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1.
    
Starches from 12 cassava varieties with different cooked root texture; i.e. mealy, firm and mealy and firm, were investigated with a particular focus on aspects of molecular structures of amylose and amylopectin. Structural elements of amylopectin were essentially constant in terms of unit chain distributions and chain lengths. All cassava amylopectins displayed two distinct chain length peaks, at DP 40–46 and at DP 11–13, with a shoulder at DP 17–19, and average chain length (CL) of amylopectins was 17–20. A fraction of extra‐long chains in the range of 0.24–1.78% was found. Amylose and amylopectin from four varieties with different textures of cooked root were isolated. Data from C‐chain distributions indicated that the molecular size of amylopectin from M‐hanatee (Hanatee), a locally adapted cassava variety, was 2.5–2.9 times smaller than those of the other varieties. Three of the four amylose samples, except that from M‐hanatee, were very similar in average DP (4120–4390), chain length (530–550) and number of chains (7.1–7.5), and composed of nearly equal numbers of linear and branched molecules. The amylose from the M‐hanatee variety showed a unique characteristic: it had smaller size (2050), shorter chain length (450), fewer chains (4.7) and a higher content of linear fraction (58%), when compared with other amyloses.  相似文献   

2.
    
This study investigated how process conditions affect the digestibility of pea starch from pea starch powder (PSP). The factors considered were resistant starch (RS), slow digestible starch (SDS) and rapidly digestible starch (RDS) content. The examined five process factors were: material/water ratio, cooking temperature, cooking time, soaking time, and heat dehydration time. Changes in process conditions mainly altered the content of RS and SDS. Analysis with Sephadex G-200 chromatography and differential scanning calorimetry revealed that RS was mainly from retrograded amylose and amylopectin, while SDS and RDS were mainly derived from amylopectin.  相似文献   

3.
    
Starches isolated from five corn cultivars namely C4, C5, C6, C8, and C15 were investigated for their physicochemical and structural properties. The amylose content of corn starches varied from 24.74 to 30.32 g/100 g among the cultivars. The starch granules showed polyhedral granule shapes and differences in their mean granule size ranged from 2.3 to 19.5 μm. The starch samples showed A-type diffraction pattern with strong reflection at 15.25, 18.11, and 23.33°. Pasting profile, textural, and thermal properties of corn starch showed the cultivar differences. Raman spectroscopy showed the major band intensities at 1340, 1082, 940, 865, 523, 485, 440, and 412 cm?1. Syneresis and turbidity of gelatinized pastes of starches varied among the cultivars and increased progressively with the increase in storage period. The present study can be used for identifying differences between corn genotypes for starch quality and could provide guidance to possible industries for their end use.  相似文献   

4.
Starches from normal rice (21.72% amylose), waxy rice (1.64% amylose), normal corn (25.19% amylose), waxy corn (2.06% amylose), normal potato (28.97% amylose) and waxy potato (3.92% amylose) were heat-treated at 100 °C for 16 h at a moisture content of 25%. The effect of heat-moisture treatment (HMT) on morphology, structure, and physicochemical properties of those starches was investigated. The HMT did not change the size, shape, and surface characteristics of corn and potato starch granules, while surface change/partial gelatinization was found on the granules of rice starches. The X-ray diffraction pattern of normal and waxy potato starches was shifted from B- to C-type by HMT. The crystallinity of the starch samples, except waxy potato starch decreased on HMT. The viscosity profiles changed significantly with HMT. The treated starches, except the waxy potato starch, had higher pasting temperature and lower viscosity. The differences in viscosity values before and after HMT were more pronounced in normal starches than in waxy starches, whereas changes in the pasting temperature showed the reverse (waxy > normal). Shifts of the gelatinization temperature to higher values and gelatinization enthalpy to lower values as well as biphasic endotherms were found in treated starches. HMT increased enzyme digestibility of treated starches (except waxy corn starch); i.e., rapidly and slowly digestible starches increased, but resistant starch decreased. Although there was no absolute consistency on the data obtained from the three pairs of waxy and normal starches, in most cases the effects of HMT on normal starches were more pronounced than the corresponding waxy starches.  相似文献   

5.
    
