Evaluation of starch analysis methods for feed samples

The objectives of this work were to evaluate the efficacies of commercial starch analyses and of starch analysis extraction and gelatinisation procedures. In Study 1, accuracy and specificity of commercially available starch analyses were evaluated with six co‐operating laboratories (five commercial, one university). Results from 11 test samples showed three laboratories with recoveries of purified starch of 92 g kg⁻¹ or less. Three and four laboratories had inflated values when samples contained glucose or sucrose, respectively. Analyses appeared to have good specificity for glucose. Incompleteness of starch detection and interference by non‐starch carbohydrates can affect commercially available analyses. In Study 2, extraction with 80:20 ethanol/water (v/v; 80EtOH) or 90:10 ethanol/water (v/v; 90EtOH) to remove low‐molecular‐weight carbohydrates, and gelatinisation with heat, alkali (KOH), 6 M urea or 8 M urea were evaluated. Extraction with 80EtOH or 90EtOH reduced interference from non‐starch carbohydrates. Gelatinisation with heat was adequate for good recoveries of starch glucose for both control (non‐extracted) and 80EtOH‐extracted samples; gelatinisation with alkali was required for 90EtOH‐extracted samples. Recoveries of pure starch samples were greatest with no extraction and heat gelatinisation. 80EtOH extraction with heat gelatinisation appears to be an adequate preparation method when removal of low‐molecular‐weight carbohydrates is desired. © 2000 Society of Chemical Industry     

不同提取方法对面包果淀粉性质的影响

本文采用湿磨法、碱法、中性蛋白酶法提取面包果淀粉,研究三种不同提取方法对面包果淀粉性质的影响。结果表明:湿磨法、碱法、中性蛋白酶法的提取率分别为23.90%、66.25%、66.05%,而碱法、中性蛋白酶法无显著性差异(P>0.05);面包果淀粉提取破损情况:碱法(4.20%)>中性蛋白酶法(2.28%)>湿磨法(1.92%);湿磨法提取面包果淀粉中蛋白质和脂肪残留量最多,碱法和中性蛋白酶法的残留量相差较小;不同方法提取的面包果淀粉溶解度和膨胀度均随温度的升高而升高,湿磨法提取的面包果淀粉溶解度和膨胀度均最大,碱法和中性蛋白酶法相差较小。经综合评价得出,中性蛋白酶法为面包果淀粉的最佳提取方法。本研究为面包果淀粉提供了一种新型绿色提取工艺,以期为面包果淀粉获得更加经济环保的工业化生产提供理论依据。     

绿茶降糖作用机制的研究

给糖尿病大鼠口服蔗糖或淀粉和绿茶提取物后,观察其对糖尿病大鼠糖耐量及血胰岛素的影响,并用比色法测定对α-葡萄糖苷酶(EC 3.2.1.20)和α-淀粉酶(EC 3.2.1.1)的抑制活性,用快速过滤法观察对兔小肠刷状缘囊泡葡萄糖转运活性的影响.结果表明,绿茶提取物明显改善蔗糖或淀粉负荷糖尿病大鼠的血糖水平.绿茶提取物显示较强的α-葡萄糖苷酶抑制活性,其α-葡萄糖苷酶的半抑制浓度(IC50)值为0.13g/L;对α-淀粉酶的抑制活性则较弱,浓度为1g/L时,其对α-淀粉酶的抑制率为21%.绿茶提取物同时明显降低兔小肠刷状缘囊泡葡萄糖转运能力,其半抑制浓度(IC50)值为3.5g/L.提示,绿茶可延缓小肠对糖的消化吸收,经常食用可能有助于延缓餐后血糖的持续升高. C 3.2.1.1)的抑制活性,用快速过滤法观察对兔小肠刷状缘囊泡葡萄糖转运活性的影响.结果表明,绿茶提取物明显改善蔗糖或淀粉负荷糖尿病大鼠的血糖水平.绿茶提取物显示较强的α-葡萄糖苷酶抑制活性,其α-葡萄糖苷酶的半抑制浓度(IC50)值为0.13g/L;对α-淀粉酶的抑制活性则较弱,浓度为1g/L时,其对α-淀粉酶的抑制率为21%.绿茶提取物同时明显降 兔小肠刷状缘囊泡葡萄糖转运能力,其半抑制浓度(IC50)值为3.5g/L.提示,绿茶可延缓小肠对糖的消化吸收,经常食用可能有助于延缓餐后血糖的持续升     

