Milling Appraisal
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Project Leader and Principal UC Investigators Jim Thompson, Agricultural engineer, UC Cooperative Extension |
Preliminary results indicate that moisture content of appraisal samples at
the time of milling and rice cultivar both have significant effect on head
and total rice fractions of the sample. Samples evaluated after one week and one month of storage showed that head rice and total rice fractions increase as moisture content of the sample decreases. The effect is greatest for long-grain rice, less for medium-grain rice, and very small for short-grain rice. A small-scale test to see if these moisture-related differences appeared with rice that had an overall low head yield indicates that the effects may be smaller. Storage time appears to have no significant effect on milling appraisal. Tests using either an open-ended vacuum probe or multi-chambered probe for sampling loads of rice suggest that variability caused by truck sampling technique is not large. U.S. Department of Agriculture and California Department of Food and Agriculture results have a relatively small variability. Standard sample drying procedures slightly reduce head rice results but do not affect total results. Lab and truck sampling variability is random. If enough samples are taken from a lot of rice, the average of the samples will be close to the quality of the lot. However, the effects of sample moisture and sample drying method are not random and can cause the appraisal results to differ considerably from the actual quality of a lot of rice. Probably the best way to deal with these potentials for error is to insure that appraisal samples are properly dried and that their moisture content is equal to the moisture content of the lot they represent.
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