THE SUSCEPTIBILITY OF CEREAL STARCHES TO AMYLOLYSIS DURING GERMINATION AND MATURATION

During the maturation of normal and high amylose barley the susceptibility of the raw starches to attack by α-amylase remains constant until the moisture content of the grain falls below about 60%. Thereafter the starch develops a resistance to amylolysis which is directly proportional to the loss of grain moisture. The mean diameter of the starch granules of barleys and malt remains unchanged during digestion but the blue values of the residual starches decrease throughout. During the malting of wheat and barley the bulk of the starch solubilized is the amylopectin fraction although amylose is increasingly utilized when germination is prolonged. When high amylose barley is malted the blue value of the starch declines steadily throughout the growth period, suggesting that the spatial arrangements of the molecules within the granule influence the solubilization of the starch. The susceptibilities of wheats and normal and high amylose barleys to amylolysis were significantly lower than those of the corresponding malted products.     

Effects of Wheat Starch Contents on Malt Qualities

The relationships between wheat starch content and wheat malt qualities were studied in the present work. Six wheat varieties that were typical in starch, protein content and amylopectin/amylose ratio were selected from 12 wheat varieties and germinated under the same conditions. The decreased degree of total starch content after malting had a positive correlation (r = 0.8020, P < 0.1) with the amylopectin/amylose ratio of the raw wheat. Extracts of wheat malts were influenced by starch content and the amylopectin/amylose ratio of the raw wheat. When the amylopectin/amylose ratio was in the range 3.65:1?3.93:1, extracts of the malts had significant positive correlation (r = 0.967, P = 0.002) with the starch content of the raw wheat. In this investigation a suitable amylopectin/amylose ratio (3.65:1 to 3.93:1), a high starch content and a low protein content were the characteristics of a wheat variety suitable for malting.     

MORPHOLOGY OF STARCH GRANULES IN CEREAL GRAINS AND MALTS

During malting, amylases have limited action on large starch granules of barley endosperm but rapidly degrade the small granules. In contrast, the small starch granules of wheat endosperm are resistant to enzymic attack. High levels of exogenous gibberellic acid increase the production of α-amylase and encourage the appearance of radial channels in the partially-degraded large starch granules. These endo-corroded granules are mainly found in the proximal (embryo) half of the endosperm where levels of α-amylase are much higher than at the distal end. Degradation of malt starch can therefore result from enzymic attack both outside and inside the granules. Malting of barley reduces the population of small starch granules which are slower to gelatinize than large granules at the infusion mashing temperatures of 65° C. During germination of barley multiple starch granules are rapidly synthesized in single amyloplasts in the scutellum. The endosperm of high amylose barley is devoid of small starch granules and the average size of the large granules is reduced. Steeliness in sorghum is related to the close packing of the starch-protein matrix rather than to unequal distribution of protein. The significance of these results is discussed, particularly in relation to the morphology of starch granules, the nature of their outer covering, the distribution of amylopectin and amylose within the granule, and the site of enzymic attack.     

Effects of Malting on Phase Transition Behaviour of Starch in Barley Cultivars with Varying Amylose Content

The effect of malting on the phase transition behaviour of starch in barley cultivars with varying amylose content was studied using differential scanning calorimetry (DSC). A slight elevation in the melting transition temperature of amylopectin of malt starch and a pronounced decrease in gelatinisation enthalpy for both malt flour and starch were observed for all samples. Evidence was provided from the calorimetric data and the ¹³C CP/MAS NMR spectra that starch-lipid interactions in the form of complexes are enhanced as a result of malting. There was also a large reduction in the melting transition temperature of the amylose-lipid complexes of malt flours, presumably due to partial degradation of amylose in malt, whereas the transition enthalpies of the complexes increased for both malt flours and starches. The DSC transition characteristics of the three good malting barley cultivars grown in different locations and of their respective malts showed that environmental conditions during starch synthesis have a great influence on starch granule organization, and thereby affect the thermal stability of amylopectin crystallites.     

