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1.
A second unusually high viscosity peak appeared at the cooling stage (50°C) of a Rapid Visco‐Analyser (RVA) profile of short‐term stored (two months at room temperature) whole grain sorghum flour, while freshly ground flour had a typical pasting curve with one viscosity peak at the 95°C holding period. The formation of the second viscosity peak was caused by liberation of free fatty acids (FFA), mainly palmitic (15.6%), oleic (41.9%), and linoleic (37.9%) acids from stored flour. After the flour samples were pretreated with pepsin or the protease thermolysin, the second peak disappeared in the presence of FFA while the high viscosity was partially retained, indicating that flour protein was another essential component to the production of the actual peak. Effects of dithiothreitol (DTT), pH, and NaCl on RVA profiles of stored flour suggested that disulfide‐linked protein and electrostatic interaction are required for the peak production. In the presence of sufficient FFA, similar cooling stage viscosity peaks appeared in the RVA profiles of flour samples from maize, rice, millet, and wheat; thus, the effect was not unique to sorghum flour. Coinciding with previously reported findings from our laboratory of a three‐component interaction and discernable complex in a model system, a similar three‐component (starch, protein, and FFA) interaction was revealed in natural flour systems resulting in formation of an unusual and notably high cooling stage viscosity peak. Practical applications and an interaction mechanism are discussed.  相似文献   

2.
Relationships between the structural properties of raw and extruded corn starches and their functionalities were investigated using mixtures of these starch types. Extruded starch had higher water absorption and water solubility indices, and produced lower RVA viscosity profiles when compared with raw starch. It also had no differential scanning calorimetry (DSC) endotherm. Gel cohesiveness and adhesiveness of both starch types were similar, while extruded starch gels were softer. Extruded starch produced lower Rapid Visco Analyser (RVA) viscosity profiles than raw starch due to starch degradation during extrusion. The raw and extruded starch components had negative interaction coefficients, thus RVA viscosity parameters were lowered as the fraction of extruded starch in the mixture increased. Starch degradation in the extruded starch was a likely significant factor associated with low viscosity profiles. Mixtures of raw and extruded starches could be commercially prepared to obtain finished starch products with a range of functional attributes.  相似文献   

3.
Pasting profiles of selected starches were compared by using a Micro Visco‐Amylo‐Graph (MVA) and a Rapid Visco Analyser (RVA). Effects of cooking (heating/cooling) rate and stirring speed on starch pasting properties were examined. The pasting viscosity of a starch suspension (8%, w/w, dsb) was measured at a fast (6°C/min) and slow (1.5°C/min) cooking rate while being stirred at either 75 rpm or 160 rpm. The pasting temperatures (PT) of all starches were higher when measured at the fast cooking rate than those at the slow cooking rate, except for wheat measured by using the RVA. PT was also higher when measured at the slow stirring speed (75 rpm) than at the fast stirring speed (160 rpm) in both RVA and MVA. When stirring speed increased from 75 rpm to 160 rpm, peak viscosity of all starch pastes except potato decreased measured by using the RVA, but increased by using the MVA. In general, amylograms of these starches obtained by using the MVA showed less breakdown, but greater setback viscosity than did that obtained by using the RVA. Differences in starch pasting properties between MVA and RVA, measured at the same cooking and stirring rates, were attributed mainly to the difference in spindle structure.  相似文献   

4.
The physiochemical characteristics of β‐glucan in oat and barley foods can affect human physiological response. A method for continuous measurement of β‐glucan viscosity with a Rapid Visco Analyzer (RVA) was developed to overcome the complexity of the common protocols based on in vitro digestion methods. The effects of several parameters on viscosity and solubility were considered. Oat cereal foods showed different RVA viscosity profiles depending on their physiochemical characteristics. Products high in starch exhibited a high initial viscosity that was reduced by α‐amylase action, whereas products with low amounts of starch exhibited a slow increase in viscosity. The viscosity of all samples reached a plateau in the viscosity curve after 1–2 hr, which is the key for obtaining reproducible results. Optimum digestion condition was achieved using sodium phosphate buffer (pH 6.9) and 1% β‐glucan dispersion at 37°C and 160 rpm. A particle size of <0.6 mm gave more consistent viscosities than did larger particles without affecting the solubility of β‐glucan. Pancreatin and α‐amylase concentrations affected the viscosity profile by influencing the digestion rate of protein and starch in the samples, but pepsin had limited influence at pH 6.9. Highly significant Pearson correlation between the in vitro digestibility protocol and RVA methods was achieved, indicting that the developed method could be used as an effective alternative for measurement of β‐glucan viscosity.  相似文献   