Characteristics and “Fodal”-Factor of Mango Seed Kernel Starch

Starch prepared from mango seed kernels is characterized by a low protein and fat content. Infrared studies proved the presence of amine and carboxyl groups of amino acids at wave numbers of 1485 and 1650 cm⁻¹ respectively, whereas the phosphate group had been detected at 1150 cm⁻¹. The contents of amylose and amylopectin were 39.9 and 60.1 respectively, reducing value was 1.54 and the alkali number was 10.10. The percentage of soluble material associated with starch was 2.11, whereas the percentage of branching of the mango seed kernel starch was 4.23. The glucose residues per end group were 23.62 and those per a segment were 11.81. Corn starch showed approximately the same values, whereas rice starch showed different results. The intrinsic viscosity was 1.72, 1.83 and 1.33 for mango seed kernel, corn and rice starches respectively, and the corresponding “Fodal” factors were 0.947, 0.983, and 0.992. X-ray analysis indicates that mango seed kernel starch possesses an “A” type of X-ray diffraction diagram.     

The effect of starch isolation method on physical and functional properties of Portuguese nuts starches. I. Chestnuts (Castanea sativa Mill. var. Martainha and Longal) fruits

The functionality of starch from chestnut (Castanea sativa Mill.) fruits isolated by alkaline and enzymatic methods were assessed. The studied properties included: solubility, swelling power, pasting properties, synaeresis, turbidity, and thermal and rheological behaviours. In addition amylose and resistant starch content were also evaluated. Results showed that the starch isolation method induced changes in most of those properties. Extracted starches (with high contents of amylose and resistant starch) showed low and similar swelling solubility values for all of the samples. Gelatinisation temperatures were also similar (61.5-63.0 °C), but the enzymatic method induced lower consistencies at 95 °C and after holding at this temperature. High values of setback were found, which were clearly affected by the isolation method. This parameter presented lower values for starches isolated by alkaline method (160 BU and 235 BU, respectively for Martainha and Longal). Starches did not present a peak consistency during pasting. Turbidity and synaeresis values were low at room temperature. Synaeresis increased when pastes were stored at low temperatures. This effect was more evident for the material isolated by enzymatic method. All of the isolation starches presented low enthalpy values (3.0-3.5 J/g), but the activation energy was higher for Martainha starches and for starches isolated by A3S method. Pastes showed viscoelastic behaviour, with a predominance of elastic property, forming strong gels after cooling. Longal variety seems to be less resistant to the effect of isolation method. In general starches isolated by the alkali method present the best functional properties as a food ingredient.     

Technical Note: Effect of Sample Processing Procedures on Measurement of Starch in Corn Silage and Corn Grain

Methods for processing feedstuffs before analysis can affect analytical results. Effects of drying temperature (corn silage), preservation method (corn grain), and grinding method (corn silage and grain) on starch analysis values were evaluated. Corn silage samples dried at 55 or 105°C and grain samples dried at 55°C were ground to pass the 1-mm screen of an abrasion mill or cutting mill and analyzed for free glucose and starch corrected for free glucose. Starch analyses were performed in triplicate to assess the effect of treatment on precision of starch determination. Drying at 105°C decreased free glucose and tended to decrease starch detected in silage. Decreased free glucose and starch values in silages dried at 105°C may have been caused by the destruction of glucose and production of Maillard products through nonenzymatic browning. Maillard products with reducing activity could potentially interfere with the glucose oxidase-peroxidase glucose detection method used. Compared with the cutting mill, grinding samples through the abrasion mill increased the precision of starch measures in silage, likely due to the effect of the finer particle size produced by the abrasion mill allowing more accurate subsampling of a more homogeneous matrix. Starch values were greater for grain ground with an abrasion mill than with a cutting mill, with the difference greater for dry-rolled than for high-moisture corn. For starch analysis of corn silage and corn grain, drying at lower temperatures (55°C) in forced-air ovens and grinding through the 1-mm screen of an abrasion mill or its equivalent is recommended.     

