水浸法削减大米粉中镉的工艺优化及对其品质影响

Optimization of Removal of Cadmium from Rice Flour by Water Soaking and Its Effect on Quality

采用响应面法优化水浸法削减镉污染的大米粉中镉的工艺条件,在最优条件下测定水浸法对大米粉营养成分的影响,并用扫描电镜、差示扫描量热仪、X射线衍射、红外光谱等方法分别研究水浸法对大米粉形态、热力学特征、淀粉晶体结构及官能团的影响。结果表明:水浸法削减大米粉中镉的最佳条件为水浸温度42℃、料液比1∶3(g/m L)、水浸时间47 h,此时镉含量为(0.459±0.006)mg/kg,大米粉中的镉去除率达到(61.75±4.31)%,处理后大米粉中镉含量为(0.176±0.003)mg/kg。在最佳工艺条件下,大米粉中的蛋白质含量显著降低(P<0.05),脂肪、淀粉、灰分也略有下降(P<0.05)。大米粉水浸后糊化起始温度降低,而峰值温度变化很小,说明大米粉晶体片层被破坏,稳定性降低,大米粉中直链淀粉含量可能升高,但水浸处理并没有破坏米粉内淀粉粒晶体成分。水浸大米粉面间距有略微的降低,说明水浸可能导致大米粉产品较原料产品的硬度、咀嚼度、回弹性、黏聚性下降。大米粉在水浸过程中并没有产生新的化学键或基团。

The conditions for removing cadmium from rice flour by water soaking were optimized using response surface methodology. The effects of the optimized treatment on nutrient retention were determined. We also investigated the effects on the morphology, thermodynamic characteristics, starch crystal structure and functional groups of rice flour by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR), respectively. The results showed that the optimal conditions that provided the maximum remove rate of cadmium of (0.459 ± 0.006) mg/kg (cadmium content (0.176 ± 0.003) mg/kg) were determined as follows: temperature 42 ℃, solid to water ratio 1:3, and soaking time 47 h. Under these conditions, protein content of rice flour decreased significantly (P < 0.05), and the contents of fat, starch and ash decreased slightly. The onset temperature of gelatinization of rice flour starch decreased after water soaking, while the peak temperature changed little, indicating damaged crystal layer, reduced stability and possibly increased amylose content of rice starch. On the other hand, the soaking treatment did not destroy the crystal components of starch granules in rice flour. The d-spacing of the soaked rice flour decreased slightly, indicating that soaking may lead to deterioration in hardness, chewiness and resilience and cohesiveness. No new chemical bonds or groups were formed during the process of water soaking.