| The retrogradation of starch is self-association during storage after gelatinization, it can markedly effect on quality of starchy foods. So it is an important and unresolved technology problem in food industry. To study retrogradation, gelatinized high amylose rice starch (HA-RS) with 66.7% w/w water content was stored at 4 oC different days as model. It was investigated that the effect of new additive and physical technology on preventing the retrogradation. Then rapid molecule vibration spectrum was used to monitor the retrogradation process and fractal theory was used to characterize fractal growth of this process. The major content and results were as following:The effect of natural antioxidative extracts including tea polyphenols (TPLs), blueberry extract (BE) and grape seed extract (GSE) on the retrogradation of HA-RS were investigated. TPLs-fortified HA-RS exhibited retarding the retrogradation as assessed by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The temperature and enthalpy of starch gelatinization obviously decreased as the TPLs level increased. Gelatinization To, Tp and Tc of starch with 16%TPLs sample were respectively 8.93, 5.69 and 5.13 oC lower and enthalpy of gelatinization reduced by 2.27J/g. After storage at 4 oC, enthalpy and recrystallization of starch retrogradation gradually decreased with the increase of TPLs content. HA-RS with 16% TPLs had almost no retrogradation enthalpy and recrystallization until storage of 15 days. It was observed at same magnification by SEM that the size of retrograded starch granules decreased and appeared cancellous shape with adding TPLs increased. The overall results demonstrate that the marked inhibitory effect of TPLs on the retrogradation of HA-RS. Subsequently, it found that high active TPLs could interact with HA-RS to form hydrogen band through Rapid Visco Analyzer (RVA), 1H-NMR and FT-IR analyses, so this interaction might disturb self-association of starch retrogradation during storage. In addition, two other natural antioxidant extracts-blueberry extract (BE) and grape seed extract (GSE) also behaved the retarding the retrogradation of HA-RS, and BE has a better effect than GSE. The effect on preventing the retrogradation of TPLs, BE and GSE were all better than trehalose which is publicly known anti-retrogradation additive. The sequence of capability was TPLs > BE > GSE > trehalose.It was studied that degradation methods of chitosan and the effect of product on preventing the HA-RS retrogradation. Chito-oligosaccharides (COS) were prepared using enzyme hydrolysis and hydrogen peroxide (H2O2) degradation, respectively. IR analysis proved that COS prepared by enzyme hydrolysis all had active amino-group. But this group of all the fractions of COS prepared by 6mL/30min H2O2 degradation was damaged. Subsequently, the effect of 8% COS (based on starch weight) on the retrogradation of HA-RS after storage for seven days at 4 oC was investigated. It found that the fraction of 5k < COSM < 10k had the best ability to prevent the retrogradation. Moreover, retrogradation ratio of HA-RS with this fraction was reduced by 14.5% as compared with the control and recrystallization ratio was only 58.52% of the control. Then, the inhibition capability of the fraction of 10k < COSM < 30k was followed. But the fraction of COSM < 5k has no this effect. Therefore, it stated that the size of molecular weight of COS decided the effect on preventing the retrogradation. But all the fractions of COS prepared by 6mL/30min H2O2 degradation had no effect on retarding the retrogradation due to changes in the structure. Therefore, molecular size and existence of active amino-group of COS determined the capability of anti-retrogradation.Multiple instant heating -stirring preventing the retrogradation of high amylose rice flour (HA-RF) and HA-RS were investigated. The results indicate that three instant heating (100 oC)-stirring (500 r/min) had a clear effect on retarding the retrogradation of HA-RF. Treated HA-RF by three instant heating-stirring exhibited the lowest retrogradation enthalpy (3.04J/g dry flour) as compared to the control (5.93J/g dry flour) in DSC analysis and had almost the least recrystallization (52.32% of the control) by XRD. The observation by SEM stated that treated HA-RF by this way granules had a more honeycomb-like structure and reduced the crystal morphologies. The gelatinized HA-RF by three instant heating-stirring treatments enlarged mesh of network structure by SEM section observation, it implied that network structure had more gathered water by this method treatment. But this physical technology had no effect on the retrogradation of isolated HA-RS. The different results of treated HA-RF and HA-RS by this physical technology might be due to rice protein having anti-retrogradation function after treatment.It was investigated that Fourier transform infrared (FT-IR) and Laser Confocal Micro-Raman (LCM-Raman) spectroscopy for rapid monitoring the retrogradation process of HA-RS. The results indicate the relative intensity of some vibrational modes reduced regularly with increasing extent of the retrogradation including O-H (3415cm-1) stretching, C-H (2927.46cm-1) stretching, C-O and C-C (1155.17cm-1) stretching, C-O-H (1081.89cm-1) bending, undetermined (1043.32cm-1, 1020.18cm-1 and 998.96cm-1) modes, skeletal modes of pyranose ring (609.41cm-1 and 578.55cm-1) in FT-IR spectra and C-O stretching and C-O-H bending (1122.37cm-1), C-O-H (1082.83cm-1) bending, C-C (1050.05cm-1) stretching, C-H (854.31cm-1) deformation, skeletal modes of pyranose ring (440.66cm-1) in Raman spectra. By the correlation analysis between retrogradation enthalpy of DSC and the relative intensity reciprocal of above vibrational modes, these peaks of 1081.89cm-1, 1043.32cm-1, 1020.18cm-1, 609.41cm-1, 578.55cm-1of FT-IR and 854.31cm-1, 1082.83cm-1, 1050.05cm-1 of LCM-Raman had correlation coefficient above 0.9, so these vibrational modes listed above may be as index to quantify the retrogradation. Meantime, the sensitivity of LCM-Raman was higher than FT-IR.It was studied that the probability of fractal theory to characterize process of starch retrogradation. SEM was adopted to observe section feature of retrograded HA-RS stored at 5, 10 and 15d. The surface topography of retrograded starch had self-similarity and manifested fractal characteristics. Based on professional fractal software analysis, fractal behavior of various retrograded starch was remarkable. The fractal dimensions of retrograded samples stored at 15d, 10d and 5d were respectively 1.8267, 1.7803, and 1.7333. The extent of retrogradation (retrogradation enthalpy) and the fractal dimension had a linear relationship, linear equation was y = 0.0358x + 1.5934. Cluster-Cluster aggregation model was used to simulate the fractal growth process of starch retrogradation. Simulation results resembled the feature and fractal dimension of the experimental results, so this model can be characterize the growth mechanism of starch retrogradation.
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