Optimization Of Preparation Process And Determination Of Structure And Properties Of Loquat Nuclear Resistant Starch

Loquat(Eriobotrya japonica Lindl.)originated in China,is loquat genus of rosaceae,widely planted in the south of China,often as a fresh fruit in summer.Loquat pulp is not only sweet and juicy,but also rich in protein,vitamins,organic acids,carotene and other nutrients,which is loved by people.Resistant starch,also known as slow digestible starch,is an indigestible carbohydrate,which has good performance in maintaining intestinal health,inhibiting lipid metabolism,lowering blood sugar and reducing the occurrence of diabetes.As a new dietary fiber,resistant starch has been paid more and more attention.Researchers have prepared resistant starch with good properties from many kinds of starch.The leaves,skins and flesh of loquat have been proved to extract a variety of antioxidant substances and have been well utilized.However,the seeds of loquat are basically discarded in the process of eating,which causes pollution and is not conducive to the reuse of loquat resources.Loquat seeds account for about 25%of the whole fruit and contain a large amount of starch,which can be used to prepare starch and modified starch.On the basis of investigating the fruit quality of white meat loquat and yellow meat loquat,this paper studied the optimal preparation process of loquat kernel resistant starch,and observed the morpHology,physical and chemical properties,antioxidant activity and in vitro digestibility of loquat starch and resistant starch.Through the study of starch and resistant starch in loquat kernel,the direction of recycling loquat kernel was established to save and develop biological resources and increase the added value of products.1.Analysis of appearance quality indexes of loquat fruit.Select suzhou dongshan introduced.cultivation variety:white loquat,jade crown red loquat eggs,analysis of three kinds of loquat quality indicators,white jade of loquat TSS(soluble solid)in multiple measurement is best,followed by red crown jade and eggs,and white jade of loquat fruit shape index,edible rate is better than the other two loquat,white loquat is better than the yellow flesh loquat.2.Optimal preparation technology of loquat kernel starch.The preparation methods of resistant starch mainly include pressing heat method,de-branched method,microwave and ultrasound-assisted extraction method,etc.In this paper,ultrasonic assisted enzymatic method was used to prepare resistant starch of loquat kernel.Four factors including starch milk concentration,ultrasonic power,enzyme addition amount and enzymatic hydrolysis time were selected to obtain the optimal preparation process through orthogonal experiment:The optimal preparation conditions were starch milk concentration of 35%,ultrasonic power of 180W,enzyme dosage of 25u/g and enzymatic hydrolysis time of 10h.3.Determination of structure and properties of nuclear starch and resistant starch in different loquat cultivars.The structure and properties of starch and resistant starch in fruit kernel of white jade,crown jade and qingshi loquat were determined.The amylose content of white jade loquat was the highest,and that of green jade and crown jade decreased successively.Under the same conditions,the content of white jade loquat was the highest,which proved that the resistant starch prepared from loquat kernel with high amylose content had higher extraction rate.Under the light microscope,the three loquat starches showed smooth and round appearance,with nearly round appearance and roughly the same shape.However,the integrity of resistant starch grains was destroyed,presenting irregular clumps of different sizes.Under the observation of scanning electron microscope,the starch grains were mostly large and irregular,and the structure of starch grains disappeared,leaving only the hard and dense crystalline area of amylose.The crystal structures of white jade,crown jade,green loquat starch and resistant starch were observed by polycrystalline X-ray powder diffractometry.It was found that the three original loquat starch had strong diffraction peaks at 17°,and weak diffraction peaks at 150 and 23°,which were typical C-type starches.The resistant starch showed a strong absorption single peak at 17° and an insignificant peak at 20-23°,presenting b-type crystal characteristics.Fourier transform infrared spectroscopy(FTIR)was used to analyze the short-range ordered structure of starch.The band ratio of starch at 1045cm1/1022cm-1 was lower than that of resistant starch,indicating that the short-range ordered structure of resistant starch was higher.The temperature range was controlled from 50? to 90?,and the solubility and swelling degree of starch and resistant starch were measured every 10?.It was found that the solubility and swelling degree of starch increased with the increase of temperature.When the temperature was 60-70?,the solubility and swelling degree of starch increased significantly,and the expansion degree of starch was higher than that of resistant starch.4.Determination of antioxidant activity and in vitro digestibility of loquat resistant starch.Antioxidant activities including DPPH free radical scavenging,superoxide anion free radical scavenging,ABTS scavenging,total antioxidant activity,nitrite scavenging and-OH scavenging were measured by using the prepared loquat resistant starch.The results showed that loquat resistant starch had good antioxidant capacity.It was found that loquat resistant starch had good anti-digestion ability by simulating digestion of gastric juice and intestinal juice.