Laboratory Wet-Milling of Grain Sorghum With Abbreviated Steeping to Give Two Products
✍ Scribed by Xueju J. Xie; Paul A. Seib
- Book ID
- 101367101
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 217 KB
- Volume
- 54
- Category
- Article
- ISSN
- 0038-9056
No coin nor oath required. For personal study only.
✦ Synopsis
Grain sorghum is an important crop in Africa, Asia and North America. Grain sorghum plants are more tolerant than maize (corn) to semi-arid and cool climatic conditions, and the grain is used for food and feed [1,2]. Grain sorghum and maize starches may be used interchangeably, although the granules of grain sorghum starch are somewhat larger [3]. Maize is wet-processed commercially to yield starch, cooking oil (germ), gluten, steep liquor, and hull/fiber. The starch is further converted into a number of value-added products, including modified starches, sweeteners, organic acids, biodegradable plastics, and additives, among others.
Beginning in 1948 grain sorghum was wet-processed at one plant in the USA [3,4]. That plant was closed in 1975, and except for one mill in Sudan (Richard R. Hahn, private communication, 2000), grain sorghum is not wetprocessed industrially due to the abundance of maize. Furthermore, the yields of oil and starch from grain sorghum are reduced because its germ is small and its starch is associated with cross-linked proteins that resist wet-fractionation [4][5][6][7]. In some cultivars, 3-4% of starch may be encased in the middle layer of sorghum's pericarp, which causes shattering of the bran, that then contaminates other milling fractions. In others, the grain sorghum responds to injury to its glume by producing purple-appearing phenolics that may discolor the starch [4].
Except for the size of the germ, the other negative factors attributed to wet-milling of sorghum can be circumvented by choice of raw material. When contrasted to the cost of maize, grain sorghum sells at approximately a 10% discount to maize in the USA, and its small kernels hydrate quickly during steeping [8]. Davis [9] presented evidence that the oil in the germ of grain sorghum might be changed readily to a high-oleic type through conventional