湿热处理对藜麦淀粉流变和体外消化性质及结构的影响

Effect of Heat Moisture Treatment on the Rheological,in Vitro Digestive Properties and Structure of Quinoa Starch

湿热处理因其安全、绿色、环保、高效的特点被广泛应用于淀粉的改性。本研究采用不同含水量的湿热处理(分别为20%、25%和30%,处理温度为120℃,处理时间为10 h)对藜麦淀粉进行改性并对其流变性质、体外消化性质和结构进行了测定。结果表明:所有样品均为剪切变稀型非牛顿流体,湿热处理后藜麦淀粉的表观粘度均显著降低,且随着湿热处理含水量的增加而降低。频率扫描实验结果表明随着湿热处理含水量的增加,藜麦淀粉的储能模量G'呈不断降低趋势,而损耗模量G''和损耗因子呈不断增加的趋势。触变实验表明,随着湿热处理含水量的增加样品的触变环面积不断降低。体外消化结果表明,湿热处理能够显著降低藜麦淀粉中的快速消化淀粉含量(P<0.05),且藜麦淀粉中的慢性消化淀粉含量随着湿热处理含水量的增加而显著增加(P<0.05)。在30%含水量下,湿热处理后淀粉所含慢性消化淀粉含量最高,为24.93%,相较原淀粉提高了31.42%。X-衍射结果表明湿热处理后藜麦淀粉的晶型未发生变化,均为A型结晶,但处理后淀粉的相对结晶度显著降低(P<0.05)。傅里叶红外结果表明湿热处理会降低淀粉的整体有序性,但会增加藜麦淀粉中双螺旋结构含量。扫描电镜下观察到相较于原淀粉,改性后的藜麦淀粉出现粘结团聚,部分颗粒表面会出现部分塌陷的现象。本研究结果表明,湿热处理能够显著改变藜麦淀粉的流变学性质,提高藜麦淀粉的慢消化淀粉含量。淀粉的含水量是影响湿热处理改性效果的主要因素。相关结果将为藜麦淀粉的应用提供理论依据。

Heat moisture treatment(HMT)is a widely used method for starch modification due to its safe,green,environmentally friendly,and efficient characteristics.In this study,quinoa starch was modified by HMT with varying moisture contents(20%,25%,and 30%)at a temperature of 120°C for 10 hours,and its rheological properties,in vitro digestive properties,and structure were further evaluated.The steady rheology results indicated that all the samples were shear-thinning non-Newtonian fluids.After undergoing HMT,the apparent viscosity of quinoa starch decreased significantly.Additionally,the samples'apparent viscosity decreased as the moisture content of HMT increased.The results of frequency sweep showed that the storage modulus G'of quinoa starch decreased with the increase of moisture content of HMT,while the loss modulus G'',and loss factor increased with the increase of moisture content of HMT.The thixotropic results showed that the thixotropic ring area of quinoa starch decreased with the increase of the moisture content of HMT.Additionally,the results of in vitro digestion showed that the content of rapidly digestible starch in quinoa starch decreased significantly after HMT(P<0.05),while the content of slowly digestible starch(SDS)in modified quinoa starch increased significantly with the increase of moisture content of HMT(P<0.05).Notably,at a moisture content of 30%,the highest content of SDS in the modified starch was 24.93%,which was 31.42% higher than that of the native starch.XRD results indicated that the crystal form of quinoa starch remained unchanged after HMT,with all crystals being A-type.However,the relative crystallinity of quinoa starch decreased significantly after HMT(P<0.05).The Fourier transform infrared spectroscopy results showed that the overall order of quinoa starch decreased,while the content of double helix structure in quinoa starch increased after HMT.SEM observations revealed that the modified quinoa starch tended to agglomerate,and some of the particle surfaces collapsed compared to native quinoa starch.The study results suggested that HMT could significantly alter the rheological properties of quinoa starch and increase its SDS content.The study found that the modification effect was primarily affected by the moisture content of the starch.These findings provided a theoretical basis for the application of quinoa starch.