乳清蛋白酶改性综述

乳清蛋白通过改性 ,可以加强其功能性质 ,从而合理利用资源 ,开发新产品 ,扩大在食品中的应用。乳清蛋白的改性方法有化学改性、物理改性和酶改性。酶改性主要包括水解和交联。其中 ,用转谷氨酰胺酶改性具有比较大的发展潜力。     

马铃薯凝胶淀粉的理化特性研究

通过与玉米淀粉和马铃薯淀粉相比较,系统研究了马铃薯凝胶淀粉的理化特性,包括:粘度的测定;热糊与冷糊的稳定性;不同pH值及电解质(NaCl)和非电解质(蔗糖)存在下的粘度曲线;凝胶强度;冻融稳定性. 结果表明:马铃薯凝胶淀粉比天然淀粉具有优良的热糊与冷糊的稳定性,电解质(NaCl)和非电解质(蔗糖)的存在,对马铃薯凝胶淀粉的热糊与冷糊的稳定性基本上无影响,凝胶强度高,冻融稳定性好,尤其是耐酸性能强,可作为凝胶剂而广泛应用于各种食品加工体系。     

Evaluation of the Degree of Starch Gelatinization by a New Enzymatic Method

In this work, a new enzymatic method is proposed to evaluate the degree of starch gelatinization in starchy food and feed. The procedure developed is based on the fact that the gelatinization process enhances the chemical reactivity of inert starch granules towards amylolytic enzymes. Aqueous suspensions of maize starch were treated at different temperatures to obtain different degrees of gelatinization, from 25 °C (control without gelatinization) until 95 °C. Heated samples were then incubated with a glucoamylase. The enzymatic activity was measured by the glucose released during the digestion time by using a standard glucose oxidase method. The initial velocity value of the enzymatic reaction (V_i) was selected as the parameter to quantify the degree of starch gelatinization (DG). Changes in granule morphology and the starch available for hydrolysis were evaluated by photomicrographs. The new method was standardized and compared with DSC and viscosity measurements in order to check its efficiency, considering the DG observed by photomicrographs. A good agreement was observed between the DG calculated by V_i and by DSC (correlation coefficient r = 0, 97), thus V_i reflect the degree of starch gelatinization as well as DSC. These results show that the developed enzymatic procedure is an effective method to evaluate the DG in starchy foods and feeds.     

酶解改性对燕麦粉中淀粉含量及消化性的影响

为研究酶解对燕麦粉的淀粉含量和消化性的影响,本文采用双波长法测定天然燕麦粉、焙烤燕麦粉、酶解燕麦粉中直链淀粉、支链淀粉及总淀粉含量,并测定其快速消化淀粉、慢速消化淀粉和抗性淀粉含量以评价其消化性,利用红外光谱仪及电镜对其结构和颗粒形貌进行分析。结果表明,与天然燕麦粉相比,焙烤燕麦粉中直链淀粉、支链淀粉及总淀粉含量没有显著变化(p>0.05),但酶解改性燕麦粉变化极显著(p<0.01),分别下降了77.97%、43.55%、46.19%;焙烤燕麦粉中快速消化淀粉、慢速消化淀粉和抗性淀粉含量没有显著变化(p>0.05),但酶解改性燕麦粉变化极显著(p<0.01),分别下降了82.29%、57.06%、33.48%;经淀粉的红外光谱及1047/1022、1022/995 cm^-1特征吸收比值没有显著变化(p>0.05)。经焙烤和酶解改性的燕麦粉中大淀粉颗粒表面出现较多的凹陷,而酶解改性后的淀粉中含有的小颗粒较少,且表面的凹陷程度不同。酶解改性极显著降低了燕麦粉的直链淀粉、支链淀粉、总淀粉、快速消化淀粉、慢速消化淀粉及抗性淀粉含量(p<0.01),会对燕麦粉加工性能及营养价值产生影响。     

