超声处理对马铃薯淀粉结构特性及理化性质的影响

为了研究超声对马铃薯淀粉微观结构及理化性质的影响,以马铃薯淀粉为原料,通过扫描电子显微镜、激 光共聚焦显微镜、X射线衍射、傅里叶变换红外光谱、差示扫描量热法、快速黏度分析、偏光显微镜观察等方法, 研究了超声对马铃薯淀粉微观结构及理化性质的影响,揭示超声对马铃薯淀粉的机械力化学效应。结果表明：由于 马铃薯淀粉颗粒内部“狭长的脐点区”结构比较疏松,超声处理对马铃薯淀粉可产生显著机械力化学效应;随着超 声时间延长,马铃薯淀粉颗粒内部依次经过受力阶段、聚集阶段、团聚阶段;同时由于超声处理引起了马铃薯淀粉 颗粒结构变化,故导致了马铃薯淀粉理化性质显著变化。     

研磨对豌豆分离蛋白应用特性的影响

为改善豌豆分离蛋白应用特性,扩大其在食品工业的应用.该文采用研磨干法处理豌豆分离蛋白,研究其持水性、持油性、泡沫特性、乳化性能、凝胶性能等应用特性变化;并根据研磨后豌豆分离蛋白结构特征,分析研磨对应用特性的影响机理.结果表明:研磨对豌豆分离蛋白形态结构及亲水性基团产生了显著影响,进而影响了豌豆分离蛋白应用特性.研磨时间...     

Effect of grinding on the structure of pea protein isolate and the rheological properties of its acid-induced gels

The purpose of this study was to expand the application range of pea protein isolates by improving the rheological properties of their acid-induced gels. A pea protein isolate was ground for different durations, and changes in the structure and properties of its gels were studied. Furthermore, the influence mechanism of grinding on gelation was revealed. The results showed that grinding slightly changed the secondary structure of the pea protein isolate and had a great impact on its tertiary structure. Compared with the unground pea protein isolate, the solubility of the ground pea protein isolate increased from 45.89% to 69.84%, and the water-holding capacity of the gels increased from 52.04% to 94.67% at 7.5 min of grinding. After grinding for 15 min, the particle size of the pea protein isolate decreased from 1292.4 to 945.7 nm, and the polydispersity index decreased from 0.387 to 0.321. Rheological measurements showed that the storage modulus (G′), viscosity and recovery of protein gel samples improved after grinding. Thus, grinding enhanced the potential of protein gels for new applications.     

高压均质预处理对玉米淀粉阳离子化、结构和性能的影响

为探究高压均质机械力作用对淀粉化学活性的影响,本研究采用处于3 种不同机械力作用阶段的玉米淀粉 为原料,湿法制备了阳离子淀粉。通过扫描电子显微镜、激光共聚焦显微镜、偏光显微镜、X射线衍射分析、快速 黏度分析、差示扫描量热分析等手段研究了高压均质预处理对阳离子淀粉结构及性能的影响。结果表明：高压均质 预处理可破坏淀粉晶体结构,能提高淀粉化学活性。聚集阶段变化最为显著,该阶段阳离子淀粉峰值黏度、透光 率、化学活性最高,取代度和反应效率增幅分别达43.80%、43.86%。     