The morphology and microstructure of maize starches with different amylose/amylopectin ratios (waxy: 0/100; normal maize: 23/77; Gelose 50: 50/50; Gelose 80: 80/20) were studied by microscopy with ordinary and polarized light, scanning electron microscopy (SEM) and X‐ray diffraction (XRD). Generally, the granules of the amylopectin‐rich starches were more regular in shape than those of the amylose‐rich starches, but the surfaces of the amylose‐rich starches were smoother than those of the amylopectin‐rich starches. The birefringence and particle size of the granules were waxy > normal maize > G50 > G80, which also corresponds with the trend of molecular weight. Waxy and normal maize starches showed typical A‐type patterns, while G50 and G80 show B‐type patterns. Crystallinity increases with increasing the amylopectin content.  相似文献   

6.
    
The molecular‐level features of starch in relation to the changes in rice functionality during storage are not yet fully elucidated. This work investigated the effects of rough rice storage conditions on starch fine structures and physicochemical properties. Dried rough rice samples (medium‐grain Bengal and long‐grain Cypress) were stored at 4, 21, and 38°C in temperature‐controlled chambers and then periodically removed and evaluated after 1, 3, 5, 7, and 9 months. Flour (powdered head rice) and starch (extracted from head rice by alkali steeping) samples were evaluated for pasting and thermal properties. High‐performance size‐exclusion chromatography and high‐performance anion exchange chromatography were used to characterize starch molecular size and amylopectin chain‐length distribution, respectively. Significant changes in starch fine structure were observed primarily on the 38°C lots, and to some extent on the 21°C lots. The decreased amylose: amylopectin ratio, shortened amylopectin average chain length, and the shift in chain‐length distribution to shorter branch chains were implicative of molecular‐level starch degradation. The flour and starch samples showed inconsistent trends in pasting and thermal properties, thus suggesting the role of not only starch but also its interaction with non‐starch components in rice aging.  相似文献   

7.
Njavara, a medicinal rice, was assessed for its nutrient composition and physicochemical properties, in order to understand its therapeutic properties. Dehusked Njavara rice consisted of 73% carbohydrates, 9.5% protein, 2.5% fat, 1.4% ash and 1628 kJ per 100 g of energy. Physicochemical properties and nutritive components of dehusked rice of Njavara were evaluated and compared with two commonly consumed non-medicinal rice varieties – Jyothi (red coloured) and IR 64 (brown coloured). The carbohydrates, fats, apparent amylose equivalent, fatty acid profile and triglycerides of Njavara were comparable to Jyothi and IR 64. However, Njavara rice had 16.5% higher protein, and contained higher amounts of thiamine (27–32%), riboflavin (4–25%) and niacin (2–36%) compared to the other two rice varieties. The total dietary fibre content in Njavara was found to be 34–44% higher than that of Jyothi and IR 64. Significantly higher phosphorus, potassium, magnesium, sodium and calcium levels were found in Njavara rice, compared to the other two varieties. The cooking time of dehusked Jyothi and IR 64 varieties were found to be 30 min, while Njavara needed longer time to cook, (38 min). The cooked rice of Njavara was slimy in nature, probably due to the presence of non-starch polysaccharides.  相似文献   

8.
    
Three different methods, including autoclaving, autoclaving–debranching, and purification, were used to prepare Kudzu-resistant starch (KRS) from Kudzu starch (KS). The physicochemical properties, such as thermodynamic properties, pasting properties, solubility, swelling, and coagulability, as well as the in vitro digestive characteristics of the three kinds of KRS were studied. The results showed that the morphology of starch granules of KRS prepared by autoclave, autoclave enzymatic hydrolysis, and purification methods was changed and the relative crystallinity was significantly decreased compared with the original starch. X-ray diffraction (XRD) showed that KRS exists in the form of C and C+V crystalline form. There was a significant increase in the pasting temperature and a remarkable decrease in the peak viscosity and the expansion degree of the KRS prepared by all three methods. The solubility of the resistant starch (RS) obtained by autoclaving–debranching and that by purification were both increased compared to that of native KS, while the solubility of the RS obtained by autoclaving was decreased. Meanwhile, the retrogradation of the three RS was also improved to varying degrees. The contents of RS in the samples were: P-KRS (71%) > DA-KRS (43%) > A-KRS (42%) > KS (9%). Simulated human in vitro digestion experiments showed that RS has stronger antidigestibility properties than native starch. Among them, the RS prepared by the purification method has stronger antidigestive properties, and it is predicted that it may have a better potential value in regulating blood glucose. These results indicated that the processing properties of KRS, especially the digestibility, are significantly improved and can be used as a new functional food ingredient, which deserves thorough study.  相似文献   

9.
    
