Structure and physicochemical properties of defatted and pin‐milled oat bran concentrate fractions separated by air‐classification4

Oat bran concentrate (OBC) was defatted by supercritical carbon dioxide, pin‐milled and air‐classified into five fractions (<15, 15–18, 18–24, 24–30 and > 30 μm). β‐glucan content (% dry weight) of defatted OBC, its subsequent pin‐milling and the air‐classified fractions in ascending particle size was 14.3, 17.0, 4.3, 5.8, 12.6, 14.7 and 22.4, respectively. High‐performance size‐exclusion chromatography equipped with multi‐angle laser‐light scattering and refractive index detectors showed that amylopectin was the predominant molecule present in all OBC powders but was present in greater concentration in fractions collected that were < 24 μm. Fractions >24 μm, which had the highest β‐glucan contents had higher starch gelatinisation temperatures (measured using differential scanning calorimeter), and had substantially higher peak, breakdown, final and setback paste viscosity (measured using Rapid Visco Analyser, Foss North America, Eden Prairie, MN, USA) compared with the other lower‐β‐glucan containing fractions. No differences in water retention of 25% (w/w) oat powders in water (measured using thermogravimetric analyser) were observed among defatted OBC, its subsequent pin‐milling and the five fractions separated by air‐classification. In particular, differences in pasting properties show that defatted, pin‐milled OBC that is fractionated by air‐classification will have different food applications depending on particle size collected.     

Differences in Gelatinisation Behaviour Between Starches from Australian Wheat Cultivars

The gelatinisation behaviour of starches isolated from 16 Australian wheat cultivars with a wide range of pasting properties was studied using the Viscoamylograph (VAG), Rapid Viscoanalyser (RVA) and Differential Scanning Calorimetry (DSC). VAG and RVA characteristics varied between cultivars as did the enthalpy and temperatures of gelatinisation, as measured by DSC. Significant correlations existed between RVA and VAG values for maximum viscosity and breakdown. The enthalpy of the amylose/lipid complex transition, measured by DSC, was significantly correlated with each of maximum paste viscosity, breakdown, setback and viscosity at 50°C as measured by VAG, and maximum viscosity and breakdown as measured by RVA. Starch properties that significantly correlated to gelatinisation behaviour included amylose content and the proportion of small starch granules, which had a negative relationship with VAG data for maximum viscosity, breakdown and viscosity at 50°C. Similar correlations existed for RVA data except for setback. Amylose content was also significantly correlated with the enthalpy of the amylose/lipid complex transition.     

Effect of genotype and environment on the concentrations of starch and protein in, and the physicochemical properties of starch from, field pea and fababean

BACKGROUND: The effects of genotype and environment and their interaction on the concentrations of starch and protein in, and the amylose content and thermal and pasting properties of starch from, pea and fababean are not well known. RESULTS: Differences due to genotype were observed in the concentrations of starch and protein in pea and fababean, in the onset temperature (To) and peak temperature (Tp) of gelatinization of fababean starch, and in the pasting, trough, cooling and final viscosities of pea starch and fababean starch. Significant two‐way interactions (location × genotype) were observed for the concentration of starch in fababean and the amylose content, To, endothermic enthalpy of gelatinization (ΔH) and trough viscosity of fababean starch. Significant three‐way interactions (location × year × genotype) were observed for the concentration of starch in pea and the pasting, trough, cooling and final viscosities of pea starch. CONCLUSION: Differences observed in the concentrations of starch and protein in pea and fababean were sufficient to be of practical significance to end‐users, but the relatively small differences in amylose content and physicochemical properties of starch from pea and fababean were not. Copyright © 2011 Society of Chemical Industry     

Chemical and Physical Properties of Kiwifruit (Actinidia deliciosa) Starch

Chemical and physical properties of kiwifruit (Actinidia deliciosa var. ‘Hayward’) starch were studied. Kiwifruit starch granules were compound, irregular or dome‐shaped with diameters predominantly 4–5 µm or 7–9 µm. Kiwifruit starch exhibited B‐type X‐ray diffraction pattern, an apparent amylose content of 43.1% and absolute amylose content of 18.8%. Kiwifruit amylopectins, relative to other starches, had low weight‐average molecular weight (7.4×10⁷), and gyration radius (200 nm). Average amylopectin branch chain‐length was long (DP 28.6). Onset and peak gelatinization temperatures were 68.9°C and 73.0°C, respectively, and gelatinization enthalpy was high (18.5 J/g). Amylose‐lipid thermal transition was observed. Starch retrograded for 7 d at 4°C had a very high peak melting temperature (60.7°C). Peak (250 RVU), final (238 RVU) and setback (94 RVU) viscosity of 8% kiwifruit starch paste was high relative to other starches and pasting temperature (69.7°C) was marginally higher than onset gelatinization temperature. High paste viscosities and low pasting temperature could give kiwifruit starch some advantages over many cereal starches.     

