Structure and functional properties of sorghum starches differing in amylose content

Starches were isolated from grains of waxy, heterowaxy, and normal sorghum. To study the relationship between starch structure and functionality and guide applications of these starches, amylose content, amylopectin chain-length distributions, gelatinization and retrogradation, pasting properties, dynamic rheological properties, and in vitro enzyme digestion of raw starches were analyzed. Heterowaxy sorghum starch had intermediate amylose content, pasting properties, and dynamic rheological properties. Stress relaxation was a useful indicator of cooked starch cohesiveness. Cooked heterowaxy sorghum starch (10% solids) had a viscoelastic-solid type of character, whereas cooked waxy sorghum starch behaved like a viscoelastic liquid. Amylopectin of normal sorghum starch had a slightly higher proportion of chains with degree of polymerization (DP) of 6-15 (45.5%) compared with amylopectin of heterowaxy starch (44.1%), which had a gelatinization peak temperature 2 degrees C higher than normal sorghum starch. Heterowaxy sorghum starch contained significantly lower rapidly digestible starch (RDS) and higher resistant starch (RS) than waxy sorghum starch.     

Processing of novel elevated amylose wheats: functional properties and starch digestibility of extruded products

Different types of novel wheat lines with different starch contents and amylose/amylopectin ratios, relating to defined alterations in the number and activity of starch synthase IIa genes, were processed by pilot-plant extrusion. Two types of products were produced: pure wholemeal products and breakfast cereals made from wholemeal/maize blends. Lower apparent shear viscosity was obtained in the extruder with lower starch content and higher amylose/amylopectin ratio flours (SSIIa-deficient line). The bulk density of the products decreased with increasing extrusion temperature and was always higher for the triple-null line. The bulk density was not completely explained by the melt shear viscosity, suggesting the importance of the fillers (fibers, brans) in the process of expansion and structure acquisition. The different mechanical properties were explained by the density and by the material constituting the cell walls. Enzyme-resistant starch (RS) content and hydrolysis index (HI) were not correlated to the extrusion temperature, but RS was higher in pure wholemeal products and in the SSIIa-deficient line. These results are discussed in terms of starch molecular architecture and product microstructure.     

挤压制备高直链玉米淀粉脂工艺优化及结构功能特性

为提高淀粉-脂质复合物制备效率,拓宽其在低血糖指数食品中的应用,以高直链玉米淀粉和胡麻油为原料,双螺杆挤压为核心制备技术,复合指数为评价指标,采用单因素和正交优化试验获取最佳制备工艺条件,并对复合物结构及特性进行测定分析。结果表明,优化工艺参数为胡麻油与淀粉质量比0.24、喂料水分40%、机筒温度125 °C、螺杆转速150 r/min,在此条件下复合物的复合指数为85.63%。通过傅里叶红外光谱及形态学观察,表明胡麻油与淀粉分子发生结合,说明双螺杆挤压制备淀粉脂是可行的;挤压淀粉-脂质复合物表现较强的热稳定性、抗消化特性和较低的黏弹性。根据以上结果可知挤压处理促进淀粉与脂质分子的有效复合,进而改变淀粉分子的结构及理化特性, 研究结果可为淀粉-脂质复合物在低血糖指数食品中的应用提供参考。     

Structural and functional properties of actinomycetal communities in chernozems and saline soils of Ukraine

In the profiles of ordinary and southern chernozems, the total numbers of amylolytic microorganisms and actinomycetes decreased with the depth by 2.4–4.2 and 3.4 times, respectively; in the profiles of solonetz and solonchak soils, by 4.2–5.3 and 4.8 times, respectively. In the genetic horizons of the ordinary and southern chernozems, the share of actinomycetes amounted to 29–30% of the total population of microorganisms; in the saline soils, it increases with the depth from 23 to 43%. In the chernozems, Streptomyces violaceomaculatus (Roseus section), St. sporoherbeus (Azureus), St. aerionidulus (Cinereus), St. enduracidicus (Cinereus), and St. grisinus (Cinereus) predominated; in the saline soils, St. violaceomaculatus and St. aerionidulus prevailed. In the ordinary chernozem, the Berger-Parker index was 1.5 times higher than in the southern chernozem. High similarity was found between the streptomycete communities in the chernozems (the Sorensen coefficient was 0.78). In the solonetzes, the species richness of the streptomycetes was higher by 1.7 times than in the solonchaks. In the chernozems, the similarity of the streptomycete communities was higher than in the solonchaks (0.78 and 0.60, respectively).     

