米茶的消化特性研究

以大米为原料,经浸润和焙炒等工序制得米茶。分别采用胰酶-糖化酶和胃蛋白酶-胰蛋白酶模拟淀粉和蛋白质在人体中的消化进程,研究动植物油脂、焙炒时间和焙炒温度对米茶淀粉和蛋白消化特性的影响,为米茶的加工提供基础数据。焙炒工艺会影响米茶的消化特性;焙炒可抑制米茶中淀粉的消化过程,有利于血糖指数的降低;添加油脂对米茶的消化有明显的抑制作用,对米茶消化液中葡萄糖含量有显著下降作用,但油脂的种类对淀粉的消化率抑制影响不大;过高的焙炒温度(200℃以上)和时间(35 min以上)会使米茶蛋白质的消化性能降低;焙炒对米茶消化后的绝对氨基酸含量基本无影响,焙炒会降低米茶酶解消化后游离赖氨酸和苏氨酸的含量,但适宜的焙炒条件对必需氨基酸的含量影响不大。     

磨粉方式对苦荞粉粉质特性及体外消化特性的影响

选用超微、石磨、钢磨、湿磨4种磨粉方式对苦荞籽粒进行磨粉,分析比较苦荞粉破损淀粉含量、粒径分布、微观结构、水合特性、冻融稳定性、黏度特性等粉质特性并采用酶解法模拟体外淀粉消化测定不同时间点的总淀粉水解率。研究结果显示:磨粉方式对苦荞粉粉质特性及体外消化特性影响差异显著,其中超微粉碎能显著减小苦荞粉粒径大小(D[4,3]=32.09μm),提高其亮度值(L=88.92)以及淀粉对酶的敏感度;湿磨粉淀粉颗粒形态完整,破损淀粉质量分数最低,为4.25%,冻融稳定性好,回生值低(3 732 cP),不易老化;石磨粉粉糊衰减值低,粉糊热稳定性好,淀粉水解缓慢;刚磨粉对各项指标的影响均不突出。不同磨粉方式对苦荞粉的影响不一,超微粉是一种理想的苦荞深加工食品原料,湿磨粉则适合冷冻食品加工,石磨粉更适合慢消化食品加工,而刚磨粉适合与普通食品用粉。     

十种食用豆粉及其淀粉的消化特性研究

以花芸豆、豇豆、小利马豆、小扁豆、鹰嘴豆、小红芸豆、红芸豆、小黑芸豆、小白芸豆和绿豆10种食用豆为试验材料,湿磨法提取豆类淀粉,采用改进的Englyst法测定食用豆粉及其淀粉的体外消化特性。结果表明,食用豆粉的消化特性有差别。生的食用豆粉的RDS、SDS和RS质量分数分别为4.3%~16.6%、17.3%~29.6%、55.0%~78.0%;蒸煮后的RDS、SDS和RS质量分数分别为61.2%~70.6%、2.3%~9.0%、24.0%~34.0%;蒸煮后食用豆粉的RS含量明显低于生的豆粉。生的食用豆淀粉的RDS、SDS和RS质量分数分别为8.1%~18.0%、10.8%~27.1%、56.2%~80.8%;而蒸煮后的RDS、SDS和RS质量分数分别为80.6%~91.3%、0.7%~8.7%、8.0%~11.0%。食用豆粉的RS含量显著高于淀粉,表现出高的抗消化性。蒸煮后食用豆粉及其淀粉的水解速率和水解程度明显高于原豆粉及淀粉,蒸煮熟化促进了消化特性。     

酶促合成肉豆蔻酸淀粉酯的性质及结构表征

为提高淀粉的反应活性,采用氢氧化钠尿素法对马铃薯原淀粉进行处理,以处理后的马铃薯淀粉和肉豆蔻酸为原料,Novozyme 435为催化剂,在无溶剂体系中制备了取代度为0.018~0.065的肉豆蔻酸淀粉酯,并对其部分理化性质进行研究。结果表明:与原淀粉相比,预处理淀粉溶解度和透明度显著增加(P0.05),其膨胀度、冻融稳定性、乳化性和乳化稳定性均显著降低(P0.05)。同时,肉豆蔻酸淀粉酯的性质与其取代度密切相关,与原淀粉相比,随着取代度的增加,酯化淀粉冻融稳定性、乳化性和乳化稳定性随之升高,而其溶解度、膨胀度和透明度随之下降。扫描电子显微镜(SEM)、傅里叶红外光谱分析(FTIR)、疏水性测定对预处理淀粉及不同取代度的肉豆蔻酸淀粉酯进行观察、测定、分析,结果表明,淀粉颗粒结构被破坏,酯化淀粉具有较好的疏水性,FTIR验证了预处理淀粉及酯化淀粉的生成。     

