Proportion Of Amylose Research Articles

Effect of fermentation with Rhizopus oligosporus on some physico-chemical properties of starch extracts from soybean flour

Studies were carried out on the changes that occurred on some selected physico-chemical properties of starch extracts from soybean flour when fermented with Rhizopus oligosporus. This was done in order to increase the utilization potentials of the flour. Starch extracts were obtained from flour obtained from fermented soybean using R. oligosporus with a fermentation period of between 0 and 72 h. Some physico-chemical properties, as well as the amylose, amylopectin, and the pasting characteristics of the starch extracts were determined using standard methods. Increasing trends with increasing fermentation period were observed with respect to most of the physico-chemical characteristics investigated, except for the reconstitution index that showed decreasing trends. While the peak, breakdown and final viscosities also decreased, the swelling power and solubility slightly increased with increase in fermentation period. The proportion of amylopectin which was constantly high showed further slight increases with fermentation, apparently because of the decreasing proportion of amylose probably due to utilization by the mould R. oligosporus used for fermentation.

Structure and Viscoelastic Properties of Starches Separated from Different Legumes

AbstractA comparison between the morphological, structural, thermal and viscoelastic properties of starches separated from pigeon pea, chickpea, field pea, kidney bean and blackgram was made. The shape of the starch granules in the different legumes varied from oval to elliptical or spherical. X‐ray diffraction of the legume starches indicated a typical C‐pattern (mixture of A‐ and B‐type). Granules of blackgram and pigeon pea starch had a higher degree of crystallinity than those of field pea and kidney bean starches. Apparent amylose content of field pea, kidney bean, chickpea, blackgram and pigeon pea starch was 37.9%, 36.0%, 34.4‐35.5%, 32.9‐35.6% and 31.8%, respectively. Distribution of isoamylase‐branched materials among the starches revealed that the proportions of long and short side chains of amylopectin ranged between 13.6‐18.5% and 41.7‐46.5%, respectively. Field pea and kidney bean starch had the highest apparent amylose content and the lowest amount of long side chains of amylopectin, respectively. Blackgram and pigeon pea starch possessed higher proportions of both long and short side chains of amylopectin than field pea and chickpea starches. The onset, peak and conclusion temperatures of gelatinization (To Tp and Tc, respectively) were determined by differential scanning calorimetry. To and Tc ranged from 59.3 to 77.3°C, 66.8 to 79.6°C, 55.4 to 67.6°C and 68.3 to 69.3°C, respectively, for chickpea, blackgram, field pea and kidney bean starch. The enthalpy of gelatinization (ΔHgel) of field pea, kidney bean, chickpea, blackgram and pigeon pea starches was 3.6, 3.0, 2.6‐4.2, 1.6‐1.7 and 2.6 J/g, respectively. Pastes of blackgram and pigeon pea starches showed lower storage and loss shear moduli G′ than field pea, kidney bean and chickpea starches. The changes in moduli during 10 h at 10°C revealed retrogradation in the order of: field pea> kidney bean> chickpea> blackgram> pigeon pea starch. In blackgram and pigeon pea starches, the lower proportion of amylose plus intermediate fraction and higher proportion of short and long side chains of amylopectin are considered responsible for the higher crystallinity, gelatinization temperature and enthalpy of gelatinization.

An extruded breakfast cereal made from a high amylose barley cultivar has a low glycemic index and lower plasma insulin response than one made from a standard barley

Himalaya 292 is a novel hull-less barley cultivar with lower total starch content, a higher proportion of amylose and a substantially higher content of soluble and insoluble fibre. The high fibre content suggests that the grain may have potential as an ingredient in health promoting foods. In this study, 29 healthy volunteers consumed extruded whole grain breakfast cereal made from Himalaya 292 (123 g) or a commercial hull-less barley (cv Torrens) (76 g) each supplying 50 g carbohydrate. Glycemic indices were 77 ± 13 (SEM) and 50 ± 9 for Torrens and Himalaya 292 breakfast cereals respectively ( P = 0.004). On this basis, the Himalaya 292 cereal is a low glycemic index food. The glycemic load (the product of glycemic index and the available carbohydrate content of a 60 g serve divided by 100) of the new cultivar was 10.1 ± 1.8 compared to 25.3 ± 4.3 for the Torrens breakfast cereal ( P < 0.001). The plasma insulin response to the test meal was 26% lower for Himalaya 292 than for Torrens ( P = 0.023). The data confirm that Himalaya 292 may be of value in foods designed to assist in the prevention and management of diabetes.

