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Production Know How

Production Know How
6
Aug

Water Quality

 

File Courtesy: 
http://www.knowledgebank.irri.org
6
Aug

Water Quality

 

File Courtesy: 
http://www.knowledgebank.irri.org
6
Aug

Planting Techniques

1. The most suitable planting technique depends on locality, soil type, and crop ecosystem.        
2. Crops can be direct seeded or transplanted. Similarly transplanted crops can be established manually or by machine. 3. Direct seeded crops tend to mature faster than transplanted crops but have more competition from weeds.

File Courtesy: 
http://www.knowledgebank.irri.org
6
Aug

Moisture content of Paddy grains

6
Aug

Gel consistency

Gel consistency

1. Gel consistency measures the tendency of the cooked rice to harden after cooling. Within the same amylose group, varieties with a softer gel consistency are preferred, and the cooked rice has a higher degree of tenderness.

2. Harder gel consistency is associated with harder cooked rice and this feature is particularly evident in high-amylose rice.

3. Hard cooked rice also tends to be less sticky. Gel consistency is determined by heating a small quantity of rice in a dilute alkali.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Alkali Spreading Value (ASV)

Alkali Spreading Value (ASV)

1. GT is inversely related to the alkali spreading value (ASV). In fact, it is the ASV which is normally measured to have an idea of the GT.

2.When rice is treated with dilute alkali, the starch molecules present in rice get degraded resulting in disintegration of the grain.

3. Depending upon the variety, the changes in the grain shape may vary from no apparent effect to a completely dispersed grain.

File Courtesy: 
CRRI
6
Aug

Amylose content

Amylose content

1.Starch makes up about 90% of the dry matter content of milled rice.

2. Starch is a polymer of glucose and amylose is a linear polymer of glucose.

3. The amylose content of starches usually ranges from 15 to 35%.

4.High amylose content rice shows high volume expansion (not necessarily elongation) and high degree of flakiness.

5. High amylose grains cook dry, are less tender, and become hard upon cooling. In contrast, low-amylose rice cooks moist and sticky.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Gelatinization temperature

Gelatinization temperature

1.The time required for cooking milled rice is determined by gelatinization temperature or GT.

2. Environmental conditions, such as temperature during ripening, influence GT.

3. A high ambient temperature during grain development results in starch with a higher GT.

4. GT of milled rice is evaluated by determining the Alkali spreading value.

5.In many rice-growing countries, there is a distinct preference for rice with intermediate gelatinization temperature.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Chemical characteristics

Chemical characteristics include

  • Gelatinization temperature
  •  Amylose content
  • Gel consistency
File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Chalkiness

Chalkiness

1.If part of the milled rice kernel is opaque rather than translucent, it is often characterized as “chalky”.

2. Chalkiness disappears upon cooking and has no effect on taste or aroma, cooking and eating qualities, however it reduces milling recovery when it is in excess

3. Excessive chalkiness is caused by interruption during the final stages of grain filling.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Whiteness

Whiteness

1.Whiteness is a combination of varietal physical characteristics and the degree of milling.

2. In milling, the whitening and polishing greatly affect the whiteness of the grain.

3. During whitening, the silver skin and the bran layer of the brown rice is removed.

4.Polishing after whitening is carried out to improve the appearance of the white rice.

5. During polishing some of the bran particles stick to the surface of the rice which polishes and gives a shining appearance.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Head rice

Head rice

1. “Head rice” or head rice percentage is the weight of head grain or whole kernels in the rice lot.

2. Head rice normally includes broken kernels that are 75-80% of the whole kernel.

3. High head rice yield is one of the most important criteria for measuring milled rice quality.

4. Broken grain has normally only half of the value of head rice.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Milling degree

Milling degree

1.The degree of milling is a measure of the percent age of bran removed from the brown rice kernel.

2. Milling degree affects milling recovery and influences consumer preferance.

3. Apart from the amount of white rice recovered, milling degree influences the colour and also the cooking qualities of rice.

4. Unmilled brown rice absorbs water poorly and does not cook as quickly as milled rice.

5. The water absorption rate improves progressively up to 25%, milling degree after which, there is very little effect.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Physical characteristics for Quality characteristics of milled rice

Physical characteristics include
• Milling degree,
• Head rice,
• Whiteness
• Chalkiness

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Quality characteristics of milled rice

Quality characteristics of milled rice include

  •   Physical
  • Chemical characteristics.
File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-milled-rice
6
Aug

Yellowing

Discoloration / yellowing

1. Yellowing is caused by over-exposure of paddy to wet environmental conditions before it is dried.

2. This results in a combination of microbiological and chemical activities that overheat the grain.

3. These fermented grains frequently possess partly gelatinized starch cells and generally resist the pressures applied during grain milling.

4. While the presence of fermented grain does not affect milling yields, it does downgrade the quality of the milled rice because of the unattractive appearance.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-paddy
6
Aug

Seed Soil Contact

1. To begin the germination process, the seed absorbs a certain amount of moisture from its surroundings.

2. In a dry seed bed, absorption occurs after distribution through the seed being in contact with moist soil or being submerged in water.

3. For seeds to make good contact with the soil, soil peds (clods) need to be similar in size to the seed and actually make physical contact with the seed.

4. Seed soaking or seed priming prior to planting expedites the absorption process and is often used to increase the rate of plant establishment.

File Courtesy: 
http://www.knowledgebank.irri.org
6
Aug

Immature grains

1.The amount of immature paddy grains in a sample has a major effect on head rice yield and quality.

2. The immature rice kernels are very slender and chalky and this results in excessive production of bran, broken grains and brewer’s rice.

3. The optimal stage to harvest grain is at about 20-24% grain moisture or about 30 days after 50% flowering.

4. If the harvest is too late, many grains are lost through shattering or dry out and are cracked during threshing, which causes grain breakage during milling

Damaged grains:

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-paddy
6
Aug

Seed health

Refers to the presence or absence of disease-causing organisms such as fungi, bacteria and Virus and pests such as cutworms, insects. Seed health testing is necessary because,

1) Seed borne inoculum may give rise to progressive disease development in the field.

2) Imported seed lots may introduce new diseases.

Methods of examining seed-borne diseases:

a. Direct examination: Nematode galls, smut balls, discoloured seeds sclerotia of sheath blight (with microscope).

File Courtesy: 
http://www.knowledgebank.irri.org
6
Aug

Cracked grains

1.Overexposure of mature paddy to fluctuating temperatures and moisture conditions leads to development of fissures and cracks in individual kernel.

2. Cracks in the kernel are the most important factor contributing to rice breakage during milling.

3. This results in reduced milled rice recovery and head rice yields.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/quality-characteristics-of-paddy
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