RICE GRAIN

RICE GRAIN- QUALITY, TEST, MILLING AND 

USES OF RICE

STRUCTURE OF RICE

THE RICE GRAIN CONSIST OF AN OUTER PROTECTIVE COVERING, THE HULL (HUSK) AND THE EDIBLE RICE CARYOPSIS OF FRUIT (BROWN, CARGO, DEHULLED OR DEHUSKED RICE). BROWN RICE CONSISTS OF THE OUTER LAYERS OF PERICARP SEED COAT AND NUCELLUS, THE GERM OR EMBRYO WHICH ARE MATERNAL TISSUE AND THE ENDOSPERM. THE ENDOSPERM CONSISTS OF THE ALEURSOME LAYER, THE SUBALLEURONE LAYER AND THE STARCHY  OR INNER ENDOSPERM PIGMENT IS CONFINED TO PERICARP. THE ALLEURONE LAYER ENCLOSES THE EMBRYO.

THE INEDIBLE HULL CONSTITUTE 16-20% (MEAN 20%) OF THE ROUGH RICE WEIGHT. BROWN RICE CONSISTS OF 1-2% PERICARP, 4-5% ALLEURONE, NUCELLUS AND SEED COAT, 1% EMBRYO, 2% SCUTELLUM AND 90-91% ENDOSPERM. THE ALLEURONE AND EMBRYO CELLS ARE RICH IN PROTEIN BODIES CONTAINING GLOBOIDS AND PHYTATE BODIES AND IN LIPID BODIES.

THE ENDOSPERM CELLS ARE THIN WALLED AND PACKED WITH AMYLOPLASTS CONTAINING POLYHEDRAL COMPOUND. STARCH GRANULES ABOUT 3-9 MICRO METER IN SIZE. PROTEIN OCCURS MAINLY IN THE FORM OF LARGE(1-2 MICRO METER) AND SMALL (0.5-0.8 MICROMETER) SPHERICAL; PROTEIN BODIES AND CRYSTALLINE PROTEIN BODIES SPHERICAL PROTEIN BODIES ARE RICH IN PROLAMINE (ALCOHOL SOLUBLE PROTEIN) & CRYSTALLINE PROTEIN BODIES ARE RICH IN GLUTELIN (ALKALI SOLUBLE PROTEIN), SPHEROSOMES ARE PRESENT IN SUBALLEURONE OR TWO OUTERMOST CELL LAYER.

VARIOUS PARAMETERS USED TO JUDGE THE QUALITY OF RICE ARE:-

·          

      ALKALI SCORE

·         WATER UPTAKE

·         COOKING QUALITY

·         DIMENSIONS

·         COLOR

·         1000 KERNEL WEIGHT

·         BULK DENSITY

·         TRUE DENSITY

·         PERCENT POROSITY

·         SURFACE AREA

ALKALI SCORE:-

IT HELPS IN DETERMINING THE APPROXIMATE GELATINIZATION TEMPERATURE OF THE GIVEN VARIETY OF RICE. IN THIS 8 OR 10 KERNALS ARE PLACED IN KOH SOLUTION, FOR 24 HOURS OR OVERNIGHT. KOH TRIES TO BREAK THE KERNEL. OBSERVED HOW MANY  KERNELS ARE DISINTEGRATED & CALCULATE PERCENT DISINTEGRATION. IF DISINTEGRATION IS MORE , GELATINIZATION TEMPERATURE IS LESS & RICE IS OF LOW QUALITY.

PROCEDURE:-

·         TAKE 8 RICE KERNALS AND KEEP THEM SYMMETRICALLY ON THE PETRIPLATE.

·         ADD 1.8% KOH SOLUTION ENOUGH TO COVER THE KERNELS OR IMMERSE THE KERNEL.

·         PLACE THE COVER OF PETRIPLATE.

·         KEEP IT FOR OVERNIGHT.

·         NOTE DOWN THE MICRO-ORGANISMS OF KERNELS DISINTEGRATED.

