芋头淀粉的分离和纯化

用重结晶法可以得到纯度较高的芋头直链淀粉和支链淀粉。直、支链淀粉的蓝值分别是1 1 8和 0 2 0 ,λmax分别为 61 4nm和 5 87nm ,芋头淀粉中直链淀粉含量为 1 4 7%。高效液相色谱表明 ,芋头支链淀粉的分子质量具有较宽的分布 ;重均聚合度 ,大米支链淀粉 >芋头直链淀粉 >大米直链淀粉 >芋头支链淀粉 ;分散度 ,芋头支链淀粉 >芋头直链淀粉 >大米直链淀粉 >大米支链淀粉 ;芋头支链淀粉中 ,长支链所占比例 >短支链 ;分散度 ,长支链 >短支链。     

乳酸菌发酵对玉米的改性作用

在玉米米粉制作的过程中,发酵的方法能改良玉米的性质使其具有可加工性、改善玉米的不良风味.玉米自然发酵的过程中,乳酸菌为最主要的优势作用菌种.对乳酸菌发酵的过程进行详细的解析表明:从化学成分上来讲,发酵作用降低了灰分、可溶性糖、脂肪的含量,使蛋白质、淀粉所占比例提高;从淀粉结构来讲,发酵使直链淀粉含量增加,支链淀粉分子量朝着接近大米支链淀粉分子量的范围发展.DSC测试表明经过发酵后的玉米糊化温度降低,为玉米制作米粉提供必要条件,乳酸茵改性作用的研究为科学地控制发酵工艺提供参考.     

分离方法对锥栗淀粉分离组分结构特性的影响

对分离方法影响锥栗淀粉分离组分的结构特性进行了研究。结果表明：分离方法对锥栗直链淀粉、中间成分和支链淀粉的微观结构、碘亲和力、蓝值、平均聚合度（DP）、平均链长（CL）和摩尔平均链数（NC）影响较大;与锥栗原淀粉相比,三种方法分离得到的直链淀粉、中间成分和支链淀粉的结晶度均出现下降;分离方法对锥栗直链淀粉、中间成分和支链淀粉结晶相的晶型及它们与碘形成复合物的λmax没有影响。     

淀粉分子结构与α-淀粉酶酶解性能的相关性

以6种不同来源的淀粉为研究对象,分析了淀粉分子结构对其α-淀粉酶酶解性能的影响。结果表明,α-淀粉酶酶解直链淀粉的效率要低于支链淀粉,且直链淀粉含量并非导致淀粉酶解性能差异的主要因素;支链淀粉的链长分布对α-淀粉酶酶解效率有较大影响,其平均链长与α-淀粉酶酶解效率的线性相关性显著。     

陈放对大米淀粉特性及米粉凝胶品质影响的研究

研究了陈放对大米直链淀粉含量、糊化值和对米粉凝胶品质的影响.研究采用9100型古物分析仪和快速粘度仪.结果表明:陈放以后,直链淀粉含量增加,支链淀粉含量减少,糊化温度会有所下降;同时陈放一定时间胶稠度变小,凝胶品质比新米更好.     

不同直链淀粉含量大米淀粉性质的研究

以4种不同直链淀粉含量的米淀粉为原料,采用扫描电镜(SEM)、全波长自动扫描仪,质构仪等对其颗粒形貌、淀粉-碘复合物性质、ATP指标及透明度性质进行观察研究。结果表明,不同直链淀粉含量的大米淀粉颗粒形貌差异不大,均呈现不规则多边形,表面不光滑;随着直链淀粉含量的增加,淀粉颗粒的平均链长和聚合度不断增大,优糯3号淀粉颗粒内部短链数量较多,随着直链淀粉含量的增加淀粉颗粒内部的长短链比率逐渐趋近于1;淀粉糊的质构性质测定显示出淀粉糊的硬度、胶着性和咀嚼性随着直链淀粉含量的增加呈现出明显的上升趋势,弹性随着直链淀粉含量的增加变化不大,而凝胶的粘聚性明显下降;糊透明度随直链淀粉含量的增大而不断降低。     

酵母菌发酵生淀粉提高马铃薯淀粉回生率机理研究

以马铃薯淀粉为原料,淀粉回生率为考察指标,研究酵母菌发酵对马铃薯淀粉回生率的影响。通过对比发酵前后马铃薯回生淀粉的可见和红外吸收曲线,分析了酵母菌发酵提高马铃薯淀粉回生率的机理。结果表明,纤细酵母菌发酵马铃薯淀粉可使马铃薯淀粉回生率由12%提高到39.4%,提高了2.28倍。发酵后马铃薯回生淀粉中直链淀粉的最大可见吸收波长为587.8 nm,大于发酵前的569.6 nm。酵母菌发酵马铃薯淀粉提高其回生率的原因有两方面:一是发酵过程产生的酶使马铃薯支链淀粉脱支生成直链淀粉,增加了参与回生直链淀粉的量;二是发酵过程使马铃薯淀粉中醛基部分转变为伯醇基,进而生成糖苷键,增加直链淀粉链长,有利于淀粉回生过程晶体长大。     

