BRAZILIAN HULL-LESS AND MALTING BARLEY GENOTYPES: I. CHEMICAL COMPOSITION AND PARTIAL CHARACTERIZATION

Barley represents an important source of total dietary fiber (TDF) and β‐glucans. The chemical composition and partial characterization of two Brazilian barley experimental lines, hull‐less and malting, are reported. The range in diameter of the A‐ and B‐type granules was similar in both barley lines, 15 to 28 µm and 8 to 10 µm, respectively. Higher values for total starch, damage starch, ash, TDF and insoluble dietary fiber (IDF) were observed in the malting line while β‐glucan content was similar in both samples. The malting barley line had higher values of total isolated starch, as well as residual protein and total lipids in starch. The starch from the hull‐less barley line had lower swelling power and higher solubility than malting barley.     

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.     

Fine Structure,Thermal and Viscoelastic Properties of Starches Separated from Indica Rice Cultivars

Starches were separated from indica rice cultivars (PR‐113, Basmati‐370, Basmati‐386, PR‐115, IR‐64, and PR‐103) and evaluated using gel permeation chromatography (GPC), X‐ray diffraction, differential scanning calorimetry (DSC) and dynamic viscoelasticity . Debranching of starch with isoamylase and subsequent fractionation by GPC revealed 9.7–28.3% apparent amylose content, 3.7–5.0% intermediate fraction (mixture of short amylose and long side‐chains of amylopectin), 20.6–26.6% long side‐chains of amylopectin and 45.8–59.4% short side‐chains of amylopectin). IR‐64 starch with the highest crystallinity had the highest gelatinization temperatures and enthalpy, T_o, T_p, T_c, and ΔH_gel being 71.8, 75.9, 82.4°C and 5.1 J/g, respectively, whereas PR‐113 starch with lower crystallinity showed the lowest gelatinization temperatures (T_o, T_p, T_c, of 60.8, 65.7 and 72.2°C, respectively). Basmati‐386 starch exhibited two endotherms during heating, the first and second endotherm being associated with the melting of crystallites and amylose‐lipid complexes, respectively. T_o, T_p, T_c and ΔH_gel of the second endotherm of Basmati‐386 starch were 99.0, 100.1, 101.1°C and 2.0 J/g, respectively. During cooling, Basmati‐386 also showed an exotherm at a peak temperature of 87°C. PR‐113 starch with the highest amylose content and the lowest content of short side‐chains of amylopectin had the highest peak storage modulus (G′= 1.6×10⁴ Pa). The granules of PR‐113 starch were the least disintegrated after heating. The effects of heating starch suspensions at different temperatures (92°C, 130°C and 170°C) on intrinsic viscosity [η], transmittance and viscoelasticity were also studied to evaluate the extent of breakdown of the molecular structure. The intrinsic viscosity of starch suspensions heated at 92, 130 and 170°C ranged between 103–114, 96–110 and 28–93 mL/g. Transmittance value of starches cooked at 92°C decreased with increase in storage duration. All starches except PR103, cooked at 130°C also showed decrease in transmittance during storage, however, at lower rate. PR103 starch heated at 130°C did not show any change in transmittance up to a storage time of 48 h. The changes in viscoelasticity of starch pastes cooked at different temperatures during cooling and reheating were also evaluated. G′ and G′′ increased with decrease in temperature during cooling cycle. Starches heated at 130°C with apparent amylose content ≤ 21.2% showed an improvement in G′ and G′′ in comparison to the corresponding starches heated at 92°C, this improvement was observed to be higher in starches with lower amylose content. All starches heated at 170°C had a higher proportion of breakdown in molecular structure as indicated by lower G′ and G′′ than the same starches heated at 130 and 92°C.     

Studies on the morphological,thermal and rheological properties of starch separated from some Indian potato cultivars