5.
Genetic variation in the physical properties of sweet potato starch.   总被引:10,自引:0,他引:10  
Sweet potato starch, prepared from 44 genotypes adapted to Philippine conditions, showed wide variation and distinctly different pasting profiles in Rapid Visco-Analyzer (RVA) analysis at 11% and 7% starch concentration. At 11% starch concentration, the pasting profiles were type A, characterized by high to moderate peak with a major breakdown and low cold paste viscosity. At 7%, the pasting profile was generally type C, characterized by the absence of a distinct peak with none to very slight breakdown and high cold paste viscosity. However, differentiation among genotypes was better achieved from RVA pasting profiles at 11% starch concentration. Peak viscosity (PV) and hot paste viscosity (HPV) at 11% starch paste concentration had significant negative correlation with amylose content. PV, HPV, and setback ratio were significantly correlated to adhesiveness of the starch gel. Sweet potato starch generally had high swelling volume but low solubilities at 92.5 degrees C.  相似文献   

6.
对转cry1Ab基因抗虫水稻矮秆突变体的品质性状与原亲本秀水11进行了对比分析,发现在最高粘度、热浆粘度和冷胶粘度等RVA谱特征值上两者有显著差异,而在外观品质、碾磨品质、表观直链淀粉含量、胶稠度和淀粉粘滞特性的崩解值、消减值等淀粉食用品质方面基本相同,在蛋白、脂肪、灰分、矿物质和氨基酸等关键营养成分上也不存在显著差异,在蒸煮后的矮杆突变体米粒中也未检测到Cry1Ab杀虫蛋白。  相似文献   

7.
香稻品种RVA谱多样性研究   总被引:2,自引:1,他引:1  
对来自不同种植区域的593份香稻材料(香糯稻152份,香籼稻342份,香粳稻99份)进行了RVA谱的多样性分析。结果表明,香糯稻以最终粘度的变异系数最大,为42.9,香籼稻和香粳稻以回生值的变异系数最大,分别为71.9和76.1。按遗传多样性指数(Shannon-wiener多样性指数)的分级标准计算,不同种质资源RVA谱特征值的分级情况复杂,除了峰值时间分布相对集中外,其他特征值的分级情况差别较大。RVA谱各特征值的遗传多样性指数均大于1.0,香糯稻峰值粘度和最终粘度的遗传多样性指数高达2.02和2.01,香籼稻和香粳稻均以回生值的遗传指数最高,分别为2.09和1.99。不同香稻种质间的淀粉糊化特性潜在分异明显。  相似文献   

8.
Studies on samples of 20 hard-grained wheat cultivars and a commercial flour that varied in starch and protein quality showed that both characteristics influenced the texture of Japanese alkaline noodles (ramen). Flour swelling volume (FSV) and flour pasting characteristics (peak viscosity and breakdown) determined with a Rapid-Visco Analyser (RVA) assessed independently of α-amylase effects, were negatively correlated with total texture score. Protein quality, as indicated by farinograph stability, was positively correlated with total texture score. RVA pasting characteristics were substantially affected by small levels of α-amylase, and inactivation by means of 1 mM AgNO3 was a critical requirement in characterizing the quality of the starch component of flour.  相似文献   

