration the treated rice was soft and relatively fragile. To minimise damage and breakage of rice grains, a vibratory feeder was used to convey the rice into the heating apparatus) .

Step 3. The initial moisture content prior to heat treatment (step 2) was 30-40 weight % and the rice was fed into the furnace at a rate which resulted in an out put of about 680kg/hr. After the final heat treatment as described in step 2, the rice grains were found to vary in moisture content from 6 to 20%. The processed rice was allowed to equilibrate for 24 hours. An average moisture content of the rice after equilibration was 11-13%.

On exit from the heating apparatus, the rice density was found to be 0.4 to 0.36g/ml. Following final equilibration as described in step 3, density of the processed rice was 0.38g/ml.

Cooking

The rice so produced was found to be cooked after holding at boiling point for 1 minute, removing from heat and standing for 3 minutes. The rice was also cooked after holding at boiling point for 2 minutes, removing from heat and standing for 2 minutes. It was found that the rice could be cooked for up to 5 minutes before deterioration occurred.

Examples 2-13

In examples 2-13, the procedure of example 1 was repeated expect in step 1, the rice was allowed to equilibrate for 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 24 hours respectively. The resulting rice was similar to that obtained in example 1 and the cooking conditions were found to be the same as for the rice obtained in example 1.

Examples 14-15 In examples 14-15, the procedure of example 1 was repeated except that the rice was hydrated in a water bath for 10 and 15 minutes respectively.

The resulting rice was similar to that obtained in example 1 and the cooking conditions were found to be the same as for the rice obtained in example 1.

Example 16

Step 1.

The rice produced in preparative example 2 was hydrated by soaking in a water bath for 5 minutes. The rice was then drained and allowed to equilibrate for 12 hours. After equilibration the average moisture content of the rice was between 20-35 weight %.

Step 2.

The hydrated and equilibrated rice was then contacted with hot gas from the furnace at a temperature of 140° C for 12 seconds.

Step 3.

The initial moisture content prior to heat treatment (step 2) was 20-35 weight % and the rice was fed into the furnace at a rate which resulted in an out put of about 6l5kg/hr. After the final heat treatment as described in step 2, the rice grains were found to be approximately 15-18% in moisture.

The bulk density of the rice at exit from step 2 heat treatment was 0.67g/ml-0.70g/ml.

The grains were then dried to a moisture content of 12% by passing ambient temperature air through the rice.

Cooking

The rice so produced was found to be cooked after holding at boiling point for 4 minutes, removing from heat and standing for 1 minute or by holding at boiling point for 5 minutes.

Example 17

Example 16 was repeated except at step 2 the hydrated rice was contacted with hot gas from the furnace at a temperature of 100° C.

The resulting rice was similar to that obtained in example 16 and the cooking conditions were found to be the same as for the rice obtained in example 16.

Example 18 The process of example 16 was repeated except that in step 2 the hydrated rice was heated at a temperature of 150° C.

Example 19

The procedure for example 16 was repeated except in step 1 the rice was hydrated by soaking in a water bath for 1 minute.

Example 20

Step 1. The barley produced in preparative example 3 was hydrated by soaking in a water bath for 60 minutes. The barley was then drained and allowed to equilibrate for 1-12 hours. After equilibration the average moisture content of the barley was between 20 and 35 weight %.

Step 2.

The hydrated and equilibrated barley was then contacted with hot gas from the furnace at a temperature of 485° C for 12 seconds.

The initial moisture content prior to heat treatment (step 2) was 20-35 weight % and the rice was fed into the furnace at a rate which resulted in an out put of about 680kg/hr. After final heat treatment as described in step 2, the barley grains were found to be 4 to 8% in moisture.

Bulk density of processed barley at finish of step 2 was 0.40g/ml-0.46g/ml.

On exit from the heating apparatus (step 2) the barley was passed through rollers to slightly crack or disrupt the surface of the grain.

The barley so produced was found to be cooked after holding at boiling point for 2 minutes, removing from heat and standing for 2 minutes.

Examples 21 to 25

The procedure of example 20 was repeated except at step 1, the barely was soaked in a water bath for 15, 20, 25, 30 and 40 minutes respectively.

The resulting barley was similar to that obtained in example 20 and the cooking conditions were found to be the same as for the barley obtained in example 20. Examples 26 -28

Example 20 was repeated but at step 2 the temperature of the furnace was varied to 490°C, 495°C, 500°C respectively.

The resulting barley was similar to that obtained in example 20 and the cooking conditions were found to be the same as for the barley obtained in example 20.

