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1.
A method using Raman spectroscopy was recently developed for the determination of the degree of acetylation in modified wheat starch. In this article, we show that the method can be generalized to a wide range of starches of different botanical origin and amylose content. Calibration sets were used to develop regression equations for 11 types of acetylated starches, including cereal (rice, maize, wheat) and noncereal (potato and sweetpotato) sources. The calibration lines were then used to predict the level of acetylation of starch samples with unknown level of acetylation using their Raman spectra. In each case, R2 > 0.98 for linear regression of Raman vs. titrimetric determination of acetylation. The Raman-based calibration curves allow fast and nondestructive determination of the degree of acetylation for different types of starches.  相似文献   

2.
A method using Raman spectroscopy was recently developed for the determination of the degree of substitution of succinate in waxy maize starch. In this paper it is demonstrated that the method can be generalized to a wide range of starches of different amylose contents and botanical origins. Raman calibration sets were used to form regression equations for five types of succinylated starches, that is, waxy, regular, and two high-amylose maize samples (47 and 66% amylose, respectively) and wheat. The derived calibration curves can be used to find the degree of substitution in samples with unknown levels of succinylation. The Raman calibration lines had linear correlation coefficients of 0.995 or better and enable the fast and nondestructive determination of the degree of substitution of succinate for different types of starches with minimal sample preparation. Also discussed is the potential utility of Raman spectroscopy to simultaneously determine the degree of substitution of succinate and amylose content, using previously determined calibration curves developed for the amylose content of maize starches.  相似文献   

3.
Maize starches extracted from selected maize cultivars with 0.2–60.8% amylose contents were used to produce bihon-type noodles. Starch dough using a pregelatinized starch binder was prepared and extruded through a laboratory-scale extruder simulating the traditional process of making bihon in the Philippines. The normal maize starches with amylose content of ≈28% were successfully used for bihon-type noodle production, but waxy maize starches with 0.2–3.8% amylose content and high-amylose maize starches with 40.0–60.8% amylose content failed to produce bihon-type noodles. Viscoamylograph profile parameters and swelling volume are significantly correlated to amylose content of maize starch samples evaluated. These physicochemical properties may be used to indicate that the starch samples at normal amylose levels may be used for bihon-type noodles. Starch noodles produced in the laboratory were not significantly different in terms of either cooking quality or textural properties from two commercially produced maize noodle samples, except for adhesiveness. The laboratory process and fabricated extruder can be used to produce bihon-type noodles.  相似文献   

4.
Physicochemical properties of starches from eight coix (Coix lachrymajobi L.) accessions were investigated. There was considerable variation in most measured traits, generally corresponding to the separation into waxy and normal amylose types. The amylose contents of five normal coix ranged from 15.9 to 25.8%, and those of three waxy coix were 0.7–1.1%. Swelling power of waxy coix starches varied between 28.6 and 41.0 g/g, generally higher than waxy maize. Normal coix starches had significantly higher gelatinization peak temperature (Tp) than the normal maize, 71.9–75.5°C. The Tp of waxy coix starches was 71.1–71.4°C, similar to waxy maize. Rapid Visco-Analyser (RVA) pasting profiles of normal coix showed little variation and closely matched the normal maize starch profile. Pasting profiles of waxy coix showed more variation and had lower peak viscosities than waxy maize starch. Waxy coix starches formed very weak gels, while the gel hardness of normal coix starches was 11.4–31.1 g. Amylose content was the main factor controlling differences in starch properties of the coix starches.  相似文献   