Use of Iodine as a Tool to Understand Wheat Starch Pasting Properties

AbstractThe ability of iodine to bind amylose has been used to understand a variety of structural and functional aspects of starch in food systems. In this study, the changes in starch granule swelling, polymer leaching and their relationship to pasting properties was investigated by adding iodine to the starch slurry at either room temperature or 95°C. The objective of the study was to investigate the contribution of leached and solubilized starch polymers on the pasting behavior of wheat starch. The addition of very small amounts of iodine (0.1%, dry basis, db) at room temperature increased peak and final pasting viscosities as compared to when no iodine was added. Further increases in iodine concentration resulted in a decrease in peak and final pasting viscosities. The amount of iodine required to completely inhibit granule swelling was more than that required to minimize amylose leaching from the granule. Adding increasing amounts of iodine at 95°C to the starch slurry resulted in the gradual decrease in peak and final pasting viscosities. The contrasting effects of iodine on paste viscosity behavior when added at room temperature or at 95°C suggest that the contribution of extra‐granular amylose on the setback viscosity is minimal and a larger proportion of amylose is retained in the intragranular spaces.

Resistant starch in cereals: Exploiting genetic engineering and genetic variation

Some of the starch consumed by humans is not digested in the small intestine. Such starch, known as resistant starch, is fermented in the large intestine and leads to the production of short chain fatty acids. Increased consumption of resistant starch is associated with improved cardio-vascular health. A high proportion of amylose in the starch consumed is correlated with increased resistant starch but other unknown aspects of starch structure may also influence the digestibility of starch. Detailed investigation of the starch biosynthetic pathway has revealed that reducing the activity of specific isoforms of branching enzymes and starch synthases can lead to increased amylose. Methods to alter the expression of and detect mutations in targeted genes involved are discussed.

Resistant starch formation in temperature treated potato starches varying in amylose/amylopectin ratio

Two genetically modified potato starches derived from the same mother line (64%, 1% and 23% amylose, respectively) were used to study the bioavailability after various heat treatments. The conditions for the treatments were of minor importance for resistant starch (RS) formation and hydrolysis results, as compared to the proportion of amylose. A high amylose content gave lower hydrolysis index (HI) and higher amounts of RS than starches with less amylose. Retrograded amylopectin contributed to a decreased HI, although only the high amylose line showed sufficient reduction in predicted glycaemic indices (GI). The line with high amylose content contained 25–30% RS vs. in the range of 0–5% for the other starches. Results could neither be explained by the presence of intact granules, nor by the content of retrograded amylose. Therefore, a synergistic effect between the starch components was suggested to affect the RS and starch hydrolysis.

A Novel Barley Cultivar (Himalaya 292) with a Specific Gene Mutation in Starch Synthase IIa Raises Large Bowel Starch and Short-Chain Fatty Acids in Rats

Himalaya 292 (Hordeum vulgare, var. himalaya 292) is a novel, hull-less barley cultivar with a single nucleotide change in the gene encoding starch synthase IIa (EC 2.4.1.21). This leads to loss of enzyme activity, resulting in a grain with less total starch and a higher proportion of amylose. These changes, plus higher total and soluble nonstarch polysaccharides (NSP), could increase its resistant starch (RS) content. Accordingly, rats were fed a diet containing stabilized whole-grain barley flours from Himalaya 292 or two commercial varieties (Namoi or Waxiro) or wheat or oat bran at equivalent NSP concentrations for 14 d. There were favorable significant changes in a number of bowel health-related indices. Fecal output by rats fed Himalaya 292 was higher than by those fed Namoi or oat bran, whereas total large bowel digesta mass was higher than in those fed WAXIRO: Cecal starch concentrations and pools were higher in rats fed Himalaya 292 than in all other groups. Fecal and cecal digesta pH was lower in rats fed Himalaya 292 than in all other groups except that fed oat bran. Colonic digesta pH was lower in rats fed Himalaya 292 than in those fed wheat bran or NAMOI: Fecal total SCFA excretion was higher in rats fed Himalaya 292 than in those fed Namoi or oat bran. Although cecal total SCFA pools did not differ among groups, colonic SCFA were higher in rats fed Himalaya 292 than in those fed Namoi or WAXIRO: These data indicate that changes in Himalaya 292 grain composition result in greater RS with consequent alterations in large bowel SCFA and pH when fed to rats.

