Near-Infrared Analysis of Rice
Rice is one of the most important crops for feeding mankind. In 2013, rice was the world’s second largest grain crop, (corn being first), and half of the world’s population consumed rice. With the growth of the world population and global economic development, the demand for rice will continue to increase. To efficiently supply this surging demand, it is important to improve rice varieties, quality, and crop yield.
Since the 1950s, scientists have been searching for parameters that can define cooking quality and processing characteristics of rice, as well as their chemical and physical testing methods. For example, amylose content and alkali diffusion values are widely used worldwide in rice breeding. Amylose content is related to water absorption, swelling, viscosity, and the glossiness of rice. The alkali diffusion value is related to the gelatinization temperature of milled rice starch granules. The viscosity of rice paste during heating and cooling is often measured as an indicator of the milling properties of rice flour. Although the content of protein is not often used in rice breeding, it is an important factor because it directly affects cooking time, texture, and nutritional value. The fat content is also an important nutrient of rice; it has a significant influence on the flavor, appearance, and quality. Additionally, the fat content in rice decreases with the extent of processing.
The traditional testing procedures for rice processing are very time consuming and cannot be used as online monitoring methods. For example, the iodine blue method is used to test the amylose content; it uses chemical agents, takes a long time, and has extremely poor reproducibility. Another example is the alkaline diffusion test which requires soaking the milled rice overnight in 1.5 or 1.7% KOH liquid. The viscosity property test takes over 1.5 hours.