9.
The effect of starch crystallinity and phosphorus on starch gelatinization and retrogradation were studied using wide-angle X-ray powder diffraction, cross polarization/magic angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectroscopy, 31P NMR spectroscopy, Rapid Visco Analyzer (RVA) and differential scanning calorimetry (DSC). Two starches differing significantly in peak viscosity (cv. Stephens, 283 BU; cv. Crew, 560 BU) were comparable in amylose content and starch crystallinity, while differing significantly in phospholipids content. Starch of lower peak viscosity had a higher phospholipids content and showed a slower rate of retrogradation. Starch from Stephens (0.098% phosphorus) had an enthalpy value of retrograded starch of 2.2 J/g after 14 days of storage, while starch from Crew (0.062% phosphorus) had an enthalpy value as high as 4.4 J/g. Defatting with a hot n-propanol and water (3:1) mixture caused substantial changes in peak viscosity. Peak viscosity for starch from Crew decreased by 75 RVU due to defatting, while starch from Stephens decreased by as much as 125 RVU. After defatting with the hot n-propanol water mixture, the rate and extent of starch retrogradation were comparable between the prime starches, which differed significantly in peak viscosity.  相似文献   

10.
吕军  姜秀英  刘军  解文孝  韩勇  沈枫 《核农学报》2021,35(10):2214-2222
淀粉是稻米胚乳的主要成分,解析其理化特性对改良水稻品质具有十分重要的意义。为了探究心白稻米淀粉的理化特性,本研究以经EMS诱导粳稻品种辽星1号获得的心白突变体xb1为材料,利用扫描电镜、激光粒度分析仪、RVA快速黏度分析仪、差示扫描量热仪等方法,对形态结构、淀粉颗粒结构和粒径分布、糊化特性及热力学特性等进行了分析。结果表明,与野生型相比,突变体xb1籽粒的粒宽、粒厚和千粒重均显著降低;淀粉结构和淀粉粒粒径分布均发生改变,淀粉粒粒径值大于13左右的淀粉粒数量明显低于野生型;突变体种子中蛋白质含量极显著高于野生型,总淀粉含量极显著低于野生型,而直链淀粉含量没有明显改变;在支链淀粉分支结构上,聚合度(DP)在6~9之间的短链及25~35之间的中长链比例有所增加,而DP值在10~24之间的中短链及36~50之间的长链比例有所减少;突变体xb1淀粉的糊化起始温度(To)、峰值温度(Tp)、终止温度(Tc)和糊化距离(Tr)均未发生明显改变,只有热焓值(△H)极显著提高。同时,突变体xb1的RVA谱特征值中,热浆黏度(HPV)、峰值黏度(PKV)、冷胶黏度(CPV)和消减值(SBV)极显著提高,崩解值(BDV)和回复值(CSV)极显著降低。本研究结果为探索垩白形成的生理机制以及进一步的基因克隆奠定了基础。  相似文献   

11.
Three wheat flours, three wheat starches, a regular maize starch and a waxy maize starch were subjected to a number of different RVA profiles. Five different initial temperatures were used, 40, 50, 55, 60, and 65°C, with different initial holding times (0–3 min), heating times (2fl–10 min), holding times at 95°C (0–6 min), cooling times (2–6 min), and final hold times (0–10 min) being applied. A range of final temperatures of 30–60°C was also utilized. Significant variations in viscosity were observed with these conditions, particularly in wheat starch and flour. The most important parameters causing these variations were the initial temperature, the heating rate, and the final holding time. Short initial holding times also resulted in a wider spread of values for peak viscosity although there was little effect on the mean value and no significant effect on the holding strength or final viscosity. The final temperature was also important in that lower temperatures gave more viscous gels. Provided that the desired cooling rate could be achieved, varying the cooling time had no effect on the peak or trough viscosities and only a very minor effect on the final viscosity. If final temperatures of 40°C or lower are to be used, the cooling conditions and final hold time would need to be adjusted so that maximum viscosity could be achieved. A proposal for a standard Rapid Visco Analyser (RVA) procedure is: at least 1 min at 50°C, heat to 95°C over 4 min, hold at 95°C for 4 min, cool to 50°C in 3 min, and hold at 50°C for 4 min. These conditions should minimize variation within samples and should allow a better comparison between samples.  相似文献   