Enzymatic synthesis and properties of highly branched rice starch amylose and amylopectin cluster

We enzymatically modified rice starch to produce highly branched amylopectin and amylose and analyzed the resulting structural changes. To prepare the highly branched amylopectin cluster (HBAPC), we first treated waxy rice starch with Thermus scotoductus alpha-glucanotransferase (TSalphaGT), followed by treatment with Bacillus stearothermophilus maltogenic amylase (BSMA). Highly branched amylose (HBA) was prepared by incubating amylose with Bacillus subtilis 168 branching enzyme (BBE) and subsequently treating it with BSMA. The molecular weight of TSalphaGT-treated waxy rice starch was reduced from 8.9 x 10(8) to 1.2 x 10(5) Da, indicating that the alpha-1,4 glucosidic linkage of the segment between amylopectin clusters was hydrolyzed. Analysis of the amylopectin cluster side chains revealed that a rearrangement in the side-chain length distribution occurred. Furthermore, HBAPC and HBA were found to contain significant numbers of branched maltooligosaccharide side chains. In short, amylopectin molecules of waxy rice starch were hydrolyzed into amylopectin clusters by TSalphaGT in the enzymatic modification process, and then further branched by transglycosylation using BSMA. HBAPC and HBA showed higher water solubility and stability against retrogradation than amylopectin clusters or branched amylose. The hydrolysis rates of HBAPC and HBA by glucoamylase and alpha-amylase greatly decreased. The k cat/ K m value of glucoamylase acting on the amylopectin cluster was 45.94 s(-1)(mg/mL)(-1) and that for glucoamylase acting on HBAPC was 11.10 s(-1)(mg/mL)(-1), indicating that HBAPC was 4-fold less susceptible to glucoamylase. The k cat/ K m value for HBA was 15.90 s(-1)(mg/mL)(-1), or about three times less than that for branched amylose. The k cat/ K m values of porcine pancreatic alpha-amylase for HBAPC and HBA were 496 and 588 s(-1)(mg/mL)(-1), respectively, indicating that HBA and HBAPC are less susceptible to hydrolysis by glucoamylase and alpha-amylase. HBAPC and HBA show potential as novel glucan polymers with low digestibility and high water solubility.     

Kinetics of formation and functional properties of conjugates prepared by dry-state incubation of beta-lactoglobulin/acacia gum electrostatic complexes

The formation of conjugates between beta-lactoglobulin and acacia gum based on electrostatic complexes formed at pH 4.2 was investigated upon dry-state incubation for up to 14 days at 60 degrees C and 79% relative humidity (RH). By means of SEC-HPLC and RP-HPLC, it was shown that the beta-lactoglobulin incubated alone was able to form polymers with molecular masses higher than 200 kDa until 50% of the initial monomeric protein disappeared after 14 days. In the presence of acacia gum at initial protein to polysaccharide weight mixing ratios of 2:1 and 1:2, only 35% of the initial beta-lactoglobulin monomers disappeared after 14 days. Using RP-HPLC, an apparent reaction order of 2 was found for the disappearance of monomeric beta-lactoglobulin both in the presence or absence of acacia gum. However, the reaction rate was faster in the absence of acacia gum. SDS-PAGE electrophoresis with silver staining confirmed the formation of beta-lactoglobulin/acacia gum conjugates. The solubility curves of the incubated beta-lactoglobulin showed a minimum around pH 4-5. By contrast, the minimum of solubility of the beta-lactoglobulin/acacia gum incubated mixtures shifted to lower pH values compared to initial mixtures. The conjugates exhibited higher foam capacity than the incubated protein as well as lower equilibrium air/water surface tension. Conjugation at ratio 1:2 led to increased interfacial viscosity (300 mN s m(-1) at 0.01 Hz) compared to beta-lactoglobulin alone (100 mN s m(-1) at 0.01 Hz), but similar interfacial elasticity (30-40 mN m(-1)). The foam capacity of the conjugates was significantly higher than that of the incubated beta-lactoglobulin as well as foam expansion and drainage time, especially at pH 5.3, i.e., higher than the pH of formation of the conjugates.     

