Post harvest Rice

Threshing

Thresh immediately after reaping rice to avoid quantity losses and deterioration of grain quality and do not keep reaped rice on wet paddy field several days.Use foot pedal thresher or traditional method to beat rice against the tarpaulin spread over the ground to avoid contamination with sand and other foreign matter.

  

Manual Rice threshing                              Rice threshing using a foot pedal threshing machine

Drying paddy by Sun drying method 

Grain moisture content (GMC) of the harvested paddy roughly ranges from 20 to 30 % depending on weather condition.Adjusting grain moisture content to 14 % is necessary for dehusking/milling operation to minimize cracked grain and for long storage and 13 % for seeds makes long storagewithout deterioration.

Dry paddy properly to a safe GMC of 14 % by spreading in a thin layer (5 cm) on  concrete drying yard or tarpaulins and turning over periodically (every 30 to 60 min)   for even drying

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Sun-dry slowly for 2-3 days (6-8 hours perday) depending on weather condition to reduce breakage during milling and avoid rapid dryness (1 or 2 cm thickness ofpaddy layer) of paddy within short period such as one day.

 

Checking the moisture contents by biting the de-husked rice:

-Be crushed by biting (about 20%)

-Be cracked by biting without a sound (about 18%)

-Be cracked with a click sound (about 15%).

Milling

Milling is a crucial step in post-production of rice. The basic objective of a rice milling system is to remove the husk and the bran layers, and produce an edible, white rice kernel that is sufficiently milled and free of impurities.

Depending on the requirements of the customer, the rice should have a minimum number of broken kernels.

Photo: Mini Rice milling machine

Winnowing Paddy by machine or traditional winnower (Urutaro)

Winnow to separate chaff and empty grains from the well filled matured grains by using winnowing machine or a traditional winnower (Urutaro).

 

Photo: Traditionally winnowing rice                                              Using a winnowing machine

Bagging and storing paddy for long time:

• Grains under 13 – 14 % of grain moisture content (GMC) can be stored for long time without quality deterioration. 
• Store grain bags indoors on pallets or logs to protect paddy from moisture migration under good air ventilation.  
• Paddy is stored in bag or lofts. Husked rice is disinfected with actelic (100 gr. for 100 kg of rice) or 50 gr of Super Grain Dust in 90 Kgs of rice. Cocoons are also used by people who can afford them.
• Factor affecting quality and quantity consists of as follow:

1) Physical factors: temperature, humidity

2) Chemical factor: moisture, enzyme action, oxidation

3) Physiological factor: respiration, heat generation

4) Biological factor: pest, microorganism, rat.

 

Pallet