The starches separated from five different Indian potato cultivars (Kufri Chandermukhi, Kufri Badshah, Kufri Jyoti, Kufri Sindhuri and S1) were investigated for morphological, thermal, rheological, turbidity and water-binding properties. The starch separated from all the five potato cultivars had a granule size ranging between 15–20 μm and 20–45 μm. The shape of starch granules varied from oval to irregular or cuboidal. Starch isolated from cv. Kufri Badshah had largest irregular or cubiodal granules while starch from cv. Kufri Chandermukhi had small and oval granules. The transition temperatures and enthalpy of gelatinization (ΔH_gel) were determined using differential scanning calorimetry (DSC). The enthalpy of retrogradation (ΔH_ret) of gelatinized starch was also determined after 14 days of storage at 4°C using DSC. Kufri Chandermukhi starch showed the lowest ΔH_gel and ΔH_ret while Kufri Badshah starch showed the highest values. ΔH_gel and ΔH_ret values of 12.55 J/g and 6.42J/g, respectively, for Kufri Chandermukhi starch against 13.85 J/g and 8.61 J/g, respectively, for Kufri Bhadshah starch were observed. Rheological properties of starches from different potato cultivars, measured using the Dynamic Rheometer during heating and cooling, also differed significantly. The starch from cv. Kufri Badshah showed the highest peak G′ and G″ and lowest tan δ. The starches having higher peak G′(G′ at gelatinization temperature) showed higher breakdown in G′ and vice versa. The turbidity of gelatinized aqueous starch suspensions from all potato cultivars increased with increase in storage period. Starches with low water binding capacity had higher G′ and G″ and lower tan δ values.     

Physicochemical properties of starch isolated from Antiaris africana seeds in comparison with maize starch

Antiaris africana seeds yielded 29.6% starch which showed appreciable high contents of ash, protein, and fat. The average diameter of A. africana starch granules was 3.98 µm compared to 8.93 µm for maize starch. A. africana starch had a C‐type XRD pattern and crystallinity of 41.5%. A. africana starch had higher AM content (24.1%) than maize starch (20.9%). The gelatinization onset temperature of A. africana starch (66.7°C) was higher than maize starch (63.1°C), but its gelatinization temperature range (8.57°C) and enthalpy (13.97 J/g) were lower than the values for maize starch (14.02°C, 14.65 J/g). The pasting temperature (P_t) and setback (V_s) were lower and breakdown (V_b) higher for A. africana starch (P_t = 82.5°C, V_s = 173.8 RVU, and V_b = 121.42 RVU) than for maize starch (P_t = 84.9°C, V_s = 183.73 RVU, and V_b = 78.58 RVU). The GPC analysis gave M_w of 2.18 × 10⁷ g/mol and radius of gyration of 95.1 nm for Antiaris starch. Antiaris starch paste exhibited poor freeze‐thaw stability but its small granule size indicates potential for application as dusting starch.     

Starch granule-associated proteins of hull-less barley (Hordeum vulgare L.) from the Qinghai-Tibet Plateau in China

BACKGROUND: The starch granule‐associated proteins (SGAPs) are the minor components of the starch granules and a majority of them are believed to be starch biosynthetic enzymes. The Qinghai‐Tibet Plateau in China, one of the centres of origin of cultivated barley, is abundant in hull‐less barley resources which exhibit high polymorphism in SGAPs. RESULTS: The SGAPs of hull‐less barley from Qinghai‐Tibet Plateau were analysed by one‐dimensional (1‐D) SDS‐PAGE, 2‐D PAGE and ESI‐Q‐TOF MS/MS. In the 1‐D SDS‐PAGE gel, four proteins including a 80 kDa starch synthase, actin, actin 4 and ATP synthase β‐subunit were identified as novel SGAPs. A total of six different bands were identified as starch granule‐bound starch synthase I (GBSSI) and the segregation of the novel GBSSI bands in F₁ and F₂ seeds derived from yf127 × yf70 was in accordance with Mendel's law. In the 2‐D PAGE gel, 92 spots were identified as 42 protein species which could be classified into 15 functional groups. Thirteen protein species were identified as SGAPs for the first time and multiple spots were identified as GBSSI. CONCLUSION: This study revealed novel SGAPs in hull‐less barley from the Qinghai‐Tibet Plateau in China and these will be significant in further studies of starch biosynthesis in barley. Copyright © 2011 Society of Chemical Industry     

The influence of steep regime and germination period on the malting properties of some hull‐less barley lines

Following field trials in 2008 and 2010, six lines, derived by mutation in the hull‐less barley cultivar Penthouse, were selected to provide a range in grain β‐glucan content. These lines, along with Penthouse and the hulled, malting variety Optic, were then malted, using four different steeping regimes, with samples kilned after 3, 4 and 5 days of germination. The longest steep regime provided samples with optimum modification after 5 days of germination. Samples from the other steep regimes were under‐modified to varying degrees. In particular, the steeps with a single immersion gave poorly modified samples with low extracts and alcohol yields. One line, with low grain β‐glucan, gave higher alcohol yields than either Penthouse or Optic, following a regime comprising two short immersions and a single air‐rest, but there was no clear association, within the lines, between β‐glucan content and malting properties. Copyright © 2012 The Institute of Brewing & Distilling     

