Functional properties of the system gelatine/Vicia faba protein in dependence on the acetylation degree of the Vicia faba protein

By acetylation of Vicia faba protein it becomes in aqueous solution compatible with gelatine up to a substitution degree of about 50%. The swellability and brittleness of foils and the viscosity of aqueous solution of Vicia faba protein are increased by its acetylation and these changes can be observed in mixtures of gelatine with acetylated Vicia faba protein, too. A heat denaturation of aqueous solutions of acetylated Vicia faba protein or mixtures with gelatine leads to an increase of the viscosity; all these solutions show pseudo-plastic flow behaviour.     

Effect of acetylation on the functional properties of lentil (Lens culinaris) globulin

The functional properties of native and acetylated (62.5, 84.1, 90.1 and 93.0%) globulins were evaluated. Acetylation caused a shift in isoelectric pH from 4.5 to 3.5. The solubility of acetylated globulins improved considerably above pH 4.0 but deteriorated below this pH. Increasing acetylation enhanced water absorption (from 1.08 to 1.67, 1.96, 2.29 and 2.33 ml g^?1) but reduced oil absorption capacity (from 2.61 to 2.17, 2.15, 2.05 and 1.76 ml g^?1). In comparison with native globulin the relative viscosity of acetylated globulins also increased, but with an increase in acetylation level there was a decrease in relative viscosity (2.13, 1.81, 1.65 and 1.62). The emulsifying activity of 62.5% acetylated globulin increased from 54.2% for native globulin to 56.0%, but above this level of acetylation the activity decreased. Emulsion stability followed a similar behaviour. The foaming capacity of native globulin was improved by 62.5% acetylation but reduced at higher acetylation levels. Maximum foam stability was observed for 90.1% acetylated globulin. © 2002 Society of Chemical Industry     

On the viscosity behaviour of field bean protein isolates in dependence on their degree of acetylation

The increase of apparent viscosity when protein concentration is raised becomes more and more distinctly pronounced with an increasing degree of acetylation and is displaced at lower protein concentrations. Investigations of the influence of temperature on viscosity behaviour are therefore carried out on the basis of comparable initial viscosity. 20 min heat treatment at different temperatures shows that above 40 degrees C the order of magnitude of the temperature-induced increase in viscosity depends decisively on the degree of acetylation. With an increasing degree of acetylation there is a comparably stronger increase in viscosity. An increase of viscosity is also linked to increasing duration of the heat treatment. The higher the degree of acetylation, the greater--related to a defined duration of heat treatment--is the growth of viscosity. During the heating phase in cyclical temperature tests a viscosity maximum is formed at 60 degrees C, which becomes more and more distinctly pronounced with an increasing degree of acetylation. From computerised evaluation of flow curves it is generally established that the complexity of flow properties increases with increasing degree of acetylation, increasing concentration of protein and the effect of heat.     

乙酰化香蕉淀粉的特性

通过与玉米淀粉比较,乙酰化香蕉淀粉的灰分、蛋白质、脂肪含量均比乙酰化玉米淀粉高.乙酰化香蕉淀粉糊的透明率在低温下出现较小的退化趋势,但常温下淀粉糊的透明率较高且有较好的稳定性.在较高温度下,乙酰化香蕉淀粉的持水能力比原淀粉高.乙酰化作用增加淀粉的溶解度和膨胀率.乙酰化作用也增加了香蕉淀粉糊的粘度值.     

