Rice production

Rice: Pakistan is the world's fourth largest producer of rice, after China, India and Indonesia, rice is an important cash crop of the country. Rice production comprises 40 percent of Basmati (Fine) type and 60 percent of coarse types. Rice ranks as second amongst the staple food grain crop in

Pakistan and it has been a major source of foreign exchange earnings in recent years. Pakistan grows a high quality of rice to fulfill the domestic demand and also for exports. Rice accounts 2.7 percent of the value added in agriculture and 0.6 percent of GDP. Rice sowing area is estimated at 2311

thousand hectares, 10.1 percent less than last year’s area of 2571 thousand hectares. Production of the crop is estimated at 5541 thousand tonnes, against

the target of 6900 thousand tonnes shows a weak performance of 19.7 percent and to compare last year production which was 6160 thousand tonnes

shows a decrease of 10.0 percent. The production decreased due to decrease in area and affects of monsoon rain and late receding of water period in

rice fields prolonged the sowing.

Physiochemical Analysis of Rice

Introduction

ž  Rice has been cultivated in China since ancient times and was introduced to India before the time of the Greeks. Chinese records of rice cultivation go back 4,000 years.

ž  Botanical Name:                  Oryza sativa L

ž  Family:                     Gramineae

ž  Self-pollinated crop

Milling of rice

For milling the moisture should be 14%. So before milling we check the moisture of sample in moisture meter then we start the milling process.

PROCEDURE OF MILLING

ž  Paddy was dumped in the intake pit feeding the pre-cleaner.

ž   Pre-cleaned paddy moved to the rubber roll husker.

ž    Mixture of brown rice and unhusked paddy moved to the separator

ž  Unhusked paddy was separated and returned to the rubber roll husker

ž   Brown rice moved to the destoner

ž   Partially milled rice moved to the whitener

ž   Milled rice moved to the sifter

ž  Polished rice, will moved to length grader

ž  Head rice moved to head rice bin

ž  Broken moves to broken bin

ž  Pre-selected amount of head rice and broken moved to blending station

ž  Custom-made blend of head rice and broken moved to bagging station

ž  Bagged Rice moved to the market

PHYSICAL CHARACTERISTICS OF RICE

Moisture content

ž  Moisture content (MC) is essential that paddy be milled at the proper moisture content to obtain the highest head rice yield.

ž  Paddy is at its optimum milling potential at moisture content of 14% wet weight basis.

Purity

ž  Purity is related to the presence of dockage in the grain.

ž  Dockage refers to material other than paddy and includes chaff, stones, weed seeds, soil, rice straw, stalks, etc.  

ž  Unclean paddy increases the time taken to clean and process the grain.

ž  Reduce milling recovery.

Varietal Purity

ž  A mixture of varieties causes difficulties at milling and usually results in reduced capacity, excessive breakage, lower milled rice recovery and reduced head rice.  

ž  Different sizes and shaped grains make it more difficult to adjust hullers.

Milling degree

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

ž  Milling degree affects milling recovery and influences consumer acceptance.Milling degree influences the color and also the cooking behavior of rice.

ž  Unmilled brown rice absorbs water poorly and does not cook as quickly as milled rice. The water absorption rate improves progressively up to about 25% milling degree after which, there is very little effect.

Cooking Quality of Rice Kernel

Cooking means absorption of water until gel of the rice is formed

Elongation Ratio

Elongation ratio was determined as under

                    Elongation Ratio       =              Average length of twenty rice kernels after cooking

                                                                      Average length of twenty rice kernels before cooking

Water Absorption Capacity

Water absorption capacity      =        Weight of cooked rice   *100

                                                            Weight of raw rice

Volume expansion ratio

             Volume expansion ratio                   =       Volume of cooked rice

                                                                                Volume of raw rice

Chemical analysis of Rice

Gel Consistency Determination

Principle:

Ò   Consistency in mm of cold paste of 4.4% rice starch flour in 0.2N KOH

Reagents

Ò  0.2 N KOH

Ò  Dissolve 11.2 g of Potassium Hydroxide ( dehydrated) in 1000 mL D-water

Ò  0.025% Thymol Blue in Alkohol

Ò  Take 0.025 g of Thymol Blue and dissolve in 100 mL of 95% Ethanol

procedure

ž  100mg flour take in culture tube

ž  Add 0.2 ml of Thymol Blue in the test tube only to wet then shake.

ž  Dispersed the mixture immediately with glass rod

ž  Mouth Covered Tubes are placed in boiling water bath  for 8 minut.

ž  Let the tube come to cool for 5- minutes

ž  Place the tubes in Ice water/ Bath for 20 minutes

ž  Laid the tubes on the Bench top horizontally

ž  Measure the Gel length from bottom of tube to the Gel front through millimeter scale

Gel Consistency Test

ž  There are many rice varieties which have similar amylose contents and physical dimension like grain size, shape and appearance making very difficult to classify them accurately.

This gel separates rice in hard (length 36 mm or less) intermediate (length 36 to 50 mm) and soft (length over 50 mm) gel consistency

Alkali Spreading Value

ž  Alkali spreading value was determined as six whole grains of rice were taken in a Petri dish containing 10ml of 1.7% KOH. The dish was covered and placed in incubator at 30⁰C for 23 hours.