α-淀粉酶催化甜菊糖的改性研究

在本文中,通过筛选三种α-淀粉酶,以甜菊苷的转化率为指标,选用一种耐酸性的中温α-淀粉酶,其商品名称为高峰淀粉酶,将供体可溶性淀粉水解为葡萄糖基引入甜菊苷中对甜菊糖进行酶法改性以改善其味质。经试验后,对酶法催化工艺进行优化,最佳工艺条件为:供体淀粉浓度为100 g/L,底物比例(甜菊糖:淀粉)为1:10 (m/m),反应温度为60℃,加酶量为1.5 U/mL。改性后的甜菊糖产品采用高效液相色谱(HPLC)法测定甜菊苷的转化率,结果为42.5%。最后对酶法改性后甜菊糖产品进行感官味质评定,结果表明经酶法改性后的甜菊糖,味质得到显著的改善,甜味变得清淡且味道柔和,有微弱的苦味,但低浓度下基本无后苦味。经α-淀粉酶催化甜菊糖后能达到预期的味质效果,且大大降低了酶成本,为甜菊糖提供了理论与工业化基础。     

湿热处理改性淀粉的研究进展

湿热处理是改性淀粉的一种新的物理方法。本文列举了不同种类淀粉的湿热处理条件，对湿热处理影响淀粉的理化性质如颗粒形貌、糊化性质、以及对酸和酶的敏感性等作了概述。最后阐述了湿热处理对淀粉作用的机理及发展。     

淀粉物理改性技术研究进展

淀粉是一种非常重要的植物多糖,同时也是重要的工业原料。由于天然淀粉耐热、耐剪切、耐酸能力差,且易回生,因此需要对淀粉进行物理改性、化学改性和酶改性。在淀粉改性尤其是化学改性中,化学试剂易残留于改性淀粉中,所以快速、安全的物理改性越来越受到大家关注。主要概述了六种近些年常用的物理改性技术对淀粉结构及性能的影响,并从样品处理时间、损害程度和成本高低等五个方面进行比较,有助于大家选择合适的技术进行淀粉改性。     

酶法提高蛋清蛋白热稳定性的研究

蛋清蛋白由于蛋清蛋白质自身结构的关系使其具有良好的凝胶性,并且蛋清蛋白粉在加热过程中有利于凝胶性的提高。但超速溶蛋白粉制备过程中要求蛋白粉对热稳定,因此本文通过单因素试验和正交试验选出最优工艺破坏蛋清蛋白质的凝胶性,提高它的热稳定性。通过单因素试验选出最佳水解酶为碱性蛋白酶,水解时底物的最佳浓度为6%。并通过正交试验确定最佳工艺条件为:水解温度50~60℃、水解时间4h、pH值8和加酶量5U/mg。     

响应面试验优化挤出酶解复合法改性玉米淀粉工艺

利用挤出酶解对玉米淀粉进行改性,采用响应面法对影响改性工艺的主要因素耐高温α-淀粉酶添加量、挤出温度、玉米淀粉含量进行优化,通过高效液相色谱、扫描电子显微镜、X-射线衍射以及差示扫描量热仪对玉米淀粉挤出酶解复合改性前后的低聚糖组成、表观结构、结晶度以及热力学性质的变化进行分析。结果表明：当耐高温α-淀粉酶添加量40 U/g、挤出温度140 ℃、玉米淀粉含量70%时,挤出改性玉米淀粉葡萄糖当量值为19.55%。高效液相色谱分析表明挤出物低聚糖的组分能够得到较好的分离,低聚糖样品中各组分葡萄糖、麦芽糖、麦芽三糖、麦芽四糖、麦芽五糖的质量比为1.0∶3.4∶7.5∶6.0∶1.8。玉米淀粉经挤出酶解复合改性后颗粒表面出现孔洞,结晶度下降。     

Synthesis of Hydrophobic Corn Starch with High Flowability by Surface Modification

A new particle design method was proposed for the production of hydrophobic corn starch with high flowability by surface modification. The flowability and hydrophobicity of the native and modified corn starches were investigated by wettability (activation index) and flowability experiments (flow time), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). In corn starch modification, the optimal modifying agent is a mixture of tetraisopropyldi(dioctylphosphate)titanate (NDZ‐401) and methyl hydrogen silicone oil (H202), and the optimal content is 1% (w/w). The optimal content of flow agent (R972 silica) is 1% (w/w). The results indicate that the modified corn starch is a free flowing powder, which is also remarkably water repellent. The crystalline structures of the native and modified corn starches are similar, and only the surface properties are changed from hydrophilic to hydrophobic.     

