Amount Of Amylose Research Articles

Heritability and amylose content in hybrid lines of late-generation rice with colored pericarp.

Improving grain quality in rice breeding is one of the main tasks. This concerns the creation of rice varieties with colored pericarp uncommon in the Republic of Kazakhstan, and the assessment of its quality is an important stage of breeding. Rice with colored pericarp is an important dietary crop, more useful for the human body than white rice. Regardless of the type of rice, the amount of amylose in rice grain is a crucial indicator that determines the quality of rice. The paper presents the results of electrophoretic separation of spare grain proteins of rice hybrids and dihaploids with colored pericarp and their parent forms obtained as a result of the hybridization of varieties with colored pericarp (Black Rice (China), Mavr (Russia), and Yir 5815 (Ukraine)) with white rice varieties zoned in Kazakhstan. The hybridization of the rice varieties with colored pericarp with white rice varieties was carried out to obtain rice varieties with colored pericarp oriented to the soil and climate of Kazakhstan. Analyzing the results of electrophoresis and the amount of amylose, it was found that hybrid lines differed in amylose content. One of the studied hybrids was high in amylose, four had a medium amylose content, ten had a low amylose content, three had a very low amylose content, and six were glutinous. According to the results of electrophoretic separation of spare rice grain proteins, the spectrum of the enzyme determining amylose was detected in five hybrids, which corresponds to the results of spectrophotometric determination of amylose: high amylose in one hybrid and medium amylose content in four. The results show that the hybrids obtained as a result of hybridization are true hybrids and as a result of long-term selection, the amylose content in the F7-F8 hybrids stabilized. The hybrids can be used in further breeding of rice with colored pericarp.

Effect of Chemical Modification By Oxidation and Esterification Process On Properties of Starch: A Review

Starch is a carbohydrate or polysaccharide consisting of a large number of glucose units linked through glycosidic bonds and containing different amounts of amylose and amylopectin as macromolecules. Starch modification can be done physically, chemically, and enzymatically. The process of chemical modification of starch aims to separate the long glucose chains from the polymer molecules in order to reduce the high viscosity of the unmodified starch solution and thus maximize the possible amount of starch in technical applications This modification involves exploiting the many hydroxyl groups present in starch granules to introduce functional groups, resulting in changes in physicochemical and functional properties such as gelatinization, paste, and retrogradation properties of starch. Esterification and oxidation are types of chemical modification processes that can be applied to improve starch characteristics. However, the chemical modification process did not affect the morphology and had little effect on changing the structure of the starch

SELECTION OF COVARIATES IN A LOGISTIC REGRESSION MODEL FOR THE PREDICTION OF RESISTANCE TO RICE BLAST

Rice (Oryza sativa L.) has been one of the most consumed foods on the planet, with economic and social importance. Diseases, mainly blast, caused by the fungus Pyricularia oryzae, are limiting factors for the production of rice. The present work aimed to select covariables that can influence resistance to rice blast, using the selection strategy proposed by Collett. Logistic regression models were adjusted to predict disease resistance, using the ROC curve to assess the predictive capacity. The data used were obtained from a population of 413 plants, with phenotypic information collected in 82 countries and classified into five subpopulations. The research found that, out of over fifteen variables embedded to assess the disease, only three revealed to be relevant for the final adjusted model, namely: width of flag leaf (V4), the mean number of primary panicle branches (V8) and the amount of amylose from ground grains (V15). The variable V4 presented the most significant influence on disease resistance. Additionally, for each unit increase in V4, V8 and V15, it is expected to obtain 279.3, 31.9 and 9.4% increases, respectively, in the probability of resistance to rice blast.