淀粉直支比定量技术及其在食品领域中的应用

天然淀粉中含有直链和支链两种形式的α-D-葡聚糖,二者的相对含量不仅与淀粉的糊化、老化、凝胶等理化性质和食品功能有关,还决定着淀粉的经济价值。淀粉直支比定量技术在含淀粉的粮谷类作物育种、淀粉的高值化利用以及食品品质保障和创新等领域具有广泛的应用。本文综述了当前食品科学研究和加工制造领域对淀粉直支比定量技术的需求,介绍和对比了各种经典和新型淀粉直支比定量技术的原理、优缺点和适用性,对淀粉直支比定量技术在未来食品领域的潜在应用提出展望。     

Interrelations of Starch and Fungal α-Amylase in Breadmaking

The interrelation of starch in flour and fungal α-amylase in breadmaking was investigated using a low protein and a high protein flour. Loaf volume and bread quality were improved by the fungal α-amylase supplements. Gel chromatography for elution of DMSO soluble starch fraction and the results of amylose and amylopectin contents revealed somewhat similar situation in the fresh bread which differed from the elution profiles of soluble fractions of 3 and 5 day old loaves prepared with and without α-amylase supplements. Decreased recovery of starch in the DMSO soluble fractions indicated some degree of retrogradation. The higher amylose contents of the 5 day old bread crumb soluble starch fraction indicated a change in amylose and amylopectin ratio.     

Stufenweise Elutionsanalyse der Fraktionen von thermisch dispergierter Amylose-, Kartoffel- und Wachsmaisstärke

Stepwise Elution Analysis of Fractions of Thermically Dispersed High Amylose, Potato and Waxy Corn Starch. Changes in the starch constituents - the amylose and the amylopectin — from dispersions of high amylose, potato- and waxy corn starch were studied by stepwise elution analysis and determination of molecular weight. The dispersions were prepared by dispersing the pastes 1 and 3 h at 120 °C and the amyloses and amylopectins separated by means of n-butanol and methanol, resp. With the exeption of a partial separation in waxy corn starch no separation of pastes into amylose and amylopectin could be observed, probably due to the mild pasting conditions in the Brabender Viscograph. By stepwise elution analysis it could be stated that after prolonged thermic dispersing of the pastes of high amylose starch the amylose and amylopectin do no longer change, which is in good agreement with the values of molecular weight. By analogous treatment of the pastes of potato starch, however, a decomposition of amylose and amylopectin could be stated. In the dispersions of waxy corn starch the amylose molecules decompose to a degree whereafter thermic dispersing of 3 h practically no complex with n-butanol could be observed. Relatively great losses were stated at the isolation of the precipitated constituents. It was stated that the isolated amyloses of potato starch are suitable substrates for activity measurements of α-amylase in human serum and urine as well as in other biologic materials.     

The Possible Relationship of Starch and Phytoglycogen in Sweet Corn. II. The Role of Branching Enzyme I

Developing maize kernels contain three starch branching enzymes. Homogeneous branching enzyme I has now been shown to be capable of branching amylose as well as amylopectin but not glycogens. The formation of glycogen-like molecules by the further branching of amylopectin suggests that branching enzyme I plays a role in phytoglycogen formation. Its presence in nonmutant kernels which do not accumulate phytoglycogen, however, indicates that amylopectin per se is not accessible to branching enzyme I for phytoglycogen formation. Treatment of sugary (su) starch granules with enzyme I resulted in soluble phytoglycogen-like glucan. No glucan was released by treatment of nonmutant starch granules. In addition, nonsolublized amylopectin and amylose fractions of the su starch were branched during the incubations. These observations are consistent with plastid changes which show a conversion of starch granules to phytoglycogen in sugary endosperm cells.     