Example 29

The rice produced in preparative example 1 was hydrated by soaking in a water bath to reach the moisture content of approximately 67%. The rice was then frozen into 500g packs.

Re-heating

The frozen pack contents placed in a microwave dish with cover, in a microwave (750 watt) and heated on high for 9-10 minutes were found to be ready to eat.

Example 30

The rice as produced according to example 1, steps 1 to 3 above was hydrated by soaking in a water bath to reach a moisture content of approximately 60%. The rice was then frozen into 500g packs.

Re-heating

The frozen pack contents when heated as in example 29 but for 7 minutes, were found to be ready to eat.

Example 31

The rice produced in preparative example 1 was hydrated by soaking in a water bath to reach the moisture content of approximately 67%. The rice was then chilled in 500g packs.

Re-heating

The chilled pack contents placed in a microwave dish with cover, in a microwave (750 watt) and heated on high for 3 minutes were found to be ready to eat.

Example 32

The rice as produced according to example 1, steps 1 to 3 above was hydrated by soaking in a water bath to reach a moisture content of approximately 60%. The rice was then chilled in 500g packs.

Re-heating

The chilled pack contents when heated as in example 29 but for 2 minutes, were found to be ready to eat.

The rice and barley from all of the above examples when cooked or re-heated were similar to normal cooked rice or barley. The grains had good texture, were free flowing and no stickiness was observed. The grains were also not broken.

The rice from example 1 was tested by examining a few grains using light microscopy. Unstained and iodine stained grains were examined. The examinations showed total gelatinisation except for a small band of partially gelatinised starch - about 50μm wide, at the outer edge of the grain. Loss of birefringence was also observed under polarised light.

Claims

CLAIMS :

1. A method for producing a precursor to an edible product which comprises hydrating microporous cereal grain and equilibrating to a moisture content of about 18-80 weight %.

2. A method according to claim 1 wherein the cereal is hydrated and equilibrated to a moisture content of about 20-60 weight %.

3. A method for producing quick cooking cereal which comprises heating the precursor cereal prepared according to claim 1 or 2 such that there is substantial gelatinisation of the cereal.

4. A method according to claim 3 wherein the precursor cereal is heated at a temperature of about 100°-600° C.

5. A method according to claim 4 wherein the precursor cereal is heated at a temperature of about 400°-600° C.

6. A method according to claim 3, 4 or 5 wherein the precursor cereal is heated for a period of about 10-

20 seconds.

7. A method according to claim 6 wherein the precursor cereal is heated for a period of about 12 seconds.

8. A method according to any one of claims 1-7 wherein the cereal is rice.

9. Quick cooking cereal prepared according to any one of claims 3-8.

10. Quick cooking rice prepared according to any one of claims 3-7.

11. A method for producing chilled or frozen rice containing product, which product when re-heated in a conventional manner is ready to eat, which comprises the step of chilling or freezing precursor rice grain prepared according to claim 1 or 2.

12. A method according to claim 11 wherein the precursor rice is flavoured.

13. A method according to claim 11 or 12 wherein other edible foods are added to or mixed with the precursor rice before chilling or freezing.

14. A chilled or frozen food product prepared according to claim 11, 12 or 13.

15. A method for producing quick cooking cereal which comprises (i) hydrating microporous cereal grain and equilibrating to a moisture content of about

30-40 weight %; and (ii) heating the hydrated cereal by contacting with hot gases at a temperature of between 510°-570° C for a period of 10-12 seconds such that there is substantial gelatinisation of the cereal.

16. A method according to claim 15 wherein the cereal is rice.

17. Quick cooking cereal prepared according to claim 15 or 16.

18. A method for producing a chilled or frozen rice containing product, which product when re-heated in a conventional manner is ready to eat, which comprises (i) hydrating microporous rice and equilibrating to a moisture content of about 40-70 weight %; and (ii) chilling or freezing the hydrated rice.

19. A method according to claim 18 wherein the rice is flavoured and is mixed with other foods before chilling or freezing.

20. A chilled or frozen food product prepared according to claim 18 or 19.

21. A method for processing microporous cereal substantially as herein described with reference to the examples.

22. A method for producing quick cooking cereal substantially as herein described with reference to examples 1-28.

23. Quick cooking cereal produced according to any one of examples 1-28.

24. A method for producing frozen rice containing product, which product when re-heated in a conventional manner is ready to eat substantially as herein described with reference to examples 29 or 30.

25. A frozen rice containing product prepared according to examples 29 or 30.

26. A method for producing chilled rice containing product, which product when re-heated in a conventional manner is ready to eat substantially as herein described with reference to examples 31 or 32.

27. A chilled rice containing product prepared according to examoles 31 cr 32.