Reduced Amylose Effects on Bread and White Salted Noodle Quality

ABSTRACTAmylose content in wheat endosperm is controlled by three Wx loci, and the proportion of amylose decreases with successive accumulation of Wx null alleles at the three loci. The proportion of amylose is believed to influence end‐use quality of bread and Asian noodles. The objectives of this study were to determine influence of the allelic difference at Wx‐B1 locus on bread quality, bread firmness, and white salted noodle texture in a spring wheat cross segregating for the Wx‐B1 locus and in a set of advanced spring wheat breeding lines differing in allelic state at the Wx‐ B1 locus. In addition, we examined the relationship between amylose content and flour swelling properties on bread and noodle traits. Fifty‐four recombinant inbred lines of hard white spring wheat plus parents were grown in replicated trials in two years, and 31 cultivars and breeding lines of hard spring wheat were grown in two locations. Bread and white salted noodles were processed from these trials. The presence of the Wx‐B1 null allele reduced amylose content by 2.4% in a recombinant inbred population and 4.3% in a survey of advanced breeding lines and cultivars compared with the normal. The reduced amylose was accompanied by an average increase in flour swelling power (FSP) for the Wx‐B1 null group of 0.8 g/g for the cross progeny and 2.3 g/g for the cultivar survey group. The Wx‐B1 allelic difference did not affect flour protein in cross progeny where the allelic difference was not confounded with genetic background. Bread from the Wx‐B1 null groups on average had increased loaf volume and was softer than the normal group for the cross progeny and cultivar survey group. The Wx‐B1 allelic difference altered white salted noodle texture, most notably noodle springiness and cohesiveness where the Wx‐B1 null groups was more springy and more cohesive than the normal groups for both sets of genetic materials. Flour protein was more highly related to loaf volume than were FSP or amylose. Both flour protein and FSP were positively related to noodle textural traits, but especially noodle springiness and cohesiveness.

Cooking attenuates the ability of high-amylose meals to reduce plasma insulin concentrations in rats.

Postprandial glycaemic control is important in the prevention and therapy of type 2 diabetes and related diseases. Agents that may reduce postprandial glycaemia and/or insulinaemia, such as consumption of high-amylose foods, are considered beneficial; however, little is known about the dose-response relationship and the effects of cooking. The aim of the present study was to define the dose-response curve for postprandial glycaemic and insulinaemic excursions following meals of different amylose content and to compare the dose-response curves for meals containing cooked and uncooked starches. Following an overnight fast, rats ingested a test meal and blood was sampled over 2 h. The meal was given at 1.0 g carbohydrate/kg body weight, with an amylose content of 0, 270, 600 or 850 g/kg total starch. The area under the glucose curve did not differ under any condition investigated. For the uncooked-starch diets, area under the insulin curve was higher for the 0 g amylose/kg total starch meal than all other meals (P=0.0001). For the cooked-starch diets, area under the insulin curve was higher in the 0 than the 600 and 850 g amylose/kg total starch groups (P<0.01), but did not differ from the 270 amylose/kg total starch group. These results suggest that even a relatively small proportion of uncooked amylose (270 g/kg total starch) is sufficient to achieve a maximal attenuating effect on postprandial insulin concentrations as compared with 0 g amylose/kg total starch. Following cooking, however, a much higher proportion of amylose (>or=600 g/kg total starch) is needed to achieve a similar effect.

Rice Ageing. I. Effect of Changes in Protein on Starch Behaviour

AbstractPasting properties of starch were affected by storage at 37 °C; the most significant changes were seen in peak viscosity and breakdown. In contrast, storage at 4 °C retarded the changes. The composition of the leachate from the RVA pastes was significantly affected by storage temperature (P &lt; 0.01) with a lesser proportion of amylose in samples stored at 37 °C. Thus, ageing was associated with decreased leaching of starch and particularly amylose. Protease treatment increased the ratio of amylose to amylopectin in the hot‐water soluble fraction significantly (P &lt; 0.05) for samples following storage at 37 °C while the ratio did not change for samples stored at 4 °C. Of greater significance was that the ratio was the same for samples stored at both temperatures following protease treatment. Similarly, after protease treatment the peak temperatures of the gelatinisation endotherm (Tp) of samples stored at 37 °C were identical to those of the samples stored at 4 °C. Protein was considered an important factor in the ageing process and the changes in proteins associated with storage were investigated. Higher storage temperature caused a reduction in the amount of prolamin and glutelin in the propanol‐extractable fractions.