12.
Mineral content, as determined and expressed by ash content, serves as an index of wheat flour quality for flour millers and food manufacturers who prefer flour of low mineral content, even though the significance of mineral content on the functional properties of wheat flour is not well understood. We explored whether minerals have any influence on the functional properties of wheat flour and product quality of white salted noodles. Ash, obtained by incinerating wheat bran, was incorporated into two hard white spring wheat flours and their starches to raise the total ash content to 1, 1.5, or 2%. Pasting properties were determined using a rapid visco analyzer (RVA). Addition of ash increased the peak viscosity of the flours in both water and buffer solution but did not affect the peak viscosity of starch. Wheat flours with added ash showed lower pasting temperature by approximately 10°C in buffer solution. Mineral extracts (15.3% ash) isolated from wheat bran, when added to increase the ash content of wheat flour and starch to 2%, increased the peak viscosity and lowered the pasting temperature of flour by 13.2–16.3% but did not affect the pasting properties of the isolated starch. The mineral premix also increased peak viscosity of wheat flour but not in starch. Added ash increased noodle thickness and lowered water retention of cooked noodles while it exhibited no significant effect on cooked noodle texture as determined using a texture analyzer.  相似文献   

13.
Pasting characteristics of maize starch heat‐treated with six different water‐to‐ethanol ratios (%wt base 0:100, 10:90, 20:80, 30:70, 40:60, 50:50) were investigated; treated starches were called EW 0, 10, 20, 30, 40, and 50, respectively. Endotherms in DSC analysis shifted to a higher temperature as the water content in water‐ethanol mixture increased. The removed amount of fatty acids was much higher in treatments for EW 10, 20, and 30. The RVA peak viscosity of EW 10 and 20 were highest among the treated starches and setbacks were more than twice that of untreated starch. The characteristic change in the RVA viscogram corresponded to the amount of leached amylose from the granule. EW 30 displays similar properties as conventional heat‐moisture‐treated starch, but maintained a higher viscosity of ≈300 RVU throughout the heating process. In treatment with water‐ethanol mixtures, heat‐moisture treatment and defatting effects generated new types of modified starches. EW 40 and 50 had no clear pasting peak on RVA, and showed a viscosity at low temperature similar to granular cold water gelling.  相似文献   

14.
The effect of amylose-lipid (AM-L) complexes consisting of amylose populations with different peak degrees of polymerization (DP) and complexed with glyceryl monostearate (GMS) or docosanoic acid (C22) on the pasting properties of wheat and rice starches was evaluated with a rapid visco analyzer (RVA). AM-L complexes were formed by both (i) addition of lipids to amylose fractions with peak DP 20, 60, 400, or 950 at 60 degrees C or (ii) potato phosphorylase-catalyzed amylose synthesis in the presence of lipids. All AM-L complexes affected pasting properties in line with their dissociation characteristics. AM-L complexes therefore have potential as "controlled lipid release agents" with effects markedly different from those observable with emulsifier addition in starch pasting. More in particular, short chain AM-L complexes resulted in a starch pasting behavior comparable to that of cross-linked starch, as evidenced by reduced granule swelling, good viscosity stability in conditions of high temperature and shear, and a stable cold paste viscosity.  相似文献   

15.
气流粉碎对玉米淀粉结构及理化性质的影响   总被引:1,自引:1,他引:0  
为研究气流粉碎对玉米淀粉结构及理化性质的影响,该文以普通玉米淀粉为原料,通过流化床气流粉碎处理,采用扫描电子显微镜、偏光显微镜、粒度分析仪、X-射线衍射仪、红外光谱仪、差示扫描量热仪、快速黏度分析仪等分析手段研究经微细化处理前后玉米淀粉颗粒形貌、晶体结构、热力学特性、糊化特性、溶解度和膨胀度、冻融稳定性、持水能力等结构及性质的变化。结果表明,微细化处理后,淀粉颗粒形变的不规则,粒径明显减小,中位径(D50)由14.37μm减小到5.25μm,偏光十字减少,相对结晶度由33.43%降低至15.46%,淀粉颗粒结晶结构被破坏,由多晶态向无定形态转变,粉碎过程淀粉无新的基团产生;热焓值、糊化温度均降低,热糊稳定性好;溶解度、膨胀度均升高,持水能力增加,冻融稳定性好,产生较好的热糊稳定性和冷糊力学稳定性,该研究为玉米淀粉的深度加工与应用提供了理论依据及技术支撑。  相似文献   