酸解和乙酰化改性对木薯淀粉性质的影响

以木薯淀粉为原料,对酸解淀粉、乙酰化淀粉及酸解乙酰化淀粉的糊性质进行了研究,并用扫描电子显微镜、X射线衍射仪和傅里叶变换红外光谱仪对改性淀粉的形貌和结构进行了分析。结果表明:木薯淀粉经酸解改性改善了糊的透明度,膨胀度有所降低,糊化温度升高,峰值黏度显著降低,凝沉性有所改善;乙酰化改性增加了淀粉糊的透明度,膨胀度提高,降低了糊化温度,峰值黏度增加,糊的抗凝沉性增强但热糊稳定性差;酸解乙酰化复合改性显著提高了淀粉糊的透明度,降低淀粉的膨胀度及糊化温度,峰值黏度显著降低,抗凝沉性明显增强,冷、热糊稳定性提高。扫描电镜、X衍射数据及红外图谱表明,3种变性处理均没有改变木薯淀粉的晶型和基本结构,颗粒形貌也没有发生显著变化。     

Effect of low and high acetylation degree in the morphological, physicochemical and structural characteristics of barley starch

Barley starch was acetylated at two levels (low degree: LD (0.9), and high degree: HD (2.7)) substitution and the morphological, physicochemical and structural of the resultant acetylated barley starch were determined. The acetylated barley starches presented the signal at 1226 cm⁻¹ that corresponds to the C-O stretching of acetyl groups. The morphological study showed fusion of starch granules in the acetylated starch with HD. This effect was evident in the pasting test, because the viscoamylograph profile of HD starch showed the absence in peak viscosity, viscosity breakdown and viscosity setback. The peak gelatinization was similar for native and LD and decrease in the HD acetylated starch. The gelatinization enthalpy value showed difference among the samples, indicating that the loss of the ordered double helices more than the crystallinity loss was higher in the HD acetylated barley starch. In the retrogradation test, acetylation affected both retrogradation and enthalpy value, because acetylated barley starch with HD substitution at three storage days had 3.2 j/g and with LD 4.8 j/g. The molecular weight and z-average radius of gyration values decreased due to the acetylation process, indicating depolymerization of starch components as it was evidenced by the increase in short chains level in the acetylated samples.     

魔芋葡甘露聚糖的凝胶化特性

用测定动态粘弹性的方法探讨了碱存在下天然及乙酰化魔芋葡甘露聚糖(KGM)的凝胶化动力学特性。通过固有粘度和光散射的测定决定了KGM样品的分子量和其他分子参数。研究使用的KGM样品经乙酰化处理后发现其已被降解,但经乙酰化后的KGM的分子量与乙酰化度几乎不相关, 约为天然KGM分子量的1/2。当碱凝固剂(Na2CO3)的浓度为固定值时,观察到了凝胶化时间随KGM浓度的增大和温度的升高而缩短,但随乙酰化度的增加而变长的倾向。乙酰化处理后的KGM的脱乙酰基反应和后续的凝胶化过程比天然KGM缓慢,但能形成更有弹性的凝胶。以上现象表明,乙酰基团的存在对KGM的凝胶化过程起着极其重要的作用。在较为缓慢的凝胶化过程中,能够形成数量更多且分布均匀的凝胶网络结点,从而得到更具弹性的凝胶。     

Effect of reagent type on the acetylation of barley and maize starches

The objective of this work was to study the effect of reagent type on properties of acetylated barley starch (BS) and maize starch (MS) after modification with acetic anhydride (AA) and vinyl acetate (VA) at similar molar concentration for mole of glucose of both reagents. Degree of substitution (DS), morphological characteristics and granule size distribution, gelatinization and retrogradation, pasting properties, and X‐ray diffraction pattern were evaluated. Acetylation disturbs the short and long range order, and the effect was higher with AA than VA, and for BS than MS. This is due to the higher DS determined in AA–BS. In the pasting profile, acetylated starch showed the maximum peak viscosity at lower temperature, this effect was strongest for BS and anhydride acetic‐acetylation. Differential scanning calorimetry showed decrease in gelatinization parameters in acetylated starches (temperatures and enthalpy), and retrogradation was suppressed by acetylation. This effect was stronger in starches acetylated with AA despite their higher DS. This pattern can be explained from the occurrence of surface effects in acetylation with AA.     

