Characterization of nanoparticles prepared by acid hydrolysis of various starches

Various starches of different AM contents and origins such as wx maize, normal maize, high AM maize, potato, and mungbean starches were hydrolyzed using a H₂SO₄ solution (3.16 M) at 40°C for 7 days, and the starch particles were isolated from the hydrolysates by centrifugation. The hydrolysis rates varied from 61.4 to 90.9% depending on the starch type. Unexpectedly, A‐type starches were more resistant to the acid hydrolysis than B‐type starches. XRD results revealed that the starch particles with B‐crystalline type exhibited a decrease in peak intensity. In addition, in a DSC analysis, the crystals remaining in the B‐type starch particles were readily disrupted in the water dispersion so that no melting endotherm appeared. Electron microscopy confirmed that the starch particles had round or oval shapes with diameters ranging from 40 to 70 nm, which possibly represented the starch blocklets in granules. The acid degraded mainly AM and long AP chains, resulting in increasing the proportion of short chains.     

Isolation and partial characterization of Mexican taro (Colocasia esculenta L.) starch

Taro starch was isolated from Mexican variety and its morphological, physicochemical, and molecular characteristics were evaluated. Yield starch (in dry basis) was 81%, and this starch had low AM content (2.5%). Taro starch granules showed a mixture of shapes with sizes between 1 and 5 µm. Taro starch presented an A‐type XRD pattern with a crystallinity level of 38.26%. Solubility and water retention capacity did not change in the temperature range of 50–70°C and thereafter they increased as temperature increased too. Taro starch showed high peak viscosity due to its high AP content. The peak temperature of gelatinization of taro starch was 80.6°C with an enthalpy value of 10.6 J/g, with low retrogradation rate due to its low AM content. Weight‐average molar mass (Mw) and gyration radius (Rz) of taro starch were 1.21 ± 0.8 × 10⁹ g/mol and 424 ± 70 nm, respectively. Taro tuber could be an alternative for starch isolation with functional and physicochemical characteristics for food and non‐food applications.     

An SEC−MALLS Study of Molecular Features of Water‐soluble Amylopectin and Amylose of Tef [Eragrostis tef (Zucc.) Trotter] Starches

The molecular features of five tef starches along with those of commercial normal maize starch were investigated by size‐exclusion chromatography with multi‐angle laser light scattering‐differential refractive index detection (SEC/MALLS‐DRI) after solubilization in water by cooking in a household pressure cooker. The weight‐average molar mass ( ) and weight‐average root‐mean square radius of gyration (<R_g>_w) of the amylopectin (AP) of tef starches ranged from 10.1×10⁷ g/mol (156 nm) to 16.5×10⁷ g/mol (205 nm) with a mean of 13.9×10⁷ g/mol (186 nm). The AP of the tef starches was considerably smaller than that of maize starch ( = 19.6×10⁷ g/mol, <R_g>_w = 207 nm). These considerably smaller AP molecules in tef starches were most probably responsible for the low paste viscosity of tef starches as compared to maize starch. In most tef starches, the polydispersity index (PI) of the AP was broader than that of the AP of maize starch. The intermediate fraction (IN) 1.0−1.6, mean = 1.1) of most tef starches were similar to those of the IN of maize starch. The amylose (AM) (range 1.5×10⁶−3.0×10⁶ g/mol, mean = 2.2×10⁶ g/mol) and size (range 176−214 nm, mean = 191 nm) of most tef starches was also apparently similar to that of the maize starch ( = 2.3×10⁶ g/mol, <R_g>_w = 193 nm), but the polymer distribution was narrower. The AM−iodine complex of the tef starches had a λ_max range of 611−679 nm and the absorption shifted toward longer wavelengths by 8−14 nm as compared to the maize starch AM−iodine complex. The blue value (absorption at λ_max) for 1 mg/mL of tef AM had a range of 2.3−2.8 (mean = 2.5), whereas for the maize starch, the mean was 2.2. The branched nature of tef starches was also investigated by debranching with isoamylase and determination of chain lengths (DP_n) of the branches by size exclusion chromatography with refractive index detector (SEC‐RI). The AP in tef starches had a polymodal distribution with a periodicity similar to that of cereal starches. The branches had DP_n values of A = 11, B1 = 16, B2 = 46 (range 46−47), B3 = 70 (range 69−72) and B4 = 118 (range 113−123). The outer (A + B1) chains were shorter than those of maize starch AP with abundance (74%, w/w) only slightly less than that of the maize starch (75%, w/w). The slow rate of retrogradation, the slightly lower percent crystallinity, the lower gelatinization temperatures and the lower gelatinization enthalpy observed for tef starches (as compared to maize starch) are probably related to the shorter outer (A + B1) chain lengths of their amylopectin molecules, and may be the foundation of the comparably good keeping quality of tef injera, the main staple in the Ethiopian diet.     