16.
The Rapid Visco‐Analyzer (RVA) was used to characterize the pasting properties of 68 sorghum grains with a standard 23‐min temperature profile. The results showed a strong linear relationship between ethanol yield and final viscosity as well as setback. Ethanol yield increased as final viscosity decreased. A modified RVA procedure (10 min) with an application of α‐amylase was developed to simulate the liquefaction step in dry‐grind ethanol production. There was a remarkable difference in mashing properties among the sorghum samples with the normal dosage of α‐amylase. The sorghum samples which were difficult to liquefy in the mashing step had much higher peak viscosities than the samples that were easily liquefied. The results also showed that the relationship between conversion efficiency and mashing property was significant. Tannins cause high mash viscosities. There was a strong linear relationship between tannin content and final viscosity as well as peak viscosity. The modified RVA procedure is applicable not only for characterization of mashing properties but also for optimization of α‐amylase doses for starch liquefaction.  相似文献   

17.
The starch of wheat (Triticum aestivum L.) flour affects food product quality due to the temperature-dependent interactions of starch with water during gelatinization, pasting, and gelation. The objective of this study was to determine the fundamental basis of variation in gelatinization, pasting, and gelation of prime starch derived from seven different wheat cultivars: Kanto 107, which is a partial waxy mutant line, and six near-isogenic lines (NILs) differing in hardness. Complete pasting curves with extended 16-min hold at 93°C were obtained using the Rapid Visco Analyser (RVA). Apparent amylose content ranged from 17.5 to 23.5%; total amylose content ranged from 22.8 to 28.2%. Starches exhibited significant variation in onset of gelatinization. However, none of the parameters measured consistently correlated with onset or other RVA curve parameters that preceded peak paste viscosity. Peak paste viscosity varied from 190 to 323 RVA units (RVU). Higher peak, greater breakdown, lower final viscosity, negative setback, and less total setback were associated with lower apparent and total amylose contents. Each 1% reduction in apparent or total amylose content corresponded to an increase in peak viscosity of about 22 and 25 RVU, respectively, at 12% starch concentration. Of the seven U.S. cultivars, the lower amylose cultivars Penawawa and Klasic were missing the granule-bound starch synthase (GBSS; ADPglucose starch glycosyl transferase, EC 2.4.4.21) protein associated with the Waxy gene locus on chromosome 4A (Wx-B1 locus). Kanto 107 was confirmed as missing both the 7A and 4A waxy proteins (Wx-A1 and Wx-B1 loci). The hardness NIL also were shown to be null at the 4A locus. Apparent and total amylose contents of prime starch generally corresponded well to the number of GBSS proteins; although the hardness NIL tended to have somewhat higher amylose contents than did the other GBSS 4A nulls. We concluded that reduced quantity of starch amylose due to decreased GBSS profoundly affects starch gelatinization, pasting, and gelation properties.  相似文献   

18.
以2个杂交稻(淦鑫203和金优402)和4个常规稻(中531、B670、E134和ST66)为材料,于水稻乳熟期进行高温处理3d,处理温度分别为35℃和38℃,以同期田间自然温度为对照,研究乳熟期高温对不同品种早籼稻直链淀粉含量和RVA谱特征参数的影响,并对稻米淀粉RVA谱特征值与直链淀粉含量进行相关分析.结果表明,无论是对照还是高温处理,中531和B670的直链淀粉含量、消减值及回复值较低,但崩解值较高,而E134和ST66表现为直链淀粉含量、消减值及回复值较高,崩解值较低;杂交稻淦鑫203和金优402则介于两者中间.与对照相比,38℃高温显著降低淦鑫203、金优402、中531和E134的崩解值,显著提高淦鑫203、中531的消减值、显著降低金优402、中531、B670和E134的回复值.各处理淀粉RVA谱变化趋势较一致,但因品种及温度而略有差异.38℃高温处理下稻米淀粉黏滞性曲线始终低于对照,但常规稻中531和B670的RVA谱形态与对照差异不大.此外,稻米直链淀粉含量与RVA谱各特征值间存在显著相关性.  相似文献   

