| With the increasing prevalence of chronic diseases such as diabetes,cardiovascular diseases and obesity,as well as the high cost and side effects of medical treatments,people pay more and more attention to the prevention of diseases by diet.Starch is the main energy-supplying substance in cereals,and its digestibility is closely related to glycemic control.Polyphenols are common bioactive compounds found in grains,and their antioxidant effects can reduce the risk of chronic diseases caused by biomacromolecules that excessively destroyed by free radicals.Triticale,an emerging grain resource rich in starch and polyphenols,is becoming popular in food production.To promote the application of triticale in the diet of patients with chronic diseases,we analyzed the contents of basic nutrients of five triticale varieties from Agriculture University and studied the effects of two cooking methods(ordinary cooking and pressure cooking)on the composition of phenolic acids,antioxidant activity and in vitro starch digestibility of these varieties.The main methods and results were as follows:1.The nutrients of five triticale varieties were determined by the national standard methods,and the digestibility was analyzed by determining the contents of rapidly digestible,slowly digestible and resistant starch,and estimated glycemic index.The results showed that the main nutrients of these triticale varieties were starch(total:61.97%-65.46%,amylose:9.04%-14.12%,amylopectin:50.10%-55.48%)and protein(13.82%-20.09%),followed by dietary fiber(insoluble:9.53%-12.14%,soluble:0.94%-2.00%),while the contents of fat(1.24%-2.01%)and ash(1.80%-2.23%)were lower.Their contents were within the range of nutrient content of other triticale varieties at home and abroad.Except the contents of total starch and amylopectin,there were significant differences in other indexes,and No.2201 had the highest contents of protein and total dietary fiber.Although the contents of amylose and resistant starch in No.2201 were significantly lower than those of No.2202 and No.H-02,its estimated glycemic indexes was 47.53(with no gelatinization),significantly lower than that of the latter.2.The effects of cooking on total phenol content,the composition of phenolic acids and antioxidant activity of these triticale varieties were investigated.The free and bound phenolic contents of the triticale varieties were determined by the Folin-phenol method,and the composition of phenolic acids in the free and bound phenolics was further analyzed by HPLC with internal standard method.The scavenging abilities against DPPH and ABTS radicals and ferric iron reducing power were evaluated by spectrophotometric methods.The results showed that before cooking,the content of free and bound phenolics of the triticale were comparative,i.e.0.57-0.68 and 0.53-0.57 mg GAE/g,respectively,and although the content of phenols was significantly different among these varieties,the numerical difference is very small.The content of bound phenol increased significantly after cooking,but the difference between pressure cooking and ordinary cooking was small as a whole.The types and contents of phenolic acids were significantly different among these varieties.The three kinds of phenolic acids with higher content in free phenol were trans-cinnamie,ferulie and vanillic acids,and those in bound phenol were ferulic,sinapic and vanillic acids.Cooking caused a significant change in the composition of phenolic acid,and the influence of cooking methods on the composition of phenolic acid differed depending on the variety of triticale.The antioxidant capacity was significant different among these varieties,and the free phenol from No.3685 had the highest scavenging abilities against DPPH and ABTS radicals and ferric iron reducing power.In general,cooking significantly improved the DPPH and ABTS radical scavenging ability and weakened the ferric iron reducing power.The effect of cooking methods on antioxidation capacity also varied with the triticale varieties.3.We studied the effects of cooking on physicochemical properties and digestibility of triticale starch as well as analyzing the factors on starch digestibility of triticale.The scanning electron microscope analysis indicated that triticale starch was elliptic and spherical,with rough surface and obvious pits.After cooking,starch was corroded and cracked into pieces.The breaking degree of starch of No.H-02 and No.2201 was higher by ordinary cooking than by pressure cooking,while that of No.876 and No.3685 was more destroyed by pressure cooking than by ordinary cooking.The X-ray diffraction analysis revealed that the crystal structure of triticale starch was typical A-type,with crystallinity ranging from 10.43%to 11.47%.Some diffraction peaks disappeared or were diffused,and the crystallinity decreased after cooking.The pattern of diffraction peak of triticale starch by pressure cooking was almost as same as that by ordinary cooking.After cooking,the initial gelatinization temperature and enthalpy of triticale starch decreased significantly,while the gelatinization temperature range increased markedly.The analysis of starch digestibility showed that cooking led to the increase of the content of rapidly digestible starch,the hydrolysis rate of starch,and the estimated glycemic index.The estimated glycemic index of triticale by ordinary cooking(61.52-70.61)was significantly higher than that of triticale by pressure cooking(58.84-66.16).Among these triticale varieties,No.2201 had the lowest glycemic index when processed by ordinary or pressure cooking,and it may be more suitable as the food of patients with chronic diseases such as diabetes.Meanwhile,it is also necessary to further lower the ability to raise blood glucose by optimizing cooking conditions or using other processing methods.The correlation analysis showed that the content of rapidly digestible starch was positively correlated to the eGI of triticale,while the content of slowly digestible starch,resistant starch,bound phenolic acid,total phenolic acid,ferulic acid and crystallinity were negatively correlated to the eGI.Compared with No.2201,No.2201-L,No.2201-P and No.2201-L-P had significant higher content of rapidly digestible starch and estimated glycemic index,while lower content of resistant starch.This indicated that the endogenous protein and lipid of triticale may contribute to the decrease of starch digestibility. |
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