QUALITY INDICATORS FOR ROUGH RICE DURING AERATED STORAGE (ERGOSTEROL, DRY MATTER LOSS)

A method for quantitating ergosterol in wheat, maize and rice was developed using thin layer chromatography (TLC) and ultraviolet (UV) spectroscopy. The concentration of ergosterol has been proposed by others as a measure of fungal invasion in grain; ergosterol is a metabolite of fungi but not of plants. TLC was used to purify the sterol fraction of the non-saponifiable lipids extracted from grain, while UV spectroscopy was used to quantitate the concentration of ergosterol. Recovery of ergosterol from spiked samples was 84-98% for rough rice and 91-102% for corn. Delaying the extraction of the sterol band from the TLC plate for 2 h gave reduced recovery. The TLC-UV method has a repeatability of (+OR-)0.49 ug/g with obtained ergosterol values in closed agreement with quantitation by high performance liquid chromatography (HPLC).;A mathematical equation was derived to relate dry matter loss (DML) from rough rice with moisture, temperature, storage time and mechanical damage.;In rough rice stored at a moisture between 15.6-20%, the increase in the number of the damaged kernels correlated well (r = 0.96) with the increase in ergosterol level. Using the current limits on damaged kernels in U.S. grading standard, an increase in ergosterol content of >1 ug/g from its initial value would indicate that rice dropped below U.S. No. 2 grade.;DML correlated poorly with the damaged kernels (r = 0.62-0.63), except in hand-threshed Arkansas 007 rice. At high moisture, the percent damaged kernels increased disproportionately more than DML. Thus, DML cannot distinguish U.S. grades of rice as determined by damaged kernels. (Abstract shortened with permission of author.).;Storage studies were done on small samples of rough rice to develop a mathematical model for predicting safe holding or drying time for high moisture rough rice. Long-grain (Newrex and Arkansas 007) and medium-grain (Nato) rough rice were stored in aerated jars at moisture levels between 15.7 and 20% and temperatures at 35(DEGREES), 29.4(DEGREES), 23.9(DEGREES) and 18.3(DEGREES)C. Mechanical damage levels were 5.3 and 1.6% for the mechanically- and hand-threshed Arkansas 007 rice respectively. Carbon dioxide-free air, which was humidified to maintain moisture levels was passed slowly through the stored rice. Carbon dioxide generated by the respiring grain and mold was monitored with time, along with ergosterol and percent damaged kernels.