FORMULA USED:-

ALKALI SCORE= NUMBER OF KERNEL DISINTEGRATED/TOTAL NUMBER OF KERNELS*100

GELATINIZATION TEPERATURE α 1/ALKALI SCORE

COOKING QUALITY:-

COOKING QUALITY REVEALS THE QUALITY DEPENDING UPON THE TYPE OF KERNELS. COOKING QUALITY IS DEFINED W.R.T MANY CHARACTERISTICS SUCH AS TIME OF COOKING, SWELLING CHARACTERISTICS, COLOR, PASTYNESS. RAW RICE TAKES 15-20 MINUTES TO BECOME FULLY COOK IN BOILING WATER WHEREAS PARBOILED RICE TAKE 30 MINUTES FOR SOME DEGREE OF SOFTNESS. RAW RICE COOKED BEYOND 20 MINUTE BECOME PASTY.

PROCEDURE:-

·        SIX BEAKERS HAVING 50 ML OF WATER ARE TAKEN AND BOILED OVERFLAME.

·         WHEN WATER STARTS BOILING ADD 2 GM OF RICE IN EACH.

·         WITHDRAW IT FROM FLAME AFTER TIME INTERVALS OF 4, 8, 12, 20, 22, AND 24.

·         NOTE THE NATURE OF THE RICE KERNELS.

WATER UPTAKE:-

WATER UPTAKE IS DEFINED AS GRAMS OF WATER OBSERVED BY ONE GM OF RICE. IT IS A PARAMETER USE TO FIND OUT COOKING QUALITY.

PROCEDURE:-

·         TAKE 4 TEST TUBES HAVING 20 ML OF WATER IN EACH.

·         IMMERSE IT IN WATER BOTH TILL THE TEMPERATURE OF THE TEST TUBE WATER REACHES TO 80⁰C.

·         ADD 2 GM OF RICE IN EACH TEST TUBE AND KEEP IT FOR 25 MINUTES.

·         TEST TUBES ARE COOLED AND EXCESS OF WATER ID DRAINED.

·         WEIGH THE RICE TO CALCULATE WATER ABSORBED.

FORMULA USED:-

WATER UPTAKE= FINAL WEIGHT- INITIUAL WEIGHT/INITIAL WEIGHT*100

% WATER ABSORBED= GM OF H2O ABSORBED/GM OF RICE*100

DIMENSIONS:-

THIS INCLUDES LENGTH AND BREADTH OF RICE. DIMENSIONS GIVE AN IDEA ABOUT THE QUALITY OF RICE. LONG AND THIN RICE IS OF GOOD QUALITY AS COMPARED TO THICK AND SMALL RICE.

PROCEDURE:-

LENGTH:-

FOR FINDING THE LENGTH WE USE VERNIER CALLIPER. TAKE 10 KERNELS FROM EACH OF THE SAMPLE AND FIND THE LENGTH THEN TAKE THE AVERAGE. THE LEAST COUNT OF VERNIER CALLIPER IS 0.1.

BREADTH:-

FOR FINDING THIS SCREW GUAGE IS USE. TAKE 10 KERNELS FROM EACH SAMPLE AND THEN TAKE THE AVERAGE. THE LEAST COUNT OF SCREW GUAGE IS 0.001.

COLOUR:-

COLOR IS A HERIDATORY NFACTOR AND DEPENDS UPON THE TYPE OF PROCESSING AND DEGREE OF MILLING COLOR OF RICE IS WHITE TO YELLOWISH.

1000 KERNEL WEIGHT:-

IT IS DEFINED AS THE WEIGHT OF 1000 KERNELS OF RICE. THE PROPERTY GIVES AN IDEA ABOUT THE SOUNDNESS OF RICE.

PROCEDURE:-

RANDOMLY SELECT 1000 KERNELS FROM THE GIVEN SAMPLE WEIGH THEM AND THE WEIGHT BY 100. TAKE ATLEAST 5 READINGS AND THEN TAKE AVERAGE.

BULK DENSITY:-

BULK DENSITY IS A WEIGHT OF KNOWN QUANTITY OF CEREALS. IT GIVES THE SOUNDNESS OF GRAIN WITH THE HELP OF BULK DENSITY, ONE CAN CALCULATE THE SURFACE AREA REQUIRED TO STORE A PARTICULAR OF RICE.

