Reconstituted Cereal Grain

Abstract

A reconstituted cereal grain, wherein said grain comprises at least about 10 wt. % of pea fibre, at least about 25 wt. % of cereal starch in addition to said pea fibre, and at least about 0.5 wt. % emulsifier based on the dry weight of the grain; and wherein said grain has a product density of greater than about 1 kg/l. The grains have a natural appearance and cooking properties similar to parboiled milled cereal grains. Also provided are products comprising the grains.

Description

The present invention relates to high-fibre granular extruded products, in particular high-fibre rice products, and to methods of making such products.

As a staple food for nearly one-half of the world's population, rice is one of world's most important foodstuffs.

Edible rice is prepared firstly by milling the seeds of the rice plant to remove the chaff At this point, the product is called brown rice. White rice is then produced by continuing the milling process to remove the husk and the germ. The milling and polishing that converts brown rice to white rice produces a more palatable product, but significantly reduces its nutrient and vitamin content, and removes much of the dietary fibre. Milled white rice typically contains less than about 2 wt. % of dietary fibre on dry weight basis.

Dietary fibre is defined as food material, particularly plant material, that is not hydrolysed by enzymes secreted by the human digestive tract but that may be digested by microflora in gut. Plant compositions that fall within this definition include non-starch polysaccharides (NSP) such as celluloses, gums and pectin as well as lignin, resistant dextrins and resistant starches.

Extensive research has been carried out into the physiological effects of dietary fibre, which is associated with a number of health benefits. High fibre foods, because of their consistency, encourage mastication and stimulate the secretion of digestive juices. The soluble components of dietary fibre cause an increase in the viscosity of the stomach contents, thereby retarding gastric emptying. This then affects the rate of digestion and the uptake of nutrients and creates a feeling of satiety.

Soluble fibre has also been shown to lower selectively serum LDL cholesterol and to improve glucose metabolism and insulin response.

In the colon, dietary fibre tends to increase faecal bulking due to increased water retention and the insoluble dietary fibre reduces transit time. This is particularly important since the conversion of sterols to carcinogenic polycyclic aromatic hydrocarbons is known to occur with time. Epidemiological evidence suggests low faecal weights are associated with an increased risk of cancer of the colon. Dietary fibre may also bind toxins, bile acids and carcinogens. Inverse relationships between fibre intake and the incidence of obesity, heart disease, cancers (of the colon and breast), diabetes and gastrointestinal disorders have been reported. Dietary fibre may also be beneficial in weight reduction.

Brown rice contains a beneficial amount of dietary fibre in the bran layer. However, despite the associated health benefits of brown rice, milled white rice is still generally the more popular product. Certain characteristics of brown rice make it less appealing than white rice, including its darker colour, its longer cooking time, and its propensity to spoil more quickly than white rice due to fat-containing germ—which is removed when making white rice.

As an alternative to brown rice, a number of high-fibre products have been developed by coating processed white rice with dietary fibre.

JP 06-026507 discloses a processed polished rice processing method in which a water solution of one or more kinds of soluble dietary fibre such as guar gum, locust bean gum, tamarind gum and pectin is sprayed onto the surface of rice while it is being polished and then dried. JP 06-026507 discloses a process in which soluble dietary fibre is sprayed onto processed polished rice which is then boiled. During boiling, the soluble dietary fibre “melts” into the water and at the end of the cooking time has entered into the starch tissue of the rice. AU-A-2008335453 describes methods of coating powdered bran onto parboiled milled rice grains.

However, using coating methods to increase the fibre content has certain disadvantages. Rice is often washed with water before cooking, and during cooking is often boiled for up to half an hour. Both the washing and cooking stages can serve to remove or erode the high-fibre coating before it is consumed.

One approach to overcome the problems associated with using coatings is to prepare reconstituted rice kernels.

This approach has been used to incorporate vitamins and other nutrients into rice. FR-A-1530248 discloses fortified artificial kernels prepared from a mixture of semolina or flour and vitamins. The mixture is then formed into strands which are cut into rice-size pieces which are dried. The artificial kernels are mixed with natural grains in a 1:20 up to 1:1000 mixture. However, the artificial kernels often tend to disintegrate during cooking, thereby losing the vitamins to the cooking water and reducing the potential beneficial properties when the cooked rice is consumed.

