精白保胚发芽米淀粉理化性质

研究发芽对精白保胚米淀粉理化性质的影响。测定精白保胚发芽米淀粉的溶解度、膨胀度、透光率、冻融稳定性等理化性质;采用快速黏度分析仪和流变仪研究精白保胚发芽米淀粉RVA 特征值的变化和流变学特性;并与糙米、发芽糙米和精白保胚米淀粉的理化性质做比较。结果表明,精白保胚米发芽之后直链淀粉含量降低,溶解度、膨胀度和透光率增加,冻融稳定性得到改善;RVA 特征值表现为精白保胚发芽米的峰值黏度降低,最终黏度升高,崩解值降低,消减值和回升值升高;动态流变学表现为加热过程中精白保胚发芽米的储能模量(G')降低。     

精白保胚米发芽过程中淀粉酶及相关营养成分的变化

研究精白保胚米发芽过程中α-淀粉酶、β-淀粉酶和葡聚糖内切酶活力的变化,同时测定其中还原糖、总糖、淀粉及热水溶性直链淀粉的含量变化,并以发芽糙米作为对照。结果表明:精白保胚米和糙米发芽过程中α-淀粉酶和β-淀粉酶的活性先由低变高,再由高变低,精白保胚米在发芽16h时淀粉酶的活性最高,而糙米在发芽时淀粉酶活性达到最高点时间较长;葡聚糖内切酶活力随发芽时间的增加活性逐渐升高,糙米在发芽过程中葡聚糖内切酶活力高于精白保胚米。还原糖、总糖的含量随着时间的增加而升高,在20～24h后逐渐降低,精白保胚米在发芽过程中还原糖的含量高于糙米。淀粉含量随发芽时间的延长而逐渐降低,热水溶性直链淀粉的含量则不断增加。     

精白保胚米发芽过程中米谷蛋白及其氨基酸的变化

研究精白保胚米发芽过程中米谷蛋白及其氨基酸组成的变化。精白保胚米在发芽过程中,淀粉含量呈下降趋势,蛋白质的含量略有上升;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和体积排阻色谱的结果显示：发芽后米谷蛋白中含量较高的各亚基分子质量没有太大差别,但其含量有所变化,高分子质量亚基含量减少,低分子质量亚基含量增多。米谷蛋白氨基酸分析结果发现：发芽可以增加精白保胚米总氨基酸和必需氨基酸的含量,必需氨基酸组成模式更加合理。分析结果表明发芽可以提高精白保胚米的食用品质和营养价值。     

精白保胚发芽米食用品质

以糙米、发芽糙米、精白保胚米及精白保胚发芽米为研究对象,对其食用品质的主要方面,即炊饭方法、蒸煮特性、糊化特性、质构特性及感官分析进行对比评价。结果表明：精白保胚发芽米的吸水率和膨胀率均低于其他3 种大米,而米汤固体溶出物和碘蓝值均高于糙米和发芽糙米;糊化特性分析中,精白保胚发芽米与大米食用品质相关的崩解值降低,消减值升高;质构分析表明精白保胚发芽米具有最低的硬度;感官分析结果表明,精白保胚发芽米在色泽、香气、口感、滋味方面都优于未发芽米。     

精白保胚米发芽的工艺优化

精白保胚发芽米是一种营养丰富、富含保健功能成分的新型大米产品。通过单因素实验和响应曲面法对精白保胚米发芽的浸泡、发芽温度和时间及催芽方法进行了优化,获得精白保胚米发芽的最佳工艺为:在温度25℃条件下以0.5%的饱和碳酸钙溶液浸泡17h,再以超声波催芽10min,置于相对湿度90%、温度25℃的条件下发芽21h,在此条件下,发芽率可达94%以上。实验结果为精白保胚发芽米的研制和推广奠定了基础。     

微波对板栗淀粉结构和理化性质的影响

为探讨微波辐照对板栗淀粉颗粒结构和理化性质的影响,采用微波辐照板栗淀粉,通过扫描电镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、差示扫描量热仪(DSC)等研究微波处理不同时间后板栗淀粉的颗粒结构和理化特性。研究表明:与原淀粉相比,微波处理后板栗淀粉的微观形貌发生明显变化,但淀粉颗粒仍为C型晶体。随着微波处理时间的增加,直链淀粉含量增大,淀粉颗粒表面出现裂纹、孔洞和黏结越显著,淀粉颗粒的相对结晶度降低、红外光谱(1 047/1 022)cm~(-1)峰强度比值降低;淀粉膨胀度和透光率也随微波处理时间的增加而降低。DSC分析表明,微波处理80 s的淀粉相转变温度(T_o和T_p)降低、糊化焓(ΔH)减少。表明微波辐照对板栗淀粉的颗粒结构和理化特征均有显著影响。     

