2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Recent studies in the University of Arkansas Rice Processing Program indicated that Tg had a great effect on drying characteristics and milling quality of rice. Because of the similarity in compositions of corn to rice, it is expected that Tg will also play an important role in corn drying. The objective of this study was to determine the Tg of corn kernels at various moisture contents. Two corn samples at initial MCs of 20.8% and 19.2% were used. Corn kernels were conditioned to different MCs at room temperature. Three kernels were randomly taken from the bag and flattened at the tip cap end and its opposite end using sandpaper before they were positioned to the Dynamic Mechanical Thermal Analyzer (DMTA) for Tg measurement. The changes of storage modulus (E'), loss modulus (E") and tangent delta (i.e., tan(E'/E")) were recorded as a function of temperature. Around Tg, tangent delta incurred a dramatic increase. The junction of the slope before and after the changes in the tangent delta curve was defined as Tg. It was found that the Tg of the corn kernels ranged from 20 C to 80 C in the MC range of 9.5 to 22.7%. It was also found that the Tg of corn kernels was highly comparable with that of rice kernels in the entire MC range tested. This can be explained by the fact that the major composition of both corn and rice is starch that should show similar glass transition characteristics.