小麦淀粉焦磷酸钠改性工艺研究

为优化小麦淀粉磷酸酯的半干法制备工艺,以小麦淀粉为原料,选取焦磷酸钠为酯化剂来制备小麦淀粉磷酸酯.应用单因素试验与正交试验,探索了磷酸盐用量、反应温度、反应时间、pH等因素对产品取代度、反应速率的影响.研究结果表明,小麦淀粉磷酸酯的最佳制备工艺条件为:pH 6.0,反应温度为150℃,磷酸盐用量为淀粉干重的3％,反应时间控制在70 min,小麦淀粉磷酸酯的取代度最大.改性后的小麦淀粉,冻融稳定性、透明度、黏度以及溶解性和膨胀度均比原淀粉高,更适用于冷藏或冷冻食品行业.     

Characterization of Dextrins obtained by Enzymatic Treatment of Cationic Potato Starch

The substitution pattern of cationic potato starches was studied using starch hydrolyzing enzymes and a characterization of the hydrolysis products. Native and cationic starch samples were hydrolyzed with pullulanase, isoamylase, and α‐amylase and the molecular‐weight distributions of the resulting dextrins were studied using gel permeation chromatography. Isoamylase hydrolyzed the native potato starch sample readily, whereas hydrolysis with pullulanase was incomplete. Pullulanase hydrolyzed, however, cationic starch with higher DS (degree of substitution) more efficiently than isoamylase. The hydrolysis products obtained with pullulanase were separated according to charge using cation‐exchange chromatography into one unbound and two bound fractions. The unbound fraction possessed an increasing number of short chains from amylopectin with increasing DS of the starch sample. The bound material contained amylose and dextrins with sizes corresponding to the long B‐chains. The high portion of uncharged dextrins after α‐amylolysis suggested that the substitution pattern, on the molecular level, was non‐random. The composition of the unbound and bound material, obtained by ion‐exchange chromatography of α‐amylase treated starches, suggested a more intense fragmentation with increasing DS of the sample. Possibly, the substituents influence substrate conformation and thereby alter the hydrolysis patterns. It is concluded that a thorough understanding of the enzymatic hydrolysis patterns is of ultimate importance in structural studies of modified starch.     

Dual Modification of Banana Starch: Partial Characterization

Banana starch was double modified by cross‐linking and substitution, using two different cross‐linking agents, i.e. phosphorus oxychloride (POCl₃) and a mixture of sodium trimetaphosphate/sodium tripolyphosphate. The morphological and physicochemical properties and the absorption capacity for heavy metals of the modified starches were assessed. Double modified starch granules (cross‐linked carboxymethyl starches CCSA and CCSB) presented changes in the surfaces. These starches had a bigger average particle size than unmodified starch due to the swelling of the granules during the chemical modification, also aggregates were formed. The double modified banana starches presented an A‐type X‐ray diffraction pattern with slightly decreased crystallinity compared with the unmodified counterparts. The double modification of banana starch decreases the temperature and enthalpy of gelatinization and the decomposition temperature. These results are related to partial disorganization during the chemical treatment. The double modified banana starch possess sorption capacity for heavy metal ions in the order Cd²⁺ >Pb²⁺>Cu²⁺>Hg²⁺. Due to their physicochemical characteristics and absorption capacity, the double modified banana starches can be used in diverse applications.     

大蕉淀粉的复合酶法改性工艺优化

利用复合酶对大蕉淀粉进行改性研究,在单因素试验基础上进行二次正交旋转回归设计优化大蕉淀粉复合酶法改性的最佳工艺条件,并对改性前后大蕉淀粉颗粒形态进行观察比较。结果表明：复合酶法改性大蕉淀粉的最佳工艺条件为淀粉乳质量分数5%、酶用量25U/mL、60℃酶解24h。在此条件下,大蕉淀粉的水解率为16.17%,与模型预测值基本一致。扫描电镜显示,改性淀粉颗粒出现孔洞,形貌更加圆滑,粒径有所减小,分布较为均匀,可有效提高大蕉淀粉加工特性和改善产品口感。     

酶催化木薯淀粉表面松香酸酯化改性及表征

以木薯淀粉为原料,松香酸为酯化剂,氯仿为溶剂,以液态脂肪酶为催化剂,在两相体系中直接在原木薯淀粉表面进行酯化修饰合成松香淀粉酯(RAS),并利用傅里叶红外光谱(FT-IR)、电子扫描显微镜(SEM)、X-射线衍射(XRD)、热重差分析(TGA)、接触角、乳化能力及乳化稳定性等对RAS的结构及理化性能进行分析。结果表明:与原淀粉相比,FT-IR谱图中RAS在1728 cm^-1附近出现羰基特征峰,SEM图中RAS表面的酯化斑点表明木薯淀粉表面成功接上了松香酸基团;XRD和TGA结果显示木薯淀粉经松香酸修饰后结晶度下降;对比原木薯淀粉,RAS(DS=0.0502)的接触角提高了63.40%,乳化能力、乳化稳定性分别由原木薯淀粉的1.53%、1.50%,提高至31.91%、23.08%。且随着DS的升高,RAS疏水性能及乳化性能也随之提高。     