Starch properties of malted barley in relation to real degree of fermentation

Real degree of fermentation (RDF) is an important measure of brewhouse performance in the production of beer. In this work, the relationship of RDF with malted barley starch properties was investigated. Starches were isolated from 25 malted barley samples and analyzed for molecular size distribution (by HPSEC), AP structural features (by high‐performance size exclusion chromatography with multi‐angle laser light scattering and RI detectors), and thermal properties (by DSC). Cluster analysis, analysis of variance, principal component analysis, bivariate correlation, and multiple linear regression analysis were used in establishing correlations. RDF, AM, and AP content were 74.0–80.1%, 25.2–34.4%, and 65.6–74.9%, respectively. Starch gelatinization enthalpy was 6.4–8.1 J/g, and onset gelatinization temperature was 58.5–64.3°C. AP and AM content had a positive and negative impact on RDF, respectively. The effect of thermal properties (starch gelatinization and AM‐lipid complex melting) on RDF was not clear. Starch properties explained up to 86% of RDF variance to indicate that other malted barley constituents and/or properties also contribute to cultivar variations in RDF.     

Physicochemical and functional properties of fern rhizome (Pteridium aquilinum) starch

Starch isolated from fern rhizome was studied for physicochemical and functional properties. The recrystallization method was used for separation and purification of AM and AP from the starches. The fern rhizome starch contained 25.38 ± 0.40% AM. XRD studies showed that fern rhizome starch exhibited a C‐type diffraction pattern. SEM showed that granule shape was oval mostly, and the size ranged from 7 to 28 µm. The gelatinization temperature was from 58.94 ± 0.11°C to 71.73 ± 0.22°C, and the melting enthalpy was 12.86 ± 0.53 J/g. According to the viscosity measurement with Brabender viscograph, fern rhizome starch presented higher peak viscosity, which showed that it had more swelling power. Compared with corn and potato starches, fern rhizome starch had a lower transparency. The RS in the fern rhizome starch vermicelli prepared with extrusion method was around 10.49 ± 0.46%.     

Starch of diverse Mexican rice cultivars: physicochemical,structural, and nutritional features

Structure‐function relationship of rice starch is scarce in the literature. Starch was isolated from diverse Mexican rice varieties and their swelling power (SP), soluble solids (ss), thermal and pasting properties, XRD pattern, in vitro starch digestibility, and AP chain‐length distribution were evaluated. Rice starches with low SP at 60°C had higher temperature and enthalpy of gelatinization. The peak viscosity of rice starches ranged between 2426 and 3519 cP, and the samples presented high values for setback due to the AM content. Rice starches presented the typical A‐type XRD pattern with crystallinity values between 32.7 and 36.3%. Rice starches presented high amounts of short chains (A and B1), and differences were found among the cultivars. AM content for rice starches ranged between 18.4 and 22.9%, and the main fraction recorded by HPSEC was the Fraction III (short chains) with values around 60%. The uncooked rice starch samples presented high values of slowly digestible starch (SDS) and rapidly digestible starch (RDS), and differences were found among the cultivars. In cooked samples decreased SDS and increased RDS and RS. Onset temperature and enthalpy of gelatinization were correlated with the percentage of A‐chains and an opposite pattern was found with the percentage of B1 chains. AP structural characteristics affect the functional, physicochemical, and digestibility properties of rice starches.     