Properties of novel starch isolated from Castanopsis cuspidate fruit grown in a subtropical zone of Korea

To develop a plant-based biomaterial source, the physicochemical properties of starch from Castanopsis cuspidate fruit, grown in Jindo, Korea, were investigated. The starch was isolated from the fruit using an alkali steeping method. This starch had high amylose content (56.1%). The total dietary fiber and water binding capacity of starch were 7.1 and 140.8%, respectively. The swelling power of the starch increased more rapidly than that of the flour, and the solubility of the flour was higher than that of the starch but it did not change with increasing temperature. The starch exhibited B-type crystallinity, and the starch granules were polygonal or irregular shapes. The initial pasting temperature of the flour was higher than that of the starch. The peak, trough, and final viscosities of the starch were 631.1, 364.4, and 461.8 RVU, respectively. The starch for onset gelatinization temperature (T_o), peak temperature (T_p), conclusion temperature (T_c), and enthalpy of gelatinization (δH) were 56.0, 61.3, 72.4°C, and 14.1 J/g, respectively.     

Physicochemical,Thermal, Morphological and Pasting Properties of Starches from some Indian Black Gram (Phaseolus mungo L.) Cultivars

The starches separated from thirteen different black gram cultivars were investigated for physicochemical, thermal, morphological and pasting properties. Amylose content, swelling power, solubility and water binding capacity of starches ranged between 30.2–34.6%, 16.0–22.3 g/g, 14.8–17.3% and 73.5–84.5%, respectively. The diameter of starch granules, measured using a laser‐light scattering particle‐size analyzer, varied from 12.8 to 14.3 μm in all black gram starches. The shape of starch granules varied from oval to elliptical. The transition temperatures (T_o, T_p and T_c) and enthalpy of gelatinization (ΔH_gel) determined using differential scanning calorimetry, ranged between 66.1–71.3, 71.0–76.2, 75.9–80.4°C and 6.7–9.4 J/g, respectively. Pasting properties of starches measured using the Rapid Visco Analyser (RVA) also differed significantly. Pasting temperature, peak viscosity, trough, breakdown, final viscosity and setback were between 75.8–80.3°C, 422–514, 180–311, 134–212, 400–439 and 102–151 Rapid Visco Units (RVU), respectively. Turbidity values of gelatinized starch pastes increased during refrigerated storage. The relationships between different properties were also determined using Pearson correlation coefficients. Amylose content showed a positive correlation with swelling power, turbidity and granule diameter. Swelling power showed a negative correlation with solubility and setback. T_o, T_p and T_c showed positive correlation with turbidity, pasting temperature and were negatively correlated to peak and breakdown viscosity.     

Potential of Hull‐less Barley Malt for Use in Malt and Grain Whisky Production

Hull‐less (or husk‐less) barley is possibly one of the most important developments in barley in recent years. This study looked at the potential of hull‐less barley for use by the Scotch whisky industry. By modifying the malting conditions for hull‐less barley, it was possible to provide good alcohol yield as well as significant improvements in processing characteristics. The biochemistry controlling the germination of hull‐less barley was consistent with established knowledge about ‘normal’ hulled barley except that care is needed to ensure the consistency of feedstock, particularly since hull‐less barley may be prone to embryo damage during harvesting in the field. Our results indicated that the new batches of hull‐less barley studied, produced malt that gave much improved mash filtration rates in comparison with previous batches of material. These experiments demonstrated that by changing the malting conditions, to give a much shorter steeping cycle (8 h), it is possible to reduce water usage substantially in the malting industry, since only one ‘wet’ cycle was used, and also reduce germination times since optimum alcohol yield was achieved on day 4 germination rather than day 5 for conventional husked barley. This could save costs in terms of water, energy and time for the malting industry. The study also confirmed the potential of hull‐less barley for providing significant benefits for Scotch whisky distillers, both in terms of higher alcohol yields, and increased throughput, by showing that it is possible to overcome some of the filtration issues that have been previously associated with hull‐less barley. This study indicated that the new material was better suited than previous batches to both malt and grain distilling, both in terms of enzyme development and potential distillery performance, and further showed that viscosity problems associated with grain distillery co‐products can be significantly reduced when using hull‐less barley malt in the grain distillery. These would be substantial potential benefits for the Scotch whisky distilling industry.     