Crystallinity and morphology in films of starch, amylose and amylopectin blends.

Films of potato starch, amylose, and amylopectin and blends thereof were prepared by solution casting and examined using X-ray diffraction, light microscopy, transmission electron microscopy, and differential scanning calorimetry. Amylose films had a relative crystallinity of about 30% whereas amylopectin films were entirely amorphous. Blending of amylose and amylopectin resulted in films with a considerably higher degree of crystallinity than could be predicted. This is explained by cocrystallization between amylose and amylopectin and possibly by crystallization of amylopectin. The crystallized material gave rise to an endotherm detected with differential scanning calorimetry. The enthalpy and peak temperature of the transition also increased as the water content decreased. When the amylose proportion in the blends was low, separate phases of amylose and amylopectin were observed by light microscopy. At higher amylose proportions, however, the phase separation was apparently prevented by amylose gelation and the formation of a continuous amylose network. The amylose network in the films, observed with transmission electron microscopy, consisted of stiff strands and open pores and became less visible as the amylose proportion decreased. The water content of the films was dependent on the microstructure and the crystallinity.

A critical role for disproportionating enzyme in starch breakdown is revealed by a knock-out mutation in Arabidopsis.

Disproportionating enzyme (D-enzyme) is a plastidial alpha-1,4-glucanotransferase but its role in starch metabolism is unclear. Using a reverse genetics approach we have isolated a mutant of Arabidopsis thaliana in which the gene encoding this enzyme (DPE1) is disrupted by a T-DNA insertion. While D-enzyme activity is eliminated in the homozygous dpe1-1 mutant, changes in activities of other enzymes of starch metabolism are relatively small. During the diurnal cycle, the amount of leaf starch is higher in dpe1-1 than in wild type and the amylose to amylopectin ratio is increased, but amylopectin structure is unaltered. The amounts of starch synthesised and degraded are lower in dpe1-1 than in wild type. However, the lower amount of starch synthesised and the higher proportion of amylose are both eliminated when plants are completely de-starched by a period of prolonged darkness prior to the light period. During starch degradation, a large accumulation of malto-oligosaccharides occurs in dpe1-1 but not in wild type. These data show that D-enzyme is required for malto-oligosaccharide metabolism during starch degradation. The slower rate of starch degradation in dpe1-1 suggests that malto-oligosaccharides affect an enzyme that attacks the starch granule, or that D-enzyme itself can act directly on starch. The effects on starch synthesis and composition in dpe1-1 under normal diurnal conditions are probably a consequence of metabolism at the start of the light period, of the high levels of malto-oligosaccharides generated during the dark period. We conclude that the primary function of D-enzyme is in starch degradation.

The potential of organic-based amylose-ethylcellulose film coatings as oral colon-specific drug delivery systems.

Amylose-ethylcellulose film coatings obtained from organic-based solvents were investigated as potential vehicles for colonic drug delivery. Amylose, in the form of an amylose-butan-1-ol dispersion, and ethylcellulose, dissolved in either ethyl lactate, ethanol, or propanol and plasticized with dibutyl sebacate, were mixed in various proportions and applied using a fluidized bed coater to achieve a range of film thicknesses on 5-aminosalicylic acid pellets. Drug release from the coated pellets was assessed under gastric and small intestinal conditions in the presence and absence of pepsin and pancreatin using dissolution methodology, and also within a simulated colonic environment involving fermentation testing with human feces in the form of a slurry. Under upper gastrointestinal tract conditions, the rate and extent of drug release were found to be related to the thickness of the coating and the ratio of amylose to ethylcellulose within the film. Modeling of the drug release data revealed that the ratio was more important than coat thickness in controlling drug release, irrespective of the solvent used for coating. Coatings with a thick film and/or low amylose content were relatively impermeable and able to delay drug release under conditions mimicking the upper gastrointestinal tract. Furthermore, drug release was unaffected by the presence of pepsin and pancreatin and by long-term storage. Under simulated colonic conditions, drug release was more pronounced from coating formulations containing higher proportions of amylose. Colon-specificity can therefore be achieved using such systems by judicious choice of the appropriate ratio of amylose to ethylcellulose and coat thickness.