5.
The weight average molar mass (Mw) and root mean square radii of starches from waxy maize (Amioca), waxy rice flour, cassava, Hylon V, Hylon VII, and potato amylose were determined by size-exclusion chromatography (SEC) and multiple-angle laser light scattering (MALLS). Dimethylsulfoxide (DMSO) containing 50 mM LiBr was used to dissolve the starches and also served as the mobile phase. SEC with large particle size polystyrene divinylbenzene packing materials and MALLS instrumentation were evaluated for the ability to separate and determine molar mass (MM) of starch polymers, respectively. The determination of Mw by MALLS is necessary because the Mw of many cereal starches exceeds the available molecular standards by one or two orders of magnitude. The Mw depends on the method of calculation. The Mw (Berry method) of starch from waxy corn was 2.27 × 108 Da, waxy rice 8.9 × 107 Da, cassava 5.7 × 107 Da, Hylon V 2.7 × 107 Da, Hylon VII 4.8 × 106 Da, and potato amylose 1.9 × 105 Da. Recovery dropped dramatically for molecules with root mean square radii >200 nm.  相似文献   

6.
The differences in pasting properties involving gelatinization and retrogradation of rice starches from IR24 and Sinandomeng cultivars during heating‐cooling processes were investigated using a Rapid Visco Analyser (RVA)and a dynamic rheometer. The results were discussed in relation to the molecular structure, actual amylose content (AC), and concentration of the starches. Generally, both starches possessed a comparable AC (≈11 wt%), amylose average chain length (CL), iodine absorption properties, and dynamic rheological parameters on heating to 95°C at 10 wt% and on cooling to 10°C at higher concentrations. In contrast to Sinandomeng, IR24 amylose had a greater proportion of high molecular weight species and number‐average degree of polymerization (DPn). IR24 amylopectin possessed a lower DPn and greater CL, exterior CL (ECL), and interior CL (ICL). Comparing the results of RVA analysis and dynamic rheology, the gelatinization properties and higher retrogradation tendencies of IR24 starch can be related to the structural properties and depend on starch concentration. In addition, the exponent n of starch concentration for storage moduli at 25°C (G′25 ∝ Cn) increased linearly with increasing AC.  相似文献   

7.
The chemometric calibration of near‐infrared Fourier‐transform Raman (NIR‐FT/Raman) spectroscopy was investigated for the purpose of providing a rigorous spectroscopic technique to analyze rice flour for protein and apparent amylose content. Ninety rice samples from a 1996 collection of short, medium, and long grain rice grown in four states of the United States, as well as Taiwan, Korea, and Australia were investigated. Milled rice flour samples were scanned in rotating cups with a 1,064 nm (NIR) excitation laser using 500 mW of power. Raman scatter was collected using a liquid N2 cooled Ge detector over the Raman shift range of 175–3,600 cm‐1. The spectral data was preprocessed using baseline correction with and without derivatives or with derivatives alone and normalization. Nearly equivalent results were obtained using all of the preprocessing methods with partial least squares (PLS) models. However, models using baseline correction and normalization of the entire spectrum, without derivatives, showed slightly better performance based on the criteria of highest r2 and the lowest SEP with low bias. Calibration samples (n = 57) and validation samples (n = 33) were chosen to have similar respective distributions for protein and apparent amylose. The best model for protein was obtained using six factors giving r2 = 0.992, SEP = 0.138%, and bias = ‐0.009%. The best model for apparent amylose was obtained using eight factors giving r2 = 0.985, SEP = 1.05%, and bias = ‐0.006%.  相似文献   

8.
Structural characteristics of starches have been important to determine their physicochemical and functional properties. Solubilization procedures were tested to find a higher solubilization percentage and thereafter to study the structural characteristics of amylose and amylopectin. Size‐exclusion chromatography with refractive index (SEC‐RI) system using a pullulan standard curve was tested to study the amylose molar mass. Also, a microbatch system using a MALLS detector was used to determine the molar mass and gyration radius of starch and amylopectin. Microwave heating produced higher solubility percentages than autoclaving, and there was a difference between both starches. The sample solubilized with microwave heating presented higher molar mass and gyration radius values than autoclave samples, showing that this process for structural studies provided information representative of the initial starch sample. When starch components were separated, amylose showed lower purity than amylopectin. Lower purity was obtained for amylose separated from barley starch, but no difference was obtained for purity of amylopectin separated from both starches. Barley amylopectin had a higher solubility percentage than maize amylopectin. Molar mass of barley amylose was 1.03 × 105 g/mol and for maize of 2.25 × 105 g/mol. Molar mass values of amylopectin separated from both starches were lower than the starch counterparts, although the same solubilization procedure (microwave heating) was used. The difference might be due to depolymerization during separation of starch components.  相似文献   