自然发酵对大米理化性质的影响及其米粉凝胶机理研究

通过对整粒大米 (籼米 )自然发酵过程中理化性质变化的研究 ,探讨传统自然发酵米粉的凝胶机理。研究发现发酵过程中总淀粉及直链淀粉含量并无显著变化 ,蛋白、脂肪和灰分含量随着发酵的进行而明显减少 ,而游离脂肪酸的含量呈上升趋势。流变学测定发现 ,发酵法生产的米粉相对于对照样品最大破断应力减小而最大应变增加。感官评定结果表明发酵法生产的米粉柔韧筋道 ,品质更好。笔者认为自然发酵虽然未影响总淀粉和直链淀粉含量 ,但降解了蛋白和脂肪而改变了大米粉的流变性质。另外灰分的降低赋予米粉洁白的外观 ,带给产品更好的透明感     

支链淀粉结构对稻米淀粉糊化特性的影响

支链淀粉结构的不同是导致直链淀粉含量相近的水稻品种间品质差异的主要原因。本研究利用优化后的酶法测定了26个不同类型水稻品种的稻米支链淀粉的结构参数,分析了支链淀粉结构与淀粉RVA成糊特性及DSC热特性的相关性。结果表明,26个品种间平均链长、平均外链长与起始糊化温度、最高糊化温度、终结糊化温度呈正相关;A∶B值与起始糊化温度呈负相关。平均链长、平均外链长与消减值呈正相关,与峰值黏度、崩解值呈负相关;A∶B值与峰值黏度、崩解值呈正相关,与消减值呈负相关。将参试品种按AC分成11%~13%和13%~15%两组后,其支链淀粉结构与稻米淀粉RVA成糊特性及DSC热特性间的相关性与全部品种间基本一致。综上,支链淀粉结构对淀粉RVA成糊特性及糊化温度有较大影响,低平均链长、平均外链长及高A∶B值的稻米淀粉RVA成糊特性较好、糊化温度较低。     

四川地方大米品种特性对方便米粉品质的影响

以四川省农业科学研究院试验区筛选出的7种优质杂交水稻为研究对象,米粉工业常用大米作对照,通过测定原料基本成分、米粉感官品质、蒸煮品质和质构特性等指标,研究不同品种四川地方大米原料对方便米粉品质的影响,通过相关分析建立大米原料品种指标与米粉品质间的相关性。结果表明:原料米品种对方便米粉感官品质、蒸煮品质、质构特性的均有显著影响。米粉的劲道、爽滑、风味等感官指标及其综合评分,质构特性与大米直链淀粉含量均呈显著的正相关性。米粉的断条率、复水时间与大米的直链淀粉含量、蛋白质含量呈显著的负相关性,与大米的支链淀粉含量、粗脂肪含量呈显著的正相关性(P0.05或P0.01)。当大米直链淀粉含量在21.40%～25.61%时,米粉感官品质、硬度、拉伸长度和断条率均最优。采用本实验方法制作米粉时,4#、5#、6#这3种大米加工的米粉品质较好,为进一步确定四川方便米粉原料标准化提供了参考依据。     

生物发酵处理对小米淀粉分子结构及糊化特性的影响

采用0.2 g/100 m L NaOH溶液提取发酵后的小米淀粉,研究自然发酵及优势菌(乳酸菌、酵母菌)发酵后对小米淀粉颗粒特性、结晶度、官能团、分子质量、糊化及老化特性的影响。结果如下:乳酸菌、酵母菌发酵后,淀粉颗粒表面有明显的侵蚀迹象,而自然发酵淀粉颗粒表面侵蚀迹象较轻;乳酸菌发酵后小米淀粉的结晶度较自然发酵增加1.49%而酵母菌发酵减少0.33%;发酵并未改变小米淀粉官能团区的峰位,但特征峰强度减弱,乳酸菌、酵母菌发酵后小米淀粉指纹区图谱消失;未发酵小米淀粉重均分子质量为1.5×10~4~5.9×10~5 g/mol,自然发酵分子质量在2.1×10~4~5.4×10~5 g/mol,乳酸菌发酵分子质量为1.6×10~4~5.3×10~5 g/mol,酵母菌发酵分子质量为1.6×10~4~4.7×10~5 g/mol,乳酸菌、酵母菌发酵后支链淀粉长链及直链淀粉比例减少而中间及短支链淀粉的比例相对增加;乳酸菌、酵母菌发酵96 h糊化温度较自然发酵下降0.84℃和1.13℃,热焓值上升1.00 J/g和0.78 J/g;二者的回生值较自然发酵分别下降743、471 mPa·s。自然发酵的优势菌(乳酸菌、酵母菌)使小米淀粉的分子结构、糊化及老化特性发生明显变化,并在小米自然发酵过程中起主导作用。     