Characteristics of native and enzymatically hydrolyzed common wheat (Triticum aestivum) and dicoccum wheat (Triticum dicoccum) starches

The compositional, structural, and enzymatic digestibility of starches isolated from common wheat and dicoccum wheat were determined to find out the possible reason for hypoglycemic nature of dicoccum wheat. The gelatinization temperature range (65±3 °C) as well as the elution profile of both the starches on Sepharose CL-2B gel were comparable, but the peak (PV, 233 RVU) and set back viscosity (SB, 140 RVU) of dicoccum wheat starch were higher than common wheat starch (PV, 211 RVU; SB, 113 RVU) as recorded in rapid visco-analyser (RVA). The degree of crystallinity (DOC: 29%) and the thermal energy (TE: 142.35 J) of dicoccum wheat starch were considerably higher than the DOC (23%) and TE (67.82 J) of the common wheat starch. The starches were digested with alpha-amylase (human salivary), beta-amylase (barley malt), pullulanase (Klebsiella pneumoniae), and amyloglucosidase (Aspergillus niger), and the solubilized fraction was separated from the undigested fraction (residue) by centrifugation. Characterization of the sugars in the solubilized fraction from alpha-amylase were glucose, maltose, and oligosaccharides of 3–7 DP, maltose from beta-amylase, maltotriose from pullulanase and glucose from amyloglucosidase. However, the molecular weight (M _w) of the residues from the enzymatic digestion of dicoccum wheat starch was slightly higher than that of the common wheat starch. The microscopic examination of residues also exhibited a few bigger chunks in case of dicoccum wheat starch and a large number of smaller sized pieces in the case of common wheat starch. Since, starch is the major component of wheat, these parameters may help to explain subtle differences in the digestibility that exist between common wheat and dicoccum wheat.     

Impact of arabinoxylan with different molecular weight on the thermo‐mechanical,rheological, water mobility and microstructural characteristics of wheat dough

The aim of this study was to investigate the effects of arabinoxylan with different molecular weight on the wheat dough thermo‐mechanical, rheological, microstructural and water mobility properties. Arabinoxylan was extracted from wheat bran and hydrolysed by endo‐1,4‐β‐xylanase (EC 3.2.1.8 from Trichoderma reesei, 10 000 U g^?1) for 2 min (AX_M) and 10 min (AX_L), respectively. The addition of hydrolysed arabinoxylan AX_L increased the stability time, decreased the setback value of wheat dough and enhanced the values of storage modulus (G′) and loss modulus (G″), while unhydrolysed arabinoxylan (AX_H) reduced these values. Meanwhile, unhydrolysed arabinoxylan increased T₂ relaxation time while hydrolysed arabinoxylan AX_L decreased T₂₁ and T₂₂. Confocal laser scanning microscope (CLSM) results showed that the addition of hydrolysed arabinoxylan AX_L promoted the formation of a more compact and continuous protein network in wheat dough. These results revealed that compared with high molecular weight arabinoxylan, hydrolysed arabinoxylan could improve the rheological properties and processing properties of wheat dough by enhancing the interaction among water molecules, starch and gluten in wheat dough.     

A study of the effect of the drying process on the composition and physicochemical properties of flours obtained from durian fruits of two ripening stages

Durian cv. Monthong with two ripening stages (unripe and fully ripe) was subjected to microwave vacuum drying (MWD) at 5.49 W g^?1 and hot air drying (HAD) at 60 °C. With an increase in ripening degree, the starch content was significantly (P ≤ 0.05) decreased from 40.08–40.42% to 9.44–11.76%. X‐ray diffraction indicated that the crystalline pattern was changed from starch to sucrose. The starch granule morphology of durian flour was conserved for both drying conditions. Peak gelatinisation temperatures of MWD and HAD flours were increased significantly (P ≤ 0.05) from 56.71–57.32 to 60.71–61.23 °C. Using different drying methods, MWD flour had less a*‐value (P ≤ 0.05) than HAD flour. The peak viscosity and trough of the HAD unripe durian flour (5.92 RVU and 3.45 RVU, respectively) were significantly (P ≤ 0.05) lower than those of the MWD unripe durian flour (34.32 RVU and 11.57 RVU, respectively).     

