Chapter 4 of Rice Technology addresses one of the most intricate aspects of paddy processing, particularly for Indica varieties. This chapter focuses on Enhanced Aging of Paddy and Parboiled Rice, a subject critical to improving rice quality, cooking behavior, and milling yield.
Parboiling and enhanced aging involve treating paddy varieties having diverse Gelatinization Temperatures (GT) and gel consistency, both of which are intrinsic properties of starch. Managing these variations is essential to achieving uniform quality in the final rice product.
One of the simplest and fastest aging techniques adopted by rice millers is the steaming process. This method is now well established, with pressure steaming also widely practiced. While steaming does impact the chalkiness of rice, initial resistance to chalky appearance gradually diminished as millers and consumers recognized the significant improvement in cooking quality. Today, steaming has become a standard practice in modern rice milling.
However, premium rice varieties such as Basmati, Sona Masuri, Badshah Bhog, and Zeera rice have explored an alternative route—the dry heat aging method. This process employs conductive heating, followed by tempering, where paddy is rested for 60 to 300 minutes under controlled conditions. During this phase, moisture absorption is strictly avoided, and appropriate cooling is adopted.
Although dry heat aging is both complex and capital-intensive, many millers adopt it discreetly due to its fast return on investment. The primary reason is the superior palatability of the rice, with negligible increase in chalkiness and cooking characteristics comparable to 18 months of natural aging.
My exposure to Thailand’s rice milling practices prompted deeper exploration into high-moisture paddy preservation. Both steaming and dry heat aging require paddy moisture levels between 14% and 16%, whereas natural climatic conditions often reduce moisture below 12%, leading to increased grain breakage during aging.
A practical solution to this challenge is chilling the paddy, which allows rice millers to perform fast aging throughout the year without compromising grain integrity. India has developed high-quality grain chiller manufacturing capabilities, presenting a significant opportunity for the industry to achieve consistent quality and improved milling yields.
The evolution of the parboiling process has demanded significant efforts to move beyond the conventional “Kacchi and Pacchi” methods. I consider myself fortunate to have contributed to a breakthrough in this area under the mentorship of Dr. K. R. Bhattacharya, an eminent Rice Chemist, whose guidance played a pivotal role in advancing these techniques.
I also recall the industry-wide challenge of “musty smell” encountered in 1995, for which effective solutions were provided to the entire rice milling fraternity.
Today, multiple processing routes—ranging from nominal pressure steaming to high-pressure steaming—can be adopted to meet the diverse quality requirements of global customers.