| Epidemiological and clinical studies demonstrate that intake of dietary fiber can reduce the risk of chronic diseases.Cereal fiber is the main source of dietary fiber in our diet,but due to the chemical heterogeneity,cereal fibre polymers are organized in a complex hierarchical structure in the cell wall,which cause both nutritional and technological challenges for its application.Therefore,in order to give full play to the functional characteristics of dietary fiber,improve the added value of products and reduce many restrictions in application,different processing methods are usually used to it.Based on this,the effects of extrusion-enzymatic treatment on the physicochemical properties and in vitro fermentation properties of oat dietary fiber(ODF)were systematically studied in this research.The main contents and conclusions are as follows:The effects of extrusion,enzymolysis,extrusion-enzymolysis and enzymolysisextrusion on soluble dietary fiber(SDF)content of oat were compared.The results showed that combined treatment was more beneficial to the increase of SDF content than single treatment.And the extrusion-enzymatic treatment was more advantageous in increasing the SDF content of oat.The extrusion treatment in this processing method was optimized and the optimal process parameters were determined as follows: extrusion temperature 136 °C,moisture content 19%,and screw speed 339 rpm.Under these conditions,the content of SDF in oat was increased from 1% to 3.4%.Meanwhile,it was found that screw speed and extrusion temperature had significant effects on SDF content of oat,while moisture content had no significant effects on SDF content of oat.The structure of ODF was characterized before and after processing.The results showed that the crystal structure of oat dietary fiber treated by extrusion-enzymatic hydrolysis(EODF)was destroyed,which caused the lower relative crystallinity.The fiber matrix became discontinuous and loose,exposing more internal structures,and the molecular weight of SDF also significantly decreased.Infrared analysis showed that lignin in ODF was transformed into smaller phenolic compounds after processing.These structural changes result in higher SDF content and lower initial decomposition temperature of EODF.Furthermore,the structural changes significantly improve the water holding capacity,swelling capacity and oil holding capacity of EODF.Different processing conditions have great influence on the water holding capacity and swelling capacity of EODF.However,screw speed and extrusion temperature did not cause significant differences in oil holding capacity among EODF.Extrusion-enzymatic can change the fermentation characteristics of EODF.Compared with ODF,EODF can significantly lower the p H value of fermentation substrate and produce more short chain fatty acids throughout the fermentation process.EODF is better than ODF in promoting the proliferation of probiotics and inhibiting the proliferation of harmful bacteria,and can regulate the composition and abundance of gut microbial to a greater extent.Different processing conditions had little effect on p H value and acid production,but there were differences in regulating gut microbial composition.Our study contributes new insights into the processing and nutritional functions of dietary fiber. |