Thermal and Molecular Characterization of Aspergillus awamori Glucoamylase Catalytic and Starch‐Binding Domains

Aspergillus awamori glucoamylase catalytic domain, linker, and starch‐binding domain, the first and third expressed from yeast, have molecular masses of 56.2, 12.6 and 12.9 kDa, respectively, as determined by MALDI‐TOF mass spectroscopy, and have 10.2, 73.2 and 7.0 % (w/w) carbohydrate, respectively, showing overglycosylation by yeast. Unfolding of the starch‐binding domain monitored by circular dichroism is reversible at pH 6.0—8.0, with the unfolding T_m and ΔH increasing from 49.7 to 58.5 °C and from 284 to 351 kJ/mol, respectively, as pH decreases from 8.0 to 6.0. The catalytic domain unfolds irreversibly at pH 7.5, producing a single asymmetric endotherm by differential scanning calorimetry, with T_m and ΔH at a 1 °C/min heating rate being 60.9 °C and 1720 kJ/mol, but with both increasing as the heating rate increases. This suggests that unfolding is partially under kinetic control, while various tests show that it does not follow a simple two‐state irreversible model. Values of ΔH from calculated solvent‐accessible surface areas of unglycosylated catalytic and starch‐binding domains are about 100 kJ/mol lower than experimentally determined ΔH values of the corresponding glycosylated domains, showing the effect of glycosylation on unfolding enthalpies.     

Structure and Viscoelastic Properties of Starches Separated from Different Legumes

A 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 (T_o T_p and T_c, respectively) were determined by differential scanning calorimetry. T_o and T_c 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 (ΔH_gel) 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.     

The effect of starch gelatinization and solute concentrations on T g′ of starch model system

The effect of starch gelatinization on glass transitions in a starch/water model system and how the concentrations of added solutes (sucrose and sodium chloride) affect the glass transition temperatures of the gelatinized starch solution was investigated. The starch suspension samples were heat treated in a Differential Scanning Calorimeter (DSC) under different time and temperature regimes to achieve different degrees of gelatinization. The gelatinization characteristics (onset, peak and end temperatures and enthalpy) and the glass transition values of a potato starch were determined using the DSC. The results showed that the starch concentrations had no effect on gelatinization characteristics and the T_g′ of the gelatinized potato starch but had clearly increased their ΔC_p in the T_g′ region. Annealing at a temperature slightly below the T_g′ of −5 °C, led to maximal freeze‐concentration in the total/partial gelatinized starch and a higher T_g′ value at about −3 °C was obtained. The T_g′ values of the totally gelatinized starch samples were slightly lower than those of partially gelatinized samples. The T_g′ of the gelatinized starch decreased with increasing concentrations of sucrose or sodium chloride. Sodium chloride had a stronger depressing effect on T_g′ than sucrose. © 2000 Society of Chemical Industry     

Antioxidant Properties of Free,Soluble Ester and Insoluble‐Bound Phenolic Compounds in Different Barley Varieties and Corresponding Malts

Ten different barley cultivars and their corresponding malts were used to obtain different fractions. Phenolics extracted belonged to free, soluble esters and insoluble‐bound fractions. Total phenolic content (TPC) of the free fraction, as measured according to the Folin‐Ciocalteu method, ranged from 37.7 to 167.2 mg gallic acid equiv/kg of dried material (GAE/kg_dw) for barley and between 34.1 and 72.3 mg GAE/kg_dw for malt. The bound phenolic content ranged from 210.3 to 320.5 and between 81.1 and 234.9 mg GAE/kg_dw for barley and malt, respectively. The contribution of bound phenolics to the TPC was significantly higher than that of free and esterified fractions. Catechin and ferulic acid, quantified by high performance liquid chromatography with diode array detector (HPLC‐DAD), were the most abundant phenolics in the free and bound fractions, respectively. The p‐coumaric acid content was lower in hulless genotypes, as compared to hulled genotypes, showing that it is mainly concentrated in the hull. The antioxidant activities of the phenolic fractions were investigated using the radical scavenging assay (DPPH) and ferricyanide reducing power. The bound phenolics demonstrated a significantly higher antioxidant capacity compared to the free and esterified phenolics. During the malting process, a significant decrease of the bound phenolics was observed with a corresponding increase of the esterified fraction.     