Development and Testing of Methods to Screen Chickpea Flour for Starch Characteristics

Rapid screening methodology has been developed for assessing the chemical composition and the gelatinisation and pasting properties of starch using flour from chickpea seeds. The methodology allows samples to be assessed using a minimal amount of sample and for starch information to be interpreted in the presence of other components present in the flour. The starch content of the flour and the amylose content of the starch was determined by modifying existing kit-based methods (Megazyme International Ltd). Using the Differential Scanning Calorimeter (DSC), starch gelatinisation characteristics can be assessed based on temperature of gelatinisation (T_p), specific heat capacity (Cp^sp ) and half width of transition (½ΔT). Pasting properties could be assessed using the Rapid Visco Analyser (RVA), based on the determination of onset temperature for the RVA profile (T \displaystyle _o^{RVA} ), T_p − T \displaystyle _o^{RVA} and final viscosity (FV) values. The developed methodology was tested using a range of chickpea samples. No significant variation was found between the samples for starch content or for the proportion of amylose/amylopectin in the various starches. Significant variation was found in the starch properties of two of the samples, while the variation between the remaining samples was very small.     

Comparisons of physicochemical properties and antioxidant activities among pumpkin (Cucurbita moschata L.) flour and isolated starches from fresh pumpkin or flour

Physicochemical properties (pasting and thermal properties, swelling power, water solubility and antioxidant activities) and chemical composition of pumpkin flour (PF) and starches, isolated from fresh pumpkin (SFF) or flour (SFP) were compared. SFP and SFF had similar proximate composition and amylose content. Drying process during PF preparation modified starch properties. PF exhibited greater antioxidant activities (DPPH, ABTS and FRAP), but had lower β‐carotene than fresh pumpkin. SFF and SFP had higher amylose content than PF, and exhibited a B‐type X‐ray diffraction pattern with spherical and dome‐like starch granules. Peak viscosity of SFP was relatively higher than that of SFF, probably due to lower swelling power and water solubility, which indicated increased granular rigidity in the SFP starch structure. Compared with SFF and SFP, PF had significantly higher onset (T_o), peak (T_p) and conclusion (T_c) temperatures due to a lower starch content and relatively higher fibre content, which resulted in lower gelatinisation enthalpy (ΔH).     

Physicochemical properties of the starchy flour extracted from sweet potato tubers through lactic acid fermentation

The efficiency of starch extraction from sweet potato tubers was improved by lactic acid fermentation using a mixed culture inoculum. Study of the properties of the starchy flour showed that there was a significant reduction in the starch content and consequently the soluble and apparent amylose contents of fermented samples from all six varieties used. A fall in peak viscosity and viscosity breakdown was observed for fermented samples, while the pasting temperature was enhanced significantly. The fermented flour showed greater solubility and reduced swelling. Differential scanning calorimetry studies indicated a delay in gelatinisation and a fall in enthalpy of gelatinisation of the starch on fermentation. Unlike cassava, all the properties of the starch from sweet potato tubers, ie viscosity, swelling, solubility, gelatinisation temperature, amylose content and starch content, were affected by fermentation, and variation was also observed among cultivars. Copyright © 2005 Society of Chemical Industry     

Physicochemical Properties of Pin Oak (Quercus palustris Muenchh.) Acorn Starch

Physicochemical properties of acorn (Quercus palustris) starch were studied. Acorn starch granules were spherical or ovoid, with diameters ranging from 3–17 μm. Acorn starch exhibited A‐type X‐ray diffraction pattern, an apparent amylose content of 43.4% and absolute amylose content of 31.4%. Relative to other A‐type starches, acorn amylopectin had a comparable weight‐average molar mass (3.9×10⁸ g/mol), gyration radius (288 nm) and density (16.3 g mol⁻¹nm⁻³). Average amylopectin branch chain‐length corresponded to DP 25.5. Onset gelatinization temperature was 65.0°C and peak gelatinization temperature was considerably higher (73.7°C). The enthalpy change of gelatinization was very high compared to non‐mutant starches (20.8 J/g). An amylose‐lipid thermal transition was not observed. Starch retrograded for 7 d at 4°C had very high peak melting temperature (54.2°C) relative to other A‐type starches. Final (260 RVU) and setback (138 RVU) viscosity of an 8% acorn starch paste was high relative to other starches and pasting temperature was 71.5°C.     