Amylose Content and Physical Changes in Waxy Corn Starch Modification by Spontaneous Fermentation

This study aimed was to determine the changes in the ratio of amylose and amylopectin and the physical properties of spontaneously fermented waxy corn starch (WCS) granules. The results showed that the amylose content of WCS which was fermented spontaneously from 9 to 15 days experienced a significant change with native starch, namely, ± 86 – 117%. The hydrolyzed process is caused by lactic acid bacteria activity. The highest activity showed at 15th-day fermentation. Changes in starch composition also affect the swelling power, solubility, water absorption, and gelatinization profile of WCS. Starch that was fermented for 15th-days had the highest amylose percentage (24.92%) the otherwise, had the lowest swelling value compared to native starch. The percent solubility of fermented starch increased with increasing the amount of amylose and on the 15th day of fermentation, the highest value was (65.56%). Water absorption increased until the 6th-day of fermentation and then decreased due to an increase in the amount of amylose. The gelatinization profiles of native starch and fermented modified starch were of the same type.

Effect of biscuits formulated with high-amylose maize flour on satiety-related sensations and food intake

The amount of amylose within a food may elicit lower glycemic and insulin postprandial responses and thus potentially modulate the satiating effect. In this context, the effect of biscuits formulated with high amylose starch (HAS) flour on satiety-related sensations and food intake was studied. Three types of biscuits were produced: control biscuit (CRT, 0% of HAS), Amy-25 (25% HAS), and Amy-50 (50% HAS). Fifteen healthy volunteers were enrolled to conduct two in vivo experiments. In experiment 1, volunteers consumed biscuits ad libitum and their sensations of satiety and food intake were evaluated. In experiment 2, volunteers received a quantity of biscuits equivalent to the 20% of the daily estimated energy requirements, and both satiety-related sensations and food intake were checked at subsequent meal. The Amy-50 significantly reduced food intake at subsequent meal (p ˂ 0.05), compared to Amy-25 and CRT. The satiety-related sensations were not significantly affected in both experiments, excepted for intra-meal hunger variation induced by Amy-25 which resulted significantly higher (p ˂ 0.05) than Amy-50 and CRT. These findings support the need to reformulate carbohydrate rich foods commonly consumed in a dietary context, to provide consumers healthier alternatives to prevent and tackle obesity and related chronic diseases.

Piyasada Osmancık Çeşit Adıyla Satılan Pirinçlerin Kalite Özelliklerinin Orijinal Osmancık Çeşidi ile Karşılaştırılması

Bu araştırmada, piyasada satışa sunulan Osmancık çeşidi pirinçlerin kalite özellikleri, orijinal tohumluk Osmancık çeşidi ile karşılaştırılmıştır. Bu amaçla farklı satış noktalarından 17 adet Osmancık adı ile satılan pirinç örneği alınarak kalite özellikleri yönünden analiz edilmiştir. Elde edilen veriler Trakya Tarımsal Araştırma Enstitüsü’nden temin edilen orijinal tohumluk Osmancık çeşidinin sonuçları ile karşılaştırılmıştır. Çalışmalar Enstitü’den temin edilen örnekle beraber toplam 18 örnek üzerinde yürütülmüştür. Gerçekleştirilen analizler sonucunda örneklerde uzunluk 5.47-6.73 mm, uzunluk genişlik oranı 2.11-2.55, genişlik 2.59-2.85 mm, hektolitre ağırlığı 82.93-87.00 kg hl-1, bin tane ağırlığı 18.24-22.41 g arasında bulunmuştur. Pirinç örneklerinde kül miktarı % 0.37-0.48, protein miktarı % 7.10-8.12, amiloz miktarı % 27.12-30.09, toplam organik madde miktarı % 2.01-2.33 arasında değişmiştir. Örneklerin jel uzunlukları (konsistensi) 52.00-69.00 mm ve alkalide yayılma değerleri (jelatinleşme sıcaklığı) 4.00-7.00 arasında belirlenmiştir. Pişme testi sonuçlarına göre; pişme süresi 16.81-18.87 dakika, pişme kaybı % 3.90-5.16, su alım oranı 1.79-1.99 ve hacim artış oranı 1.40-1.66 arasında tespit edilmiştir. Sonuçlar genel olarak değerlendirildiğinde; satın alınan pirinçlerde alkalide yayılma değeri 4 örnekte orijinal çeşitten farklı bulunmuştur. Diğer özellikler bakımından ise pirinç örnekleri orijinal tohumluk Osmancık çeşidine yakın sonuçlar vermiştir.