马铃薯羟丙基羧甲基淀粉颗粒及分子结构变化

对马铃薯原淀粉、马铃薯羟丙基淀粉、马铃薯羧甲基淀粉、马铃薯羟丙基羧甲基淀粉分别利用红外光谱分析(FT-IR),证实了马铃薯羟丙基羧甲基淀粉的结构变化;利用X-射线衍射分析(X-RD),证实了马铃薯羟丙基羧甲基淀粉的结晶度变化,随着无序化程度降低,导致其结晶度增加;利用扫描电子显微镜(SEM)观察了复合变性前后淀粉的表观形貌变化,证实了淀粉羟丙基羧甲基化其反应不仅发生在淀粉颗粒表面,也发生在淀粉颗粒内部,同时该反应首先发生在淀粉颗粒中结构较薄弱的非结晶区。     

脱胚玉米与加酶和不加酶挤压脱胚玉米淀粉颗粒结构和热特性研究

为研究不加酶和加酶挤压对脱胚玉米颗粒结构和热性能影响,采用扫描电镜的方法观察玉米淀粉颗粒形态,采用X-射线测定脱胚玉米淀粉颗粒晶体类型,运用差示扫描量热法分析玉米淀粉的热特性,并测定其糊化度。通过扫描电镜观察未经过挤压的脱胚玉米颗粒表面光滑完整,未加酶挤压和加酶挤压的脱胚玉米颗粒形态遭到破坏,整体结构不完整,表面出现孔洞;X-射线实验测得未挤压脱胚玉米结晶度为15.84,未加酶挤压脱胚玉米结晶度为5.63,加酶挤压脱胚玉米结晶度为7.94;DSC测试结果为未挤压脱胚玉米、未加酶挤压脱胚玉米和加酶挤压脱胚玉米的起始温度分别为46.97、43.11、48.18℃,峰值温度分别为98.63、93.61、98.25℃,结束温度分别为196.79、185.20、188.54℃,焓变分别为325.40、271.30、284.80 J/g;测得糊化度值分别为0.16、0.87、0.61。表明挤压能够破坏脱胚玉米淀粉颗粒完整度,部分微晶结构遭到破坏,结晶度降低,焓变值降低,糊化度增加;加酶挤压脱胚玉米焓变值高于未加酶挤压脱胚玉米,糊化度低于未加酶挤压脱胚玉米。     

挤压剪切活化对添加耐高温α-淀粉酶脱胚玉米淀粉结构和理化特性的影响

本研究通过偏光显微镜、扫描电子显微镜、热台显微镜、X射线衍射、差示扫描量热分析、傅里叶变换红 外光谱分析等手段,研究原脱胚玉米、挤压脱胚玉米和添加耐高温α-淀粉酶挤压脱胚玉米的淀粉结构及性质变化, 并探究其相互关系,揭示挤压剪切活化对脱胚玉米的淀粉颗粒机械力化学效应。研究表明：与原脱胚玉米和挤压脱 胚玉米相比较,挤压处理对添加耐高温α-淀粉酶脱胚玉米的淀粉结构及性质产生显著影响,酶解力和糊化度增大,碘 蓝值、直链淀粉含量减小。添加耐高温α-淀粉酶挤压脱胚玉米淀粉颗粒形貌破坏,偏光十字破坏,结晶度变小;升温糊 化过程中,焓变降低;挤压使淀粉颗粒的结晶结构破坏,淀粉颗粒发生聚集,破损淀粉颗粒易糊化和裂解。     

水分含量对籼米和糯米淀粉颗粒结构的影响

本文研究了高静压条件下含水量变化对籼米淀粉和糯米淀粉颗粒结构的影响。研究表明,含水量为80%及90%的样品在压力作用下结构崩塌最显著。随着水分含量的增加,籼米淀粉及糯米淀粉的粒度增大,比表面积增大,孔径减小,结晶度先减小后增大。当水分含量较低时,压力使淀粉颗粒发生压缩塑化,结晶结构增强。傅里叶红外光谱分析发现水分含量的变化不会导致淀粉分子结构改变。     

Extraction Technique and Characteristics of Soluble Protein in Germinated Brown Rice

Effects of germination methods and extraction conditions on soluble protein yield in brown rice were investigated. Extraction temperature and solid to solvent ratio were significant factors. Highest soluble protein yields were obtained from germinated brown rice at 41.5°C for 2 h using a solid to solvent ratio of 1:10 at pH 8.5. This was about 20% higher than that from non-germinated brown rice. Characteristics of the extracted protein from germinated rice indicated an improved solubility, a lower isoeletric point, a reduction in high molecular weight components and an increase in small peptides compared to non-germinated rice.     

