Study On Preparation,Physicochemical Properties And Prebiotic Properties Of Chickpea Resistant Starch

Resistant starch, which was a focus for research on food, had some physiological functions, such as stimulating intestinal beneficial bacteria growth, increasing intestinal short chain fatty acids production and preventing colon cancer. At present, the chickpea starch researches were paid attention to the physicochemical properties and physiological functions of native chickpea starch, while there were few studies on the chickpea resistant starch, particularly on the pure chickpea resistant starch. In this thesis, the studies were concentrated on the preparation of chickpea resistant starch and the physicochemical, in vitro digestion and prebiotic properties of chickpea resistant starch samples. Main results were listed as follows:1. Study on preparation of chickpea resistant starchThe optimum preparation conditions of chickpea resistant starch were found to be pH: 2.6, starch amount:2.24 g, cold preservation time:18.7 h, autoclaving temperature:121℃, autoclaving time:30 min, and autoclaving/cooling cycle:1 cycle. The chickpea resistant starch yield was 63.0% at the optimum preparation conditions.2. Study on physicochemical and in vitro digestion properties of chickpea starch samplesThe physicochemical and in vitro digestion properties of chickpea starch samples were analyzed by elemental analysis, scanning electron microscopy, thermal gravimetric analysis, and so on. The results showed:(1) The protein residue in the chickpea starch increased with the amylase dosage used in the preparation process, and the residual protein was not evenly distributed in starch but more concentrated on some starch granules. (2) NS contained 30.72% amylose and 70.57% amylopectin and its degree of polymerization was 471. RSI, RSII, RSII-1 and RSII-2 were mainly composed of short chain amylose with a few branched chains and their degrees of polymerization were all about 41. (3) The maximum absorption of the compound of NS with iodine was at 605 nm and the blue value of NS was 0.61. The maximum absorptions of the compounds of RSI, RSII, RSII-1 and RSII-2 with iodine were all at 582 nm. The ranking order based on blue value was RSI>RSII-2>RSII>RSII-1. (4) According to thermal characteristics analysis, the appropriate enzymatic treatment could improve the thermal stability of starch, while the excessive enzymatic treatment could reduced the thermal stability of starch. (5) According to the scanning electron microscopy images, NS was oval or spherical in shape with smooth surface and varied in size; RSI and RSII showed irregular shaped, smooth surface, denser structure and a layered structure; RSII-1 showed irregular shaped, smooth surface and porous structure; RSII-2 showed irregular shaped, rough surface and a layered structure. (6) According to in vitro digestion studies, the stabilities of RSII and RSII-2 in the simulated digestive juice were higher than RSI, and the stability of RSII-1 in the simulated digestive juice was the lowest.3. Study on the crystal structures of chickpea starch samplesTwo methods, which could provide mutual corroboration, were developed for detecting the crystal structures of chickpea starch samples. One is a deconvolution method according to the X-ray diffraction (XRD) pattern of chickpea starch sample, the other is a method based on the moisture content of chickpea starch sample. Based on the deconvolution method, the results showed:(1)The RC, RCB and BP of RSI had an increase (15.32%, 4.15% and 2.98% increase, respectively) compared with NS. The result showed that the preparation processes from NS to RSI was conductive to the increase of crystalline, especially for B-type polymorphs, in starch. (2) The RC, RCB and Bp of RSII had an increase (12.78%,4.91% and 3.72% increase, respectively) compared with RSI. The result showed that the crystalline region of RSI was less susceptible to enzyme hydrolysis than its amorphous region, and moreover, B-type polymorphs in RSI were more enzymatically resistant than A-type polymorphs. (3) The RC and RCA of RSII-2 had a reduction (7.59 and 7.77% reduction, respectively) whereas the RCB remained stable (0.18% increase) compared with RSII. The results indicated that A-type polymorphs were instable in the high-concentration K2CO3 solution whereas B-type polymorphs were not affected by this treatment.4. Fourier transform infrared spectroscopic analysis of chickpea starch samplesA new method for