PSVI-32 The effects of varying amylose levels in different diets on digestibility and glycemic response in canines

Abstract This study was conducted to compare the digestibility of pulse-based diets to grain-based diets based on varying levels of amylose and study how changes in digestibility impacts glycemic response in dogs. To establish glycemic response, six diets were formulated at an inclusion level of 20% available starch with varying amylose content. A grain-based diet was formulated using rice, while pulse-based diets consisted of smooth pea, wrinkled pea (4140–4 and Amigold varieties), faba bean, or lentil. Beagles (n = 8, 4 females, 4 males) were fed the 6 different test diets for 7 days in a randomized, cross-over, blinded design. At the end of each feeding period, fecal samples were collected and beagles were fasted overnight and subjected to a glycemic test (1g/kg of diet or glucose fed). Data collected were statistically analyzed using SigmaPlot 12.0 and significance was declared at P ≤ 0.05. Amylose levels of diets varied from 4.64% to 14.82% on a dry basis. The rice-based diet had the lowest amylose content, while the wrinkled pea (Amigold variety) diet had the highest amylose content. Following the collection of glycemic response and fecal data, repeated-measures, 1-way ANOVA’s were conducted. There were significant differences observed between diets based on peak glucose levels (mmol/L, P = 0.01). The rice diet had the highest peak in glucose, while the lentil-based diet had the lowest glucose peak. Significant differences were also seen between diets based on their digestibility (P < 0.001). Rice, lentil, faba bean and smooth pea-based diets had the highest levels of digestibility, while wrinkled pea varieties had decreased digestibility. Furthermore, varying amylose found in diets can be viewed as an impacting factor on glycemic response and digestibility. Incorporating pulses with higher amounts of amylose could be utilized in dog diets to promote a low glycemic response through decreased rates of digestibility.

Fabrication of starch blend films with different matrices and their mechanical properties

The objective of the study was to determine the effects of molecular sizes of amylose (AM) and starch granules on the mechanical properties of thermoplastic starch (TPS) blend films. Leached amylose solution from cassava (CS_ AM) and mung bean (MB_AM), and two forms of amylopectin (AP) (granular; g and non-granular; ng) of waxy cassava (WxCS) starch were used. Four types of film matrices were fabricated and all TPS blend films contained same amount of AM and glycerol. Results displayed that molecular weight profiles of starch films and presence of granule remnants significantly controlled the film matrix formation, types of crystal formation, and percent of relative crystallinity (%RC) (p < 0.05). Tensile property of TPS films was controlled by %RC and presence of granule remnants. Percent elongation at break (%Eb) of TPS films increased when the films had a large range of molecular weight distribution (from 5.5 × 107 g/mol to 0.4 × 105 g/mol) and contained a high weight fraction (~58%) of starch molecules with Mw~0.4 × 105 g/mol.

Alginate and corn starch mixed gels: Effect of gelatinization and amylose content on the properties and in vitro digestibility

The aim of this work was to evaluate the effects of gelatinized and non-gelatinized corn starches with different amounts of amylose (6.62, 28.46, and 61.10%) in the alginate matrix in relation to mechanical properties and microstructure before and after in vitro digestibility. The use of alginate together with corn starch with different amounts of amylose, in the gelatinized and non-gelatinized form, resulted in gels with different morphological characteristics. All hydrogels produced with gelatinized starches showed a more closed microstructure when compared to those produced with non-gelatinized starches due to the mixed network formed by the alginate matrix and the leached chains during gelatinization. After digestion, the microstructure of these gels became more porous, and the stress at rupture decreased in relation to the initial sample, while the modifications for the sample with non-gelatinized starches were less pronounced due to the susceptibility of gelatinized starch to enzymes. Gels with gelatinized common and high amylopectin starches presented higher amounts of released glucose and a more degraded microstructure after digestion, indicating that it is a suitable system for enteric delivery. Compound release can be controlled depending on the amylose amount and the form of corn starch used in combination with alginate to produce a matrix.

