The Effect And Mechanisms Of Non-Polysaccharides On Starch Digestibility

As an important source of carbohydrate, the digestion and absorption of starch is of great significance. Reducing the digestibility of starch and slowing down the rate of starch digestion and absorption have some good preventive and controlling effect on some chronic diseases. Non-starch polysaccharides not only have a good physiological function, but also can reduce starch digestibility. In this paper, we use ordinary corn starch and guar gum as the research objects and studied the effect of guar gum on starch digestibility d under different heating conditions and different starch forms.Guar gum can restrain starch swelling, only 2% have significant differences. In the gelatinization process by Rapid Viscosity Assay (RVA), adding 2% guar gum increased the peak viscosity, final viscosity, setback and breakdown values of corn starch while decreased the pasting temperature of corn starch, and this phenomenon is more obvious with the increase of guar gum concentration. In the measurement of the phase transition by Differential Scanning Calorimeter (DSC), guar gum have no effect on To, Tp and increased Tc, expect for the 20% guar gum sample.In the heating conditions of 64? and 70?, we can find that with the increase of guar gum, the long-range order and short-range order of starch increased and the damage of starch granules was less serious. In the heating conditions of 100?, with the increase of guar gum, the short-range order of starch were improved and as all the starch samples were severely damaged.The study of the effect of guar gum on starch digestibility was divided into two forms.For powder samples, we can be found the digestion curves and HIs of all starch samples have no significant difference, guar gum gelation did not reduce the starch hydrolysis by decreasing gelatinisation degree. This is probably because the deficiency of amyloglucosidase (AMG) can not transfer the a-amylase products into glucose immediately,leading the true starch hydrolysis rate is lower than producing glucose rate, especially for the high gelatinisation degree starch. In this paper, the digestive curves were almost overlapped despite the starch samples have various gelatinisation degree. So, in the vitro digestive experiment, the ratio of a-amylase to AMG is best for 1:1.For gel state, when the addition of guar gum was 0% and 2%, comparing the starch samples with same guar gum concentration, the starch digestibility decreased with the heating temperature increasing. And 2% concentration of guar gum can not effectively decrease starch digestibility. When the addition of guar gum is over 10%,it can significantly decrease starch digestibility. By observing the cross-section of the gel after 120min digestion, we can be found that guar gum and starch mixed well when the addition of guar gum is over 10%. Guar hum surrounded, filmed and covered starch, preventing starch from escaping into the digestive juice. For the entire guar, the digestive form is from the inside to the outside as the inner starch were rarely attacked by enzymes. According to the TPA experiment and the comparison of ?-glucan, we further veritied the important of the film coated by guar gum on the decrease of starch digestibility.