Research On The Source Of Bitter Substances In Oats And The Method Of Debittering

Oat is a kind of cereal with high economic value and balanced nutrition,but the bitter tastants generated during oat processing has become a problem that hinders the further development of oat industry.So far,there are only few reports on the bitter substances in oats,including fat oxidation,avenanthamides,etc.Futhermore,there is no report on elimination of bitter substances in oats.This paper investigated the relationship between bitter intensity of oat samples and contents of lipids,phenols and protein.The correlation study between bitter intensity and content of the six kinds of fatty acids detected by GC-MS indicated that fatty acids were not the bitter tastants in oat samples.The correlation study between bitter intensity and optical density of the 6 bands obtained in SDS-PAGE electrophoresis indicated that most proteins in oats were not associated with the bitter taste in oat samples.The correlation study between bitter intensity and the 16 phenols detected by HPLC indicated the existence of bitter substances.Results of electronic tongue confirmed that there were bitter substances in oat phenols.Peak 3 and peak 4,which achieved the highest relevance ranking,were separated by preparative HPLC and identified by LC-MS,UV,FTIR and NMR analyses.The results showed that the molecular weights of peak 3 and peak 4 were 206 and 219 respectively,and the two compounds contained unsaturated bonds and sulfhydryl groups.These indiated that peak 3 and peak 4 were new substances in oats.The two susbstances were easy to dissolve in water,and were decomposed rapidly under 30?.After 5500 minutes,peak 3 and peak 4 lossed 97.05%and 74.58%of the initial content,respectively.The debittering rate of soaking method was accelerated by ultrasonic processing,and the influence of ultrasonic time,temperature and power on the debittering effect was investigated.The results showed that the bitter intensity of oat samples decreased with the prolongation of ultrasonic time until time reached 60 min,and the bitter intensity did not decrease obviously after 60 min.With the increase of ultrasonic temperature,the bitter intensity of oat samples decreased until temperature reached 60?,and the bitter intensity changed little with temperature when temperature was above 60?.When the ultrasonic power was lower than 200 W,the bitter intensity of oat samples decreased with the increase of ultrasonic power.When the power was higher than 200 W,the bitter intensity of oat samples increased with the increase of ultrasonic power.HPLC detection showed that the content of peak 3 and peak 4 in 15 debittered oat samples had obviously positive correlation with the bitter intensity of the samples,showing that peak 3 and peak 4 might be bitter substances.Response surface methodology was used to optimize the debittering process,and the optimum conditions were:ultrasonic temperature 52.4 ?,time 70 min and power 250 W.The bitter intensity of debittered sample was 1.48.Ultrasonic processing removed most bitter substances in oat samples,and the debitter rate reached 70.40%.Ultrasonic debittering reduced the content of protein,p-glucan and phenols in oat samples by 6.04%,7.03%and 46.66%,respectively.