Heat pretreatment improves the enzymatic hydrolysis of granular corn starch at high concentration

Abstract Heat pretreatment was investigated as a way to improve the α-amylase-catalyzed hydrolysis of granular corn starch at high concentration (45%, w/w). Native and preheated starches were hydrolyzed in the granular state for 1 h at 40 °C using a commercially available α-amylase. The initial dextrose equivalent (DE) value of the native granular starch (8.0%) increased significantly (to 12.6%) after pretreatment at 60 °C for 15 min. Microscopic analysis of the starch granules indicated that heat pretreatment increased the number and size of the pores and pinholes on the granule surface, which facilitated the adsorption and subsequent penetration of enzyme molecules. Furthermore, the amylose present in amorphous regions leached rapidly when corn starch was incubated at 60 °C, suggesting weaker interactions within the granules. The DE value of the hydrolysate showed a linear dependence on the amount of amylose that leached during the course of heat pretreatment (R 2 = 0.9771). Mobilization of amylose chains within the granule, caused by the heat pretreatment, may have allowed the enzyme to make greater use of amylose, which is its primary substrate during starch granule hydrolysis. In addition, a 35% reduction in the K m value showed that heat pretreatment increased the affinity of α-amylase for the starch granules. This can be attributed to the mobilization of amylose chains within the granule and expansion of the surface pinholes. These effects demonstrate that proper heat pretreatment of granular starch before amylolysis has great potential in industry.

Amylose and amylopectin molecular fractions and chain length distribution of amylopectin in 12 varieties of Ghanaian sweet potato (Ipomoea batatas) flours

ABSTRACTSweet potato (Ipomoea batatas) is a commonly cultivated root crop in tropical and subtropical regions, including Ghana. Different varieties of sweet potato have been bred, in order to expand its utilisation within the food and industrial sector. This study analysed flours made from 12 recently developed Ghanaian sweet potato varieties in terms of their amylose and amylopectin molecular fractions and amylopectin chain length distribution. Starch content of the sweet potato flours ranged from 49 to 77 g/100 g dry matter, with 11 of the varieties containing above 60 g/100 g dry matter. An orange-fleshed variety, Apomuden, had the lowest amount of starch (48.9 g/100 g dry matter), while the cream-fleshed variety Histarch had the highest (77.3 g/100 g dry matter). The flours from the 12 sweet potato varieties had intermediate amounts of amylose, within the range 10–30 g/100 g dry matter, and showed typical molecular distribution according to size-exclusion chromatography (SEC). The fine structures of amylopectin, as revealed by anion-exchange chromatography, contained features common for starches of C-type X-ray pattern, but some structural differences were also observed.

Genetic controls on starch amylose content in wheat and rice grains.

Starch accumulates in plants as granules in chloroplasts of source organs such as leaves (transitory starch) or in amyloplasts of sink organs such as seeds, tubers and roots (storage starch). Starch is composed of two types of glucose polymers: the essentially linear polymer amylose and highly branched amylopectin. The amylose content of wheat and rice seeds is an important quality trait, affecting the nutritional and sensory quality of two of the world's most important crops. In this review, we focus on the relationship between amylose biosynthesis and the structure, physical behaviour and functionality of wheat and rice grains. We briefly describe the structure and composition of starch and then in more detail describe what is known about the mechanism of amylose synthesis and how the amount of amylose in starch might be controlled. This more specifically includes analysis of GBSS alleles, the relationship between waxy allelic forms and amylose, and related quantitative trait loci. Finally, different methods for increasing or lowering amylose content are evaluated.