Effect of γ-ray irradiation on starch granule structure and physicochemical properties of rice

Irradiation, an effective method to change starch structure and its functionalities, was carried out before traditional air-drying. Effect of irradiation on the structural and physicochemical properties of rice starch and contrast with that of non-irradiated and traditional air-dried rice was studied in this research. Micrology observation of microstructure of starch, at outer and inner layer rice endosperm, showed that the starch granules would be destroyed by gamma irradiation, and the breakage was increased with increasing dose. Effect of gamma irradiation on microstructures of inner endosperm was greater than that of outer endosperm. Chemistry examination and RVA rice viscosity analysis were carried out on the air-dried rice. Apparent amylose content, gel consistency and gelatinisation temperature were all affected by irradiation pre-treatment. Apparent amylose content was decreased, and gel consistency and gelatinisation temperature were increased with increasing dose. These affects generally related to the changes of starch structure. With the analysis of RVA, six major parameters of starch pasting properties, peak viscosity (PKV), hot pasting viscosity (HPV), cool pasting viscosity (CPV), setback (CPV minus PKV), breakdown (PKV minus HPV), and peak time (PKT), were significant decreased with the increasing dose by different velocity. There were high correlation coefficient between dose and individual major parameters of starch pasting properties (range from 0.961 to 0.998). These changes of pasting properties were also due to the breakage of starch granules caused by gamma irradiation.     

Pasting and rheological properties of quinoa‐oat composites

Quinoa (Chenopodium, quinoa) flour, known for its essential amino acids, was composited with oat products containing β‐glucan known for lowering blood cholesterol and preventing heart disease. Quinoa–oat composites were developed and evaluated for their pasting and rheological properties by a Rapid Visco Analyzer (RVA) and an advanced rheometer. All quinoa–oat composites showed increased pasting viscosities with increases in oat contents. The elastic modulus G′ and viscous modulus G″ for all quinoa–oat composites were higher than quinoa, suggesting that oat products increased the viscous properties of composites. Shear‐thinning properties were observed for all the composites. Improved water‐holding capacities (WHC) were found for the composites containing quinoa with nutrim or oat bran concentrate compared to quinoa alone. All the WHC of quinoa–oat composites were increased with the higher amounts of oat components. These quinoa–oat composites have improved nutritional value and texture qualities suitable for functional food applications.     

Physicochemical,crystallinity, pasting and thermal properties of heat‐moisture‐treated pinhão starch

The effect of heat‐moisture treatment (HMT) on the properties of pinhão starches under different moisture and heat conditions was investigated. The starches were adjusted to 15, 20 and 25% moisture levels and heated to 100, 110 and 120°C for 1 h. The X‐ray diffractograms, swelling power, solubility, gel hardness, pasting properties and thermal properties of the native and HMT pinhão starches were evaluated. Compared to native starch, there was an increase in the X‐ray intensity and gel hardness of HMT starches, with the exception of the 25% moisture‐treated and 120°C heat‐treated starch. HMT reduced the swelling power and solubility of the pinhão starches when compared to native starch. There was an increase in the pasting temperature, final viscosity and setback and a decrease in the peak viscosity and breakdown of HMT pinhão starches compared to native starch. HMT increases the gelatinisation temperature of native pinhão starch and reduces gelatinisation enthalpy.     

Physicochemical and structural characteristics of starches from Chinese hull‐less barley cultivars

Fourteen hull‐less barley cultivars, collected from four major cultivated areas in China, were employed to investigate the structural and physicochemical properties of their starches in this study. Relatively wide variations in physicochemical properties of the starches were observed. Amylose content ranged from 23.1% to 30.0%, swelling power and water solubility index ranged from 12.8 to 19.9 g g^?1 and 12.7% to 23.7% respectively. Peak viscosity was from 170 to 346 Rapid Visco Unit (RVU), peak temperature (T_p) of starch gelatinisation was from 55.6 to 61.8 °C and enthalpy of starch retrogradation ranged from 0.3 to 3.1 J g^?1. Weight‐based chain‐length proportions of fa, fb₁, fb₂ and fb₃ in amylopectins ranged from 21.65% to 24.95%, 44.48% to 49.44%, 15.56% to 17.19% and 9.83% to 16.66% respectively. Correlation analyses showed that amylose content was inversely related to pasting parameters and enthalpy of gelatinisation. Pasting properties and amylopectin structures were the most important parameters to differentiate starch properties among different hull‐less barley cultivars in this study. This work will be useful for exploring applications of Chinese hull‐less barley starches in food and non‐food industries.     