The process disclosed in U.S. Pat. No. 5,609,896 uses extrusion to prepare artificial enriched rice kernels and overcomes the problems of cooking instability and subsequent vitamin loss by adding specific ingredients such as heat stabilising agents, binding agents and cross-linking agents. However, although the addition of these agents produces a more stable product, production times and costs are increased. Furthermore, such additives have been linked to allergenic reactions and have even been cited as being possible carcinogens.

WO-A-2005053433 describes processes for the preparation of enriched rice-like grains by extrusion of a mixture of rice flour or broken rice with water, one or more micronutrients such as vitamins, and an emulsifier, followed by drying. Similar products and processes are described in WO-A-2010/020640.

KR-A-20060120335 describes processes for the preparation of rice-like grains by extruding a mixture of rice flour and resistant starch, followed by drying. Fabricated rice-like grains are also described in U.S. Pat. No. 4,886,675, EP-A-1166648, EP-A-0277498 and U.S. Pat. No. 5,932,271.

WO2010/102521 describes forming reconstituted cereal grains from a multi-grain raw material that is ground and mixed with water, an emulsifier and further ingredients such as cellulose and nutrients, prior to extrusion.

CN-A-101869241 describes extruded cereal grains based on various kinds of flour, including rice flour, pearl barley, red bean or green bean flour. The grains may contain 0-12% of cellulose.

US 2004/109931 describes a reconstituted cereal grain formed from a dough that may contain 1-10% by weight (dry weight) of rice bran.

A need remains for providing an enhanced-fibre granular product which retains its stability and fibre-content whilst being washed and cooked, and also provide a palatable taste and texture when eaten. Preferably, the enhanced-fibre granular product is made via an inexpensive and simple process.

In a first aspect, the present invention provides a reconstituted cereal grain, wherein said grain comprises at least about 10 wt. % of pea fibre, at least about 25 wt. % of cereal starch in addition to said dietary fibre, and at least about 0.5 wt. % emulsifier based on the dry weight of the grain; and wherein said grain has a product density of greater than about 1 kg/l.

The term “reconstituted” signifies that the grains are not natural cereal kernels, but have been formed from a mixture or similar mixture of ingredients by a shaping process, in particular by extrusion. The grains may be of any shape. In embodiments they resemble or are substantially identical in appearance with, natural grain kernels, such as milled rice kernels or milled wheat kernels. Suitably, they are shaped to resemble closely milled rice kernels. That is to say, suitably they have a length of from about 5 mm to about 8 mm, a mid-section having a diameter of from about 1.5 mm to about 2.2 mm, said mid-section tapering to rounded or tapered ends of the kernel. In these embodiments the mid-section is substantially cylindrical, or it may be oval in cross section with an aspect ratio (maximum to minimum diameter) of less than about 1.5. In other embodiments, the grains may have a shape not found in nature, for example any of the fancy shapes such as star shapes, annular shapes or even alphabet shapes as known in the pasta art. Suitably, the cereal grain is a rice-like grain. That is to say, a grain having the dimensions of a parboiled milled rice such as long-grain rice. Suitably, the maximum dimension of each grain is from about 1 mm to about 10 mm, for example from about 2 mm to about 5 mm. Suitably, the grains of the invention are substantially homogeneous, i.e. the composition of the grain is substantially or completely uniform across the grain.

Products of the invention suitably have a product density greater than about 1 kg/liter, for example greater than about 1.1 kg/liter. Product density refers to the Archimedean density, i.e. the average density of the individual grains of the material. Thus, a product density greater than 1 kg/liter signifies that the grains will sink when placed in water. Products of the present invention may have a slightly lower product density than natural white rice due to the presence of the emulsifier.

It has been found that extruded rice grains according to the invention containing 10 wt. % or more of pea fibre can have very similar appearance and texture to natural white rice, but with a much higher dietary fibre content. The term “natural white rice” as used herein is defined white rice deriving from brown rice that has been parboiled and milled, but that has not in any way been reconstituted.

