The dark color is one of the major but negative effects of the parboiling process, and that parboiled rice with a dark color is not accepted by consumers in most countries. Grain discoloration is major concern of many of the rice millers and many are still not able to control it just because they do not have control over process parameters like the soaking temperature, steam pressure and resting time, unlike the APIT system where there is full control over process which in turn gives us uniform degree of starch gelatinization which gives uniformity in color, texture and other important quality parameters.
For every variety these parameters vary according to the output color required. The hue change of rice during parboiling and discoloration seemed to be caused by a non-enzymatic browning reaction called Maillard type reactions (a chemical reaction between amino acids and reducing sugars that give it a brown color). All these reactions speed up when there is fluctuation in soaking, steaming process parameters. Color changes of rice during soaking (by total water absorption) were attributed to inward diffusion of red and yellow pigments and outward migration of bran compounds at the rice surface and in steaming process migration of bran pigments toward the endosperm during steaming was probably a second mechanism explaining the color changes of rice.
In conventional systems only 80-85% grains get the thermal treatment properly, rest remains Un- treated due to which there are variations from batch to batch even grain to grain. Color that is required at the end is mainly dependent on the soaking temperature versus resting time .There is an inverse relationship between soaking temperature and resting time so whatever color is required parameters will vary depending upon the variety that needs to be processed . So the main crux of the discussion is if we have control over the process parameters we can have full control over the output quality of rice for which APIT has developed such technology which can give us all latest features in parboiling and steam curing processes.