Alkali Extraction of Starch from Corn Flour

The alkali steeping process was tested for extraction of starch from degerminated yellow corn flour. The effect of three process parameters, alkali concentration (0.1 and 0.4%), steep temperature (25 and 55°C) and steep time (30 and 90min) were evaluated for their effect on yield, protein and sodium contents of starch. Two-level full factorial design was used to investigate the process. The experimental results indicated that starch yield increased with increasing steep temperature and at low alkali concentration. All main effects and interactions were found to have significant effect on protein content in the extracted starch. The sodium content of the starch was effected by the three main effects and the three two-factor interaction effects. Conditions were identified that simultaneously produced a high starch yield, low protein and sodium contents were 0.1% alkali steep at 55°C for 30 min.     

慈菇淀粉糊特性研究

对慈菇淀粉糊与马蹄、绿豆、马铃薯、豌豆、玉米和木薯淀粉糊凝沉性和冻融稳定性进行比较,研究不同条件对慈菇淀粉糊黏度和透明度的影响。结果表明：慈菇淀粉糊凝沉速率较低,介于马蹄与木薯淀粉之间;冻融稳定性与木薯淀粉相似;在微酸和微碱条件下,慈菇淀粉糊的透明度下降,在强酸和强碱条件下,透明度上升;在低pH值时,淀粉糊黏度下降,pH＞7时,淀粉糊黏度上升;蔗糖和葡萄糖能增大淀粉糊的黏度,也能提高其透明度,而NaCl与CaCl2对其淀粉糊黏度和透明度的作用则相反;随剪切时间延长,其表观黏度减小,这表明慈菇淀粉糊属于典型的非牛顿假塑性流体。     

Carbohydrate composition of different varieties of cowpea (Vigna unguiculata)

Twenty varieties of cowpea with the following proximate composition: dry matter, 87–94%; crude protein, 24–33% ether extract, 1–2%; crude fibre, 2–5% and ash, 2–5% were analysed for sugar contents, starch, cell wall carbohydrates and lignin. The legume seeds exhibited a total carbohydrate content ranging from 56% to 68%, the major constituent being starch. Starch values as high as 45% to 48% were obtained for some varieties although most values ranged between 37% and 42%. Ethanol-soluble sugars were verbascose, stachyose, sucrose and raffinose in varying amounts but there were only traces of fructose and glucose. Samples had total soluble sugar contents of 6% to 13%. Values for unavailable carbohydrates for most samples were 11% to 13%. Lignin was very low and ranged from 0·6% to 1·8%.     

Effects of Solutes on Retrogradation of Stored Starches and Amylopectins: A Calorimetric Study

Starch and amylopectins from different sources were studied to know their calorimetric behavior when mixed with sucrose, glucose and sodium chloride to different concentrations, and stored to different times. It was found that for control samples of amaranth, waxy and normal corn starches slight changes in enthalpy values were observed. The three starches presented retrogradation endotherms, in the presence of sugars, after 2 storage weeks with low enthalpy values; these values tended to be higher by decreasing sugar concentration. The effect of sodium chloride on starch retrogadation was different to that of sugars; waxy corn starch did not show enthalpy values at all experimental conditions. theories on retarding effect of sugars have been proposed but the effect of salt on retrogradation until now is difficult to explain. Amylopectin in the presence of sucrose showed retrogradation endotherms after 3 storage weeks and with glucose after 4 weeks, except potato amylopectin which did not exhibit this trend at any tested condition. With sodium chloride all amylopectins presented retrogradation endotherms after 4 weeks. The different behavior of amylopectins with solutes could be explained by the different chain distribution in such macromolecules.     

发芽糙米淀粉理化特性研究

采用富集γ-氨基丁酸(GABA)的优选糙米发芽工艺条件,通过碱酶两步法提取糙米淀粉,研究发芽对糙米淀粉结构和理化特性的影响。结果表明:糙米发芽后,淀粉膨胀度增大,且随温度升高而提高;透明度升高了57.14%;峰值黏度基本不变;冻融稳定性提高,凝沉特性得到改善;淀粉凝胶的凝胶粘性有所提高,硬度和胶凝性有所降低;碘兰值减小,说明糙米发芽后其直链淀粉含量降低或聚合度减小;电镜分析结果显示,发芽后糙米淀粉颗粒变得圆滑,棱角较发芽前不明显。综上得出,发芽对糙米淀粉的理化特性具有一定的改善作用。     

A Rapid Method for the Analysis of Starch

A rapid enzymic method for starch analysis, especially in cereal products, is presented. One person can analyze 30 samples per day. The method includes a 15 min gelatinization step in a boiling water bath in the presence of a thermostable α-amylase, a 30 min amyloglucosidase incubation of a subsample, and subsequent determination of glucose with a glucose oxidase/peroxidase reagent. The method was evaluated by analysis of the starch content in various raw and industrially processed wheat samples. The method showed high precision (CV=0.6–1.0%) and accuracy. Some factors which might affect the enzymic availability of starch and thus its recovery in the analysis are evaluated and discussed.     