Furthermore, the extruded rice products according to the present invention may be cooked within 10 minutes, and the cooked product closely resembles the taste and texture of cooked parboiled milled rice. Thus, extruded rice products of the present invention provide similar or enhanced benefits relative to brown rice in terms of providing high dietary fibre content, but overcome its associated disadvantages—namely its less appealing darker colour and the inconvenience of its longer cooking time.

Furthermore, grain products of the present invention typically have a lower fat content (1.5-1.7%) than brown rice (about 3%). The higher fat content of brown rice compared with white rice leads to its greater propensity to spoil.

The present inventors have found that the use of pea fibre as the dietary fibre ingredient in the reconstituted grains is particularly advantageous because of the neutral colour and taste of the pea fibre and the outstanding texture of the resulting products after cooking.

Without wishing to be bound by theory, it is thought that the claimed combination of rice flour and emulsifier in the granular extruded products of the present invention provides a starch-emulsifier or protein-emulsifier network which helps to stabilise the integrity and shape of the product grains during cooking and enhance the texture and “bite” of the cooked product. The melting point of these complexes are in the range of 105-120° C., and therefore they do not melt under normal cooking conditions. This overcomes the problem that most reconstituted cereal grain compositions (unlike pasta) contain very little protein and therefore tend to disintegrate on cooking in excess water, especially if they contain high levels of dietary fiber.

Suitably, the product comprises from about 15 wt. % to about 35 wt. % of said pea fibre dietary fibre based on the dry weight of the grain, for example from about 20 wt. % to about 30 wt. %, more suitably about 20 wt. % to about 25 wt. % of said pea fibre dietary fibre based on the dry weight of the grain. The dietary fibre may be any food-acceptable dietary fibre such as cellulose fiber or hemicellulose fiber. A suitable cellulose/hemicellulose is pea fiber.

The maximum amount of the pea fibre dietary fibre in the products is determined by the feasibility of the handling and processing of the raw ingredients blend containing the dietary fiber, and by the appearance, taste and texture of the final extruded product and the cooked final extruded product.

The cereal starch is non-resistant starch present in addition to any resistant starch forming part of the dietary fiber component. The cereal starch may be any edible cereal starch, such as rice starch, wheat starch, or potato starch. Most suitably the cereal starch comprises rice starch. Suitably, the grain comprises from about 25 wt. % to about 73 wt. %, for example about 30 wt. % to about 60 wt. % of said cereal starch based on the dry weight of the grain, for example about 35 wt. % to about 50 wt. % of said cereal starch based on the dry weight of the grain. In embodiments, the products of the invention do not contain more than about 10 wt. % of wheat starch, more suitably they do not contain more than about 5 wt. % of wheat starch, i.e. they are not pasta products even though they can be made in a similar way to pasta.

Products of the present invention suitably comprise at least about 0.5 wt. % emulsifier based on the dry weight of the product. Suitably, about 0.5 wt. % to about 2 wt. % of emulsifier is included in the product. Suitably, the product of the present invention comprises from about 0.8 wt. % to about 1.2 wt. % of emulsifier based on the dry weight of the product. As explained above, the emulsifier is present to enhance the integrity and shape of the product grains during cooking, and could also enhance the “bite” of the cooked product.

The term “emulsifier” is used in its normal sense in food science. An emulsifier is a substance that forms or preserves an emulsion by increasing the compatibility of the contact surfaces of two components in a blend. Any food-acceptable emulsifier may be suitable for the present invention. For example, the emulsifier may be selected from the group consisting of phospholipids such as lecithin, enzyme digested lecithin/enzyme-treated lecithin, glycerin fatty acid esters (monoglyceride, MG), acetic acid esters of monoglycerides (acetylated monoglyceride, AMG), lactic acid esters of monoglycerides (lactylated monoglyceride, LMG), citric acid esters of monoglycerides (CMG), succinic acid esters of monoglycerides (SMG), diacetyl tartaric acid esters of monoglycerides (DATEM), polyglycerol esters of fatty acids (polyglycerol ester, PGE), polyglycerol polyricinoleate (PGPR), sorbitan esters of fatty acids (sorbitan ester, SOE), propylene glycol esters of fatty acids (PG ester, PGME), sucrose esters of fatty acids (sugar ester, SE) and calcium stearoyl di lactate (CSL).