There is considerable debate on the definition and measurement of the amount of amylose in starch and whether hydrophobic ligands can form a complex with amylopectin. One method for amylose determination is through the measurement of amylose‐lipid complexation using differential scanning calorimetry (DSC), with the assumption that amylopectin cannot form such a complex. As the sensitivity and methodologies used for DSC improves, the validity of this assumption needs to be tested once again. For the experimental work, α‐L ‐lysophosphatidylcholine (LPC, 10% of starch dry weight) was used as the complexing agent and waxy maize starch. Optimisation of the DSC included changing the heating rate from 10ºC/min to 40ºC/min, which resulted in a higher sensitivity enabling the recording of an endotherm associated with the dissociation of a starch‐LPC complex. The observation of the endothermic formation of such complex could only be achieved when a microcalorimeter, which analyses a much larger sample than a standard calorimeter (190 mg of dry starch compared to 13 mg) was used. There are two possible interpretations for these observations: Either waxy maize starch contains traces of amylose (~ 0.5‐0.7%) and the DSC is sufficiently sensitive to detect these amounts or the α‐1,6 glucan long branches of waxy maize starch bind linear aliphatic compounds.  相似文献   

10.
The action of amylose within the granule of normal corn starch is investigated by changes in pasting characteristics of waxy corn starch in a Rapid Visco Analyzer (RVA), using addition of soluble amylose (DP = 18) and cross-linking with epichlorohydrin. Although waxy corn starch, containing no amylose, did not show an effect of addition of amylose on pasting characteristics, by cross-linking with epichlorohydrin, the pasting peak viscosity and breakdown were greatly enhanced and set-back (viscosity increased in the cooling process after gelatinization) was generated. The cross-linking depressed the disintegration of starch granules in the swelling process, with amylose interaction, resulting in RVA pasting characteristics similar to those seen with normal corn starch containing amylose. Set-back was essentially caused by rearrangement among modified amylopectins. Addition of sodium dodecyl sulfate (SDS) to the RVA more efficiently enhanced the effect. This indicated that amylose in normal corn starch interacts with amylopectin through locally strong linkages.  相似文献   

11.
The texture properties (hardness, adhesiveness, cohesion, elasticity) of composite gels with different ratios (0:100, 6:94, 8:92, 10:90, 12:88, and 14:86, respectively) of soy 7S globulin to corn starch (amylose, amylopectin) were studied. Furthermore, the morphology and crystal structure of the mixed gels were investigated. The results showed: the addition of soy 7S globulin could weaken the hardness of corn starch (amylose, amylopectin) and increased the adhesiveness of corn amylose significantly (p < 0.05). Generally, when the additive amount of soy 7S globulin was 10%, the composite gels of soy 7S globulin and corn starch (amylose, amylopectin) appeared to have the best consistency, cohesion, and elasticity.  相似文献   

12.
    
The effect of dynamic high-pressure microfluidization on physicochemical and rheological properties of rice amylose pastes were examined. The amylose dispersions were pressurized at 60, 100, 140, and 180 MPa. The microfluidization treated rice amylose showed elevated solubility, swelling power, and moisture absorbability. The retrogradability was significantly decreased with the pressure increase. Iodine blue value showed a significant increase at 60~140 MPa, while a slight decrease at 180 MPa. The rheological results indicated that native amylose was a non-Newtonian fluid and displayed pseudoplastic fluids characteristics. The amylose moved toward a Newtonian fluid behavior and its rheopexy decreased with the pressure increased.  相似文献   

13.
    
In this study, yellow, red and purple potato starches were selected as the research objects to analyse the fine structure and the relation to the physicochemical properties. Enzymatic hydrolysis and high-performance anion-exchange chromatograph were employed to characterise the structure of clusters and φ, β-limit dextrins. The average degree of polymerisation of clusters from the yellow potato starch was larger (188.57) than in red (91.31) and purple (107.32) potato starch. The molar percentage of fingerprint B chains in yellow, red and purple potato amylopectin were 58.01%, 63.60% and 60.78%, respectively, while major part of short B chains were 15.92%, 17.16% and 16.49%, respectively. The yellow potato amylopectin showed the highest density of branches values indicated that it was more tightly branched. The Pearson correlation coefficients results indicated that the fine structure of amylopectin had significant effects on the physicochemical properties of potato starches, and we can better understanding the differences of the properties among the three potato starches by studying the amylopectin fine structure.  相似文献   

14.
    
