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An improved process for milling dehulled rice for producing firmer and less sticky rice texture

The invention relates to a patent application filed in India by Rice Tec. Inc., USA. The invention has now been accepted by the Indian Patent Office (See Gazette of India dated January 18, 1997).

bull.jpg (5174 bytes) Background and Prior Art:

Quality preferences of rice vary from country to country and region to region and are dependent on a number of factors. The rice industry, which includes breeders, farmers, processors and marketers, respond to consumer preferences across the world by developing and producing a vast array of varieties and hybrids of rice.

Attempts at controlling the cooking characteristics of a rice variety or hybrid deal with determining various physicochemical parameters of breeds of rice and then cross-breeding or using hybridisation to arrive at proper amylose content, gelatinization temperature, gel consistency, grain dimensions and other such parameters. Disadvantages of breeding are considerable time involved in breeding, uncertainty in defining the characteristics of the resulting rice when cooked, cost and complexity. A process or procedure, which reduces the need to breed different combinations of physiochemical properties into rice and yet obtain differing cooking characteristics normally associated with such different properties, would improve the efficiency of producing a commercial rice variety with specific characteristics.

bull.jpg (5174 bytes) The Present Invention

The present invention relates to a process for changing the cooking behaviour and cooked rice texture of a given rice by varying only the milling degree of the rice. A greater degree of milling produces cooked rice which is substantially softer and stickier, and a lesser degree produces cooked rice which is substantially fluffier and drier.

One aspect of the invention applies to uniform production run. The cooking behaviour and the rice texture of the cooked rice of any acceptable rice are studied. A second lot of rice is subjected to test milling and then cooked. The differences in cooking behaviour and the rice texture of the second lot is compared with those of the acceptable rice. A uniform production run is achieved by varying only the milling degree of the second lot in order to compensate for the differences.

Another aspect includes the steps of selecting a rice having a predetermined cooking behaviour and a texture when milled, and

i) Producing, after the same cooking procedure, a substantially fluffier and drier cooked rice by milling the said rice to Satake Milling Degree (SMD) of about 78 or less, while producing a rice transparency of about 2.0 or greater, or

ii) producing a substantially softer and stickier cooked rice by milling the said rice to a SMD of about 100 or greater.

Example 1

Rice variety RIA 1002, a medium amylose, intermediate gel temperature rice was dehulled and milled using a Satake commercial abrasion milling machine. When well-milled, this variety is classified as medium amylose (24% apparent amylose by weight) and intermediate gel (alkali spreading value 2.4). The machine was adjusted to produce a 68 SMD for Sample 2. A second pass through the machine of Sample 1 product, milled still longer, produced rice Sample 3 with a 116 SMD. The amylose percent of each sample was measured.

Cooking behaviour was evaluated by cooking 50 g. samples of milled rice product in excess water for various times, of 10 minutes, 15 minutes and 20 minutes. The stickiness of each cooked rice sample was assessed using the "cup test" and the moisture content of each cooked rice sample was also measured. The results were as follows:

Sample

Whiteness

Transparency

SMD

Apparent % Amylose

1

35.1

1.41

68

24.1

2

40.4

2.05

92

24.2

3.

44.7

2.70

116

25.5

Sample

Cook Time

Cooked Rice Moisture %

Stickiness Cup Test

1

10
15
20

69.0
71.6
76.9

4.5
4.0
3.0

2

10
15
20

72.4
73.8
78.4

2.5
4.0
3.0

3.

10
15
20

73.5
75.6
77.7

1.0
2.0
1.0

The results show that milling rice to a higher degree accelerates the rate of moisture absorption during cooking in excess water and that higher milling degree rice is stickier at a given moisture content than the lower milling degree rice. Higher amylose rice, according to prior art, would be expected to give a less sticky rice. The extraction of lipids from a rice sample before conducting the amylose test is known to increase the amylose measurement of medium amylose rice by about 2 percentage points. Measurements of 1% amylose on rice without lipids extraction is referred to as "apparent % amylose". All references to "amylose %" herein refer to apparent percent amylose content by weight.

bull.jpg (5174 bytes) Claims:

1. A process for milling dehulled rice for producing firmer and less sticky rice texture comprising selecting a rice having a predetermined cooking behaviour and texture, milling the said rice to Satake milling degree of at least 100 and apparent amylose content of greater than 19% by weight.

2. A process for milling dehulled rice for producing firmer and less sticky rice texture substantially as herein described with reference to the foregoing examples and accompanying drawings.

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