Characterisation of amylose and amylopectin with various moisture contents after frying process: effect of starch–lipid complex formation

Frying is commonly used to process starchy foods. This work explored the interactions of amylose (AM) and amylopectin (AP) with lipids during frying. Maize-derived AM and AP that were adjusted to various moisture contents were fried at 180 °C. The significant effects of moisture content and formation of starch–lipid complexes were confirmed. Rheological analysis indicated that the elasticity of the fried AM paste decreased. This change was observed in AM but not in AP. Viscoelasticity decreased as the initial starch moisture content was increased. The presence of a V-type structure was confirmed by XRD. In general, relative crystallinity decreased as moisture content was increased. On the other hand, the increasement of starch–lipid complex could elevated the degree of crystallisation. AM was more likely than AP to undergo complexation with lipids during frying. Increasing the moisture content of starch within 20%~60% promoted the formation of starch–lipid complexes.     

Viscoelastic properties of highly concentrated maize starch solutions in DMSO

Rheological measurements of highly concentrated dimethylsulfoxide (DMSO) starch solutions were performed. For all experiments commercial maize starch with different AM content was used. The research covered a wide range of polymer concentrations depending on linear fraction contribution and allowed to obtain a starch content up to 40% w/w. The analysis covered the time – concentration superposition method and fitting the continuous Maxwell model to the experimental data using Tikhonov regularization method. The results allowed statements about the viscoelastic behavior of non‐aqueous starch solutions, depending on their molecular structure. If the linear AM is the predominant component of the starch, the system behaves more elastic compared to those composed of branched AP. The effect of variation in molecular constitution is stronger than the effect of concentration of the dispersion. Additionally, the molecular masses of both fractions seems not to be the crucial factor for rheological properties as well as biopolymer solubility in DMSO. Relaxation spectra obtained from Maxwell model show the drift of the main peak to shorter relaxation times when the concentration of biopolymer is rising. The phenomenon testifies about the influence of starch concentration on elastic response of the system.     

Physicochemical properties of potato and cassava starches and their mutants in relation to their structural properties

Physicochemical properties [swelling power (SP), pasting behaviour and retrogradation] of five wild type (wt), five amylose free (amf), four high-amylose (ha) potato starches (ps) and one wt and amf cassava starch (cs) were investigated. While swelling of wtps occurred in two phases, amfps showed a very fast swelling and no gel of swollen granules was observed at higher temperatures (>90 °C). Haps underwent only restricted swelling. SP of cassava starches were lower than those of potato starches. Wtps leached mainly amylose (AM) during heating at low temperatures. Molecules of higher molecular weight (MW) leached out at higher temperatures. Longer amylopectin (AP) chains [degree of polymerisation (DP) > 18] inhibited swelling while short chains (DP < 14) favoured swelling. Starch pasting behaviour of 5.0 and 8.0% starch suspensions was studied using Rapid Visco Analyser (RVA). For 5.0% suspensions, increased levels of high-MW AP and decreased levels of AM molecules led to higher peak viscosity. Longer AP chains (DP > 18) depressed peak viscosity, while short chains (DP < 14) increased peak viscosity for both concentrations. At 8.0%, peak viscosity increased with starch granule size. After 1 day of storage of gelatinised starch suspensions, wtps and especially amfps showed only limited AP retrogradation. In contrast, the high enthalpies of retrograded AP (ΔH_retro) and peak and conclusion temperatures of retrogradation (T_p,retro and T_c,retro) of haps suggested partial cocrystallisation between AM and AP. Chains with DP 18–25 seemed to be more liable to AP retrogradation. Wtcs and amfcs did not retrograde at room temperature.     

Characterisation of normal corn starch using asymmetrical flow field‐flow fractionation

The apparent average molar masses (M_w,app), apparent average radii of gyration (R_g,app), diffusion co‐efficients (D_T), and hydrodynamic radii (R_h) of normal corn (maize) starch and fractions were determined using asymmetrical flow field‐flow fractionation coupled with multi‐angle light scattering and refractive index detectors (AF4/MALS/RI). AM‐type (Fraction A) and AP‐type (Fraction B) were chemically separated from normal corn starch. Normal corn starch and Fractions (A–B) were dissolved in 1 M KSCN using a high pressure microwave vessel. The effect of varying cross flow rates at a fixed channel flow rate upon the M_w,app and R_g,app distributions of normal corn starch and Fractions (A–B) were investigated. The average M_w,app of normal corn starch, Fractions (A) and Fraction (B) were 41 × 10⁶, 1.4 × 10⁶ and 39 × 10⁶ g/mol, respectively, with R_g,app values of 129, 60 and 129 nm, respectively.     