低取代度乙酰化绿豆淀粉的性质

以绿豆淀粉为原料,冰醋酸为乙酰化剂,制备低取代度的乙酰化绿豆淀粉。对乙酰化绿豆淀粉的膨润力、溶解度、凝沉性、透明度、黏性、质构特性等进行研究。结果表明：与原淀粉相比,经过乙酰化处理的绿豆淀粉透明度、膨润力、溶解度均比原淀粉有所增加,糊化温度降低,谷值黏度、末值黏度有所升高,而峰值黏度、衰减值则降低,绿豆淀粉乙酰化后凝胶特性也有所改善。     

乙酰化酸解复合变性淀粉的制备及性能研究

本文以玉米淀粉为原料,以盐酸为酸解剂,醋酸酐为乙酰化试剂,氢氧化钠为酰化催化剂对酸解乙酰基复合变性淀粉合成工艺进行了研究。考察了反应时间、反应温度、pH值、酸含量对酸解淀粉流度、乙酰化淀粉取代度及产品性能的影响。实验结果表明,升高酸解温度、增加酸解时间和酸含量将加速淀粉的降解。采用流度法测定酸解淀粉的粘度,采用酸碱滴定法测定了乙酰化酸解淀粉的取代度。     

Physical Properties of Cross-linked and Acetylated Normal and Waxy Rice Starch

Waxy and normal starches present wide biological diversity in their structure. The objective of this study was to investigate the effect of chemical modification on the physical properties of cross-linked and acetylated normal (NR) and waxy (WR) rice starch. Cross-linking increased shear stability and decreased swelling power and solubility of NR and WR, but increased viscosity, pasting temperature, and heat of gelatinization of WR, and decreased pasting temperature and heat of gelatinization of NR. Acetylation increased viscosity and solubility of NR and WR, while it increased the swelling power of NR, and decreased the swelling power of WR. Cross-linking increased hardness and adhesiveness of NR and WR gels, while acetylation increased hardness but decreased adhesiveness of the gels. Freeze-thaw stability results showed that both acetylation and cross-linking decreased retrogradation of NR, but increased it in WR.     

Effect of hydroxypropyl β-cyclodextrin on physical properties and transition parameters of amylose–lipid complexes of native and acetylated starches

The effect of hydroxpropyl β-cyclodextrin (HPβ-CD) on physical properties and digestibility of wheat, potato, waxy maize and high-amylose maize starches before and after acetylation was studied. Effect of HPβ-CD on amylose–lipid complexes in native and acetylated potato starches synthesized using α-lysophosphatidylcholine was also studied. Acetylation increased swelling factor, amylose leaching, peak viscosity and susceptibility to α-amylase hydrolysis, but decreased gelatinization temperature and enthalpy and gel hardness in all starches. HPβ-CD markedly increased swelling factor and amylose leaching in native and acetylated wheat starches but had little or no impact on other starches. Wheat starch gelatinization enthalpy decreased in the presence of HPβ-CD but gelatinization temperature of all the starches was slightly increased. HPβ-CD had no influence on enzymatic hydrolysis. Melting enthalpy of amylose–lipid complex in both native and acetylated wheat starches was decreased by HPβ-CD. Acetylation also decreased the melting enthalpy of amylose–lipid complex in wheat starch. Similar trend of thermal transitions was observed in the presence of HPβ-CD for the amylose–lipid complexes synthesized in potato starch. Acetylation reduces the complex formation ability of the amylose polymer. Similar to gelatinization, acetylation widened the melting temperature range of amylose–lipid complexes while shifting it to a lower temperature. Higher swelling and amylose leaching, and decreased gelatinization temperature and enthalpy resulting from acetylation of wheat starch is consistent with its influence on starch hydration. Similar effects resulting from the inclusion of HPβ-CD were consistent with the disruption of amylose–lipid complex by HPβ-CD which promotes granular hydration.     

