Study On The Effects Of Heat-moisture Treatment On Damaged Wheat Starch

Due to its limits in structure, native wheat starch can not fully satisfy the meet of food industrialapplication. Heat-moisture treatment (HMT) is a widely used non-chemical starch modification method,without chemical residual, simple and low cost. However, most of the current studies on HMT use nativestarches as raw material, ignore the considarable amount of damaged starches produced during industrialstarch isolation, which can not in-depth understand the mechanism of starch HMT modification. Therefore,the research on the impact of starch structure degradation and molecular reassociation at different levels onHMT modification has important theory and application value. This research uses wheat starch as rawmaterial to prepare various damaged levels, through the water bath heating and mechanical ball milling(BM). We focused on the physical-chemical property to find out the influence of preparation on structure.Then A-type starch of certain damaged level was selected to optimize HMT modification process. So, thedamaged starches are dealted with the optimal process. We analyze the effects of damaged level on HMTmodification and reveal the relationship between damage and molecular re-crystallization, through theanalysis of its properties. Finally, this article also discusses the application of BM-HMT modification inimproving flour quality. The analyzed results are shown as follows.The results of thermal damaged starch and mechanical damaged starch were shown as follow. Thestudies on wheat total starch, A-type starch and B-type starch indicats that starch characteristics can befeatured by damaged starch (DS) content and gelatinization degree. Thermal temperature has a positivecorrelation with DS content, and negative correlation with peak viscosity and setback value. Gelatinizationcharacteristics and damage degree were significantly correlated (P <0.05). For those mechanical damagedstarches, starch with higher damaged level is easily to be gelatinized and has lower hardness as well asspringness. In addition, its solubility and swelling power have significant difference (P <0.05) with eachother. Besides, we found that surface smoothness and particle integrity of starch granule with differentdamaged levels were destroyed differently and the crystallinity of starch and surface spacing decreases byelectron microscopic scanning and X-ray diffraction determination.When a certain damaged level of A-type starch was treated by different HMT processings, the resultsdecleared that DS content of100℃,25%,12h dropped obviously. It semmed that heavy resistance toretrogradation can lead to higher viscosity and lower setback value. The results of them also indicated thatstarch particle distributed aggregately and the crystallinity was the largest, which illustrated that itscrystalline has been improved significantly. So, the condition with100℃, water content of25%andduration time of12h was the most optimum technological conditions for modification by HMT.Then optimized HMT process was selected to modify DS made from thermal and mechanical damage.The results showed that HMT had greater influence on decreasing pasting properties of thermal and BMDS with higher damaged level as well as their paste viscosity leading to improve pasting properties.However, compared with the original starch, paste viscosity of DS after HMT wassignificantly modified under the appropriate conditions. This showed that damage treatmentcan improve its low paste viscosity compared with the single modification of HMT. So, the phenomenon that paste viscosity was too low to apply for its industrial application hadbecome an important reason for restricting application. DSC measurement displayed that the curveappeared two absorption enthalpy peaks after HMT. Starch of higher DS content need lower ehthaply forgelatinization. When using scanning electron microscopy observation, we observed that the surface of themodified starch granules was out of shape severely and granules fused together partically. The intensity ofX-ray diffraction peaks increase obviously. As DS content increased, its diffraction peak intensity wasincreased more significantly while its amorphous area was reduced.The technology of BM and BM-HMT modification was applied to the flour for improving its products(noodles) quality. It was concluded that both BM and HMT can improve flour patch color effectively andenhance the brightness of noodles, especially for HMT.