Food & Beverages

Biography

Biography: Himjyoti Dutta

Abstract

Parboiling is a popular post-harvest paddy processing practice in India, Pakistan and African countries. Conventional parboilng involves hydration of paddy by soaking in water followed by open steaming. Steaming under high pressure is a more recent technique practiced for industrial production of parboiled rice. Steaming is followed by drying under the sun or ovens and milling to produce staple grains. A third type called dry heat parboiling involving roasting previously soaked paddy or rice using heated sand or hot pan was earlier considered to produce only speciallity products like popped and puffed rice. However, this process involving instant heating at high temperature also encompasses the molecular changes as seen in steam parboiled rice. The step of drying is not necessary here because extensive drying occurs simultaneously during the heating step. In this study, dry heat parboiling of sufficiently soaked paddy with distinctly differnt amylose content was carried out under controlled conditions of temperature and time. Neither popping of paddy nor excessive puffing of the gelatinized kernels were allowed. The technique resulted in increased kernel hardness resulting in high head rice yield. Excessive damage to the amylopectin resulted in high water uptake properties and gave a continuously rising RVA pasting curve. XRD and DSC analyses indicated formation of starch-lipid complexes. Waxy rice varieties with no amylose content also showed the corresponding peaks, cofirming complex formation amongst amylopectin and lipid after parboiling. Occurence of retrogradation on adding water to gelatinized starch in DSC pan was evident. Dry heat parboiling also notably increased the digestibility of starch in all the varieties. The technique can therefore be effectively used for commercial paddy parboiling to produce staple rice for targeted population groups.