Evaluation of acid and enzyme hydrolytic methods for the determination of edible aroid starch content

The starch content of four edible aroid (Araceae) cultivars was determined using acid and enzyme methods of hydrolysis. Hydrolysates were analysed using ferricyanide reduction, glucose oxidase and high performance liquid chromatography methods. Differences in starch values were obtained between the method of sugar analysis used when acid hydrolysis of samples was employed. The results obtained using enzyme hydrolysis, however, showed no significant differences between the methods of sugar analysis used. The results of these experiments indicate that, to obtain accurate starch values for edible aroids using the least expensive options, it is recommended that acid hydrolysis and the glucose oxidase-peroxidase glucose-specific assay methods or enzyme hydrolysis and ferricyanide sugar analysis be used. Starch degradation of ungelatinised samples by enzymic hydrolysis was very limited and showed considerable cultivar variation.     

Maltulose Formation During Saccharification of Starch

Maltulose precursors are produced due to chemical isomerization of the reducing end glucose units during enzyme liquefaction and autoclaving of starch in the enzyme-enzyme process of glucose manufacture. The precursors are hydrolyzed during subsequent saccharification with amyloglucosidase to form maltulose as one of the products. Temperature, pH and DE of the liquefied starch during autoclaving and α-amylase treatment are important factors in controlling precursor formation, low temperature, low pH and low DE resulting in less maltulose formation. Acid liquefaction prior to saccharification does not result in maltulose precursor formation. Blocking of the reducing end glucose unit by hydrogenation to sorbitol prevents the formation of maltulose; maltitol is produced instead.     

Modifying glucose release from high carbohydrate foods with natural polymers extracted from cereals

BACKGROUND: Sustained elevated blood glucose and insulin levels are linked to many health problems that may be prevented or better managed by controlling glucose availability for uptake. Glucose release from consumed starch may be altered by the processing conditions, particle size and structural features of the food, and by the addition of dietary fibres. Many approaches to lower glucose release are not suitable for all high carbohydrate foods, especially bakery products. Methods to modulate the starch digestion without compromising product quality are required. This study describes an approach to protect the granules and alter the particle size of the starch component using an extract from barley (BE). Wheat starch was suspended in the BE at different ratios and cast dried, milled to 2–3 mm particles, or finely ground to produce different particle sizes. RESULTS: The BE treatments resulted in the formation of clusters of starch granules embedded in a matrix of fibres and protein. The rate of in vitro starch digestion was decreased, and further reduction occurred when the particle size of the starch material increased. CONCLUSION: The extract provided a physical barrier that limited the starch exposure to the digestion enzymes and water that led to reduction in starch digestion and the release of glucose Copyright © 2011 Society of Chemical Industry     

Effect of Pullulanase Debranching of Sago (Metroxylon sagu) Starch at Subgelatinization Temperature on the Yield of Resistant Starch

The effects of pullulanase debranching of sago (Metroxylon sagu) starch in the granular state and subsequent physical treatments on the formation and yield of type III resistant starch (RS 3) have been investigated. Sago starch was enzymatically debranched with pullulanase at 60°C and at pH 5.0 using different enzyme concentrations (24, 30, 40, 50 PUN/g dry starch) which was added to 20% (w/v) starch slurry and incubated for 0 to 48 h. Optimum enzyme concentration of 40 PUN/g dry starch and three debranching times (8, 16 and 24 h) have been selected for subsequent preparation of RS. Granule morphology and molecular weight distribution (MWD) of the debranched and resistant starch were examined. Debranched starch samples showed blurred birefringence patterns, a decrease in amylopectin fraction, an increase in low molecular weight fraction and a broadening of MWD. Debranched starch samples with a maximum RS yield of 7% were obtained at 8 h debranching time. Temperature cycling and incubation at certain temperature and storage time enhanced the formation of RS. Under the conditions used in this study, the optimum conditions to obtain the highest RS yield (11.6%) were 8 h of debranching time, followed by incubation at 80°C for seven days. The MWD analysis showed that RS consisted of material with relatively low degree of polymerization. This study showed that pullulanase treatment of starch in the granular state resulted in limited debranching of amylopectin but the subsequent physical treatments (incubation time/temperature) can be manipulated to promote crystallization and enhance formation of RS 3.     