PROCEDURE:-

TAKE A MEASURING CYLINDER WITH THE RICE BY FIRST FILLING THE CYLINDER UPTO 25 ML, THEN TO 50 ML AND ATLEAST 75 ML AS THE DENSITY IS MASS/VOLUME. PUTTING THE  VALUE IN THE FORMULA FIND THE VALUES FOR BULK DENSITY.

TRUE DENSITY:-

TRUE DENSITY IS FOUND BY DIPPING 10 GM OF SAMPLE TO 50 ML TOULENE SOLUTION.

FORMULA USED:-

TRUE DENSITY= WEIGHT OF SAMPLE/ FINAL VOLUME-INITIAL VOLUME

% POROSITY:-

IT IS CALCULATED BY USING TRUE DENSITY AND BULK DENSITY.

FORMULA USED:-

% POROSITY= TRUE DENSITY- BULK DENSITY/ TRUE DENSITY* 100

MILLING OF RICE:-

STEPS OF RICE MILLING:-

RECEIVING:-

ROUGH RICE (PADDY RICE) WHICH CONSISTSOF 50% OR MORE KERNELS FROM WHICH THE HULL HAVE NOT BEEN REMOVED IS RECEIVED AT RICE MILL IN BULK OR SACKS.

DRY CLEANING:-

INCOMING RECEIPTS MUST BE CAREFULLY SORTED SO THAT DIFFERENT GRADES, VARIETIES AND GRAIN SIZES CAN BE PROCESSED IN A SEPARATE LOTS. PROCESSING MACHIENERY IS ADJUSTABLE SO THAT VARYING CHARACTERISTICS OF THE INCOMING MATERIAL CAN BE ACCOMODATED IN A SERIES OF MECHANICAL AND PNEUMATIC OPERATIONS CHAFF, LUMPS OF MUD AND DIRT, FOREIGNSUBSTANCES, GRAVEL, WEEDSEEDS AND ANY OTHER DEBSIS LEFT OVER FROM PRIOR THRESHING ARE REMOVED.

SHEILLING:-

THE RICE IS PASSED THROUGH SHELLER FOR THE REMOVAL OF HULLS. ALTHOUGH HULLING STONES MAY BE USED, MOST (MODERN FACILITIES), THE SHELLER CONSISTS OF PAIRED RUBBER ROLLS WHICH TURN AT DIFFERENT SPUDS SO THAT AS THE KENELS PASS THROUGH THE MACHINE A TEARING OR PULLING AND SLIGHT CRUSHING (CRACKING) ACTION TAKES PLACE. SHELLERS ARE USED IN TANDOM WITH RECYCLING BETWEEN MACHINES TO EFFECT FINAL QUALITY CONTROL. IN THESE OPERATIONS AND THROUGH OUT ALL MILLING OPERATIONS, A MAJOR CONCERN IS THAT OF AVOIDING KERNEL BREAKAGE. AFTER HULLING THE PRODUCT IS KNOWN AS BROWN RICE.

SEPERATING:-

DUST AND HUSKS ARE REMOVED PNEUMATICALLY IN WHAT IS CALLED A FANNING MACHINE. THE HULLS MAY BE CONSUMED AS FUEL AT THE MILLING FACILITY OR COLLECTED AND MARKETED FOR USE AN INSULATION AS A SOURCE OF FURFURAL FOR CHEMICAL MANUFACTURER, AS PACKING AND SOIL MULCHING MATERIAL. EVEN WIH PRIOR SHELLING IN TANDOM SOME UNHULLED KERNELS WILL GET THROUGH. THESE ARE RECYCLED BACK TO THE SHELLING LINE. THE SEPARATION MACHINE IS SOME TIME CALLED AS PADDY MACHINE.