Suitably, the products of the invention are substantially free of added protein, that is to say protein other than the protein inherently present in the cereal and dietary fiber ingredients. Suitably there is no more than 2 wt. % of added protein, more suitably no more than 1 wt. % on dry weight basis, and most suitably no added protein. Of course, some protein is normally inherently present in the cereal and dietary fibre ingredients. Accordingly, the grains of the present invention suitably comprise from about 1 wt. % to about 10 wt. % total protein, more suitably from about 2 wt. % to about 8 wt. % protein, for example about 4 wt. % to about 6 wt. % protein on a dry weight basis.

Suitably, the products of the invention are substantially free of added gelling agents, for example glutens, alginates, alginate derivatives, or gums. The present inventors have found that the products do not need such gelling agents to maintain excellent integrity during cooking and a firm texture after cooking. Suitably there is no more than 2 wt. % of added gelling agents, more suitably no more than 1 wt. % on dry weight basis, and most suitably no gelling agents other than those incidentally present in the other ingredients.

Suitably, the products of the invention are substantially or completely free of added dietary fibre components other than said pea fibre. In these embodiments the total dietary fibre content of the products consists of the pea fibre dietary fibre from the pea fibre ingredient, together with incidental amounts of dietary fibre that may be present in the other ingredients.

Preferred products of the invention include grains, suitably rice-like grains, comprising (all percentages except moisture being on dry-weight basis):

• 25-60 wt. %, suitably 30-50 wt. % cereal flour, preferably rice flour
• 35-70 wt. %, suitably 50-65 wt. % of a cellulose or hemicellulose fiber ingredient, preferably pea fiber; and
• 0.6-1.2 wt. % emulsifier.

In a second aspect, the present invention provides a cereal product comprising, consisting essentially of, or consisting of a plurality of reconstituted cereal grains according to the invention. For example, the product may consist of the grains according to the invention. Alternatively, the reconstituted grains of the invention may be admixed with natural grains such as milled parboiled cereal grains. Since the grains of the invention are not puffed or expanded to any significant degree, such products typically have a bulk density from about 600 g/l to about 900 g/l, preferably from about 750 g/l to about 850 g/l. Bulk density (also known as tap density) is the density of the whole granular material including the interstitial air between the grains.

The above product densities and bulk densities of the products are typical of dried parboiled milled cereal products that have not been puffed or expanded. The grains and products of the present invention are not puffed or expanded to any significant degree. Indeed, the process conditions are selected as described below to minimise puffing or expansion of the grains.

For example, the rice-like grains according to the present invention can be mixed with milled parboiled rice in a proportion by weight of from about 1% to about 99%, for example from about 10% to about 80%, such as from about 30% to about 70. It may be more economical to achieve a desired level of fibre content by mixing high-fibre grains according to the invention with conventional grains than by making a product entirely from grains according to the invention having the desired level of fibre.

Therefore, for economic reasons as well as technical reasons, it is desirable for the grains according to the invention to have the highest level of dietary fibre that is compatible with the manufacturing method and desired cooking properties and texture of the products. Accordingly, the grains of the invention suitably contain at least about 20 wt % of dietary fiber on a dry weight basis, for example at least about 25 wt. % of dietary fiber on a dry weight basis. Suitably, said total dietary fibre consists essentially of pea fiber. It has surprisingly been found that excellent cooking properties and bite can be achieved even at such high dietary fiber levels.

As noted above, the grains of the invention suitably have cooking properties substantially identical to natural milled parboiled kernels.