Physico-chemical, thermal and rheological properties of starches isolated from newly released rice cultivars grown in Indian temperate climates

Starches isolated from three newly released rice cultivars were tested for different physico-chemical, thermal and rheological properties. The starch granule had either polygonal or irregular shapes with small particle size mainly falling in the range of 1–10 μm. SR-1 had more polygonal shapes than SKUAST-5 and SKUAST-27. SR-1 starch also showed significantly high (p ≤ 0.05) amount of amylose (28.6 g/100 g starch) which possibly was responsible for high swelling power (25.9 g/100 g starch), solubility (26.4 g/100 g starch) and syneresis (35.2 g/100 g starch). Thermal properties (To; Tp; Tc) and enthalpy of gelatinization (ΔHgel) also exhibited significant (p ≤ 0.05) differences thereby affecting the stability of crystalline structures among the rice starches. SKUAST-5 starch showed the lowest value for To (58.5 °C) but exhibited highest value of ΔHgel (18.5 J/g). SR-1 starch exhibited slightly higher degree of retrogradation (83.1 g/100 g starch) than SKUAST-5 (80.2 g/100 g starch) and SKUAST-27 (79.6 g/100 g starch). The flow behavior indicated differences in shear thinning behavior and hysteresis area. All samples showed high structural recovery indicating their suitable use in high shear processing. SKUAST-27 exhibited high value (42.4 g/100 g starch) of rapidly digestible starch (RDS) than SR-1 (39.8 g/100 g starch) and SKUAST-5 (39.4 g/100 g starch).

THE EFFECT OF SPRING WHEAT STARCH PROPERTIES ON FLOUR TORTILLA QUALITY

ABSTRACT Starch properties affect the end‐use quality of products made from wheat flour. Seven genotypes of wheat flour, having various amounts of amylose, were grown in North Dakota. Flour from these genotypes was tested for starch properties to assess the impact of starch on tortilla quality. Amylose content of flours ranged from 10.38 to 25.35%. Amylose content of the flours showed a correlation of 0.756 (P &lt; 0.05) to the specific volume of tortillas. Amylose content showed a correlation of 0.878 (P &lt; 0.01) to work required to stretch on day 1. There was correlation of 0.769, 0.871 and −0.760 (P &lt; 0.05) between amylose content and force to stretch on days 0, 3 and 7, respectively. Gelatinization and pasting properties of extracted starch were determined and the values were correlated to tortilla quality parameters. Wheat flour starch properties and composition significantly impact tortilla quality, and various low‐amylose flour mixtures could result in enhancement of tortilla quality.PRACTICAL APPLICATIONSTortilla is a flat bread made from either corn or wheat. They are the second highest‐selling product in the packaged bread category. In this study, flour from seven genotypes of wheat grown at three separate North Dakota locations as well as commercial flour samples were analyzed for their starch properties and tortilla quality. Results of this study showed that wheat flour starch properties and composition significantly impact tortilla quality, and various low‐amylose flour mixtures could result in enhancement of tortilla quality. We believe that tortilla industry can utilize the results of this study in their applications.

EFFECT OF STORAGE TEMPERATURE ON THE EXTENT OF BALADY BREAD STALING

The effect of storage temperature on freshness score, moisture content, alkaline water retention capacity (AWRC), the amount and composition of soluble starch as well as parting properties of balady bread were investigated. The data revealed that the temperature of storage has more important effect on the extent of bread freshness than its moisture content. The AWRC, the amount of soluble starch extracted and amylose decline sharply during the first 24hrs of storage, after which it leveled off. The component of the soluble starch was predominantly amylopectin. The amount of amylose in the soluble starch extracted from fresh bread after withdrawal from oven was small, declining sharply during the first 24hrs.of storage and this decreased slowly afterwordes. After24hrs.of storage, the decrease in soluble starch was accompanied by decreasing in amylopectin content. The refrigerator temperature is more likely to increase starch crystallization in bread and thus acceralate the rate of staling occurred than ambient temperature. No considerable changes in freshness as well as staling parameters were observed in bread stored at freezing temperature up to 72 hrs. Amylogram data showed slight decrease in the pasting temperature of bread slurries with longer storage time. The difference in peak viscosity, 15 min height, including a holding treatment at 95 C for 15 min; and after subsequent cooling to 50C (setback) gave the simillar rankings. These changes are more extensive at refrigerator temperature than at ambient temperature. Based on the data presented in this study, the AWRC, the amount of soluble starch, amylose and viscosity highly correlated with the sensory perception evaluation of bread staleness.