Stability and kinetic properties of humus-urease complexes

We have determined the kinetics and stabilities of various humus-urease preparations, extracted and purified from soil (Ceccanti, Nannipieri, Cervelli and Sequi, 1977). K_m, values of five different fractions in phosphate buffer ranged from 8 to 40 mM and were similar to those of urease extracted from various other sources. However, the optimal pH for urease activity of the soil fractions ranged from 7.5 to 8.8, in contrast to a pH optimum of about 7.0 for urease from sources other than soil. The shift in the optimal pH towards the alkaline region may be due to the influence of the negative charge of the humus matrix localized around the enzyme.Urease organo-complexes of mol. wt. < 10⁵ were slightly more resistant to thermal denaturation and to proteolysis than free urease. However, complexes of mol. wt. > 10⁵ were even more resistant, due probably to the occurrence of molecular arrangements similar to that proposed by Burns, El-Sayed and McLaren (1972a) and Burns, Pukite and McLaren (1972b). Thus although each of the five urease-active organic matter fractions exhibited different characteristics, they could be grouped into two distinct classes, according to mol. wt. and resistance to thermal denaturation and proteolysis.     

含醇溶蛋白小麦回生抗性直支链淀粉性质分析

为研究含醇溶蛋白小麦回生抗性直支链淀粉性质,该文采用醇溶法从小麦粉中提取醇溶蛋白,采用回生-酶解法分离得到小麦直、支链淀粉。通过可见光谱、红外光谱、X-射线衍射、差热扫描等方法分析研究醇溶蛋白对小麦直、支链淀粉回生的影响。结果表明,在凝胶化及回生过程中醇溶蛋白与淀粉相互作用,导致淀粉回生率增加。红外光谱研究表明,直链淀粉与醇溶蛋白在高压糊化后干燥或回生的条件下,醇溶蛋白的酰胺Ⅱ键伸缩振动从1 546 cm~(-1)降低至1 539 cm~(-1),即直链淀粉与醇溶蛋白通过氢键结合。X-射线衍射图谱显示在2θ衍射角为17°,19°,22°等的衍射峰没有发生明显变化,表明添加醇溶蛋白后,直、支链淀粉的晶型未发生明显改变。DSC结果显示直链淀粉与醇溶蛋白之间的氢键是在共同回生过程中产生的,样品中多晶结构和双螺旋结构共存。研究结果表明,淀粉中空间位阻小的6位碳原子上的羟基与醇溶蛋白中的脯氨酸和谷氨酰胺通过氢键结合,这种类型的氢键阻碍了α淀粉酶对淀粉的解离,即醇溶蛋白通过与淀粉形成新型氢键而促进了淀粉的回生。该研究提供了一种提高小麦淀粉的回生率的新技术,为进一步深入研究醇溶蛋白促进淀粉回生的机理提供理论支撑。     

Influence of amylopectin structure and amylose content on the gelling properties of five cultivars of cassava starches

Five cassava genotypes were investigated to identify the fine amylopectin structures and granule chemical compositions, which differentiated the starches into high (T(o) = 63.7 degrees C on average) and low (57.3 degrees C on average) gelatinization temperatures. The amylose contents (15.9-22.4%) and granular dimensions (12.9-17.2 microm) significantly differed among the starches. Diverse amylopectin structural elements resulted in significant swelling power, viscoelastic properties, and gel firmness. Debranched starches revealed a trimodal amylopectin distribution of three fractions: FIII (DP 12), FII (DP 24.31), and FI (DP 63) and FIII (DP 12), FII (DP 24.69), and FI (DP 67) for the low and high gelatinization starch groups, respectively. The higher proportion of FI long chain entanglement with amylose chain lengths to form longer helical structures was confirmed in the high gelatinization starch group, which developed "true" gels with better shear resistance, frequency independence, and higher gel firmness. Significant amounts of resistant starch fractions revealed the potential for application of these genotype starches in diverse foods.     