The products of the present invention are suitably made by extruding a mixture comprising a the pea fibre ingredient, a cereal flour, emulsifier and water through a suitable die plate, with a cutter to cut the extruded strands into grains. More complex extrusion methods could be used to make grains of different shapes. Heating and partial gelatinization of the starch in the mixture is performed in the extruder, or in a preconditioner. The extrusion process may be a “cooking extrusion”, sometimes referred to as “hot extrusion” method, or preferably it may be a “pasta extrusion”, sometimes referred to as “cold extrusion” process similar to pasta manufacture.

The strands exiting the extruder are cut into grains, for example pieces the size of rice grains, by a rotating knife or similar. It will be appreciated that grains in the form of any of the fancy shapes known in pasta manufacture can be prepared by extrusion. The so obtained grains are dried in a suitable dryer, such as a fluidized bed dryer or a belt dryer, to a moisture content of no more than about 15 wt. %, suitably 10-13 wt. %.

In the context of this invention, a “pea fibre ingredient” is defined as a product that contains pea fibre, but need not be entirely composed of pea fibre. For example, the commercially available pea fibre is 20-100 micrometer pea fiber from DPS/Dutch Protein Services having a maximum of 66% dietary fibre (AOAC991.43 dry basis).

Suitably, the cereal flour ingredient contains, consists essentially of, or consists of rice flour. Rice starch is the major component of natural white rice and usually forms 90-93% of the dry weight of the rice. Thus, rice starch is also a major component of rice flour. For example, commercially available rice flour Remyflo R7-250 contains a minimum of 85% rice starch (total weight basis).

In embodiments, the mixture consists essentially of, or consists of, the pea fibre ingredient, cereal flour, water and emulsifier.

In preferred embodiments of the invention, the mixture comprises, consists essentially of, or consists of the following components, based on the weight of the ingredients excluding added water:

• 25-60 wt. %, suitably 30-50 wt. % cereal flour, preferably rice flour
• 35-70 wt. %, suitably 50-65 wt. % of pea fiber; and
• 0.6-1.2 wt. % emulsifier.

Suitably, the above components make up at least about 90%, more suitably at least about 99 wt %, and most suitably substantially all of the ingredients other than water.

Any features or embodiments described herein in relation to any one aspect or embodiment of the invention may be used in relation to any other aspect or embodiment. In particular, any of the ingredients or methods described in relation to the methods of manufacture may be used to make the products according to the invention.

EXAMPLE

In these examples, rice-like granular extruded products were made by a pasta extrusion method according to the following formulation given in Table 1. The formulation contained rice flour (Remyflo R7-250), pea fibre (DPS/Dutch protein&Services) and emulsifier.

The Formulation 1 was mixed in lab batch mixtures.

processing of the formulations within the extruder was assessed.

25 the amount of steam added to the dry formulations was varied in order to produce

TABLE 1
Raw materials
Formulation
1
Rice flour/kg              75
Poly C One/kg (emulsifier) 1.2
Pea fibre/kg               75 (50)

The formulations were mixed in lab batch mixtures.

The granular extruded products were then produced using a lab-scale Polymatik extruder TPXL1. The handling and processing of the formulations within the extruder was assessed. For the formulation, the amount of steam added to the dry formulations was varied in order to produce products with different texture characteristics. The granular extruded products were then dried.

The dried reconstituted grain product samples were cooked for 10 minutes (100 g of dried reconstituted grain product per 1 litre of water). Once cooked, the characteristics of the reconstituted grain product, such as surface stickiness and texture/bite were evaluated.

The parameters of uncooked appearance, texture, bite, cooked taste, surface stickiness (cooked) and shape stability of the cooked trial samples were all compared with an “ideal standard”, which was a sample of cooked commercially available parboiled milled rice (Uncle Ben's® long grain rice with a recommended cooking time of 10 minutes). The ideal standard rice has a water uptake of from 100 to 150 g of water per 100 g of dry rice on cooking in excess water at 100C for 10 minutes.

The results of these tests can be summarized as follows.

Formulation 1 (pea fibre): processing was unproblematic. The resulting rice-like kernels had a good appearance, taste, texture and stability on cooking.

In addition, a texture measurement was prepared on the rice cooked as described above for 10 minutes in excess boiling water. For this measurement, the cooked rice was cooled in air, then 17 g samples were packaged in plastic bags and stored in a refrigerator for 24 hours. Each sample was then loaded into a test cell.