determining the relative crystallinity (RC) of starch was developed by using Fourier-transform infrared spectroscopy (FT-IR), based on hypotheses as described as follows:there is a Gaussian holocrystalline-peak (HCP) in the 1300-800 cm-1 region of FT-IR spectrum of starch which is divided into amorphous region and crystalline region; the crystalline region of HCP is the overlap of the HCP and the FT-IR spectrum of starch; the RC of starch is the ratio of the area of crystalline region to the area of HCP. The hypotheses were suitable not only for the determination of RC of chickpea starch samples, but also for the determination of RC of sweet potato starch, corn starch, wheat starch, tapioca starch and potato starch. The intra-class correlation coefficient was 0.998 (P= 0.000, n=9) and the 95% confidence interval was 0.992-1.000 for the RC determined by XRD and FT-IR. The results indicated that the RC determined by FT-IR was in agreement with that determined by XRD. Furthermore, the developed method showed good linearity, accuracy, specificity, repeatability (coefficient of variation (CV),1.1-2.9%) and good intermediate precision (CV,2.8%).5. Study on the effect of chickpea resistant starch samples on Bifidobacterium, L. rhamnosus and E. coli growthThe effect of chickpea resistant starch samples on Bifidobacterium, L. rhamnosus and E. coli growth were evaluated by in vitro anaerobic fermentation. The results showed: (1) In pure culture, RSI, RSII, RSII-1 and RSII-2 could all suppress E. coli growth and promote Bifidobacterium and L. rhamnosus growth. RSII and RSII-1 had the maximum growth inhibition to E. coli, and RSI and RSII-2 might make Bifidobacterium and L. rhamnosus entering much earlier into stationary phase and decline phase. (2) In mixed cultures of Bifidobacterium and E. coli, RSI, RSII, RSII-1 and RSII-2 could all inhibit their growth. However, RSII-2 and RSI could promote a bifidobacteria-dominant microflora, especially for RSII-2. (3) In mixed cultures of L. rhamnosus and E. coli, RSI, RSII, RSII-1 and RSII-2 could all suppress E. coli growth and promote L. rhamnosus growth. RSII, RSII-1 and RSII-2 could promote a L. rhamnosus-dominant microflora at the anaphase of fermentation. (4) In mixed cultures of L. rhamnosus and Bifidobacterium, RSI, RSII, RSII-1 and RSII-2 could all inhibit L. rhamnosus and Bifidobacterium growth, particularly for RSI. (5) In mixed cultures of E. coli, L. rhamnosus and Bifidobacterium, RSI, RSII, RSII-1 and RSII-2 could all suppress E. coli and Bifidobacterium growth and promote L. rhamnosus growth. RSI, RSII, RSII-1 and RSII-2 were all having prebiotic effect, especially for RSII-1 and RSII-2.6. In vitro study of prebiotic properties of chickpea resistant starch samplesThe effects of chickpea resistant starch samples on the prebiotic properties were evaluated by in vitro anaerobic fecal culture. The results showed:(1) RSI was having a certain prebiotic effect which could promote Bifidobacterium and Eubacterium growth and increase the proportion of beneficial bacteria. It could enhance the propionic acid production at the anaphase of fermentation and inhibit the liberation of acetic acid, lactic acid, formic acid and butyric acid. (2) RSII was having a good prebiotic effect which could promote Bifidobacterium and Eubacterium growth, suppress Bacteroides growth and obviously increase the proportion of Bifidobacterium, Lactobacillus and Enterococcus. It could increase the lactic acid production and had little effect on the propionic acid production, and could inhibit the liberation of acetic acid, formic acid and butyric acid. (3) RSII-1 was having a good prebiotic effect at the prophase of fermentation which could promote growth of Bifidobacterium, Lactobacillus and Enterococcus, inhibit Eubacterium, Clostridium histolyticum and Bacteroides growth and decrease the proportion of Eubacterium, Clostridium histolyticum and Bacteroides. It could increase the liberation of acetic acid, lactic acid, formic acid and butyric acid, and had little effect on the propionic acid production. (4)RSII-2 was having a good prebiotic effect which could promote Bifidobacterium and Eubacterium growth, inhibit Bacteroides and Clostridium histolyticum growth and increase the proportion of Bifidobacterium, Eubacterium, Lactobacillus and Enterococcus. It could increase the liberation of lactic acid, acetic acid and butyric acid and had little effect on the formic acid production, and could inhibit the propionic acid production.