Rheological characterization of acylated and dextran conjugated African yam bean (Sphenostylis stenocarpa Hochst. Ex A. Rich.) proteins

The molecular weight distribution and rheological properties of acetylated, succinylated and dextran conjugated African yam bean (Sphenostylis stenocarpa) proteins dispersion were studied. Succinylation of the protein showed the three prominent electrophoretic bands of the unmodified protein but all the bands disappeared with acetylation. Immobile band characterized dextran conjugated S. stenocarpa electrophoregram. The flow behavior indices (n) of these modified S. stenocarpa protein dispersions were in the range 0.03–0.22. This is an indication that they were pseudoplastic in nature. This pseudoplastic nature was maintained in ionic media 0.05–0.5 mol dm^?3, pH 3–8 and temperature range of 27–75 °C. The yield stresses were 0.270, 0.302 and 0.320 Pa for acetylated, succinylated and dextran conjugated protein respectively. Activation energy of acetylated and succinylated protein were in the range 6.2–8.2 and 2–5.4 J mol^?1 respectively. Thus acetylation of S. stenocarpa protein made its dispersion viscosity more susceptible to temperature change than succinylation. These results suggest that acylation and dextran conjugation of African yam bean (S. stenocarpa) protein produce protein species with different rheological properties.     

Physicochemical properties of acetylated starches from some Indian kidney bean (Phaseolus vulgaris L.) cultivars

Starches separated from four kidney bean cultivars were modified by acetylation to reduce retrogradation and increase gel stability and compared with respective native starches (data of native starch reported by Wani et al., 2010 ). Acetylation was carried out by treating starches with 0.04 and 0.08 g of acetic anhydride per gram of starch dry weight basis (dwb) at 25 °C and pH between 8.0 and 8.5. The extent of acetylation increased proportionally with the concentration of acetic anhydride used. The pasting curves of 10.7% starch determined by Rapid Visco Analyzer at 160 rpm showed that acetylation decreased the setback viscosity values by 0.64–34.58% and pasting temperature by 4.4–9.2 °C when compared with the native starch. Differential scanning calorimetry observations also revealed significant (P ≤ 0.05) decrease in gelatinisation temperature of acetylated starches than the corresponding native starches. Hardness of starch gels varied between 14.3 and 44.0 g, which was significantly (P ≤ 0.05) lower than the corresponding native starch gels.     

Flow Properties of Acetylated Chickpea Protein Dispersions

Abstract: Chickpea protein concentrate was acetylated with acetic anhydride at 5 levels. Acetylated chickpea protein (ACP) dispersions at 3 levels (6%, 45%, and 49%) were chosen for this flow property study. Effects of protein concentration, temperature, concentrations of salt addition and particularly, degree of acetylation on these properties were examined. Compared with native chickpea proteins, the ACP dispersions exhibited a strong shear thinning behavior. Within measured temperature range (15 to 55 °C), the apparent viscosities of native chickpea protein dispersions were temperature independent; those of ACP dispersions were thermally affected. The flow index (n), consistency coefficient (m), apparent yield stress, and apparent viscosities of ACP dispersions increased progressively up to 45% acetylation but decreased at 49% acetylation level. Conformational studies by gel filtration suggested that chickpea proteins were associated or polymerized at up to 45% acetylation but the associated subunits gradually dissociated to smaller units at higher levels (49%) of acetylation. Practical Application: The results of this study should be useful for chickpea protein application in food systems to make high protein functional food products.     

常用辅料淀粉及大豆分离蛋白的功能性指标评价

对不同的2-3种大豆分离蛋白/淀粉进行可以表征其吸水性、吸油性、乳化性、凝胶性等功能优劣的参数测试。根据测试结果初步判断大豆分离蛋白/淀粉的生产性能。通过初步的比较,淀粉中木薯乙酰化二淀粉磷酸酯、大豆分离蛋白中SL-906P的性能最优。其中木薯乙酰化二淀粉磷酸酯的糊化温度、峰粘度、谷粘度与终粘度、回凝度、溶胀(膨胀)度以及溶解度均优于玉米乙酰化二淀粉磷酸酯;SL-906P的氮溶解指数、乳化活性指数以及红外光谱信息(α-螺旋特征谱带积分面积)均优于SUPRO590和杜邦。     