Nanocomposites from plasticized high‐amylopectin, normal and high‐amylose maize starches

AbstractThree types of maize starch with different amounts of amylose and amylopectin were used to prepare plasticized starch/clay nanocomposite films by casting. Studies by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the intercalation/exfoliation of the plasticized starch molecules took place into the clay galleries for the three types of starch. However, the plasticized waxy starch molecules were the easiest of them all to be intercalated/exfoliated, which was reflected in the highest increment of the stress at peak of these nanocomposites. Moreover, the lowest water uptake was showed by the plasticized high‐amylose starch/clay nanocomposites. It was concluded that varying contents of amylose and amylopectin influenced the formation of intercalated/exfoliated clay structures and also affected the interactions of clay with water. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Functions of fenugreek gum with various molecular weights on the gelatinization and retrogradation behaviors of corn starch—2: Characterizations of starch and investigations of corn starch/fenugreek gum composite system at a relatively low starch concentration; 5 w/v%

Gelatinization and retrogradation behaviors of corn starch were investigated in an aqueous system in the presence or absence of fenugreek gum with various molecular weights. The addition of fenugreek gum (0.5 w/v%) increased peak viscosity of the composite system (5% starch) during gelatinization when coil overlap parameter C[ η] and weight-average molecular weight M w of the gum were larger than 2.38 and 87.0×10 4 g/mol, respectively, shifting the onset of viscosity increase to lower temperatures. It increased dynamic mechanical loss tangent tan δ of the composite system after storage at 4 °C for 24 h and also an exponent n determined by the power-law regression between dynamic complex viscosity η * and frequency ω, η *= Kω n , indicating the lowering of structural hardening of the composite system during short-term retrogradation (24-h time scale). This effect of fenugreek gum was less M w dependent when C[ η] and the M w of the gum were equal to or larger than 4.05 and 18.3×10 5 g/mol, respectively, relating to the decrease in the amount of amylose (or amylose-like components) leached out starch granules during gelatinization. The addition of fenugreek gum decreased dynamic storage modulus G′ of the composite system after storage at 4 °C for 24 h and also a constant K when C[ η] and the M w of the gum were equal to or smaller than 4.05 and 18.3×10 5 g/mol, respectively, without altering the rate constant k determined rheologically by the time-course of G′ during short-term retrogradation. The addition of fenugreek gum increased syneresis of the composite system after storage at 4 °C for 24 h when C[ η] and the M w of the gum were equal to or smaller than 0.65 and 11.1×10 4 g/mol, respectively, while decreased when C[ η] and the M w of the gum were equal to or larger than 4.05 and 18.3×10 5 g/mol, respectively, according to the rheological data. These critical M w values for fenugreek gum were compared with corresponding data for guar gum, an alternative galactomannan with a different galactose/mannose ratio, and the functions of galactomannans were discussed on the gelatinization and retrogradation behaviors of corn starch in an aqueous system.

Comparison of the physicochemical properties of barley starches after partial α-amylolysis and acid/alcohol hydrolysis

