paddy parboiling and drying

Par-boiling & Drying

E.Jayakumar, B.E (Mech).,M.Tech (FPE).,MIE.,FIV.,Charted Engineer (India)(M-153913-7),Approved Valuer (F-25667)(VII)-Machinery and Plant .Free Lancer,AGRO TRADE LINK A turn key solutionE.Mail: [email protected]: Mobile: +91 9444025375, +919940819765Phone: 04362-278398 :,Skype: Easupatham

mailto:[email protected]

Par-Boiling

Partial cooking of rice intact with husk is called parboiling.

Involves soaking, steaming, drying and milling.

Parboiled rice takes less time to cook and is firmer and less sticky

Advantages

Milling

• Dehusking is easier and costs less

• Fewer broken• Increased head and total rice

output Storage

• More resistant to insect attack Cooking

• Loses less starch and keeps longer• More fiber than regular rice

System Material feeding (Elevator) Pre Cleaner Over Head Storage Soaking Tanks Steaming tanks Water Pipe line Steam pipe line Drainage system Water circulation system Material discharge (Belt Conveyors)

https://www.youtube.com/watch?v=rFbCkD0Eb0Q

Processing

Soaking

Impregnating moisture to the required level before cooking operation.

Steaming

Raising the temp of paddy to near saturation temp of water in the presence of steam.

Drying The paddy is left at high temp and moisture level of 32%

At his stage the paddy is liable for bacterial and fungus attack

Hot aid blown through it in the dryers

It involves lot of techniques to get uniformly dried grain with desired

moisture

Techniques

Single boiled rice (white belly rice)

Double Boiled Rice - Fully translucent rice

Hot soaking method - Fully translucent rice

Steamed rice (Cured rice)

Process for Single Boiled Rice -White belly Rice

Pre-cleaning

De-stoning

Transfer to overhead bins

Discharge raw paddy in to roomtemperature water in soaking tanks

MS/SS Soaking Tanks

Remove chaff and immature grains floating on water surface

Soak for 6 to 12 h (Capacity: 2-3 tones with steaming and water circulation

arrangement)

Capacity of tank 2-3 tonesWith steaming and water circulation

arrangement.or

Soaking tank capacity of 5-10 tones

Process for Single Boiled Rice -White belly Rice Cont..

Circulate the water Drain and tempering for 2 h

Steam the paddy for 1 to 2 min after steam emergence on top

Discharge the paddy quickly from

steaming tank into cooler

Dry the paddy in Drier(Circulatory/ fluidized bed type cooler)

(Moisture content to 14%)

Unload the paddy to Storage bin / Milling Section

If 5 – 10 tones soaking tank, steam the soaked paddy in steaming vessel of capacity 0.5 to 1.0 tone / continuous

steaming vessel kept below the soaking tankNumber of tanks matching the drier capacity

Process for Double Boiled Rice - Fully translucent rice

Pre-cleaning

De-stoning


Discharge raw paddy in to soaking cum steaming tanks

MS/SS Soaking Tanks

Steam for 5 min

Add water RT water to steamed paddy (1.5 times to the paddy)


arrangement.or


Process for Double Boiled Rice Cont..

Circulate the water for half an hour

Remove floating chaff and immature

Soak for 12 to 24 hrs depending on the Variety till complete saturation of paddy

Drain the water and temper for 2 hrs


Steam paddy for 1 to 2 min after steam emergence at top

Discharge the paddy quickly from steaming tank into cooler

Dry the paddy in Drier


steaming vessel kept below the soaking tankNumber of tanks matching the drier capacity

Process for Hot soaking Method - Fully translucent rice

Pre-cleaning De-stoning


Pump hot water 95ºC in to soaking tank or

Inject steam into RT water in soaking tank to raise Temperature to 95ºC

Discharge raw paddy into hot water

Circulate for ½ h so that the hot soak water attains 650C

Soak for 3 to 5 h according to the paddy variety

Drain water and temper for 2 h


arrangement.or


Process for Hot soaking Method Cont..