9.
《Cereal Chemistry》2017,94(2):262-269
The molecular size distribution of maize starch nanoparticles (SNP) prepared by acid hydrolysis (3.16M H2SO4) and their amylase‐resistant counterparts, before and after debranching, was investigated. The weight average molecular weight (Mw) and linear chain length distribution were determined by high‐performance size‐exclusion chromatography (HPSEC) and high‐performance anion‐exchange chromatography (HPAEC), respectively. The objective was to understand the role of amylose involvement in the formation of SNP showing different crystalline structures (A‐ and B‐types). The HPSEC profiles of SNP before debranching from waxy, normal, and high‐amylose maize starches showed broad monomodal peaks. Debranched SNP from waxy maize eluted in a single narrow peak, whereas those from nonwaxy starches showed a multimodal distribution. Similar trends were also observed for the chain length distribution patterns, for which the longest detectable chains (degree of polymerization [DP] 31) in waxy maize were significantly lower than those of nonwaxy maize starches (DP 55–59). This indicated the potential amylose involvement in the SNP structure of normal and high‐amylose starches. Further evidence of amylose involvement was ascribed to the resistance of SNP toward amylolysis (Hylon VII > Hylon V > normal > waxy). The amylase‐resistant residues of SNP from high‐amylose maize starches were composed of both low Mw linear and branched chains.  相似文献   

10.
Processing conditions similar to traditional nixtamalization are now used by the industry in the production of dry maize flours (DMF). The objective of this investigation was to evaluate the effect of industrial nixtamalization on maize starch. Thus, dent maize grains were sampled from storage silos and the starch isolated (S). From the same batch of maize, DMF was obtained and the starch isolated (S‐DMF). The amylose content in the starches was quite similar (21.5–23.4%) and characteristic of a dent maize. However, nixtamalization increased the calcium content in S‐DMF. The starches investigated exhibited the typical A‐type diffraction pattern after 40 days of storage at 11–84.1% rh. However, the differential scanning calorimetry (DSC) results showed that annealing of maize starch occurred during storage at 30°C. On the other hand, industrial nixtamalization has both a melting and annealing effect on maize starch. Thus, the operative glass transition temperature (Tg), and the DSC parameters that define starch gelatinization (Tp and ΔH) showed that the proportion between crystalline and amorphous regions within the starch granule and the extent of physical damage to starch were modified by nixtamalization. As an example, Tg for S was between 60 and 62.5°C, while the S‐DMF had a Tg of 45–55°C for damaged starch and 65–70°C for annealed starch. Additionally, the extraction of the nonconstitutive starch lipids provided starches with more consistent thermal properties, particularly in the behavior of gelatinization at different water content. This last observation might have important implications in the consistency of starch physicochemical properties and, consequently, in the quality of maize products such as tortillas.  相似文献   