Zero amylose waxy (CDC Alamo), normal (Falcon), and high amylose (CDC 92-55-06-48) hull-less barley starches were isolated and subjected to α-amylase ( Bacillus licheniformis) hydrolysis (24 and 48 h; 50 and 500 U/g) and acid hydrolysis (2% HCl, 10 and 96 h) in different alcohol media (methanol, ethanol, and 1-butanol) to determine the molecular characteristics of the starch material remaining in the granules after treatments. The greatest yield of α-amylase-treated starches was obtained for the high amylose (79.9–86.6% w/w) followed by normal (61.1–76.1% w/w), and zero amylose waxy starch (44.2–64.5% w/w). Very little solubilization of starches occurred during acid/alcohol hydrolysis, and very high yields of treated starches were obtained (91–99%). Relatively small decreases in the average molecular weights ( M w) of starch components were observed after α-amylolysis; the extensive hydrolysis of the zero amylose starch (56% solubilization) caused only a threefold decrease in the M w of amylopectin. The M w of starch fractions after acid/alcohol hydrolysis was affected by the hydrolysis time and alcohol but not by the amount of amylose in the native starches; the M w and the mode of distribution of various M w species can be tailored to specific needs by choosing appropriate hydrolysis conditions. The partially enzyme-hydrolyzed normal and high amylose starches formed stronger gels (40% w/w) than their native counterparts, but waxy starch showed no evidence of network development during storage (20 h, 5 °C). The partially acid-hydrolyzed high amylose starch (2% HCl/MeOH, 10 h) showed significantly higher values of G′ compared to the native sample upon storage, whereas the partially hydrolyzed normal starch exhibited the G′ values similar to its native counterpart. Both normal and high amylose starches, hydrolyzed for 96 h, exhibited a rapid rise in G′ upon cooling but very little network development thereafter.

Environmental Factors that Affect the Ability of Amylose to Contribute to Retrogradation in Gels Made from Rice Flour

Retrogradation in rice is a trait that describes the hardening of cooked rice after storage or cooling, and it has significant implications for many consumers of rice, since many people cook rice in the morning and consume it several hours later or the next day. Tools to select against retrogradation in breeding programs are yet to be described. Here, we aim to determine the effect on retrogradation of storage time and temperature and the role of starch, protein, and lipids using gels made from Koshihikari grown in either Australia or Japan. Immediately after cooking, cooling from 60 to 40 degrees C had a minimal effect on firmness, but cooling to 20 degrees C led to significantly firmer gels. Storing the gels at low temperatures did not have an additional effect on the firmness as compared with storing the gels at 20, 40, or 60 degrees C. The removal of proteins led to significantly softer gels at all storage treatments but did not affect the change in firmness on cooling. The removal of lipids increased the rate of retrogradation and the firmness of gels significantly for all treatments. Koshihikari grown in Japan retrograded much less than Koshihikari grown in Australia. The amount of amylose that could be washed from gels made from Australian flour was much greater than for gels made from Japanese flour. After storage, only low molecular weight amylose chains were released from the gel and only after rewarming them to 60 degrees C. Despite the fact that flours from both origins were 18% amylose, the amount of long amylose chains that were complexed with lipids was much greater for the Japanese rice, and the unavailability of the complexed long amylose chains explained the lack of retrogradation in the Japanese rice. Once the long chains were released from amylose-lipid complexes, the Japanese rice retrograded. Thus, the environmental factor affecting retrogradation in this variety is type or amount of lipids synthesized, and the degree of retrogradation was determined by the availability of long chains of amylose.

Effect of starch granule structure, associated components and processing on nutritive value of cereal starch: A review

Starch is organized in concentric alternating semi-crystalline and amorphous layers in granules of various sizes within the endosperm. The amount of amylose in starch normally varies between 200 and 300 g/kg, but waxy cereals may contain negligible amounts and starch from high-amylose varieties may contain up to 700 g amylose/kg. High amylose content is associated with reduced digestibility. Fat and protein are found on the surface of starch granules, and these components may act as physical barriers to digestion. Heat treatment with sufficient water present will cause gelatinisation that will increase susceptibility for starch degradation in the digestive tract, although a linear relationship between extent of gelatinisation due to processing and digestibility has not been found. The low water content during feed processing limits the extent of gelatinisation, but gelatinisation temperature and extent of gelatinisation will be affected by properties of the starch, which in turn may affect digestibility. The effect of starch properties and feed processing on digestion in non-ruminant animals and ruminants are discussed.