This project continued to examine the relationship between moisture content and water activity on rough rice.  Researchers sampled 78 loads of rice at the Farmers Rice Cooperative receiving facility in West Sacramento.  They also conducted two laboratory tests to determine quality effects on freshly harvested rice.

As expected a very close relationship between rough rice moisture and water activity was observed.  Relative humidity in the air above a batch of rice was found to be a good indicator of rice moisture.  This could be particularly valuable in measuring safe storage conditions because storage fungi do not grow at relative humidity levels below 65 to 70 percent.  Further, previous research showed that undried rice is particularly subject to off-odor development when relative humidity exceeds 92 percent.

Scientists also examined the individual kernel moisture of all receiving samples collected.  On average a 16 percentage point spread was found between wettest and driest kernels in freshly harvested rice.  This wide spread is important because the drier kernels may be more subject to cracking in close proximity to wet kernels.  To test this relationship two batches of undried, commercially harvested rice were held for 24 hours in lidded plastic garbage cans.  The first test with M-104 showed no loss in head rice; however, the second test with organic S-102 showed a one percent decrease.  This decrease may have been influenced by the presence of high-moisture redberry weed seeds.  Samples were to be further analyzed for fissuring with a Japanese soaking test.  The preliminary finding is that free water from dew or condensation may be a more significant cause of rice cracking and reduced head quality than exposing rice to high humidity.