| As an annual herbaceous plant,potato(Solanum tuberosum L)has been widely cultivated around the world followed only wheat,rice and maize for its high yield and environmental adaptability.In 2015,Chinese government launched the grain staple food strategy of potato,and promoted its position as the wheat,corn and rice,and this plan would increase the protection of China's food security significancly.However,the content of rapid digestion starch in cooked potato is relatively high and consumption of cooked potato might induce a rapid increase in postprandial blood glucose,which will affect health adversely.Researches have shown that the rate of potato digestion was closely associated with cooking methods and phytochemicals;but to the best of our knowledge,no systematic researches have focused on this.Therefore,in order to have a better understanding on the relationship among microstructure,phytochemicals and the digestion of potato,two main studies were carried out in this study.Frist,the changes of potato nutrition,microstructure and digestion rate under different cooking conditions were analyzed,the postprandial blood glucoses were investigaeted in vivo and the changes of fecel microflora in SD mice with intaking of different cooked potato were also analyzed.Second,with the aiming of reveal the reduction mechanism of Chlorogenic acid on potato starch,the relationship between Chlorogenic acid and starch as well as Chlorogenic acid and a-amylose were studied.Particularly,the effects of Chlorogenic acid on the protection of mice with high fat diet were also studied and the main conclusions in this study were as follows:1)The nutritional contents from different varieties of potato were quiet different,the highest total phenolic was observed in Heimeiren variety,followed by Zhongshubahao,Helanshiwu and Xiapodi,while the highest content of total carotenoids was found in Zhongshubahao,followed by Helanshiwu,Heimeiren and Xiapodi.The cooking methods also showed a signifidant effect on the nutritional content.Generally,vitamin C and total carotenoids showed a cooking methods depended decrease in all potato varieties.Microwaving and steaming methods could retain more nutrition than other cooking methods.The correlation among DPPH free radical scavenging ability and total phenolic,total carotenoids,phenolic acids and vitamin C in purple potato were analyzed and results showed that the antioxidant activity was determined by multi-factor rather than single compound.2)The microstructure of potato was significantly affected by the cooking methods and eventurally showed different digestion rates during in vitro simulatied digestion.The X-ray diffraction of raw potato showed a typical B type structure,while after cooking,the crystal form disappeared and after storing at low temperature for a period of time,the gelatinized starch was re-formed due to the retrogradation process and those results were also confirmed by the DSC results.The in vivo postprandial blood glucose test also showed that cooking methods changed the glycemic index(GI)of potato;the boiled potato showed the highest GI(103 ±6),followed by microwave-reheating(93 ±5),cooling(86 ±7),stir-frying(74 ±6)and frying(69 ±5).3)Consumption of potato with different cooking methods had a significant effect on the weight of SD mice.The average weight in fried group was the highest,followed by boiling group,stir-fried group and control group.No significant differences in blood glucose and blood lipids were observed,but the compositions of fecal microflora in different groups do show significant differences.Compared with the initial group,the ratio of Bacteroides and Firmicutes in stir-fried group and the control group did not change much,while the fried group was significantly decreased.Additionally,we also found that the fecal microflora in different feeding groups changed gradually with the prolongation of feeding time and indicated that the composition of the fecal flora was a dynamic change process.Thus,analysis between the the beginning and the end of feeding might not enough.4)The cell wall of potato affected the microstructure and thermodynamic properties of starch gelatinization and retrogration.The starch with cell wall showed a higher of To,Tp and Tc,while the ?H was much lower.However,the digestion rate of potato starch with or without cell wall showed no significant difference.The addition of Chlorogneic acid decrease the To,Tp,Tc and ?H of potato starch as well as decrease the regtrograte rate of gelatinizated starch.Additionally,Chlorogneic acid showed a good inhibitory effect on a-amylase(competitive and noncompetitive inhibitory type).With auto-docking analysis,it could be found that Chlorogenic acid-specific binding with a-amylase in the active region,suggesting that the inhibition of a-amylase by Chlorogenic acid was activated by binding to the active region.5)Chlorogenic acid cold inhibit the increase of body weight,improve the blood glucose,blood lipid levels and decrease the accumulation of fat in liver and adipose tissue in C57BL/67 mice.The transcripts in mice liver were also analyzed and results indicated that compared with the HFD(high fat diet)group,about 2,022 transcripts were up-regulated and 990 were down-regulated in the Control group.Compared with the CAL(Chlorogenic acid)group,about 2,741 transcripts were up-regulated and 1736 were down-regulated in Control group.While compared with the HFD group,869 transcripts were up-regulated and 1113 were down-regulated in HFD group.According to the annotations of KEGG pathway,about 14 pathways(80 genes involved)involved in carbohydrate metabolism were found between the control group and CAL group,while 15 pathways(100 genes involved)between Control and HFD group and 6 pathways(18 genes involved)between CAL and HFD group.6)Chlorogenic acid improved the composition of fecal microflora in high fat fed mice at different levels significantly.Compared with the HFD group,the ratio of Bacteroides and Firmicutes in the control and CAL group was much higher,indicating that Chlorogenic acid could relieve microflora composition in HFD group.In addition,the proportion of some microflora in CAL group was significantly higher than that of the control group and HFD group(such as the proportion of Bacteroides in CAL group was significantly higher than that of the control group and HFD group.)... |
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