碾轧处理对乙酰化淀粉品质的影响及作用机理

为研究碾轧处理对乙酰化淀粉品质的影响及其作用机理,本文以甘薯淀粉为原料,研究不同碾轧处理时间(0、2、5、7、18 h)对乙酰化甘薯淀粉的品质、结构和理化性质的影响,采用机械力化学相关理论分析碾轧处理对乙酰化甘薯淀粉品质影响的作用机理。结果表明:碾轧处理2和7 h后,乙酰化甘薯淀粉的反应效率分别增加到74.45%和75.40%,其它品质(溶解度、膨胀力和峰值黏度)也显著提高。甘薯淀粉在碾轧处理2 h后,与原淀粉相比,结晶度降低且位于17.8 °处的衍射峰消失,T₂值增大,糊化焓和峰值黏度减小,热稳定性减弱;碾轧处理5 h后,溶解度、膨胀力和峰值黏度都减小,但淀粉的热稳定性增大;与处理2 h后相比,结晶度变大,T_2,2值消失;碾轧处理7~18 h后,结晶度、糊化焓和热稳定性显著降低,T_2,1值增大,碾轧处理18 h后淀粉分子晶体区域的双螺旋结构呈短程有序方式排列。这些变化表明碾轧处理可对甘薯淀粉颗粒产生显著的机械力化学效应。随着碾轧处理时间的增加,淀粉颗粒内部依次经历了受力、聚集和团聚阶段。机械力化学对淀粉颗粒作用的三个阶段具有不同的影响机制,为今后研究制备高品质变性淀粉先进装备奠定一定的理论基础。     

碾轧对马铃薯淀粉的机械力化学效应

以马铃薯淀粉为原料,研究碾轧处理对淀粉结构和性质的影响。通过扫描电子显微镜、X射线衍射、差示扫描量热仪、傅里叶变换红外光谱仪、快速黏度分析仪、偏光显微镜等手段揭示碾轧对马铃薯淀粉的机械力化学效应。结果表明,碾轧处理对淀粉颗粒的无定形区、结晶区产生不同程度的机械力化学作用,导致马铃薯淀粉性质发生显著变化。由此推断淀粉颗粒内部依次发生了受力、聚集和团聚效应。     

Water properties in wheat flour dough I: classical thermogravimetry approach

Thermogravimetric analysis allowed inspection of the behavior of water within a wheat flour dough. In such a system water is partitioned between coexisting phases which are none the less far from the true thermodynamic equilibrium. The vaporization rate revealed that water is released in two main steps, the first corresponding to a mere diffusion process, the second being instead related to the desorption of water more tightly bound to the gluten network. It was observed that the overall dough moisture, the extent of mixing, the dough resting time after mixing can modify water partition between phases and the way water is released during the temperature scan. Some effect was also recognized in dough samples to which original water soluble proteins had been added.     

Extraction and characterization of cellulose nanocrystals from cotton fiber by enzymatic hydrolysis-assisted high-pressure homogenization

Cellulose nanocrystals (CNCs) have attracted increasing attention in the field of nanomaterials because of its high aspect ratio, good structure, and high thermal stability. In this study, enzymatic hydrolysis-assisted high-pressure homogenization was applied as an environmentally friendly technique to extract CNCs from cotton-derived microcrystalline cellulose (MCC). The overall optimization of enzymatic pretreatment was conducted by response surface methodology, and the maximum CNCs yield was 40.09% under the optimized experimental conditions. The extracted CNCs under the optimal conditions showed needle-like shape with a length of 100–250 nm and a width of 5–10 nm and exhibited an overall particle size range of 3–80 nm. The basic chemical structure of cellulose was not changed after enzymatic hydrolysis and high-pressure homogenization. The CNCs exhibited slightly lower crystallinity and higher thermal stability than MCC. High aspect ratio CNCs extracted in this present study have great potential as a reinforcing agent in biodegradable packaging materials.     

Development and evaluation of two ELISA formats for the detection of β-lactoglobulin in model processed and commercial foods

Milk proteins have many functional properties, making them valuable food ingredients. However, they are a frequent cause of food allergy, especially in children. The aim of the present work was to develop and evaluate two immunoassays (indirect competitive and double antibody sandwich formats) for the detection of undeclared milk proteins in foods. Antisera raised to β-lactoglobulin was used in the competitive assay and antibodies isolated by immunoadsorption in the sandwich ELISA. Results obtained indicated that the sandwich format could detect lower percentages of powdered milk added to processed model foods than the competitive format. Likewise, the sandwich assay could discriminate better than the competitive assay between commercial foods with declared or non-milk ingredients. The antibody population used to recognize the target protein as well as the particularities of each ELISA format greatly influence the determination of immunoreactive β-lactoglobulin present in processed food.