Steam for 1 to 2 min after emergence of steam on top

Quick discharge of steamed paddy from steaming tank to cooler

Dry the paddy in Drier



steaming vessel kept below the soaking tank

Number of tanks matching the drier capacity

Circulatory/fludised bed type cooler

IBR Boiler

Process for cured/steamed rice

Discharge raw paddy in to

soaking tanks

Steam for few min as per requirement (5-15 min)

Transfer to Tempering bin (3-4h)

Drying(Hot air temperature 65°C)

Temper the paddy for 12 h before milling

IBR Boiler

CuringThe accelerated effect of ageing in rice is

called curing. It can be achieved by steaming of fresh paddy /paddy stored for few months.

Drying

Grain Drying Principles and methods

◦ Reduce the moisture from grain to a safe level of storage .

◦ It is a critical step for maintaining grain quality and minimize the storage and processing losses.

◦ Drying is need because the high moisture grain will cause heat build up (Hot spot) from respiration of microorganisms, low thermal diffusivity of grain ,increased the mold growth, reduced starch and sugar content.

Why drying need?

High moisture grain will cause : Heat build - up (Hot spot)

From respiration of microorganisms and grain itself Low thermal diffusivity of grain Increased the temperatures accelerate the mold growth, Reduced starch and sugar content.

Drying mechanism

Two fundamental steps occur during drying

◦ Water migration migration from grain interior to surface.◦ Water evaporation from the surface to the surrounding air.

Moisture content decreases rapidly at first but slows down as grain dries.

Drying rate decreases with moisture content increases with air temperature.

Removal of water from grain during drying causes a reduction in grain quantity

Moisture content can be calculate :

Drying mechanism

Moisture Shrink % =

Equilibrium moisture content:

During drying, moisture content depends on temperature and relative humidity of surrounding air

When surrounding air is “dry” grain would loss moisture.

When surrounding air is “humid” grain would absorb moisture

Drying air Properties :

Vapor Pressure◦ Partial pressure exerted by the water vapor molecules in moist

air.

Relative humidity◦ Ratio of the mole fraction of water vapor in the air to the mole

fraction of water vapor in saturated air

Humidity ratio◦ Mass of water vapor per unit mass of dry air

Dry bulb temperature◦ Air temperature indicated by an ordinary thermometer

Wet bulb temperature ◦ Air temperature indicated by thermometer whose bulb is

covered with a wet wick

Dew point temperature-◦ Temperature at which moisture condensation will occur as air is

cooled


Enthalpy-◦ Heat content of the moist air per unit mass of dry air above a

certain reference temperature.

Specific volume◦ Volume per unit mass of dry air.

Specific Heat◦ Measurable physical quantity of heat energy required to change

the temperature of air by a given amount.


Effect of Drying on grain qualities:

Low and uniform moisture content

Minimum broken and damage kernels

Low susceptibility to subsequent breakage

Retained nutritional value

High viability

Good visual and organoleptic properties.

Drying Methods

Sun dryingMechanical Drying

L.S.U Dryer Developed at Louisiana state university (LSU) Continuous mixing type dryer Developed specifically for rice to ensure gentle treatment,

good mixing & good air to grain contact Consists of rectangular chamber, holding bin, blower with

duct, grain discharging mechanism and air heating system Layers of inverted V shaped channels are installed in the

drying chamber; heated air is introduced through these channels at many points

Alternate layers are air inlet & outlet channels; arranged one below the other in an offset pattern

Inlet port consists of few full size ports & two half size ports; all ports are of same size arranged in equal spacing

Ribbed rollers are provided at the bottom of drying chamber for the discharge of grain

L.S.U Dryer

1. Garner 2. Duct 3. Dry material outlet 4. Hopper 5. Continuous flow 6. Door 7. Roof

Process

Dry the paddy at 100°C of Hot air till the on line moisture meter shows 20%

At the moisture of 18-17% transfer the paddy to tempering bin( 3-4 h)

Reduce the hot air temperature to 80°C till the paddy moisture percent falls to 14 -13%

Temper the paddy for 12 h before milling

Future is not something we wait it is something we should create

-Swami VivekanandaE.Mail: [email protected]: Mobile: +91 9444025375, +919940819765Phone: 04362-278398 :,Skype: Easupatham

mailto:[email protected]

paddy parboiling and drying

Food