三种改性方法对青香蕉淀粉物化性质的影响

为了探求一种既尽可能保留青香蕉淀粉的天然特性,又能改善其加工特性的改性方法,对比了复合酶法、乳酸发酵法和挤压膨化法对青香蕉淀粉特性的影响。结果表明：三种改性方法中,复合酶法能够显著提高抗性淀粉的质量分数;通过比较三种改性淀粉的理化特性,复合酶法和乳酸发酵法使结晶度由18.13%分别增加到20.19%和22.06%,而挤压膨化法使结晶度大幅下降至2.16%。复合酶法淀粉的分子解聚程度低,能较好保持原淀粉的颗粒形态,且有助于提高淀粉糊的热稳定性、冷稳定性和凝沉性。而乳酸发酵法和挤压膨化法使热稳定性降低,凝沉性减弱,但能够提高冷稳定性;加工特性研究表明,复合酶法对香蕉原淀粉的色泽影响较小,有助于改善淀粉糊的透明度,提高香蕉淀粉的感官品质。挤压膨化改性淀粉在透明度、溶解度和吸水性方面均有所改善。而乳酸发酵改性对冻融稳定性的影响较小。综上而言,复合酶法是较理想的改性方法。     

离子液体在淀粉和纤维素改性中的应用

近些年来,随着我国改革开放的深入和人民生活水平的提高,人们对食品安全提出了越来越严格的要求.同时由于人们环境意识的日益增强以及绿色化学的兴起,使新型绿色溶剂离子液体广泛应用于食品工业中并且逐渐发挥出巨大的作用,尤其是在淀粉和纤维素改性中的应用.结合国内外相关文献对离子液体在淀粉和纤维素改性中的应用进行总结.在总结的过程中,对淀粉和纤维素在离子液体中改性的发展历程、机理以及相关特点等方面进行论述,探讨了离子液体对淀粉和纤维素改性的影响,并阐述了离子液体在淀粉和纤维素的改性的发展前景和限制因素.     

Effect of Enzymatic Hydrolysis of Wheat Starch on Amylose‐Lipid Complexes Stability

In the process of enzymatic hydrolysis of wheat starch to glucose, the presence of amylose‐lipid complexes (AML's) decreases swelling and dissolving capacity and the water binding capacity of starch, thus impeding the access of amylolytic enzymes to the starch granules. The aim of the work was to define the relationship between the stability of AML's and the conditions of the enzymatic hydrolysis of wheat starch such as the kind of enzymatic preparation (only amylolytic or both amylolytic and lipolytic) and time of hydrolysis. Hydrolysates were produced from wheat starch liquefied with bacterial α‐amylase BAN 240L, subjected to further treatment with the enzymatic preparation Spezyme GA 300W, containing glucoamylase and lysophospholipase and, for comparison, only with a glucoamylase preparation (AMG 300L). The effect of amylolytic and lipolytic enzymes on the stability of AML's in the process of wheat starch hydrolysis was estimated. The amount of fatty acids released during hydrolysis was determined with gas‐liquid chromatography (GLC) and by differential scanning calorimetry (DSC) measuring the enthalpy of decomposition of AML's. The investigations revealed a differentiated effect of the individual enzymatic preparations on the degree of degradation of AML's. Amylose‐lipid complexes were more susceptible to the attack of preparation Spezyme GA 300W than to the digestion by α‐amylase BAN 240 L and glucoamylase AMG 300L.     

酶法红薯多孔淀粉的制备

多孔淀粉是一种新型酶变性淀粉,采用α-淀粉酶和糖化酶复合酶解法制备红薯多孔淀粉,对其工艺条件进行研究,当α-淀粉酶∶糖化酶为1∶7(体积比),反应温度45℃,反应时间28 h,pH5.6,加酶浓度0.5%,淀粉浆浓度65%时,可得到吸油率较高的多孔淀粉。