不同碱对木薯淀粉结构的影响

为研究不同碱对木薯淀粉结构的影响,利用第IA主族碱金属氢氧化物配制的碱/醇溶液对木薯淀粉进行处理。通过偏振光显微镜、激光共聚焦显微镜、扫描电子显微镜、X-射线衍射分析、傅里叶变换红外光谱仪对处理木薯淀粉进行表征,并对其直链淀粉和总还原糖含量进行检测。结果表明,不同碱/醇溶液处理均不影响木薯淀粉颗粒形貌的完整性。红外结果显示没有产生新的官能团,但处理木薯淀粉在3412 cm-1处的峰向高波数方向移动,且其强度均小于原木薯淀粉。此外,随着碱金属元素所在周期的增大,碱/醇溶液处理对木薯淀粉内部结构的破坏明显增强,木薯淀粉的晶型发生变化,其相对结晶度由原来的22.03%降至15.07%,淀粉颗粒中直链淀粉含量由22.30%逐渐降低至16.51%。所有处理样品中的总还原糖含量均高于原木薯淀粉。综上可知,不同碱/醇溶液处理对木薯淀粉结构的影响表现出明显的差异。     

新型氧化剂微波干法制备氧化淀粉及其性能研究

干法制备变性淀粉已逐步在国内推广,它具有流程短,能耗低,操作简便等优点。采用微波干法工艺,研究了二氧化氯、氯酸钠两种氧化剂制备氧化淀粉(分别为氧化淀粉A和氧化淀粉B)的工艺和变性淀粉的性能。工艺研究表明,两种氧化剂均能通过微波干法制备氧化淀粉,而氧化淀粉A和氧化淀粉B的羧基含量分别为(0.068±0.002)%和(0.586±0.002)%。性能研究表明,氧化淀粉的热黏度稳定性得到了改善,氧化淀粉B的冻融稳定性较好,经2次冻融,析水率仅为23.7%;氧化淀粉A耐碱性能好,耐酸性较差,氧化淀粉B则具有较好的耐酸耐碱性;X-射线衍射结果表明淀粉的氧化反应主要发生在淀粉的无定型区,而晶体结构仍与原淀粉相同。     

Starch and Amylopectin - Effects of Solutes on Clarity of Pastes

The effect of sucrose, glucose and sodium chloride at different concentrations on clarity of starch and amylopectin pastes was studied. It was found that clarity of amaranth, waxy corn and normal corn starch pastes tended to increase by increasing carbohydrate concentrations. The percentage of transmittance (%T) values for the same starch sample with sucrose and glucose did not present significantly differences (α=0.05). The starches with sodium chloride did not show a defined pattern. The %T for amaranth and waxy corn amylopectin pastes with all solutes tended to increase by increasing solute concentration. Interestingly, the %T values among all amylopectins at a given solute concentration were significantly different (α=0.05) probably due to different chain length proportion in such amylopectins. The same amylopectin in presence of sucrose and glucose did not show %T significantly different (α=0.05) but with sodium chloride those values were different (α=0.05).     

微射流均质结合非淀粉酶处理法对大米蛋白-淀粉复合体分离效果的研究

采用微射流处理结合非淀粉酶处理对碎米中蛋白质-淀粉复合物进行解聚处理,并研究所获得蛋白质及淀粉产品的性质。结果表明:此方法能够有效分离碎米中蛋白质及淀粉;获得的蛋白质与碱法提取的蛋白质相比,更具天然性;淀粉产品比碱法提取的淀粉有更低的峰值温度及更高的峰值粘度。由此可见,微射流结合非淀粉酶处理是高效分离碎米中蛋白质及淀粉,并获得高品质产品的一种有效途径。