COMPUTER SIMULATION OF THE β-AMYLOLYSIS OF STARCH COMPONENTS*

In an attempt to model quantitatively the product distributions arising from the degradation of starch by the conjoint action of α- and β-amylase, such as occurs in the commercial mashing of malted cereal, a computer program has been written to simulate the amylolysis of amylose or amylopectin or a mixture of these components. Using Monte-Carlo techniques the program simulates the action of either α-amylase or β-amylase or both enzymes acting conjointly. The program was tested for pure β-amylolysis. Parameters were estimated by a non-linear regression technique and predicted product concentrations were compared with relevant experimental data for amylose and amylopectin substrates and for mixtures of these starch components. The simulation model accurately predicted the results of amylolysis except at high product concentrations where the deviations between predicted and experimental values ranged from 1% to 4%.     

Localisation of Amylose and Amylopectin in Starch Granules Using Enzyme-Gold Labelling

The independent localisation of amylose and amylopectin in a range of dry and hydrated native starch granules with varying amylose content (0—70 %) has been indirectly visualised using enzyme-gold cytochemical markers. Increasing amylose content was clearly demonstrated to result in distinct changes in granule architecture. In the absence of amylose (waxy maize starch) a framework of closely packed concentric layers of amylopectin exists in the granules. Low amylose content (potato starch) results in alternating layers of densely packed amylopectin and amylose molecules. High amylose content (amylomaize starch) granules were shown to possess an amylopectin centre surrounded by an amylose periphery encapsulated by an amylopectin surface. Elongated granules without the amylopectin centre were also observed in high amylose starches suggesting a relationship between amylopectin, amylose and granule shape. A model of starch granule architecture is proposed where increased compartmentalisation of amylose and amylopectin is observed in granules containing increasing levels of amylose.     

燕麦发芽过程中淀粉及其相关酶活性的动态变化

研究了裸燕麦发芽过程中淀粉及其相关酶活性的动态变化。结果表明,发芽过程中,燕麦还原糖和可溶性糖含量及α-淀粉酶、β-淀粉酶和总淀粉酶活力明显地先增加后降低;直链淀粉、支链淀粉和总淀粉的含量均随着发芽的进行呈下降趋势,发芽72 h分别降低了25.86%、11.08%和17.31%。相关性分析表明,燕麦发芽期间还原糖、可溶性糖含量分别与α-淀粉酶、β-淀粉酶及总淀粉酶活力呈显著正相关,而直链淀粉、支链淀粉及总淀粉含量均与淀粉酶活力呈显著负相关。     

The Mechanism for the Synthesis of Starch and Its Relationship to the Newly Proposed Structural Model for DNA. Part I.

The physical and chemical properties of starch and glycogen can be explained on the basis that glycogen is converted into amylose and amylopectin by a debranching enzyme (isoamylase) which removes the external α-1,6-linked branches of the glycogen. This precursor glycogen exists in all corn endosperm examined: ae high amylose, normal dent, waxy, and sweet corn. Analyses of amylopectins show that they behave as statistical condensation polymers (the model-V of Erlander and French) which have been debranched. Further support for the mechanism is given by the fact that the chain length and degree of branching of the interior part of all amylopectins is essentially the same as that of its precursor glycogen. Any mechanism for starch synthesis must, however, consider the complexing of enzymes because both amylopectin and glycogen behave as if they were strongly complexed to proteins. Thus proteases can destroy these complexes and viscosity differences of various barley geneotype starches can be correlated to protein content. Acid hydrolysis studies on corn amylopectins suggest that the type of protein complexed with amylopectin changes with both endosperm maturity and corn variety. Amylose synthesis from debranched chains can be correlated with the ability of chromosomes to regulate when and in what sequence an enzyme is synthesized. The proposed model for desoxyribonucleic acid (DNA) – which is a hollow cylinder with the bases on the outside – can explain how these regulators (genetic repressors and inducers) can function. „Proofs”︁ for the Watson-Crick model such as X-ray analyses, hypochromism, and molecular dimensions are shown to be erroneous.     