Starch Properties of a Waxy Mutant Line of Hull‐less Barley (Hordeum vulgare L.)

Endosperm starch isolated from an amylose‐free waxy mutant hull‐less barley line, Shikoku Hadaka 97, had an amylose content of 0.3% and higher swelling power than ordinary waxy barley cultivars/lines with amylose contents of 2.2—6.5%. A highly significant correlation was observed between amylose content and swelling power among waxy barley starches. No clear differences were detected in the chain‐length distribution profiles or thermal properties between the amylose‐free starch and ordinary waxy starch. The chain‐length distribution profile of waxy barley starch was slightly different from that of normal barley starch. Gelatinization temperatures and gelatinization enthalpy of waxy barley starch were higher than those of normal barley starch. Significant correlations were observed between amylose content and thermal properties of starch samples analyzed. Waxy barley starch stained with a concentrated iodine‐potassium iodide solution showed a ghost‐like appearance.     

Effect of Osmotic Pressure on Starch: New Method of Physical Modification of Starch

A new method of physical modification of starch in the presence of high concentrated salt solution is presented, called “Osmotic Pressure Treatment” (OPT). OPT was introduced in order to produce the same physically modified products as obtained by conventional heat‐moisture treatment (HMT) of starch. Potato starch was selected for the comparative study of the two methods. For the OPT method, potato starch was suspended in a saturated solution of sodium sulfate and heated in an autoclave at 105°C and 120°C ,which corresponded to the calculated osmotic pressures of 328 and 341 atm (332 and 345 bar, respectively) (assuming sodium sulfate dissociates completely) for 15, 30 and 60 min, respectively. For the HMT method, starch with 20% moisture content was placed in a Duran bottle, then the same heat treatment method in the autoclave was applied. Light and scanning electron microscopy (SEM) showed that OPT of starch changed the shape of the starch granules to a folded structure, while the starches remained unchanged after HMT. The RVA viscogram for the OPT starch exhibited a decrease in the peak viscosity without a breakdown and an increase of the pasting temperature when increasing the temperature and time, which was in an agreement with the viscosity patterns for the HMT starches. X‐ray diffraction patterns were altered from B to A+B for the HMT and from B to A type for the OPT starch when treated at 120°C. After OPT, the gelatinization temperatures (T_o, T_p, and T_c) of the starch increased significantly with increasing temperature and time, whereas only the T_c of starch increases after HMT. The biphasic broadening of the peaks (high T_c‐T_o) can be explained by an inhomogeneous heat transfer during HMT. Narrow peaks in the DSC curve can be an indication for a better homogeneity of the OPT samples. However, both methods provide a similar decrease in the gelatinization enthalpy (ΔH). The amylose‐amylopectin ratio calculated from the HPSEC patterns was strongly increased for HMT starches at 105°C for 60 min and 120°C for 30 min and decreased after treatment at 120°C for 60 min. For OPT starches the ratio was strongly increased at 120°C for 15 min and decreased after prolong heating. The OPT provides a uniform heat distribution in the starch suspension. This allows the modified starch to be produced on a larger scale.     

Chemical and Physical Characterisation of Grain Tef [Eragrostis tef (Zucc.) Trotter] Starch Granule Composition

Chemical and physical properties of starch granules isolated from five grain tef (Eragrostis tef) varieties were characterised and compared with those of maize starch. Endogenous starch lipids extracted with hot water‐saturated n‐butanol and total starch lipids extracted with n‐hexane after HCl hydrolysis were 7.8 mg/g (mean) and 8.9 mg/g (mean), respectively, slightly lower than in the maize starch granules. The starch phosphorus content (0.65 mg/g) was higher than that of maize starch but virtually the same as reported for rice starch. The starch granule‐swelling factor was lower than that of maize starch and extent of amylose leaching was higher. The starch X‐ray diffraction pattern was characteristic of A type starch with a mean crystallinity of 37%, apparently lower than the crystallinity of maize starch and more similar to that reported for rice and sorghum starches. The starch DSC gelatinisation temperature was high, like for other tropical cereals; T_o, T_p, T_c and ΔH were in the range 63.8—65.4, 70.2—71.3, 81.3—81.5 °C and 2.28—7.22 J/g, respectively. The lower swelling, apparently lower percentage crystallinity and lower DSC gelatinisation endotherms than maize starch suggest that the proportion of long amylopectin A chains in tef starch is smaller than in maize starch.