BRAN REMOVAL:-

THE BRAN LAYERS ARE REMOVED. THE INNERMOST OR POLISH LAYER MAY REMAIN. THIS MACHINE IS AN ADAPTATION OF THE MACHINE USED TO HULL COFFEE AND HENCE IN THE TRADE IT IS COMMONLY REFERRED TO, THROUGH INCORRECTLY AS A HULLER. IN A SERIES OF RUBBING ACTIONS, THE BROWN COAT IS REMOVED AND ASPIRATED AWAY TO A BRAN COLLECTOR. AT THIS POINT THE PRODUCT IS KNOWN AS UNDERMILLED RICE. IN SOME PLANTS,  PEARLING OPERATION MAY FOLLOW. THIS ESSENTIALLY IS A REFINEMENT OF BRAN REMOVAL OPERATION. MOST RICE BRAN IS USED IN ANIMAL FEEDS.

BRUSHING:-

THE RICE PRODUCTS TO BRUSHING MACHINE WHERE IT IS SCOURED TO REMOVE THE INNER MOST BRAN COAT, ALSO KNOWN AS POLISH. THIS MACHINE CONSISTS OF A RAPIDLY REVOLVING VERTICAL CYLINDER EQUIPPED WITH OVERLAPPING PIECES OF HIDE.  A HIGH POLISH IS IMPOTED TO THE SURFACE OF RICE AND THE PRODUCT IS CALLED POLISHED RICE. THE POWDERY POLISH SUBSTANCES (MOSTLY CHO) IS COLLETED AND IS ALSO USED IN ANIMAL FEED.

TRUMBLING:-

POLISHED OR UNCOATED RICE MAY BE MARKETED AT THIS POINT, OR THE PRODUCT MAY BE PASSED TO TRUMBLING MACHINES, WHERE THE KERNELS ARE COATED WITH GLUCOSE AND TALE. THE COATING IS PREFERRED BY SOME MARKETS AND DOES NOT DETRACT FROM THE NUTRITIONAL VALUE OF THE PRODUCT.

SCREENING AND SEPERATNG:-

IN SCREENING AND SEPERATING THE WHOLE RICE KERNELS, BROCKERS AND RICE FLOUR ARE SEPERATED, THEN THEY ARE GRADED PACKAGED SEPERATELY AND MARKETED.

USES OF RICE:-

1.       RICE IS USED AS A STAPLE FOOD IN MANY COUNTRIES.

2.       RICE WITH A LOW STARCH GELATINIZATION IS  PREFERRED  IN RICE PUDDING, BREADS & CAKES & BEER ADJUNCTS, THIS ALLOWS STARCH GELATINIZATION AT LOWER PROCESSING TEMPERATURES, PARTICULARLY IN THE PRESENCE OF SUCROSE.

3.       WARY AND LOW AMYLOSE RICES ARE PREFERRED FOR RICE WINE(FOR HIGHER ETHANOL YEILD) AND IN FROZEN SAUCES, DESSERTS AND SWEETS BECAUSE OF THE SLOW STALING RATE.

4.       RICE BY PRODUCTS INCLUDING THE OUTER BRAN LAYERS, GERM AND POLISH ARE THE POTENTIAL SOURCE OF FOOD FOR HUMANS, THESE BY PRODUCTS ACCOUNTS FOR APPROX 10% OF PADDY RICE WEIGHT.

5.       THE HULLS OF THE RICE MAY BE CONSUMED ASFUEL AT THE MILLING FACILITY, OR COLLECTED AND MARKETED FOR USE AS INSULATION, AS A SOURCE OF FURFURAL FOR CHEMICAL MANUFACTURES, AS PACKING AND SOIL MULCHING MATERIAL.

6.       RICE-BRAN IS USED AS ANIMAL FOOD.

7.       RICE-FLOUR (GLUTINOUS AND WARY) IS USED FOR THICKENING OF VARIOUS PRODUCTS SUCH AS GRAVIES, WHITE SAUCES ETC.

8.       IN INDIA, SEVERAL TYPES OF DISHES ARE PREPARED FROM RICE FLAVORED WITH SPICES AND OTHER INGREDIENTS . OTHER RICE PREPARATIONS INCLUDE PARCHED RICE, PUFFED RICE AND FERMENTED PREPARATION LIKE IDLI AND DOSA.