低支链淀粉品种米的储藏性和食味品质评价

摘要：储藏米的生理品质与食味品质变化程度对于消费者的认可度至关重要。本研究讨论了不同储藏温度对低直链淀粉品种米（Yumepirika）的储藏性和食味品质影响。稻谷具有比糙米更加优越的储藏性。在低温条件下储藏,稻谷脂肪酸含量增加2.9 mg,糙米脂肪酸含量增加15.8 mg,这表明低支链淀粉糙米应该在更低的温度下保存。食味试验表明室温条件下储藏的糙米具有最低黏度值和综合评价值。经过2 a的储藏期,超低温储藏和低温储藏能够保持米的活力和食味品质与基准米相似的水平。     

Structural parameters and functional patterns of simulated earthworm burrow systems

Summary Earthworm burrow systems have been simulated by modelling, from field observations, five main characteristics of burrow units: density (number of burrows per unit volume), mean length, angular orientation, middle coordinates and diameter. The functional properties of the burrow systems have been analysed using structural parameters, i. e. number of full perforations, mean available burrow surface and minimal burrow spacing, and by estimating the shortest pathway through the burrow system. The simulations are used to study the effects of each of the main characteristics on structural parameters and the shortest pathway. This work reveals that the specific role of density is to lead to a threshold by determining an optimal horizontal distance, and that the mean length governs the vertical critical dimension of the system. These simulations may be applied to explain the nature of field burrow systems.     

Thermal properties of partially hydrolyzed starch-glycerophosphatidylcholine complexes with various acyl chains

Complexes of starch and monoacyl-sn-glycerophosphatidylcholine (GPC) containing various acyl (myristoyl, palmitoyl, and stearoyl) chains were subjected to hydrolysis with glucoamylase (EC 3.2.1.3). The enzyme hydrolyzed approximately 40% of starch control and 20-28% of starch-GPC complexes. Among the GPCs examined, 1- and 2-monomyristoyl-sn-GPC showed the highest resistance to enzyme hydrolysis, and the hydrolysis rate of starch-GPCs was greater with longer chains. Enzymatic hydrolysis strongly affected the thermal properties of the starch. After enzymatic hydrolysis of starch-GPC complexes for 24 h, their thermograms had broader peaks with lower enthalpies than the corresponding starch without enzyme; however, the starch-GPC complexes showed little change. The surface of starch-GPC granules was less eroded. These results showed that the increasing amount of starch-GPC complexes could be more resistant to hydrolysis.     

Physicochemical and functional properties of buckwheat protein product

This study was conducted to compare the physicochemical and functional properties of buckwheat protein product (BWP), soy protein isolate (SPI), and casein. BWP was prepared from buckwheat flour by the method including alkaline extraction and isoelectric precipitation. The amino acid composition of BWP was very similar to that of buckwheat flour. The protein solubility (PS) of BWP was much greater than that of SPI at all pH levels (pH 2-10) but lower than that of casein at pH 7-10. The isoelectric point of BWP was around pH 4. The higher aromatic hydrophobicities (ARH) of BWP, SPI, and casein were obtained at lower pH levels (pH 2-3). The emulsifying stability (ES) of BWP was lower than those of SPI and casein at high pH levels (pH 7-10). At all pH levels, BWP formed a thin emulsion. Regression analysis showed that the ARH of BWP was significantly associated with the ES. Although the water holding capacity of BWP was quite lower than that of SPI, its fat absorption capacity was slightly higher than those of SPI and casein. These results indicated that the physicochemical properties of BWP were different from those of SPI or casein. Thus, BWP is a potential source of functional protein for possible food application.     