Effect of sugars on the thermal and rheological properties of sago starch.

Studies have been undertaken to investigate the effect of sugars on the thermal and rheological properties of sago starch. Sugars were found to increase the gelatinization temperature T(gel), and gelatinization enthalpy DeltaH. T(gel) and DeltaH increased in the following order: control (water alone) < ribose < fructose < glucose < maltose < sucrose. The increase in DeltaH was greater for 50% starch compared to 10% starch samples. The swelling factors in the presence of sugar were higher compared to the control for sugar concentrations below 25% but were lower at sugar concentration greater than 25%. These effects are discussed in terms of the antiplaticizing effect of the sugars compared to water, the influence of sugar-starch interactions and also the effect of the sugars on water structure. The storage modulus G', the rate constant of gelation k, and the gel strength were significantly reduced in the presence of sugars. Generally G' and k decreased in the following order: control (water alone) > hexose > disaccharide > pentoses. This has been attributed to the reduced proportion of amylose leached following gelatinizatison. In the presence of hexoses the freeze-thaw stability of starch gels decreased while in the presence of disaccharides and pentoses the freeze-thaw stability was slightly improved.

Transcript accumulation and utilization of alternate and non-consensus splice sites in rice granule-bound starch synthase are temperature-sensitive and controlled by a single-nucleotide polymorphism.

Granule-bound starch synthase (GBSS), a product of the waxy gene in rice (Oryza sativa L.), is necessary for the synthesis of amylose in the endosperm. In an extended pedigree of 89 rice cultivars, we have previously shown that all cultivars with more than 18% amylose had the sequence AGGTATA at the leader intron 5' splice site, while all cultivars with a lower proportion of amylose had the sequence AGTTATA. This single-nucleotide polymorphism reduces the efficiency of GBSS pre-mRNA processing. It also results in alternate splicing at multiple sites, some of which have non-consensus sequences. Here we demonstrate that this same G-to-T polymorphism is also associated with differential sensitivity to temperature during the period of grain development. Cultivars with the sequence AGTTATA have a substantial increase in accumulation of mature GBSS transcripts at 18 degrees C compared to 25 or 32 degrees C. The selection of leader intron 5' splice sites is also affected by temperature in these cultivars. A 5' splice site -93 upstream from that used in high-amylose varieties predominates at 18 degrees C. At higher temperatures there is increased utilization of a 5' splice site at -I and a non-consensus site at +1. Potential implications of differential 5' splice site selection and associated differences in 3' splice site selection on transcript stability and translational efficiency are discussed.

Roles of Water-Soluble and Water-Insoluble Carbohydrates in the Gelatinization and Retrogradation of Rice Starch

The roles of water-soluble carbohydrates leached from starch granule and water-insoluble ones left in starch granule in the gelatinization were studied relating to gel hardness in the retrogradation. In the case of whole starch gel, hardness of rice starch gel was lower in the presence of lipids than it was in the absence of lipids, and an increase in hardness during storage at 5°C was retarded by the presence of lipids. The characteristic of water-insoluble fraction paste of gelatinized normal rice starch was the opposite to that of whole starch gel. This seems to be due to the shortage of amylose in the paste. When the proportion of amylose was high in the mixture of normal rice starch and waxy one, both the water-solubility and the gel hardness were strongly affected by lipids. On the contrary, the effects of lipids were hardly seen when the proportion of amylopectin was high in the mixed starches. Amylopectin of rice starch in the presence of amylose showed a considerable increase in complex formation.

Normal starch content and composition in tubers of antisense potato plants lacking D-enzyme (4-α-glucanotransferase)

Transgenic potato (Solanum tuberosum L.) plants were created with sense and antisense copies of the potato D-enzyme (disproportionating enzyme; EC␣2.4.1.25) cDNA linked to patatin and cauliflower mosaic virus 35 S promoters, and screened for D-enzyme activity in tubers. Transformants with sense constructs mostly had wild type D-enzyme activity but two plants had only about 1% wild-type activity. Transformants with antisense constructs had activity ranging from 90% to about 1% of wild type. Three 35 S antisense plants with very low activity were analysed in detail. Western blot analysis showed that D-enzyme was present in greatly reduced amounts in tubers and in leaves, whereas plastidic starch phosphorylase (EC 2.4.1.1) was unaffected. The lack of D-enzyme resulted in slow plant growth but development was otherwise apparently normal. Furthermore, the starch content of tubers was not appreciably altered in amount, proportion of amylose, molecular weight of debranched amylopectin, or branch chain length, despite the lack of D-enzyme. These results do not indicate a direct requirement for D-enzyme in the synthesis and accumulation of storage starch in tubers. The results are discussed in terms of the known reactions catalysed by D-enzyme and possible involvement of D-enzyme in starch metabolism.