11.
The development of genetically modified starches has relied on the use of maize (Zea mays L.) endosperm mutant alleles that alter starch structural and physical properties. A rapid method for predicting amylose content would benefit breeders and commercial handlers of specialty starch corn. For this reason, a study was conducted to investigate the use of near-infrared transmittance spectroscopy (NITS) as a rapid and nondestructive technique for predicting grain amylose content (GAC) in maize. Many single- and double-mutant inbreds and hybrids were used to create a calibration set for the development of a predictive model using partial least squares analysis. A validation set composed of similar genetic material was used to test the prediction model. A coefficient of correlation (r) of 0.94 was observed between GAC values determined colorimetrically and those predicted by NITS; however, the predicted values were associated with a large standard error of prediction (SEP = 3.5). Overall, NITS discriminated well among high amylose and waxy genotypes. The NITS calibration was used to determine levels of contamination by normal kernels in waxy and high-amylose (Amy VII) grain samples intended for wet milling. In both cases, a 5% contaminated sample could be detected from pure samples according to predicted NITS values.  相似文献   

12.
Starch nanoparticles (SNP) from maize starches of varying amylose content (0–71%) were prepared by acid hydrolysis (3.16M H2SO4, at 40°C up to 6 days) followed by repeated water washings. During the washing cycles, nonwaxy starches (normal, Hylon V, and Hylon VII) had suspended particles in the water washings, which were not evident in waxy starch. Microscopic examination revealed the presence of SNP in the “cloudy supernatants” of nonwaxy starches and in the “final washed residue” of waxy maize. The objective of this study was to collect SNP fractions accordingly and determine whether variation in the native starch amylose content would influence the yield, morphology, and crystallinity of the SNP. In nonwaxy starches, the yield of SNP increased up to 26.6% with hydrolysis time and was proportional to the amylose content. Morphology of SNP differed with starch type: flat/elliptical (500 nm) in waxy, oval/irregular (50–200 nm) in normal, oval/round (40–50 nm) in Hylon V, and square/polygonal (50–100 nm) in Hylon VII. X‐ray diffraction confirmed the presence of A‐type crystals in SNP from all starch types and a crystalline transformation from B‐ to A‐type in Hylon starches. The relative crystallinity of SNP was higher than their native starch counterparts.  相似文献   

13.
It has long been recognized that limitations exist in the analytical methodology for amylose determination. This study was conducted to evaluate various amylose determination methods. Purified amylose and amylopectin fractions were obtained from corn, rice, wheat, and potato and then mixed in proportion to make 10, 20, 30, 50, and 80% amylose content starch samples for each source. These samples, considered amylose standards, were analyzed using differential scanning calorimetry (DSC), high-performance size-exclusion chromatography (HPSEC), and iodine binding procedures to generate standard curves for each of the methods. A single DSC standard equation for cereal starches was developed. The standard curve of potato starch was significantly different. Amylose standard curves prepared using the iodine binding method were also similar for the cereal starches, but different for potato starch. An iodine binding procedure using wavelengths at 620 nm and 510 nm increased the precision of the method. When HPSEC was used to determine % amylose, calculations based on dividing the injected starch mass by amylose peak mass, rather than calculations based on the apparent amylose/amylopectin ratio, decreased the inaccuracies associated with sample dispersion and made the generation of a cereal amylose standard curve possible. Amylose contents of pure starch, starch mixtures from different sources with different amylose ranges, and tortillas were measured using DSC, HPSEC, iodine binding, and the Megazyme amylose/amylopectin kit. All the methods were reproducible (±3.0%). Amylose contents measured by these methods were significantly different (P < 0.05). Amylose measurements using iodine binding, DSC, and Megazyme procedures were highly correlated (correlation coefficient >0.95). DSC and traditional iodine binding procedures likely overestimated true amylose contents as residual butanol in the amylose standards caused interference. The modified two-wavelength iodine binding procedure seemed to be the most precise and generally applicable method. Each amylose determination method has its benefits and limitations.  相似文献   