Characterization and functional properties of lactosyl caseinomacropeptide conjugates

Ovine caseinomacropeptide (CMP) was modified with lactose through Maillard reaction under 44% relative humidity and 40 degrees C for various periods (0-11 days). Different lactosylated CMP forms were separated by capillary electrophoresis and reversed phase high-performance liquid chromatography (RP-HPLC) and identified by RP-HPLC coupled with electrospray ionization mass spectrometry (ESI-MS). Around 55-60% of CMP was lactosylated under the conditions assayed, with the monolactosylated form being the most abundant one, followed by the di-, tri-, and tetralactosylated species. During the first days of incubation amino acid analyses showed a decrease in lysine and NH(2)-terminal methionine, which coincided with an increase in the furosine content. However, from the ninth day of incubation, further degradation of Amadori compounds prevailed over their formation. Solubility, heat stability, and emulsifying capacity of the native and modified CMP were investigated. Lactosylation improved the emulsifying activity, but it did not modify the great solubility and heat stability of native CMP.     

热处理对木薯全粉品质的影响

为充分发挥木薯资源的应用优势,增加木薯的消费途径和产品价值,该文将研究制备具有良好口感、方便食用的木薯全粉。通过筛选热处理的温度、时间,以及预煮和蒸煮工序的组合方式,同时利用响应曲面法研究确定木薯全粉的制备工艺参数,提高热处理过程中木薯细胞的分离效率。结果表明影响木薯全粉细胞完整性的热处理因素依次为蒸煮温度、蒸煮时间、预煮温度、预煮时间,其最佳值分别为95℃、16 min、10 min、66℃。在此条件下生产的木薯全粉游离淀粉质量分数较低,为8.4%,制备的木薯全粉具有理想的细胞完整度。同时,研究分析了木薯加工过程中氢氰酸的变化,以及木薯全粉的黏度性质、热力学特性、吸水、吸油和冻融稳定性,从而为木薯全粉在食品工业上的应用提供理论参考。     

Improving bioavailability and stability of genistein by complexation with high-amylose corn starch

Genistein, like other phytochemicals, has beneficial health effects, but its bioavailability is limited. This research studied the effect of complexation of genistein with starch on genistein bioavailability. Genistein release from these complexes was tested in vitro under simulated intestinal conditions and in vivo in rats fed high-amylose corn starch (HACS)-genistein complexes (experimental group) as compared to those fed a physical mixture of HACS and genistein (controls). In vitro results showed that genistein release is sustained and fits the normal transit time of food in the intestine. The genistein concentration in the plasma was twice as high in the experimental group versus controls; the genistein concentration in the urine was also higher in the experimental group but lower in the feces. These results indicate that starch-genistein complexes increase genistein bioavailability and suggest that starch can affect the bioavailability of additional food components.     

Preparation and functional properties of rice bran protein isolate

Rice bran protein isolate (RBPI) containing approximately 92.0% protein was prepared from unstabilized and defatted rice bran using phytase and xylanase. The yield of RBPI increased from 34% to 74.6% through the use of the enzymatic treatment. Nitrogen solubilities of RBPI were 53, 8, 62, 78, 82, and 80% at pHs 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, respectively. Differential scanning calorimetry showed that RBPI had denaturation temperature of 83.4 degrees C with low endotherm (0.96 J/g of protein). RBPI had similar foaming properties in comparison to egg white. But emulsifying properties of RBPI were significantly lower than those of bovine serum albumin. The result of amino acid analysis showed that RBPI had a similar profile of essential amino acid requirements for 2-5-year-old children in comparison to that of casein and soy protein isolate.     