Impact of Guar and Wheat Bran on the Physical and Nutritional Quality of Extruded Breakfast Cereals

Two non‐starch polysaccharides, guar gum and wheat bran, were used at 15% replacement level in a cereal base to produce an extruded breakfast cereal product from both wholemeal and high‐ratio wheat flour mixes. The inclusion of the non‐starch polysaccharides into the flour bases had no significant effect on the expansion ratio of the products. However, the product density and bulk density of the extruded products increased with guar gum and wheat bran addition. The pasting properties of the raw flour and polysaccharide base as well as the extruded products were altered with the incorporation of polysaccharides, with guar gum‐enriched products showing elevated peak and final viscosity readings. This appeared to be related to moisture manipulation and hence the regulation of gelatinisation. In vitro starch hydrolysis of the raw bases and the extruded samples illustrated that the extrusion process significantly increased the availability of carbohydrates for digestion. Additionally, the inclusion of non‐starch polysaccharides in the raw bases significantly reduced the rate and extent of carbohydrate hydrolysis. This potentially glycaemic reducing action was also evident in the extruded products where the incorporation of guar gum at 15% yielded a reduction of starch hydrolysis of 36% in the wholemeal base and 32% in the high‐ratio white wheat flour base.     

Physicochemical properties,digestibility and expected glycaemic index of high amylose rice differing in length-width ratio in Sri Lanka

Gelatinization, pasting, digestibility and estimated glycaemic index of six high amylose rice varieties differing in length/width ratio were studied. Amylose content ranged narrowly (27.8–29.1%). Resistant starch content ranged from 0.44% to 1.4%. In contrast to gelatinisation enthalpy, gelatinisation temperature (GT) ranged narrowly (76.7–77.4 °C). For all rice varieties, melting temperature of amylose-lipid complex I and II was around 99 °C and 110 °C, respectively. The enthalpy of amylose-lipid complex I and II ranged between 0.18–0.87 and 0.23–0.55, respectively. Expected in vitro glycaemic index (GI) of all tested varieties was similar (88.2–92.4). The results showed that the size of the rice grain (length/width) and resistant starch content had no apparent impact on the GI of high amylose rice. The dominant factors determining the digestibility and glycaemic response of the tested high amylose rice varieties seemed to be amylose content and the GT. Besides the pasting temperature, other pasting properties varied significantly but were not correlated to starch digestibility and estimated GI among the six rice varieties. Thus, RVA pasting properties, except for pasting temperature, may not be good predictors for the GI of these high amylose rice.     

Effects of high hydrostatic pressure on microstructure,physicochemical properties and in vitro digestibility of oat starch/β-glucan mixtures

Oats do not contain gluten protein, and oat dough structure is formed mainly through the hydrogen bonding of starch and β-glucan. As a non-thermal processing technology, high hydrostatic pressure (HHP) is mainly used to modify starch and protein in food processing. This study investigated the effects of HHP treatment on the morphological, structural, thermal, pasting and in vitro digestion properties of oat starch/β-glucan mixtures. Results showed that β-glucan interconnects with amylose through hydrogen bonding and has a protective effect on the crystalline region of oat starch. Effect of HHP treatment on the crystal structure of mixture system goes through crystal structure perfection stage, crystallisation disintegration and gelatinisation stage. After 300–400 MPa treatment, the changes in particle surface were not obvious, the phase transition temperature, the ΔH_gel and the PT of mixtures increased, while the particle size, viscosity and BD values decreased. After 500–600 MPa treatment, mixtures were completely gelatinised, most of the particles swelled and deformed, the particle size increased significantly. The principal component analysis results show that the complexes were distributed in the same region with similar properties after the 300–400 MPa and 500–600 MPa treatments, respectively.     

Structure‐Viscosity Relationships for Thai Rice Starches

The viscosities of five Thai rice starches with different amylose contents were measured by rotational rheometry and using a Rapid Visco Analyser. The viscosity response was interpreted in terms of the swelling volume and the structural properties of the granule determined by calorimetry, infrared spectroscopy and X‐ray diffraction. It was found that the waxy rice starches had a higher swelling volume resulting in a higher viscosity than the other rice classes. Critical concentrations for close packing, identified from the concentration where the flow behaviour departs from Newtonian, were 2.5%, 1.5% and 1.10% for the high amylose, medium amylose and waxy rice starch, respectively. An exception to this was a commercial high amylose starch that had a critical concentration similar to the medium amylose category. This was ex‐plained in terms of a relatively higher loss of short‐range molecular order on gelatini‐sation as shown by FTIR for this starch. Medium amylose Jasmine rice starch, extracted from rice that had been aged for 5 months, showed differences in granule size, crystallinity, pasting profile and enthalpy of gelatinisation when compared with the results for starch extracted from freshly harvested rice. This was provisionally interpreted in terms of granule damage during the extraction process, though more work would be required to confirm this interpretation.     

