AGRICULTURAL RESEARCH COUNCIL INSTITUTE FOR AGRICULTURAL ENGINEERING

AGRO-PROCESSING OF RICE AND SORGHUM

Introduction to the General Principles of Agro-Processing: Faced with the current economic realities, farmers worldwide are searching for new options of surviving, as well as expanding their business. One of the many opportunities to grow markets, turnover and profits, is by adding value to farm produce through further processing. Most value-added food products available to consumers have been processed in some way or other, even if the processing is as simple as cleaning produce before it is packed in plastic- or net bags. Two types of processing methods may be performed on raw materials:  Primary Processing: this type of processing includes the simplest of processes such as washing, peeling, chopping, ageing, the milling of wheat for flour production, and the processing of sugarcane;  Secondary Processing: this type of processing involves the conversion of primary processed products into more complex food products and includes procedures such as mixing, depositing, layering, extruding, drying, fortifying, fermentation, pasteurisation, clarification, heating etc.

Agro-Processing of Rice and Sorghum:  Rice Brown rice is the whole rice kernel with all the outer layers (bran and husk) removed. Canned rice is a convenience product which preserves cooked, ready-to-eat rice in a hermetically sealed can or metal pouch. There are basically two types of canned rice products available today, namely wet packs and dry packs. Wet packs contain rice in an excess of water, brine or broth. Dry packs contain no added liquid or excess moisture. The product is free flowing from the can and is prepared for serving by heating in boiling water or in the microwave oven. Gun puffed rice is ready-to-eat puffed breakfast cereal that only requires the addition of milk prior to consumption. Oven puffed rice products are popular ready-to-eat breakfast cereals. Oven puffed rice may also be used as ingredients in granola and various confectionery products to provide a crunchy, chewy character. Parboiled rice: Parboiling involves the partial cooking of rice while in its hull (rough rice/paddy), straight after harvest, prior to drying and refining. Parboiling has a significant effect on the characteristics of the rice. Pre-cooked infant rice cereal is a convenience breakfast cereal product that only requires the addition of milk or water for reconstitution. The product is generally regarded as hypoallergenic and may be flavoured and fortified. Quick cooking rice is white or brown rice that has been pre-cooked to increase the rate of water penetration into the kernel to reduce the cooking time. Rice flakes are consumed as a ready-to-eat breakfast cereal with added milk. It may also be included as an ingredient in multi-grain breakfast cereals. Rice flour is manufactured by grinding white rice using a dry milling process. Rice starch is manufactured from broken rice bits that are unsuitable for other processing options, by means of a wet milling process. Although whole rice kernels can be used, it is not feasible on a large-scale. Shredded rice is a ready-to-eat breakfast cereal produced by shredding rice to produce a latticework ribbon network that may be layered to produce a biscuit. White rice is manufactured by hulling, pearling and polishing rough rice.

Left: Popped sorghum vs popped corn Above: Gun-puffed Rice

 Sorghum Sorghum beer (Small scale) is the beverage obtained by microbial souring and mashing of sorghum malt followed by a process that removes coarse material and by the subjecting of the liquor (wort) so produced to alcoholic fermentation. The final product is transparent, pink-brown in colour, with an acidic taste. Sorghum beer (Medium scale) is the beverage obtained by microbial souring and mashing of sorghum malt followed by a process that removes coarse material and by the subjecting of the liquor (wort) so produced to alcoholic fermentation. The final product is transparent, pink-brown in colour, with an acidic taste. Sorghum flour (Small scale) is a staple food that has high domestic demand for certain rural communities. It is also used for the small-scale production of bakery products, snack foods and as ingredients in other foods. Sorghum flour (Medium scale) is a staple food that has high domestic demand for certain rural communities. It is also used for the small-scale production of bakery products, snack foods and as ingredients in other foods. Popped sorghum is a crisp, white, expanded grain snack made from sorghum kernels in much the same way as popcorn. It is much smaller than popcorn, about 0.5cm in the expanded form, but this is understandable, as the kernels are so much smaller than maize/corn kernels. Popped sorghum has a sweet taste with a typical sorghum aroma. Sorghum malt is the dried cereal obtained from germinated sorghum kernels. It is primarily used for the brewing of sorghum beer.

Public domain images courtesy of en.wikipedia.org

The manual on the Agro-Processing of Cereal Crops Vol. 1 & Vol. 2 contains complete information on the products discussed above as well as many other processing methods and products available to the cereal processor and is available from the ARC – Institute for Agricultural Engineering. Contact: Elmarie Stoltz, 012 842 4017, [email protected].