Interaction of cationic starch derivatives and cellulose fibres in the wet end and its correlation to paper strength with a statistical evaluation

The adsorption onto a softwood pulp of cationic modified starches with a degree of substitution (DS) ranging from 0.015 to 0.130 and native potato starch was investigated using a method based on size exclusion chromatography‐multi angle laser light scattering (SEC‐MALLS). This technique provides information about the amount and molecular composition of the adsorbed starch product such as the AP–AM‐ratio, the average MW and molar mass distribution. Factors influencing adsorption, like the electrolyte content in the suspension and the initial starch polysaccharide concentration, were investigated. Furthermore, hand sheets were made and the resulting mechanical paper strength was tested. Results were analysed statistically using analysis of variance. Representative results were discussed in detail. In general, low‐substituted cationic starch (DS 0.030) exhibited a higher degree of adsorption and resulted in high paper strength when there was a low electrolyte content in the starch–pulp‐suspension. However, high amounts of electrolytes impeded electrostatic interaction of the charged groups of the starch polysaccharides and cellulose fibre due to partial screening and therefore strongly limited adsorption. This resulted in lowered mechanical paper strength. The water quality of the suspensions had little impact on the polyelectrolyte adsorption of the highly substituted cationic starch (DS 0.100). However, paper strength was markedly higher in the case of starch adsorption where there was a high ionic content and when both starch polysaccharides–AP and AM– were adsorbed. The initial starch concentration determined starch adsorption both quantitatively and qualitatively and subsequently paper strength as well. The relation between adsorption behaviour and paper strength was discussed, particularly in the case of 6% initial starch concentration. In deionised water (DW), the low‐substituted starch (DS 0.03) adsorbed onto the pulp to a greater extent with an AP–AM‐ratio similar to that of the initial starch. Moreover, this achieved the best strength properties in contrast to 36 dGH, where less starch adsorbed and that being almost exclusively AP. In water with 36 dGH, the highly substituted starch (DS 0.100) with both the AP and AM was absorbed and this resulted in higher paper strength. In contrast, AM was almost exclusively adsorbed in DW. Increasing the initial starch concentration increased the amount adsorbed while subsequently changing the AP–AM‐ratio towards increased AM adsorption and decreased AP adsorption in the case of DS 0.100 in DW. Exclusive adsorption of AM markedly lowered the development of the paper strength.     

Effect of acid treatment on the physicochemical and structural characteristics of starches from different botanical sources

Starch and starch derivatives (maltodextrins) are used as encapsulating materials. Starch for use as encapsulating material could be subjected to mild acid treatment. However, the granule size and organization of starch components (AM and AP) play an important role in the acid treatment. The aim of this research was to produce modified starch that might be used as encapsulate material, applying moderate acid‐treatment with 3 N sulphuric acid in a ratio 1:5 w/v for 3 h at 60°C, in starches from different granule size, evaluating their morphological, physicochemical, and structural features. Acid treatment has an effect in the AM content and the outcome was higher in starch with larger granule size. Bimodal granule size distribution was found in acid‐treated rice and maize starches. Erosion and exo‐corrosion were observed in acid‐treated starches with SEM. The XRD pattern did not change with the acid treatment, the native and acid‐treated samples showed similar crystallinity values, except rice starch. The branching degree was higher for modified potato starch, showing higher branching points, modified starches had shorter chains with increased A‐chains, and decreased B3+ chains, and the effect was higher in cereal starches; modified starches had a higher degree of retrogradation and they did not show pasting properties. The internal organization given by the granule size is an important parameter in the acid treatment of starches as it affected their physicochemical and structural features, and in the end, their functionality as encapsulate agent.     

Structural properties and gelatinisation characteristics of potato and cassava starches and mutants thereof

The molecular size of amylopectin (AP) and amylose (AM), AP chain length distribution, crystallinity and granular structure (morphology and granule size distribution) of five wild type potato starches (wtps), five AM free potato starches (amfps), four high-AM potato starches (haps), one wild type cassava starch (wtcs) and one AM free cassava starch (amfcs) were investigated and related to their gelatinisation characteristics. Starches with higher levels of short chains [degree of polymerisation (DP) 6–9 and DP 10–14)] had lower gelatinisation onset (T_o), peak (T_p) and conclusion (T_c) temperatures, whereas higher contents of longer chains (DP 18–25 and DP 25–80) led to higher gelatinisation temperatures. Gelatinisation enthalpies (ΔH) increased with degree of crystallinity. The granules of wtps were larger than those of amfps and haps, respectively. No differences in morphology were observed between wtps and amfps granules, but the haps granules had more irregular surfaces and showed multi-lobed granules.     