Amylopectin structure of heat–moisture treated starches

The effects of heat–moisture treatment (HMT; moisture content of 25%, at 100°C for 24 h) on starch chain distribution and unit chain distribution of amylopectin in normal rice, waxy rice, normal corn, waxy corn, normal potato, and waxy potato starches were investigated. After HMT, starch chain distribution (amylose and amylopectin responses) of waxy corn and potato starches were identical to those of untreated starches, whereas the chromatographic response of waxy rice starch showed a slight decrease, but with a slight increase in peak tailing. This result indicated that HMT had no (or very limited) effect on the degradation of amylopectins. Analysis of unit chain distribution of amylopectins revealed that waxy characteristics affected the molecular structure of amylopectin in untreated starches, i.e., the CL of normal‐type starches was greater than that of waxy‐type starches. After HMT, the CL and unit chain distribution of all starches were no different than those of untreated starches. The results implied that changes in the physico‐chemical properties of HMT starches would be due to other phenomena rather than the degradation of amylopectin molecular structure. However, the thermal degradation of amylopectin molecules of waxy starches could occur by HMT at higher treatment temperatures (120 and 140°C).     

The use of the rapid visco analyser (RVA) to sequentially study starch properties in commercial malting barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis>)

The aim of this study was to evaluate the use of the rapid visco analyser (RVA) instrument as a tool to sequentially analyse barley (Hordeum vulgare) malting varieties in order to visualise and interpret the effect of amylose and amylose complexes on its pasting properties. The RVA sequential profiles derived from the barley samples analysed showed a large peak (peak viscosity, PV) at the start of each cycle alternating with viscosity troughs during the hot paste viscosity cycle. The sequential cycles caused a slight decrease in both PV and (final) FV values in all barley varieties analysed. The addition of silver nitrate to the barley flour samples tends to slightly increase the PV value independently of the time of the analysis. The development of this methodology will provide with better tools to study starch pasting properties as well as to study the interactions between amylose and amylopectin with other compounds in various malting varieties.     

Properties and applications of starch modifying enzymes for use in the baking industry

Enzyme technology has many potential applications in the baking industry because carbohydrate-active enzymes specifically react with carbohydrate components, such as starch, in complex food systems. Amylolytic enzymes are added to starch-based foods, such as baking products, to retain moisture more efficiently and to increase softness, freshness, and shelf life. The major reactions used to modify the structure of food starch include: (1) hydrolysis of α-1, 4 or α-1, 6 glycosidic linkages, (2) disproportionation by the transfer of glucan moieties, and (3) branching by formation of α-1, 6 glycosidic linkage. The catalytic reaction of a single enzyme or a mixture of more than two enzymes has been applied, generating novel starches, with chemical changes in the starch structure, in which the changes of molecular mass, branch chain length distribution, and the ratio of amylose to amylopectin may occur. These developments of enzyme technology highlight the potential to create various structured-starches for the food and baking industry.     

Starch Biosynthesis. I. The Size Distributions of Amylose and Amylopectin and Their Relationships to the Biosynthesis of Starch

Equations for the size distributions of both linear and branched polymers were applied to debranched amylopectin, linear amylose, and branched amylose polymers. The experimental size distribution of linear amylose corresponds to the broad size distribution of an A–B condensation polymer, whereas that of debranched amylopectin linear chains corresponds to the much narrower Poisson size distribution. These dramatic differences illustrate that different types of enzymes synthesize the linear chains of amylose as compared to those of amylopectin. These results support the previously proposed mechanism. The polymodal behavior of debranched amylopectin is due to the existance of individual Poisson-type polymers created by tier structures in a statistically formed precursor glycogen. Equations were developed which enable the calculation of the percentages of these individual Poisson polymers. When applied to the differences between shx and Bomi barley amylopectins, it is concluded that both studies agree that two different short, inner tier, A-chains exist, where the longer chain is located in the more external third tier in the amylopectins. In amylose, three different polymers exist: A linear amylose A–B type condensation polymer, a branched amylose which behaves as a statistical A–R–B₂ type polymer, and an intermediate, non-statistically branched amylose polymer.     