添加淀粉对马铃薯米粉品质的影响

研究3种常用淀粉对马铃薯米粉品质的影响,为马铃薯米粉加工提供参考依据。分别将0%、5%、10%、15%、20%和25%的玉米、小麦和马铃薯淀粉添加到马铃薯全粉占比30%的米粉中,测定米粉蒸煮、色差、质构和拉伸性能指标的变化。结果:添加不同淀粉使得米粉的含水量显著减小(p<0.05);玉米、小麦以及5%~20%马铃薯淀粉可使米粉透射比显著增大(p<0.05);10%玉米淀粉能使碘蓝值显著增大(p<0.05);添加10%玉米、5%小麦以及5%~20%马铃薯淀粉,能使吐浆值显著减小(p<0.05);但3种淀粉对断条率影响均不显著。添加10%玉米、10%小麦和5%马铃薯淀粉能使米粉亮度L*显著减小(p<0.05),色度值a*和b*亦发生不同改变。5%~15%玉米淀粉可有效改善米粉硬度、峰值负载,但添加量达到20%时峰值负载形变量显著减小(p<0.05);小麦淀粉可改善弹性,添加10%~15%可有效改善硬度,15%和20%可改善峰值负载和咀嚼性;马铃薯淀粉可提高米粉硬度,但添加量达20%时米粉变得黏连。在实际生产中建议玉米和小麦淀粉添加量分别为5%和10%。     

Thermal Degradation of Starch in Parboiled Rice

Raw and variously parboiled Intan rice (intermediate-amylose variety) starch was fractionated in Sepharose CL-2B column into a larger-molecule (Fr I) and a smaller-molecule (Fr II) fraction. The amount of Fr I decreased and that of Fr II increased in parboiled as compared to raw rice, the extent of change increasing with increasing severity of processing. The proportion of polysaccharide and “amylose” in Fr I decreased from 70% and 40% of total, respectively, in raw rice to 16% in parboiled rice prepared by 3 kg/cm² gauge steam pressure. Simultaneously, the λ_max of its iodine complex increased from 570 to 588 nm in Fr I and decreased from 635 to 620 nm in Fr II. The change was marginal or low after steaming at ambient pressure or after sand roasting. The data show that thermal degradation of starch must be considered as another contributor, in addition to starch gelatinization and reassociation, to the peculiar properties of parboiled rice.     

Structures and Physicochemical Properties of Acid‐Thinned Corn,Potato and Rice Starches

The structures and physicochemical properties of acid‐thinned corn, potato, and rice starches were investigated. Corn, potato, and rice starches were hydrolyzed with 0.14 N hydrochloric acid at 50 °C until reaching a target pasting peak of 200—300 Brabender Units (BU) at 10% solids in the Brabender Visco Amylograph. After acid modification the amylose content decreased slightly and all starches retained their native crystallinity pattern. Acid primarily attacked the amorphous regions within the starch granule and both amylose and amylopectin were hydrolyzed simultaneously by acid. Acid modification decreased the longer chain fraction and increased the shorter chain fraction of corn and rice starches but increased the longer chain fraction and decreased the shorter chain fraction of potato starch, as measured by high‐performance size‐exclusion chromatography. Acid‐thinned potato starches produced much firmer gels than did acid‐thinned corn and rice starches, possibly due to potato starch's relatively higher percentage of long branch chains (degree of polymerization 13—24) in amylopectin. The short‐term development of gel structure by acid‐thinned starches was dependent on amylose content, whereas the long‐term gel strength appeared dependend on the long branch chains in amylopectin.     

Effect of amylose content and rice type on dynamic viscoelasticity of a composite rice starch gel

Amylose content is an important indicator to determine the utility of raw milled rice. Indica type rice with high amylose content is usually used for manufacturing rice noodles, while Japonica rice may be mixed partially to adjust the noodle texture. The effect of amylose and rice type on dynamic viscoelasticity of rice starch gel was investigated using a model starch composite in this study. The information will be helpful to control and obtain the required noodle texture by combination of different rice types. The results show that nonwaxy Indica and waxy Japonica rice starches in a composite mixture were incompatible and demonstrated their individual gelatinization behavior during heating. High amylose starch showed higher moduli and lower loss tangent values, as well as higher retrogradation rate. The starch gel made from Japonica rice starch showed a slow retrogradation rate even containing a similar amount of amylose to Indica starch. The storage modulus of the gel made from higher amylose rice was shown to be more independent of frequency. Not only amylose content but also chain length distribution in amylopectin affected the dynamic viscoelasticity of rice gel. Japonica rice starch, with fewer super-long chains in amylopectin, retrograded slower after gelatinization than Indica rice, thus the paste is too sticky for production of rice noodles.     