Determination of molar mass distribution of tapioca starch using asymmetrical flow field flow fractionation

The apparent average molar masses (M_w,app) and apparent average radii of gyration (R_g,app) of native tapioca starch and fractions were determined using asymmetrical flow field flow fractionation (AF4) coupled with multi‐angle light scattering and RI detectors (AF4/MALS/RI). AM‐type (Fraction A) and AP‐type (Fraction B) were chemically separated from native tapioca starch. Native tapioca starch and Fractions (A and B) were dissolved in 1 M KSCN using a high pressure microwave vessel. The effect of varying cross flow rates at a fixed channel flow rate upon the M_w,app and R_g,app distributions of native tapioca starch and Fractions (A and B) were investigated. The average M_w,app values for native tapioca starch, Fraction (A) and Fraction (B) were 59 × 10⁶, 2.1 × 10⁶ and 19 × 10⁶ g/mol, respectively, with average R_g,app values of 165, 73 and 87 nm, respectively. Hydrodynamic radii (R_h) values for native tapioca starch and fractions were determined directly from AF4 experimental parameters.     

Effects of heating modes and sources on nanostructure of gelatinized starch molecules using atomic force microscopy

Potato and corn starches were subjected to convective and microwave heating. The effects of microwave heating on nanostructure of starch molecules were studied by atomic force microscopy (AFM). Potato starches formed networks with the height from 0.3 to 11.0 nm under microwave radiation. Chains were observed dissociated from the networks with a nanoparticle head. Starch chains can be rod-like conformations or thinner linear structures on nanometer scale. Rod-like chains were about 1.0 nm in height, while the thinner chains were about 0.3 nm. However, corn starches did not show any networks under microwave processing. The capped chains of corn starches were similar to those of potato starches. The results revealed that microwave heating caused incomplete gelatinization of starch by comparison with convective heating. Heating modes influence the potato starch much than that on corn starch. The results can be applied on material selection for microwaved food development.     

Physical properties of barley and oats cultivars grown in high altitude Himalayan regions of India

In this study, some selected physical properties of oats and barley viz seed size, shape, gravimetric properties, density characteristics, angle of repose, static coefficient of friction and terminal velocity were determined at a constant moisture content of 8.0 %. These properties are often required for designing of food processing appliances. The average of the principle diameters was found to be 4.96 ± 0.50, 5.34 ± 0.31, 6.00 ± 0.26 and 5.41 ± 0.44 mm and 1,000-grain weight was 41.9 ± 0.2, 40.06 ± 0.02, 36.66 ± 0.01 and 36.51 ± 0.02 g for hulled barley, hulless barley, Sabzaar oats and SkO-20 oats, respectively. The grains were narrow and elongated having an average sphericity of 50.55 ± 3.7, 47.923 ± 1.8, 32.578 ± 1.3 and 35.69 ± 2.1 %, respectively. The physical properties of the flours like angle of repose, flowability, bulk and true density were also determined. The value of angle of repose was found to be 50.44 ± 0.27⁰, 63.45 ± 0.34⁰, 46.86 ± 0.25⁰ and 44.49 ± 0.10⁰ for the flour of hulled barley, hulless barley, oats Sabzaar and SKO-20, respectively. The flours had poor flowability having a compressibility index of 33.69 ± 0.12, 34.32 ± 0.87, 27.94 ± 1.23 and 27.5 ± 0.74 and Hausner’s ratio 1.58, 1.52, 1.38 and 1.37, respectively.     