Preparation and Characterization of Starch Acetate

Acetylation of native hydrolyzed and oxidized, maize starch has been studied. The different factors affecting acetylation process were investigated. These factors include liquor ratio, acetic anhydride, perchloric acid concentration, reaction time and temperature. Also investigated were characterization and application of the acetylated starches in textile warp sizing. The acetyl content increases to reach a maximum and then decreases on increasing either liquor ratio or perchloric acid concentration. Also it increases with increasing acetic anhydride concentration within the range examined whereas the actylation reaction efficiency % decreases. Hydrolysis of starch prior acetylation inhances the susceptibility of the starch towards acetylation whereas oxidation do the reverse. The solubility of acetylated starches derived from hydrolyzed or oxidized starches increases more than that of acetylated native starch. The solubility depends on the extent of acetylation and of the modification prior acetylation. Acetylation of starch improves its sizeability of cotton yarns.     

Chemical and gel electrophoretic characterization of acetylated faba bean protein isolates

The extent of modification of amino and hydroxyl groups in acetylated faba bean protein isolates was determined. Gel electrophoretic studies of unmodified and acetylated faba bean legumin and protein isolates were carried out in acidic and alkaline buffer systems as well as in a SDS-containing system. A remarkable increase of O-acetylation was found after the N-acetylation has reached a degree of about 60%. Structure changes of the proteins were indicated from the gel electrophoresis patterns in the same region of modification. The quantity of acetyl residues fixed on hydroxyl groups in exhaustively modified protein isolates corresponds to 40 % of the total amount of acetyl groups introduced into the proteins. The SDS electrophoresis of the acetylated legumin and protein isolates revealed a remarkable increase of the molecular mass of the acidic α-polypeptide chains only, which is an experimental proof of a preferential acetylation of the latter ones. This gives confirmation of the structural model in which the α-chains are proposed to be situated on the surface of the protein.     

Sequence requirements for Nalpha-terminal acetylation of yeast proteins by NatA

NatA is the major N-terminal acetyltransferase of the yeast Saccharomyces cerevisiae. In this study, we took advantage of our recent data on N-terminal acetylation of proteins of the yeast protein map to update the list of proteins with known NatA-dependent acetylation status. Furthermore, using the information available on the acetylation status of 100 novel proteins, we re-examined the rules for acetylation by NatA. The results refine our previous knowledge on NatA substrate specificity depending on the N-terminal and penultimate residues. In particular, we found that the acetylation frequencies of Ser-, Thr- and Ala-, the three residues most often acetylated by NatA, are higher than previously reported. In addition, comparison of the N-terminal region of acetylated and non-acetylated proteins revealed differences in amino acid composition that extend over the 25 first amino acid residues: acetylated proteins are characterized by a higher frequency of glutamate and glutamine and a lower frequency of lysine, arginine and histidine. We suggest that the particularities in amino acid composition of the N-terminal region of acetylated proteins facilitate its interaction with the Nat1p subunit of NatA and its guidance to the catalytic subunit Ard1p.     

乙酰化对红薯淀粉性质的影响

以红薯淀粉为原料,醋酸酐为乙酰化剂,制备低取代的乙酰化红薯淀粉.通过制备不同取代度乙酰化淀粉(DS 0.044～0.096),与红薯原淀粉进行比较,对乙酰化淀粉的透明度、凝沉性、溶解度、溶胀度、黏度和质构特性等进行深入研究.结果表明,与原淀粉相比,红薯淀粉经乙酰化作用后,凝沉性明显减弱,乙酰化红薯淀粉透明度、溶解度和溶胀度都随着取代度的增加而增加,且明显高于原淀粉.乙酰化红薯淀粉的糊化温度降低6～10℃,最终黏度和回生值显著降低,硬度显著降低.