Cultivar and environmental effects on quality characters in wheat. I. Starch

The composition of starch in wheat is an important determinant of grain quality, especially for white-salted noodles. Starch consists of 2 types of polymer, amylose and amylopectin, and occurs in predominantly larger A-type and smaller B-type granules. High starch pasting peak viscosity is desirable for white-salted noodles, and is influenced by the waxy genes coding for granule-bound-starch synthase (GBSS), which are involved in the synthesis of amylose. To study cultivar and environmental effects on the proportion of A-type granules, the proportion of amylose in starch, starch pasting peak viscosity, and grain hardness, 7 cultivars were grown in 15 environments which differed for temperature during grain filling. These cultivars varied in grain hardness classification and for the presence of GBSS coded by the Wx-B1 locus. Cultivars null for Wx-B1 GBSS had higher pasting viscosity than those with Wx-B1 GBSS, verifying the null requirement for cultivars suitable for white-salted noodles. However, the relationship between amylose concentration and pasting viscosity was complex, indicating that Wx-B1 influences pasting viscosity beyond its influence on the proportion of amylose and amylopectin. Environments with a high level of accumulated temperatures above 30ºC during the first 14 days after anthesis produced grain with a high proportion of A-type granules, even when irrigated. The proportion of amylose also increased with increasing accumulation of temperatures above 30ºC during the first 14 days, but was not influenced by temperature to the same extent as granule type. Environmental variation in pasting peak viscosity was large, but not related to high temperature. The hardness of grain was related to accumulated temperatures above 30ºC during the second 14 days after anthesis, with the increase in hardness much greater in soft-grained than hard-grained cultivars.

Use of alternate splice sites in granule-bound starch synthase mRNA from low-amylose rice varieties.

The rice Waxy gene encodes a granule-bound starch synthase (GBSS) necessary for the synthesis of amylose in endosperm tissue. We have previously shown that a CT microsatellite near the transcriptional start site of the GBSS gene can distinguish 7 alleles that accounted for more than 80% of the variation in apparent amylose content in an extended pedigree of 89 US rice cultivars (Oryza sativa L.). Furthermore, all the cultivars with 18% or less amylose were shown to have the sequence AGTTATA at the putative leader intron 5' splice site, while all cultivars with a higher proportion of amylose had AGGTATA. Here we demonstrate that this single-base mutation reduces the efficiency of GBSS pre-mRNA processing and results in alternate splicing at three cryptic sites. The predominant 5' splice site in CT18 low-amylose varieties is 93 bp upstream of the splice site used in intermediate and high amylose varieties and is immediately 5' to the CT microsatellite that we previously demonstrated to be tightly correlated with amylose content. Use of the leader intron 5' splice site at either -93 or -1 in conjunction with the predominant 3' splice site results in formation of a small open reading frame 38 bp upstream of the normal ATG and out of frame with it. This open reading frame is not produced when any of the 5' leader intron splice sites are used in conjunction with an alternate 3' splice site five bases further downstream which was observed in all rice varieties tested.

Influence of growth conditions on barley starch properties

Air equilibrated barley starch comprises amylopectin, amylose, lipid and water. The structure of amylose and amylopectin, and the proportion of amylose in granules is under genetic control and is therefore subject to genotypic variation. The amount of lipid (which is essentially all lysophospholipid) is similarly under genetic control. Environment and especially environmental temperature do, however, have a regulatory effect on the size of starch granules, the amylose to amylopectin ratio and the amount of lipid (which is essentially all complexed with amylose) within barley starch. High growth temperatures probably facilitate amylopectin crystallisation and increase gelatinisation temperatures, (and to some extent the enthalpy of gelatinisation), but delay the onset and depress the extent of swelling of granules when heated in water.