14.
Phosphorylated starches were prepared with sodium tripolyphosphate (STPP) at pH 6, 8, and 10 from waxy (wx, 3.3% amylose), normal (22.4% amylose), and two high-amylose (ae, 47 and 66% amylose) maize starches. After phosphorylation, the gelatinization peak temperature (Tp) decreased and pasting peak viscosity (PV) increased for all the starches except wx, which showed a slight increase in gelatinization temperature. There was a substantial effect of phosphorylation pH on paste viscosity. More crosslinking was found in ae starches with phosphorylation at pH 10. Sodium ions apparently decreased PV of all the phosphorylated starches while only slightly affecting PV of native starches. Phosphorylation increased swelling power of some of the starches, with maximum swelling power at phosphorylation pH 8 and minimum at pH 10. Maximum swelling power for wx starch after preparation was at pH 8 and minimum at pH 6. After phosphorylation, the clarity and freeze-thaw stability of all the starches was greatly increased compared with the native starches. Phosphorylation increased digestibility of ae starches but had little effect on wx and normal starches. After phosphorylation, the adhesiveness, springiness, and cohesiveness of all starch gels generally increased, the hardness of 47% ae and wx starches increased, and that of normal starches decreased. Enthalpy of gelatinization decreased after phosphorylation with the greatest decrease observed for ae starches. When the phosphorylation pH increased from 6 to 10, the brightness (L*) of all the phosphorylated starches decreased, while a* and b* of all the phosphorylated starch increased. Scanning electron micrographs showed some erosion on the surface of starch granules after phosphorylation.  相似文献   

15.
《Cereal Chemistry》2017,94(3):554-559
The physicochemical properties of starches from cultivated Pueraria thomsonii Benth were examined and compared with those of P. lobata (Willd.) Ohwi and other root starches, and the effect of pueraria root starches on the improvement of buckwheat noodle quality was investigated. The total content of isoflavones in P. thomsonii root starches was higher than in P. lobata root starches, and the size and uniformity of those particles displayed a significant difference. The gel stabilities of pueraria root starches were similar and more favorable than those of potato starch and sweet potato starch. For the amylose molecular properties of pueraria root starches, the λmax and blue value index were higher than those of the potato starch and the sweet potato starch, whereas the amylose content and degree of polymerization were much lower in comparison. However, amylopectin branch lengths of pueraria root starches were shorter. Thus, pueraria root starches could improve the quality of buckwheat noodles and enhance their nutritional function. Therefore, pueraria root starches may be regarded as raw materials that influence the quality of buckwheat noodles.  相似文献   

16.
Physical and functional properties of starches isolated from 93 noncultivated genotypes of nine Amaranthus species from a world germ plasm collection and an additional 31 cultivated Amaranthus genotypes obtained from China were tested. A wide variation was found in the properties tested among the Amaranthus species and among genotypes within the same species. When comparing starches from cultivated and noncultivated genotypes, it was generally found that amylose was lower; starch pasting profiles were more consistent with higher peak viscosity, lower breakdown, and lower setback; the gelatinization temperature was lower; and energy of enthalpy was higher. Under cool storage, the hardness of cultivated starch pastes was lower and the adhesiveness was higher. As expected, amylose content was a primary factor affecting the physical and functional properties of Amaranthus starch. Compared with reference maize, rice, and wheat starches, Amaranthus starch tended to have lower hot paste viscosity and lower cool paste viscosity; and higher gelatinization temperatures and higher energy of enthalpy. Furthermore, Amaranthus starch pastes showed less change of gel hardness and adhesiveness after cold storage. The environmental effect on the different properties of starch varied among Amaranthus species. It is suggested that Amaranthus starches can be developed for a wide range of food uses.  相似文献   