The test cell was in the form of a rectangular enclosure having a cross-section of 5.8 cm². The top of the enclosure was open to admit a piston of an Instron stress tester. The bottom of the enclosure was closed by a perforated plate having 39 uniformly spaced circular holes of diameter 3 mm for extruding the rice.

The test cell was mounted in an Instron load measurement device equipped with a rectangular piston of area 5.8 cm² for fitting closely into the rectangular cell to press the rice through the holes in the bottom of the cell. The piston was pressed down at 100 mm/minute, programmed to descend 105 mm, and the maximum load on the piston was determined. A high maximum load was therefore indicative of a relatively firm cooked rice product. A low maximum load was indicative of a rice product that is soft or easily disintegrated. Each measurement was repeated at least 10 times. The results were as follows:

Ideal Standard Rice (Reference Example)

A commercially available pea fiber (20-100 micrometer pea fiber from DPS/Dutch protein services having a maximum of 66% dietary fiber by AOAC This pea fiber is a cellulose/hemicellulose dietary fiber. The pea fiber products measured with a maximum load of from 100 to 149 kN for 14 samples, mean 135 kN, indicating that these samples are softer than the ideal standard rice.

Overall, the products comprising dietary fibre in the form of pea fibre provided reconstituted grain products which very closely resembled the commercially available rice, in terms of appearance, taste and texture.

The above examples have been described for the purpose of illustration only. Many other examples falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims

1-13. (canceled)

14. A reconstituted cereal grain, wherein said grain comprises at least about 10 wt. % of pea fibre, at least about 25 wt. % of cereal starch in addition to said pea fibre, and at least about 0.5 wt. % emulsifier based on the dry weight of the grain; and

wherein said grain has a product density of greater than about 1 kg/l.

15. The reconstituted cereal grain according to claim 14, wherein said product comprises from about 15 wt. % to about 35 wt. % of said pea fibre dietary fibre based on the dry weight of the grain.

16. The reconstituted cereal grain according to claim 15, wherein said product comprises from about 20 wt. % to about 30 wt. % of said pea fibre based on the dry weight of the grain.

17. The reconstituted cereal grain according to claim 14, wherein said product comprises from about 35 wt. % to about 95 wt. % of said cereal starch based on the dry weight of the grain.

18. The reconstituted cereal grain according to claim 17, wherein said product comprises from about 45 wt. % to about 85 wt. % of said cereal starch based on the dry weight of the grain.

19. The reconstituted cereal grain according to claim 14, wherein said grain comprises at least about 80 wt. % of starches based on the dry weight of the grain.

20. The reconstituted cereal grain according to claim 14, wherein said cereal starch comprises, consists essentially of, or consists of rice starch.

21. The reconstituted cereal grain according to claim 14, wherein said cereal grain is a rice-like grain.

22. The reconstituted cereal grain according to claim 14, comprising, consisting essentially of, or consisting of:

35-50 wt. % rice starch;

15-35 wt. % pea fibre;

8-15 wt. % moisture;

0.6-1.2 wt. % emulsifier;

1-5 wt. % protein;

less than about 2% lipids; and

at least about 80% total carbohydrate.

23. The reconstituted cereal grain according to claim 22, comprising 40-45 wt. % rice starch.

24. The reconstituted cereal grain according to claim 22, comprising 20-30 wt. % pea fibre.

25. A cereal product comprising, consisting essentially of, or consisting of a plurality of reconstituted cereal grains according to claim 14.

26. The cereal product according to claim 25, comprising, consisting essentially of, or consisting of a mixture of the reconstituted cereal grains according to the invention with milled parboiled cereal grains.

27. The cereal product according to claim 26, wherein said product has a bulk density from about 600 g/l to about 900 g/l.

28. The cereal product according to claim 27, wherein said product has a bulk density from about 750 g/l to about 850 g/l.

29. The cereal product according to claim 23, wherein 100 g of the product has a water uptake of from about 90 g to about 140 g on cooking in excess water at 100° C. for 10 minutes.