不同米淀粉精细结构对其回生特性的影响

选用4种不同的淀粉,通过考察回生特性,探究相对分子质量、链长分布、短程有序性、相对结晶度及半结晶层状结构等精细结构影响回生特性的机理。结果表明：与糯米淀粉和粳米淀粉相比,小米淀粉和黑米淀粉回生值、硬度和热焓值较大,糯米淀粉储藏前后硬度和回生后的热焓值均较小,具有较好的抗回生特性。研究发现,这是由于小米淀粉和黑米淀粉的直链质量分数较高(小米淀粉15.55%、黑米淀粉11.22%),支链淀粉峰M_w较大(小米淀粉M_w=2.12×10⁷ g/mol、黑米淀粉M_w=2.25×10⁷ g/mol)、半结晶层厚(小米淀粉d=6.978 4 nm、黑米淀粉d=6.698 6 nm),且中长链占比大(小米淀粉B1链占比40.91%),易形成稳定的双螺旋结构,具有更高的表面有序度(小米淀粉0.76、黑米淀粉0.70),回生后2种淀粉分子重排更有序稳定。     

超声处理对糙米淀粉的结构与理化特性的影响

以糙米淀粉为原料,探究不同超声时间处理对糙米淀粉的分子结构及理化特性的影响.结果 表明:与原淀粉相比,超声处理10 min的改性淀粉的官能团和化学键组成没有变化.超声处理10 min能够将糙米淀粉的粒径显著降低43.18％,崩解值从577 cP降低到388 cP,峰值黏度经过超声处理后降低,在30 min达到最低157...     

Comparison of Starch Physicochemical Properties from Medium‐Grain Rice Cultivars Grown in California and Arkansas

The starch molecular structure and physicochemical properties of two medium‐grain rice cultivars from Arkansas (Bengal, Medark) and from California (M202, M204) were determined and compared when they were grown in their respective locations and grown together in Arkansas to better understand the impacts of genetics and environment on starch characteristics. Both M202 and M204 contained significantly higher amylose contents (13.2‐15.3%) compared with the Arkansas cultivars (11.6‐12.4%). Starch from the Arkansas rice cultivars exhibited higher pasting and gelatinization temperatures and higher enthalpy values. Rice amylopectin from the California cultivars consisted of a smaller proportion of intermediate chains (DP 13‐24), and had a lower molecular weight and a smaller radius of gyration. When the four cultivars were grown together in Arkansas, the ranges for amylose content narrowed (10.6‐12.4%), their differences in thermal and pasting properties became smaller, and the molecular characteristics of amylose and amylopectin changed for all four cultivars. This study demonstrated that genetics, location, and crop year all contributed to variations in rice starch fine structure and physicochemical properties.     

高效排阻色谱-多角度激光散射分析淀粉分子特征

本研究利用高效排阻色谱与多角度激光散射分析仪、示差折光仪串联建立淀粉结构分析的方法并得出相关分子特征参数。结果表明：采用Berry 法三阶拟合可推导得出淀粉绝对分子质量及其分布、平均旋转半径(rz)、多分散系数。普通玉米淀粉、蜡质玉米淀粉、小麦淀粉、糯米淀粉、大米淀粉及马铃薯淀粉的重均分子质量Mw (rz)分别为17.94 × 107g/mol (79nm)、18.11 × 107g/mol (81.1nm)、7.86 × 107g/mol (50.4nm)、13.04 × 107g/mol (62.9nm)、64.3 × 107g/mol (64.3nm)及7.73 × 107g/mol (75.9nm)。该方法可作为一种简便、快速的测定淀粉分子结构的现代分析技术。     

不同提取方法对粳米淀粉结构的影响

本实验从淀粉形态学、直链淀粉含量、支链淀粉分子量和支链淀粉侧链分布等方面研究碱法、酶法、SDS结合超声波法提取对粳米淀粉结构的影响.得到以下结论:碱法提取对粳米淀粉结构影响最大,其次是SDS结合超声波法,酶法提取影响最小;与酶法提取的支链淀粉相比,碱法和SDS结合超声波法提取的支链淀粉分子量有所下降,并且侧链中长B链含量下降,而中B链、短B链和A链的含量增加.     

