Rice hull silica and a rice hull carbon ash were evaluated as adsorbents for the soy oil bleaching process under commercial temperature and pressure conditions. Their performance in adsorbing pigment, phospholipid, free fatty acids, and peroxides was compared with that of a commercial bleaching clay and silica hydrogel. With the exception of phospholipid binding, rice hull‐derived adsorbents were ineffective. Rice hull silica showed potential as a phospholipid adsorbent but was not as effective as the synthetic silica hydrogel on an adsorbent weight basis. However, it was a superior adsorbent when the data were expressed as adsorbate bound per unit surface area. The low surface area of the rice hull silica limits its commercial viability. It may have value in areas of the world where rice hulls are plentiful and an inexpensive phospholipid adsorbent is required for oil processing. Research is in progress to increase the surface area of rice hull silica for commercial oil processing.
A one minute rapid equilibrium extraction for total oil in soybeans was developed and factors influencing the extraction were examined. Comparisons of the rapid equilibrium extraction with a Goldfisch extraction were made, using 100 mesh flour on ten cultivars over a three year period. The equilibrium extraction consists of slurrying 100 mesh flour in hexane until an equilibrium between oil content inside and outside of the soybean particle is achieved. One minute was required for equilibration of 98% of the oil in the soybean flour, and one hour was required for complete equilibration when compared with a five hour Goldfisch extraction. Accuracy and precision of the method were excellent when proper technique was followed. A comparison of the rapid equilibrium and the Goldfisch extractions showed similar changes in oil content due to changes in soybean flour moisture and in preheating the soybeans. The amounts of phospholipid extracted from fine flour were considerably less than usually extracted from flakes under commercial conditions. The correlation between the rapid equilibrium and Goldfisch extractions for ten cultivars was excellent (r=0.9956) when analyzing 100 mesh flour. Environmental conditions caused significant interactions between cultivars and years of production.
Forrest' soybeans were stored for two years, and the extracted lipids were assayed for hydroperoxide content. The crude lipid was separated by high-performance liquid chromatography {HPLC), and three hydroperoxide peaks plus the triglyceride peak were measured every two months. There was a lag in hydroperoxide production for the first nine months followed by a steady increase for the remaining twenty-two months. This method of measuring changes in lipid oxidation should be useful for monitoring seed changes in germination and vigor during storage.
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