Lotus seed starch （15%, w/w） was subjected to ultra-high pressure （UHP） at 500 MPa for 10～60 min. The effects of UHP on the structural, pasting, and thermal properties of starch were investigated using solid-state 13C CP/MAS NMR, differential scanning calorimetry （DSC）, HPSEC-MALLS-RI, and a rapid visco analyzer. The 13C CP/MAS NMR results revealed a reduction in the relative crystallinity and peak intensity of the crystalline state with increasing the UHP time. The molecular weight of native starch was 1.433 × 107 Da, which was higher than that of the UHP-treated starch. Viscograms of UHP-treated starch revealed an increase in paste viscosity, peak time, and pasting temperature and a reduction in breakdown and setback viscosity compared to the native starch. Furthermore, the DSC results showed a reduction in gelatinization temperature and gelatinization enthalpy with increasing the UHP time.
Semen coicis resistant starch is a type of starch which has undergone retrogradation. In this study,the structural characteristics of Semen coicis native starch,high-amylose maize starch,and heat-moisture treated Semen coicis resistant starch were investigated. The field emission scanning electron microscopy results indicated that compared to Semen coicis native starch and high-amylose maize starch,the surface of heat-moisture treated Semen coicis resistant starch was rough and full of irregular layered strips. The Fourier transform infrared spectroscopy measurements indicated the degree of ordered structure values of Semen coicis native starch,high-amylose maize starch,and heat-moisture treated Semen coicis resistant starch are 1.355,1.372,and 1.410,respectively,and the degree of double helix values is 1.931,1.942,and 2.027,respectively,indicating that the degree of ordered structure and double helix structure of heat-moisture treated Semen coicis resistant starch is both higher than those of Semen coicis native starch and high-amylose maize starch. ^（13） C nuclear magnetic resonance spectroscopy showed that Semen coicis native starch and high-amylose maize starch exhibited A-type crystal structures,while heat-moisture treated Semen coicis resistant starch displayed B-type crystal structures. The relative crystallinity of Semen coicis native starch,high-amylose maize starch,and heat-moisture treated Semen coicis resistant starch is 76.41,85.36,and 87.25,respectively,and the percentages of amorphous region are 5.78,4.72,and 4.39,respectively. Additionally,heat-moisture treated Semen coicis resistant starch could increase the proliferation of Bifidobacterium bifidum more than Semen coicis native starch or high-amylose maize starch. Bifidobacterium bifidum displayed a higher tolerance under simulated gastrointestinal tract conditions such as low p H,bile acid,pepsin,and trypsin in heat-moisture treated Semen coicis resistant starch medium than in Semen coicis native starch or high-amylose maize starch media.
In this paper, the time dependent effects of various pressure treatments on the characteristics of lotus-seed starch which was modified by ultra-high pressure （UHP） were investigated. The results showed that the polarization cross of lotus-seed starch granules was weakening gradually with increasing the treatment time, which indicated the termination of their ordered crystallite structures. The morphologies of granules were collapsed once the UHP was kept at 500 MPa for 60 minutes. The particle size analysis demonstrated that the granule size and distribution of lotus-seed starches increased as the treatment time was prolonged. X-ray diffraction studies showed that the intensity of the feature diffraction peaks of starch decreased and eventually disappeared with increasing the treatment time, and B-type transformation pattern was observed. The Fourier transform infrared spectra （FTIR） analysis of starch showed that the UHP is a physical modification processing because no new groups formed. The research showed that UHP processing at certain degree is capable to achieve the modification of lotus-seed starch. It is of significance for the deep processing of lotus-seed products.