高直链玉米淀粉添加对挤压荞麦面条结构、蒸煮品质及消化特性的影响

制备挤压荞麦面条,研究不同添加量（10%、20%、25%、30%）的高直链玉米淀粉（m/m,基于全粉）对挤压荞麦面条结构、蒸煮品质及消化特性的影响。结果表明,随着高直链玉米淀粉添加量的增加,挤压面条直径减小,糊化度降低。X射线衍射结果表明添加高直链玉米淀粉后,面条除了V型结晶峰外还存在未完全糊化的直链淀粉的典型B型峰。热力学性质结果也表明直链淀粉发生部分糊化。添加高直链玉米淀粉后,面条色泽变浅变亮,最佳蒸煮时间缩短,蒸煮损失率由9.90%增加到12.43%。当高直链玉米淀粉添加量为25%时,面条开始出现断条。面条硬度由2 105.709 g显著增加至3 680.401 g,弹性由0.961降低至0.866。扫描电镜结果表明,随着高直链玉米淀粉添加量的增加,致密的面条结构逐渐出现裂纹,且面条截面有较多未完全糊化的淀粉颗粒。淀粉体外消化实验表明,随着高直链玉米淀粉添加量的增加,淀粉水解率逐渐下降,预计血糖指数减小,抗性淀粉含量增加。当高直链玉米淀粉添加量为30%时,挤压荞麦面条的预计血糖指数从74.28降至66.31,抗性淀粉含量从34.43%增加至47.86%。     

Rice Starch Molecular Size and its Relationship with Amylose Content

The composition and starch molecular structure of eight rice varieties were studied. Waxy and non‐waxy (long‐, medium‐, and short‐grain) rice varieties from California and Texas were used. The amylose contents were measured using the Concanavalin A method and were found to be related to the type of rice: waxy ≈ 1.0%, short and medium grain 8.7–15.4%, and long grain 17.1–19.9%. The weight‐average molar masses (M_w) of the starches varied from 0.52 to 1.96×10⁸ g/mol. As would be expected, a higher M_w of rice starch correlated to lower amylose content. The range of M_w of amylopectin was 0.82 to 2.50 ×10⁸ g/mol, and there was also a negative correlation of amylopectin M_w with amylose content. Amylose M_w ranged from 2.20 to 8.31×10⁵ g/mol. After debranching the amylopectin with isoamylase, the weight‐average degree of polymerization (DP_w) for the long‐chain fraction correlated positively with a higher amylose content. California and Texas varieties were significantly different in their amylose content, starch M_w (short‐ and medium‐grain only), and amylopectin M_w (p < 0.05).     

Morphology and physicochemical changes in rice flour during rice paper production

Rice flour samples from four steps of rice paper processing were prepared from rice grain, Chainart 1 variety: wet-milled flour (WMF), 24 hour soak-milled flour (24SF), 48 hour soak-milled (48SF), and dried rice paper (DRP). Decrease in protein, fat and amylose content occurred during prolonged fermentation but increase of ash content due to addition of salt occurred. Because of lactic acid bacteria activity, increases occurred in titratable acidity as lactic acid in soaking water during fermentation. Scanning electron microscopy revealed that starch granule surfaces wilted and showed corrosion channels with longer fermentation. Pasting and thermal properties of the four samples were significantly different; 24SF and 48SF showed lower peak viscosity, breakdown and final viscosity. Increasing fermentation time increased gelatinization temperature, endothermic energy and relative crystallinity. The results suggest that lactic acid and enzyme hydrolysis during fermentation in rice paper processing caused significant decrease in amorphous structure and increase in crystallinity in rice starch.     

Physicochemical properties of flour recovered from broken rice noodles during production

Flour recovered from broken rice noodles was evaluated by microscopy, X‐ray diffractometry, differential scanning calorimetry, in vitro starch digestibility, pasting and gel texture analyses. Rice noodle making processes destroyed the granular and crystalline structures of rice flour (RF), but the process‐induced recrystallised amylopectin and amylose‐lipid complexes were observed. Higher level of resistant starch in broken rice noodle flour (BRNF) was due to the retrograded amylose, which formed during noodle making. The absence of pasting temperature and low pasting viscosity of BRNF were distinct from those of RF, whereas gel textures of both flours were similar. BRNF‐added rice noodles showed lower hardness, but the other cooking and texture qualities were close to the one without BRNF. Up to 17% of BRNF could be incorporated into composite rice noodle making. This study thus provided an approach to the management and utilisation of food processing wastes.