Distribution of amylose,nitrogen, and minerals in rice kernels with various characters

The distribution of chemical constituents is known not to be even within a rice kernel. To improve the eating quality of rice or to give it some special traits by adjusting the milling intensity, we investigated the distribution of amylose, nitrogen (N), and specific minerals (P, K, Mg, Ca, and Mn) in rice kernels of 11 cultivars with various characteristics cultivated under similar conditions. The distributions of these constituents were determined using flour samples prepared consecutively by abrasive milling from the outer to the inner portions of hulled rice. In all the cultivars tested, N and the minerals were found to be more abundant in the outer than in the inner portion, but amylose was rich in the inner portion. P, Mg, K, and Mn were extremely rich in the outer portion, while N and Ca were only relatively rich there. Koshihikari, which is the most popular cultivar in Japan because of its excellent eating quality, showed the highest Mg/K ratio in the outermost portion of polished rice. The color of flour samples became pure white going from outside portions toward the center of the kernel, even if the sample was from red rice or purple-black rice because only the surface of hulled rice contains pigments. These findings suggest that the outer portion contains various compounds other than starch and the inner portion contains relatively pure starch. Rice palatability and other characteristics can be improved through controlling the degree of milling using the biased distribution of chemical constituents within a rice kernel.     

人造沸石对甘薯不同链长直支链淀粉的分离效果

柱层析法是根据混合物中各组分的理化性质差异,利用混合物中各组分在固定相和流动相中分配系数不同,经过多次分配将组分分离纯化。该文采用回生法分离甘薯直、支链淀粉后再进行二次回生,以窄化其分子链长,并采用柱层析法分离出不同分子量分布范围的淀粉组分,直、支链淀粉组分总制备率均大于2.4%。可见光谱及分子量分布研究表明,粒径为1～3 mm的人造沸石适合分离支链淀粉,粒径为4～6 mm的人造沸石适合分离直链淀粉。经大沸石分离,聚合度大的直链淀粉分子依赖沸石表面吸附,洗脱速度快,先被洗脱下来,聚合度较小的直链淀粉分子进入沸石孔隙内部,吸附力大,后被洗脱下来;经小沸石分离,甘薯支链淀粉组分F1b中分子量小、均一度高的组分先被洗脱下来,F2b中分子量大、均一度低的组分先被洗脱下来,说明甘薯直、支链淀粉的分支度对淀粉组分的分离也有一定影响。X射线衍射表明,甘薯直链淀粉组分在18.9°、23.4°、27.2°、29.3°、32.3°、33.7°附近出现强衍射峰,甘薯支链淀粉组分在21.6°、22.9°、23.9°、26.5°、27.1°、29.3°、34.1°、35.8°、39.5°附近也出现明显的衍射峰,此时甘薯直、支链淀粉的分子量分布指数(PDI,polydispersity index)均接近1.0。人造沸石柱层析可制备出分子量分布范围极窄的甘薯直、支链淀粉,该类淀粉表现出类似金属盐的X射线衍射峰,可作为深入研究淀粉大分子空间结构变化的材料。显微图片显示直链淀粉是由多个线型分子聚集在一起,呈典型的"柳条"状,而支链淀粉呈典型的"树枝"状。该研究提供了一种大量制备分子量分布范围极窄的直、支链淀粉的简单、高效方法,为深入探索淀粉大分子聚集过程中的形态变化创造了有利条件。     

Some nutritional and functional properties of defatted wheat germ protein

Defatted wheat germ protein (DWGP) was isolated by alkaline extraction at pH 9.5 and subsequent isoelectric precipitation at pH 4.0, and its nutritional and functional properties were studied. The results showed that the amino acid content of defatted wheat germ was as high as 26.793 g/100 g, and the contents of eight essential amino acids were all relatively high. The isoelectric point of DWGP was 4.0. When pH >6.0, the DWGP had high solubility with a nitrogen solubility index of 70%. The emulsifying activity and emulsifying stability of DWGP were similar to those of bovine serum albumin and a little higher than those of casein. DWGP had good foaming capacity, but its foaming stability (FS) was not very good. However, the FS of DWGP can be improved through physical, chemical, or enzymatic methods. Moreover, DWGP had excellent water retention (WR); especially at pH 8.0 and a temperature of 70 degrees C, the WR of DWGP was the highest at 229.4%. DWGP offers is a potential source of functional protein isolate for possible food applications.