Physicochemical, morphological, thermal, and pasting properties of starches, isolated from basmati (HBC-19 and Bas-370) and non-basmati (Jaya, a coarse cultivar; P-44 and HKR-120, the medium cultivars and Sharbati, fine cultivar) rice cultivars grown in India were studied. The amylose content of starches from different cultivars ranged from 2.25 (Jaya) to 22.21 g/100 g of starch (HBC-19). Jaya, HKR-120, and P-44 cultivars showed soft gel consistency as 84, 73, and 69 mm, respectively, whereas Sharbati, Bas-370 and HBC-19 cultivars showed medium gel consistency as 54, 53, and 58 mm, respectively. Swelling power (at 95°C) indicated a significant positive correlation with amylopectin content (r = 0.828, p < 0.05) and gel consistency (r = 0.983, p < 0.01). Turbidity had a highly significant positive correlation with solubility (r = 0.919, p < 0.01) and amylose content (r = 0.945, p < 0.01). Starch form Jaya cultivar showed the presence of smallest size granules (2.4–5.7 μm) with an average size of 3.96 μm, whereas Bas-370 showed the presence of largest size granules (3.3–6.7 μm) with an average size of 5.0 μm. The transition temperatures, enthalpy of gelatinization (ΔHgel), peak height index (PHI) and gelatinization range were determined using differential scanning calorimetry (DSC). The starch from Sharbati cultivar showed highest onset temperature (To), peak temperature (Tp), conclusion temperature (Tc), enthalpy of gelatinization and peak height index (PHI) of 68.8°C, 73.2°C, 79.0°C, 11.56 J/g and 2.63 respectively. Pasting temperature of rice starches varied from 68.9°C (Jaya) to 74.5°C (Sharbati). The peak viscosities observed were in the range of 2223 to 3297 cP, lowest for HBC-19 starch and highest for Jaya starch.  相似文献   

15.
    
Granule size, amylose content, degree of crystallinity, thermal, pasting, and gel textural properties of starches separated from thirty seven maize cultivars grown in East China were studied with a laser particle size analyzer, spectrophotometer, X‐ray diffractometer, differential scanning calorimeter, Rapid Visco Analyser, and texture analyzer. Various correlations between the physicochemical properties were observed. The correlation coefficient between To and Tp, between To and Tc, and between Tp and Tc were 0.967, 0.879, and 0.941 (p<0.01), respectively. Amylose content was correlated negatively with Tc (r=‐0.640, p<0.01). Pasting temperature was positively correlated to Tp (r=0.738, p<0.01). Significantly positive correlations were observed between amylose content and final viscosity, between amylose content and setback (r=0.665 and 0.735, respectively, p<0.01) and between peak viscosity and breakdown (r=0.893, p<0.01). Trough viscosity was positively correlated to final viscosity and setback (r=0.851 and 0.704, respectively, p<0.01). Significant correlations existed between final viscosity and setback, and hardness (r=0.972 and 0.615, respectively, p<0.01). There was a significant interrelationship between setback and hardness (r=0.655, p<0.01).  相似文献   

16.
    
One potential source of starch is the tropical legume baby lima bean (Phaseolus lunatus) that contains around 56—60% of starch. The objectives of this work were to evaluate this starch's physicochemical and functional properties and compare it with the properties of other starches. The chemical composition of lima bean starch was: 10.16% moisture, 0.20% protein, 0.67% fiber, 0.14% ash, 0.54% fat, 98.43% starch and 0.013% phosphorus. The amylose content was higher (32.7%) than that of other cereal and tuber starches but similar to other legume starches. The average granule size (diameter 17.9 μm) was comparable to that of corn starch and of other legume starches. The granule was heterogeneous, presenting an oval shape. The gelatinization temperature was 80.16 °C (range 75—87 °CC), which is similar to other legume starches but higher than that of corn starch. The molecular size (alkali number 3.22), was smaller than that of potato starch but similar to that of corn starch. Compared to corn starch, the gels were firmer and presented a higher degree of retrogradation even at high concentrations. The water solubility was positively correlated with the temperature: i.e., 1.8, 3.4, 8.5 and 12.3% at 60, 70, 80 and 90 °C, respectively. The swelling power had the same behaviour: 2.6, 3.3,12.8 and 19.9 g of water/per gram of starch at 60, 70, 80 and 90 °C, respectively. The amylogram showed that the viscosity (680 Brabender units) and stability were higher than those of commercial corn starch (252 Brabender units). The use of this starch in the preparation of syrups with high glucose contents, as well as in baked and canned products that require heating, is suggested.  相似文献   

17.
    