Physicochemical Property of Huaishan (Rhizoma Dioscorea) and Matai (Eleocharis dulcis) Starches

The physicochemical properties of starch, the main component in tuberous root of Huaishan (Rhizoma Dioscorea) and corm of Matai (Eleocharis dulcis) was investigated and compared with those of a Japanese yam, “Yamanoimo” starch, and potato starch. Mean particle sizes of Huaishan and Matai starches were 24 ± 5 μm and 12 ± 5 μm, respectively. X-Ray diffraction pattern suggests that Huaishan starch was B-type or C-type just close to B-type and Matai starch was A-type or C-type just close to A-type. Apparently, the intermediate component (IntCom) of Huaishan starch, which was obtained by fractionation of the starch into amylose and amylopectin, may still contain amylose and amylopectin. IntCom of Matai starch has an intermediate nature between amylose and amylopectin. It is concluded that the amylopectin molecules of Huaishan starch contain a larger amount of longer branch-ed chains and those of Matai starch contain a larger amount of shorter branched chains. Amylograms of Matai and Huaishan starches suggest that the gelatinized starches are difficult to retrograde. Digestibility of Huaishan starch by an α-amylase was the highest among the tested starches.     

芭蕉芋直链和支链淀粉纯品的提取及其光谱分析

分离提纯芭蕉芋淀粉中的直、支链淀粉,表征其纯度,建立快速测定芭蕉芋淀粉中直链淀粉含量的双波长法。正丁醇结晶法分离纯化直、支链淀粉;光吸收特性分析法表征直、支链淀粉纯度;根据双波长法原理,在测定波长617nm,参比波长504nm处测定芭蕉芋淀粉中直链淀粉含量。分离提纯得到的直、支链淀粉最大吸收波长分别为630～645nm和548～554nm,蓝值分别为1.167±0.209和0.122±0.001,均处于相应分布范围,表明提纯后直、支链淀粉的纯度较高;直链淀粉在0～80mg/L浓度范围内与吸光度呈线性关系,r=0.9998。正丁醇结晶法能有效地分离纯化芭蕉芋直、支链淀粉;光吸收特性分析法可有效地表征直、支链淀粉纯度;双波长法操作简便、准确,无需分离即可快速测定芭蕉芋淀粉中直链淀粉含量。     

Studies on the Starches of Barley Genotypes. A Comparison of the Starches from Normal and High-Amylose Barley

Starches have been isolated from two barley genotypes, the normal American variety “Glacier (C. I. 9676)” and a mutant with a low mean-starch-granule-size designated “Glacier (Ac 38)”. Iodine titration has confirmed that the mutant has a starch of high amylose-content. Both starches have been fractionated to yield their component amylose and amylopectin, and the properties of these fractions examined. The two amylose fractions show very similar properties, but the amylopectin fraction isolated from the starch of “Glacier (Ac 38)” is apparently anomalous with respect to chain-length, β-amylolysis limit, and iodine uptake. This behaviour — which is comparable with that exhibited by the amylopectin fractions of the other high amylose-content starches from pea and maize — has similarly been shown to be due to heterogeneity in the polysaccharide rather than to an increase in the average-length of the external chains.     

Über die Nachweisbarkeitsgrenze für Amylose und Amylopektin in Gemischen. Chromatographische Untersuchungen

On the Limit of Detectability of Amylose and Amylopectin in Mixtures. Chromatographic Tests Detection of smaller amounts of amylopectin in amylose by column chromatography as well as by paper chromatographic capillary analysis is rather difficult. In the latter test procedure a faint detectability of amylopectin is reached only at a 6:4 amyloselamylopectin ratio. By column chromatography amylopectin can already be traced at a 8:2 amyloselamylopectin ratio. The intenser blue colour of the amylose-iodine complex covers the amylopectin in particular zones on the Al₂O₃-column and on the paper chromatographs, whereas amylose in smaller amounts can be traced without difficulty in amylopectin preparations. The question, wether the v₃-zone which appears at a higher intensity with amylopectin is identical with the one that appears during degradation of starch and amylose by thermal process, acid hydrolysis, fermentation or oxydation, has yet to be solved.