淀粉分子结构对形成抗性淀粉的影响

考察了几种大米淀粉和土豆淀粉形成抗生淀粉的能力,用分子排阻色谱的方法研究其分子结构。认为土豆淀粉比大米淀粉更适用来生产抗性淀粉。     

Structural characterization of rice starch in rice cake modified by Thermus scotoductus 4-alpha-glucanotransferase (TS alpha GTase)

ABSTRACT:  Rice cake was produced with a thermostable 4-α-glucanotransferase from Thermus scotoductus (TSαGTase). Starch molecular fine structure, texture, and retrogradation for the enzymatically prepared rice cake were investigated and compared to those for control rice cake. The amylose content in TSαGTase-treated rice cakes decreased, whereas branched and linear malto-oligosaccharides ranging from maltose to maltoheptaose increased slightly. The average molecular weight of the enzyme-treated rice starch in rice cake decreased as amylopectin macromolecules were cleaved and reorganized into small amylopectin clusters. The number of shorter side chains (degree of polymerization [DP] < 9) increased, whereas the number of longer side chains (DP > 10) decreased through the disproportionation reaction of TSαGTase. After 24 h of storage at 4 °C, the enzyme-treated samples demonstrated significantly lower melting enthalpy of retrograded starch (0.4 mJ/mg) compared to that of the control (1.4 mJ/mg). The results indicated that TSαGTase treatment effectively inhibited starch retrogradation in rice cakes. It is suggested that the reduction of amylose content, the rearrangement of amylopectin, and the production of malto-oligosaccharides caused by TSαGTase treatment are responsible for the ineffective molecular reassociation of rice starch in rice cake.     

Structure‐Functionality Changes in Starch Following Rough Rice Storage

The molecular‐level features of starch in relation to the changes in rice functionality during storage are not yet fully elucidated. This work investigated the effects of rough rice storage conditions on starch fine structures and physicochemical properties. Dried rough rice samples (medium‐grain Bengal and long‐grain Cypress) were stored at 4, 21, and 38°C in temperature‐controlled chambers and then periodically removed and evaluated after 1, 3, 5, 7, and 9 months. Flour (powdered head rice) and starch (extracted from head rice by alkali steeping) samples were evaluated for pasting and thermal properties. High‐performance size‐exclusion chromatography and high‐performance anion exchange chromatography were used to characterize starch molecular size and amylopectin chain‐length distribution, respectively. Significant changes in starch fine structure were observed primarily on the 38°C lots, and to some extent on the 21°C lots. The decreased amylose: amylopectin ratio, shortened amylopectin average chain length, and the shift in chain‐length distribution to shorter branch chains were implicative of molecular‐level starch degradation. The flour and starch samples showed inconsistent trends in pasting and thermal properties, thus suggesting the role of not only starch but also its interaction with non‐starch components in rice aging.     

Rice Starch Diversity: Effects on Structural,Morphological, Thermal,and Physicochemical Properties—A Review

Abstract: Rice starch is one of the major cereal starches with novel functional properties. Significant progress has been made in recent years on the characterization of rice starches separated from different rice cultivars. Studies have revealed that the molecular structure and functional properties are affected by rice germplasm, isolation procedure, climate, agronomic conditions, and grain development. Morphological studies (microscopy and particle size analysis) have reflected significant differences among rice starch granule shapes (polyhedral, irregular) and in granule size (2 to 7 μm). Nonwaxy and long‐grain rice starches show greater variation in granular size than the waxy starches. Rice starch granules are smaller than other cereal starches with amylose contents varying from virtually amylose‐free in waxy to about 35% in nonwaxy and long‐grain rice starches. Amylose content appears to be the major factor controlling almost all physicochemical properties of rice starch due to its influence on pasting, gelatinization, retrogradation, syneresis, and other functional properties. Waxy rice starches have high swelling and solubility parameters, and larger relative crystallinity values than nonwaxy and long‐grain starches. However, nonwaxy rice starches have a higher gelatinization temperature than the waxy and long‐grain starches. The bland taste, nonallergenicity, and smooth, creamy, and spreadable characteristics of rice starch make it unique and valuable in food and pharmaceutical applications. This review provides recent information on the variation in the molecular structure and functional properties of different rice starches.