Avocado starch was extracted from the kernels of the fruit Persea americana Miller (Fam. Lauraceae) and evaluated for its potential as an alternative to maize starch as a pharmaceutical excipient. Its physicochemical and thermal properties were evaluated and compared with those of maize starch. Granules prepared with avocado and maize starch pastes as binder were evaluated for their flow, friability and compaction characteristics. The average yield of starch extracted from the fresh kernels of P. americana was 20.5 ± 0.55% w/w. The scanning electron micrograph (SEM) showed that avocado starch has two characteristic granule shapes; triangular and circular both having an approximate equal distribution. The triangular shaped granules are larger (28 to 32 µm) than the circular (6 to 9 µm). The foaming capacity of avocado starch was 19.05 ± 0.6%, its swelling, moisture uptake and paste clarity were generally lower than that of the maize starch. Avocado starch gel exhibited an extent of syneresis after freeze–thaw that increased cumulatively with increase in number of freeze–thaw cycles. The glass transition (Tg) and gelatinisation temperatures for avocado starch were higher than that of maize starch. The melting temperatures (Tm), ash value, as well as the various densities of avocado starch showed similarities with those of maize starch. The granules prepared with avocado starch pastes as binder showed superior compactibility and mechanical strength to those of maize starch but with similar flow characteristics. Avocado starch generally showed distinct physicochemical and binder properties with some similarities to the standard maize starch.  相似文献   

18.
    
The relationship between amylose to amylopectin ratio and functional properties of maize starch blends (system I) and “model mixtures” (system II) made of waxy and high amylose maize starch were investigated using the Rapid Visco Analyser (RVA). A 4‐5% difference in amylose content caused significant difference in RVA curves and their first derivatives. Based on the first derivative of the RVA curves four different parameters (Peak 2, Peak Time 2, Peak 3, Peak Time 3) were defined. Peak viscosity and parameters were negatively correlated with amylose content confirming that amylopectin is mainly responsible for water uptake. The final viscosity of starch was very high and decreased as amylopectin or amylose was added, indicating that this parameter is the most sensitive to interactions in starch. In system II amount and characteristics of amylopectin seemed to primarily determine the pasting properties. Traditional RVA curves and parameters proved to be feasible to detect the differences between gel properties of the two systems after cooling. First derivative viscograms and alternative parameters seemed to be suitable to demonstrate the importance of interactions between the starch components during gelatinization. Our results confirmed that the Rapid Visco Analyser is a sensitive rheological tool for evaluating effects of starch structure and chemical composition on functional properties providing valuable help for food technologists.  相似文献   

19.
The influence of amylose and amylopectin on structural reorganization occurred during annealing was studied for normal and waxy corn starches. Annealing caused an increase in crystallinity in the waxy corn starch, whereas the number of pores on the granule surface, observed by SEM, increased especially for normal corn starch. Amylose and amylopectin chains of the annealed normal corn starch were degraded to greater extension during enzymatic hydrolysis than those of the native starch. On contrary, the annealing caused a protective effect on waxy corn starch amylopectin toward the enzymatic reaction suggesting that this treatment promoted a better interaction between amylopectin chains of waxy corn starch. The amylose molecules of normal corn starch may have impaired the mobility of amylopectin molecules and restricted the reorganization of the crystalline structure during the annealing. The major increase in pores number on the granule surface of annealed normal corn starch, resulted of the endogenous amylase action during annealing, could facilitate the exogenous enzymes’ role in the degradation of the starch granules’ amorphous area.  相似文献   

20.
Kaempferol glycosides can be hydrolyzed to their aglycone kaempferol during cooking under acidic conditions and in the oral cavity and the intestine by glycosidases. Kaempferol was oxidised by nitrite under acidic conditions (pH 2.0) to produce nitric oxide (NO), and the nitrite-induced oxidation of kaempferol was enhanced and inhibited by 10 and 100 mg of starch ml−1, respectively. The opposite effects of starch were discussed by considering the binding of kaempferol to starch and starch-dependent inhibition of the accessibility of nitrous acid to kaempferol. Kaempferol inhibited α-amylase-catalysed starch digestion by forming starch/kaempferol complexes, and the inhibitory effects increased in the order of amylopectin < soluble starch < amylose. The different effects of kaempferol were discussed to be due to the difference in binding sites of kaempferol between amylose and amylopectin. From the present study, dual-function of kaempferol became apparent in the digestive tract.  相似文献   

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