17.
Formation of ordered structures from disordered amylose is practically important. The thermal behavior of high-amylose maize starches was studied during cooling, following heating, and during subsequent reheating. Four commercial high-amylose genotype maize starches with varying amylose contents (ae du, ae su2, and ae [nominally both 50 and 70% amylose]) were heated to either 120, 140, 160, or 180°C, cooled to 5°C, and reheated to 180°C in a differential scanning calorimeter. Each starch was studied with its native lipid, as well as in reduced-lipid and lipid-free form. On cooling of lipid-containing starches, two distinct exotherms were observed and attributed to amylose-lipid complex formation and to amylose chain association. A distinct exotherm at ≈75°C was attributed to amylose-lipid complex formation. The exotherm attributed to amylose chain association on cooling varied according to the initial heat treatment, lipid level, and starch type. Starches with higher amylose contents showed larger exotherms on cooling. For initial heat treatments to 120 or 140°C, a broad exotherm beginning at ≈95°C was observed on cooling. In contrast, for initial heat treatments to 160 and 180°C, a sharper exotherm with a peak temperature below ≈55°C was observed. Upon reheating, samples that had been initially heated to 120 or 140°C showed a peak at >140°C that was attributed to the melting of ordered amylose. Starches initially heated to 160 or 180°C did not show this peak. This work illustrates that initial heating temperature, as well as lipid content and amylose content, all affect amylose chain association during cooling. Thus, this work suggests strategies for controlling ordering of amylose during processing.  相似文献   

18.
The effects of amylose content and other starch properties on concentrated starch gel properties were evaluated using 10 wheat cultivars with different amylose content. Starches were isolated from grains of two waxy and eight nonwaxy wheat lines. The amylose content of waxy wheat lines was 1.4–1.7% and that of nonwaxy lines was 18.5–28.6%. Starch gels were prepared from a concentrated starch suspension (30 and 40%). Gelatinized starch was cooled and stored at 5°C for 1, 8, 16, 24, and 48 hr. The rheological properties of starch gels were studied by measuring dynamic viscoelasticity with parallel plate geometry. The low‐amylose starch showed a significantly lower storage shear modulus (G′) than starches with higher amylose content during storage. Waxy starch gel had a higher frequency dependence of G′ and properties clearly different from nonwaxy starches. In 40% starch gels, the starch with lower amylose showed a faster increase in G′ during 48 hr of storage, and waxy starch showed an extremely steep increase in G′. The amylose content and concentration of starch suspension markedly affected starch gel properties.  相似文献   

19.
Waxy maize starch was chemically modified to varying benzylation levels and the degree of benzylation substitution was measured using a nuclear magnetic resonance (NMR) method. Fourier Transform (FT) Raman spectra of the chemically modified starches were acquired and aromatic C=C stretch Raman bands characteristic of the benzylation modification were used to derive a calibration curve for the Raman intensity of these marker bands versus the degree of benzylation substitution. The best‐fit linear regression to the plotted data gave a linear correlation coefficient of 0.997. The FT‐Raman technique provides a fast, nondestructive method for the measurement of the degree of benzylation substitution of modified waxy maize starches and should be applicable for use with benzylated starches from other botanical sources.  相似文献   

20.
Native starch granules of 11 selected cultivars (potato, waxy potato, sweet potato, normal maize, high‐amylose maize, waxy maize, wheat, normal barley, high‐amylose barley, waxy barley, and rice) were treated with a calcium chloride solution (4M) for surface gelatinization. The surface‐gelatinized starch granules were investigated using light microscopy and scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). In general, those starches with larger granule sizes required longer treatment time to complete the gelatinization. The salt solution treatment of starch was monitored by light microscopy and stopped when the outer layer of the granule was gelatinized. The surface gelatinized starch granules were studied using scanning electron microscopy. On the basis of the gelatinization pattern from calcium chloride treatments, the starches could be divided into three groups: 1) starches with evenly gelatinized granule surface, such as normal potato, waxy potato, sweet potato, maize, and high‐amylose maize; 2) starches with salt gelatinization concentrated on specific sites of the granule (i.e., equatorial groove), such as wheat, barley, and high‐amylose barley; and 3) starches that, after surface gelatinization, can no longer be separated to individual granules for SEM studies, such as waxy barley, waxy maize, and normal rice. The morphology of the surface gelatinized starch resembled that of enzyme‐hydrolyzed starch granules.  相似文献   

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