Theory of 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 of broken kernels. Milling system A rice milling system can be a simple one or two step process, or a multi stage process. In a one step milling process, husk and bran removal are done in one pass and milled or white rice is produced directly out of paddy. In a two step process, removing husk and removing bran are done separately, and brown rice is produced as an intermediate product. In multistage milling, rice will undergo a number of different processing steps. Depending on whether the the paddy is milled in the village for local consumption or for the marketing rice milling systems can be classified into the categories village rice mills and commercial mills. THREE GENERAL TYPES OF RICE Rough rice Also called paddy rice. Rice as it comes from the field. Rice kernels are still encased in their inedible, protective hull. Brown rice, husked rice or cargo rice the least processed form of rice. It has the outer hull removed, but still retains the bran layers that give it a characteristic tan color and nut-like flavor. Brown rice is edible but chewier texture than white rice. Cooking time of brown rice is longer than milled rice Milled rice Also called white rice, or rice after milling which includes removing all or part of the bran and germ from the rough rice. Theory of Drying There are different strategies in drying this are the following: De-centralized on-farm drying Ideally the paddy needs to be dried on farm level immediately after harvest, which is mostly done through sun-drying, if the weather is favorable. For the production of better quality rice and the prevention of the weather risk farm level dryers can offer solutions, if certain criteria are met. Centralized drying economics of scale in drying can often only be reached through centralized dryers in a strategic location where enough paddy can be collected to be dried in a machine with sufficient capacity. Centralized drying can be done by farmers’ cooperatives or small contract operators at village level, at local rice mills or at collection points in the trading system The drying process Drying of grain involves exposing grain to air with low relative humidity (RH) which will lead to evaporation of the moisture in the grain and then the moisture’s removal away from the grain. Since drying practices can have a big impact on grain or seed quality, it is important to understand some fundamentals of grain drying. Requirements in POST HARVEST Submitted to:Prof.Abdon Mariano Submitted by:Eric Gulbin
Posted on: Tue, 12 Nov 2013 01:13:00 +0000
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