Methodologies for producing amylose: A review

Three main in vitro approaches can be distinguished for obtaining amylose (AM): enzymatic synthesis, AM leaching, and AM complexation following starch dispersion. The first uses α-d-glucose-1-phosphate (G1P), a glucosyl primer with a degree of polymerization (DP) of at least 4 and phosphorylase (EC 2.4.1.1), commonly from potatoes. Such approach provides AM chains with low polydispersity, the average DP of which can be manipulated by varying the reaction time and the ratio between G1P, primer, and enzyme dose. AM leaching is the result of heating a starch suspension above the gelatinization temperature. This approach allows isolating AM on large scale. The AM DP, yield, and purity depend on the heating rate, leaching temperature, shear forces and botanical origin. High leaching temperatures (80–85°C) result in mostly pure AM of DP >1000. At higher temperatures, lower purity AM is obtained due to amylopectin leaching. Annealing as pretreatment and ultracentrifugation or repetitive organic solvent-based precipitations after leaching are strategies, which improve the purity of AM extracts. When AM is separated by complex formation, complete dispersion of starch is followed by bringing AM into contact with, e.g., n-butanol or thymol. The resultant complex is separated from amylopectin as a precipitate. Complete starch dispersion without degradation is critical for obtaining AM of high purity. Finally, higher DP AM can be converted enzymatically into AM fractions of lower DP.     

The measurement of metabolisable energy in samples of oats,barley and wheat using chicks

For each of the cereals oats, barley and wheat, metabolisable energy concentrations were estimated in 16 samples of known origin and chemical composition. Each sample was fed at three levels of substitution with a fishmeal/vitamin supplement. There was not a significant difference in metabolisable energy concentration among individual samples within the barley and wheat groups. Significant differences found among values for the oat samples did not seem to correlate in any meaningful way with chemically determined components. The overall mean values with standard deviations found for oats, barley and wheat respectively were 11.9±0.29, 12.6±0.23 and 13.6 ± 0.29 MJ kg^?1 dry matter. These results are discussed and compared with values published recently for laying hens and roosters and with average figures from tables of feedingstuffs composition in current use.     

Substitution of wheat starch with non-wheat starches and cross-linked waxy barley starch affects sensory properties and staling of Arabic bread

Substitution of starch from barley, corn, oat, potato, rice or sorghum for prime wheat starch in the formulation of Arabic bread resulted in breads with significantly (P < 0.05) different textural attributes from regular wheat bread except for barley starch. Substitution of waxy barley starch (957 g kg⁻¹ amylopectin) for wheat starch (279 g kg⁻¹ amylopectin) resulted in bread that was not significantly different from regular wheat bread when assessed in the fresh state. However, upon aging, the waxy barley starch-containing bread staled at a significantly (P < 0.05) faster rate than regular wheat bread. Breads made with waxy barley starch cross-linked with 50, 200 or 500 ppm phosphorus oxychloride showed higher enthalpy of melting (ΔH) upon aging and staled faster than the bread formulated with waxy barley starch. These findings suggest that amylopectin retrogradation is one of the determinants of Arabic bread staling and that cross-linking promotes recrystallisation of amylopectin, possibly by keeping the polymer chains in close proximity. The rate of staling in breads formulated with cross-linked waxy barley starch decreased with increasing levels of cross-linking, possibly owing to restrictions in the degree of starch swelling. © 1999 Society of Chemical Industry     

Gelatinisation and Retrogradation Behaviour of Some Starch Mixtures

Differential scanning calorimetry (DSC) and dynamic rheological measurements were used to characterise the behaviour of potato‐waxy maize, potato‐barley and waxy maize‐barley starch mixtures. Gelatinisation and retrogradation were studied at two starch concentrations, 20% (w/w) and 50% (w/w). In the DSC gelatinisation thermograms of the mixtures it was possible to recognise features of the thermograms of the individual components, indicating that each starch gelatinised independently of the other starch in the mixture. The retrogradation enthalpy was measured in the DSC after four and seven days of storage at 6 °C. The lowest values of retrogradation enthalpy for the mixtures were found for the waxy maize‐barley and potato‐barley mixtures, particularly at 20% starch concentrations and in the ratios 25:75 and 50:50, correspondingly. The retrogradation enthalpy measured for most starch mixtures corresponded to the calculated value, assuming that each starch contributed to the enthalpy according to its proportion in the mixture. Storage and loss moduli were measured for gelatinised starch suspensions during cooling from 90 to 6 °C, and then during a holding period at 6 °C for up to 6 h. The moduli for the mixtures were in most cases in between the values obtained for the individual starches.