19.
优质小麦子粒淀粉组成与糊化特性对氮素水平的响应   总被引:1,自引:0,他引:1  
在大田条件下,选用3个不同类型优质小麦品种: 豫麦47(强筋品种)、山农8355(中筋品种)和豫麦50(弱筋品种),设置3个氮肥水平: 施N 0、15和30 g/m2,研究了小麦子粒淀粉的粒度分布、直支链淀粉组成、糊化特性及其对氮素水平的响应。结果表明,优质小麦子粒中淀粉粒的粒径分布范围为1~45 μm,其数目分布呈单峰或双峰曲线变化,体积和表面积分布均呈双峰曲线变化,峰谷位于10 μm处; 据此可将淀粉粒分为两种类型: A型大淀粉粒(10~45 μm)和B型小淀粉粒(1~10 μm)。优质小麦子粒淀粉粒组成存在显著的基因型差异。强筋品种豫麦47子粒中B型淀粉粒的比例较高,弱筋品种豫麦50子粒中A型淀粉粒的比例较高,中筋品种山农8355居中。施氮水平对优质小麦子粒中淀粉的粒度分布存在显著影响。在本试验条件下,随氮素水平的提高,强筋品种豫麦47子粒中A型淀粉粒的比例提高,而B型淀粉粒的比例下降; 增施氮肥后弱筋品种豫麦50和中筋品种山农8355子粒中B型淀粉粒的比例增大,而A型淀粉粒的比例降低,且前者变化的幅度较大。适量增施氮肥提高优质小麦子粒中的淀粉含量,氮肥用量进一步增大后,淀粉含量降低; 增施氮肥后优质小麦子粒中直链淀粉含量降低。增施氮肥对优质小麦子粒淀粉的糊化特性存在较大影响,且此影响的趋势因基因型和施氮量而异。其中强筋品种豫麦47表现为低谷粘度、最终粘度、反弹值、糊化温度和峰值时间提高,而高峰粘度和稀懈值降低; 当氮肥用量增大至30 g/m2时,糊化温度和峰值时间降低,而以粘度为单位的参数均提高。弱筋品种豫麦50表现为增施氮肥后,RVA参数呈下降趋势,与之相对应中筋品种山农8355的呈上升趋势。相关性分析表明,B型淀粉粒的数目、体积和表面积比例与高峰粘度和稀懈值存在显著正相关; 与低谷粘度、最终粘度和反弹值存在显著负相关。子粒中直链淀粉含量、支链淀粉含量和总淀粉含量与高峰粘度和稀懈值呈显著负相关,与低谷粘度、最终粘度、反弹值和峰值时间呈一定程度正相关; 直链淀粉相对含量与RVA特征参数之间的相关趋势与子粒中直链淀粉含量的趋势一致,但均未达显著水平。由此可以认为,氮肥通过调控小麦子粒中淀粉的直、支链组成和粒度分布而影响其糊化特性。  相似文献   

20.
The objective of these studies was to find alternative Rapid Visco Analyser (RVA) viscoelastic parameters that are predictable by near‐infrared spectroscopy (NIRS). Currently, RVA instruments are widely used in assessing cooking and processing characteristics in rice. The ability to predict RVA parameters by NIRS would be useful in rapidly determining rice pasting qualities, but NIRS does not correlate with the traditional parameters (peak viscosity, final viscosity, breakdown, consistency, and setback). Alternative RVA parameters were sought by collecting RVA and NIRS data for a total of 86 short, medium, and long grain rice cultivars. The amylose contents were 0.41–24.90% (w/w) and protein concentrations were 8.47–11.35% (w/w). Partial least squares (PLS) regression models generated for the entire NIR spectrum against the RVA curve showed viscosity at 212–228 sec (80°C ± 1) varied linearly with NIR spectra (1,100 to ‐2,500 nm). Regression coefficient values were R = 0.961 for 212 sec and R = 0.903 for 228 sec. The PLS correlation coefficient for the prediction of amylose at 212–228 sec decreases along with the NIRS correlation to the same time frame. An opposite trend was observed for the correlation with protein at 212–228 sec. This comparison suggests the importance of amylose and protein in water absorption during this time frame.  相似文献   

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