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The powder of freeze-dried sweet corn was stored under different conditions at 4, 20 and 37°C for 12 weeks, and the stability of lutein and its isomers during storage were studied. It was found that total lutein content declined depending on storage conditions and the kind of lutein isomer. The highest residual of all-trans-lutein was found stored at 4°C with vacuum and dark. Under the storage of air and light at 37°C, major isomers 9-cis-lutein, 9'-cis-lutein, 13'-cis-lutein and 13-cis-lutein showed significant increases by 35.0, 50.0, 38.4 and 37.1%, respectively, of its original content after 12 weeks of storage, which indicated isomerization might take place during storage. The kinetics of all-trans-lutein degradation under different conditions followed first order kinetics well, the apparent rate constant values were lowest under vacuum and dark and highest under air and light at each storage temperature, confirming potential detrimental effects of oxygen and light on lutein loss. [ABSTRACT FROM AUTHOR]

Polysaccharides in sweet corn cob may have many bioactivities. In this study, an efficient ultrasound-assisted extraction (UAE) technique has been developed to recover crude polysaccharides from sweet corn cob (SCCP). Ultrasound power was determined at 250 W based on the single factor test, extraction temperature (40 - 60°C), duration (30 - 60 min) and ratio of volume to weight (20 - 40 mLg-1) were then chosen to further optimize extraction conditions by response surface methodology (RSM). The statistical analysis revealed that the optimal conditions to obtain the highest yield of SCCP were of 54.7°C, 42.8 min and 27.9 mLg-1, and the polysaccharide extraction yield (0.56%) obtained from optimized UAE proved its higher efficiency when compared with the conventional method. Also, the results showed that the extraction of polysaccharides followed first-order kinetics model well. [ABSTRACT FROM AUTHOR]