Physicochemical, pasting and thermal properties of tuber starches as modified by guar gum and locust bean gum

This study was carried out in order to compare the functional characteristics of isolated starch from five tuber crops, yam, taro, sweet potato, yam bean and potato, as well as effect of guar gum (GG) and locust bean gum (LBG) on pasting and thermal properties of tuber starches. The results showed that total amylose content of five tested starches ranged from 17.85% to 30.36%. The results of pasting behaviour showed that potato starches exhibited the highest peak viscosity and yam starch presented a stable curve with little breakdown viscosity. Addition of GG and LBG resulted in a significant increase in peak, final viscosity, breakdown and setback viscosity for all tuber starches ( P  < 0.05), but a slight decrease in pasting temperature. The gelatinisation enthalpy (Δ H ) for starches with GG and LBG was slightly lower than those of the starches alone in yam and sweet potato, but not in taro and yam bean.     

Physicochemical properties and in vitro digestibility of flours and starches from taro cultivated in different regions of Thailand

This research aimed to study physicochemical properties and in vitro digestibility of flours and starches from taro cultivated in different regions of Thailand, that is, Kanchanaburi (KB), Chiang Mai (CM), Phetchaburi (PB) and Saraburi (SB). Taro starches were extracted from taro flours using either water or alkaline extraction. The taro flours had significantly (P ≤ 0.05) larger particle size, higher pasting and gelatinisation temperatures, and resistant starch content but lower total starch content, whiteness (L* value), paste viscosities and clarity than their corresponding extracted starches. All the taro starches exhibited polygonal and irregular granules and gave A-type X-ray diffraction pattern. The alkaline-extracted taro starches had significantly (P ≤ 0.05) higher extraction yield, total starch content, L* value, pasting and gelatinisation temperatures, and paste clarity but lower granular size, amylose content, resistant starch content, paste viscosities and relative crystallinity than their water-extracted counterparts.     

Physicochemical and Gelatinization Properties of Starches Separated from Various Rice Cultivars

Morphological, viscoelastic, hydration, pasting, and thermal properties of starches separated from 10 different rice cultivars were investigated. Upon gelatinization, the G′ values of the rice starch pastes ranged from 37.4 to 2057 Pa at 25 °C, and remarkably, the magnitude depended on the starch varieties. The rheological behavior during gelatinization upon heating brought out differences in onset in G′ and degree of steepness. The cultivar with high amylose content (Goami) showed the lowest critical strain (γ_c), whereas the cultivars with low amylose content (Boseokchal and Shinseonchal) possessed the highest γ_c. The amylose content in rice starches affected their pasting properties; the sample possessing the highest amylose content showed the highest final viscosity and setback value, whereas waxy starch samples displayed low final viscosity and setback value. The onset gelatinization temperatures of the starches from 10 rice cultivars ranged between 57.9 and 64.4 °C. The amylose content was fairly correlated to hydration and pasting properties of rice starches but did not correlate well with viscoelastic and thermal characteristics. The combined analysis of hydration, pasting, viscoelastic, and thermal data of the rice starches is useful in fully understanding their behavior and in addressing the processability for food applications.     

Influence of whey protein isolate on pasting,thermal, and structural characteristics of oat starch

We investigated the effects of different concentrations of whey protein isolate (WPI) on oat starch characteristics in terms of pasting, thermal, and structural properties. The pasting properties of the starch showed that hot paste viscosity increased with the addition of WPI in the system, and relative breakdown decreased. Thermal analysis showed a significant effect of WPI on oat starch by increasing the peak temperature of differential scanning calorimeter endotherms. The X-ray diffraction and Fourier transform infrared spectroscopy studies revealed that WPI increased the ordered structuration of starch paste, as evident by an increase in relative crystallinity; in addition, a decrease in infrared bands at 1,024 cm^?1 and 1,080 cm^?1 suggested decreased gelatinization of oat starch granules. Overall, WPI at different concentrations affected the oat starch gelatinization properties.