超高压处理对玉米淀粉结构及糊化特性的影响

利用光学显微、X-射线衍射、差示扫描量热、快速黏度分析技术研究了超高压处理对玉米淀粉结构及糊化性质的影响。结果显示,超高压处理能使玉米淀粉糊化,处理压力为500 MPa及600 MPa时完全糊化所需保压时间分别为15 min和5 min,但400 MPa超高压处理30 min也不会使淀粉糊化。超高压糊化过程中,淀粉颗粒结构逐渐破坏膨胀,结晶结构由A型向V型转化,RVA黏度曲线峰值黏度逐渐消失。适宜条件的超高压处理对淀粉颗粒同时具有韧化和晶体破坏作用。其中,400 MPa超高压处理5~10 min时,淀粉颗粒内部韧化作用占优,因而表现为相对结晶度、糊化温度(T_o,T_p)及糊化焓增加,而RVA曲线峰值黏度降低。     

海藻酸钠与钙离子对大米淀粉糊化的影响

为了探究海藻酸钠与钙离子对大米淀粉糊化的影响,分别采用快速黏度分析仪和流变仪测定了大米淀粉在海藻酸钠和钙离子存在下的成糊特性与淀粉糊状态,并用扫描电子显微镜观察了大米淀粉的糊化显微结构。结果表明,钙离子对大米淀粉的成糊特性无显著性影响;海藻酸钠将体系黏度提高了135%,并使大米淀粉糊呈现似液状态(tanδ1);在体系水分蒸发脱离的条件下,海藻酸钠与钙离子形成了网状凝胶结构,并使大米淀粉糊呈现稳定的似固状态(tanδ1)。因此,海藻酸钠与钙离子能够在大米淀粉糊化过程中形成浓缩诱导型胶凝,从而使大米淀粉糊的结构状态相对固定化。     

Effect of modified resistant starch of culinary banana on physicochemical,functional, morphological,diffraction, and thermal properties

Resistant starch has received much attention for both its potential health benefits and functional properties. The present study revealed that the culinary banana can be a potential source for production of resistant starch type III. The results showed that resistant starch yield can be increased using debranching enzyme (Pullulanase EC 3.2.1.41) and hydrothermal process. The three repeated autoclaving and cooling (hydrothermal) cycles followed by storage at –20ºC, increased the resistant starch yield from 12.3 to 26.4%. The use of debranching enzyme and subsequent retrogradation at –20ºC increased the resistant starch yield up to 31.2%. The modified resistant starch when compared to culinary banana starch evinced better stability. The modified resistant starch was analyzed using scanning electron microscopy, Fourier transform infrared, x-ray diffraction, and thermogravimetric diffraction analysis to determine the structural changes which proved that the modification occurred substantially.     

Effects of fatty acid and emulsifier on the complex formation and in vitro digestibility of gelatinized potato starch

The effects of fatty acid, monoacylglycerol, and polyglycerol fatty acid ester with varying chain length in their acyl chains on the extent of complex formation (complex index) and in vitro enzymatic digestibility of gelatinized potato starch were investigated. The complex index increased with increase in the concentration of the ligands (fatty acid, monoacylglycerol, and polyglycerol fatty acid ester), with the plateau in the complex index value depending on the type of ligands. In comparison of complex index among fatty acid-samples, the complex index maximum increased as the chain length increased up to octanoic acid and then decreased. In comparison of complex index among fatty acid-, monoacylglycerol-, and polyglycerol fatty acid ester-samples at each acyl chain, the complex index maximum followed the order polyglycerol fatty acid ester > monoacylglycerol > fatty acid. Fatty acid, monoacylglycerol, and polyglycerol fatty acid ester with long acyl chains greatly reduced the enzymatic hydrolysis of starch. Polyglycerol fatty acid ester with palmitic acid chains was the strongest inhibitor of starch hydrolysis, suggesting that further complex formation may occur during the hydrolysis of gelatinized starch (enzyme-annealing).     

AMYLOLYSIS OF SORGHUM STARCH AS INFLUENCED BY CULTIVAR,GERMINATION TIME AND GELATINISATION TEMPERATURE

The susceptibility to amylolysis of starches derived from two improved Nigerian sorghum cultivars were evaluated at assay temperatures between 50°C and 75°C. Enhancement of gelatinisation rates at temperatures up to 65°C was not significant inspite of the apparent grain modification due to germination for four days. Greater starch gelatinisation rates (20–22%) were achieved in this study compared to previously reported values, suggesting possible roles for cultivar and malting methods. There was a statistical correlation between starch gelatinisation rates over the temperature range 65°C–75°C and the duration of grain germination (r=0.91 for KSV8 and r=0.5 for SK5912 starches). Gelatinisation rate and temperature were affected significantly by assay pH. The occurrence of two pH related maxima of starch gelatinisation for both cultivera at all temperatures examined indicates the possible presence of two sets of “binding forces” within the starch granules and features of starch retrogradation .     

Cooking and Sensory Properties of Pork Crumbles as Affected by Pregelatinized Potato Starch, Crumble Diameter and Fat Content

Pork crumbles were processed at two fat levels (15, 40%) with or without addition of modified pregelatinized potato starch and into two sizes (0.95 cm, 1.90 cm diameters). Following precooking and reheating, large-diameter crumbles were softer and more juicy than small crumbles. Those with 40% fat were less firm and had lower precooking yields, but they still received high juiciness scores even when processed without modified pregelatinized potato starch. Potato starch provided improvements in precooking yields, and reduced fat retention during precooking and reheating.