Physicochemical Properties of Starch Isolated from Bracken (Pteridium aquilinim) Rhizome

Bracken (Pteridium aquilinum) is an important wild plant starch resource worldwide. In this work, starch was separated from bracken rhizome, and the physicochemical properties of this starch were systematically investigated and compared with 2 other common starches, that is, starches from waxy maize and potato. There were significant differences in shape, birefringence patterns, size distribution, and amylose content between bracken and the 2 other starches. X‐ray diffraction analysis revealed that bracken starch exhibited a typical C‐type crystalline structure. Bracken starch presented, respectively, lower and higher relative degree of crystallinity than waxy maize and potato starches. Ordered structures in particle surface differed among these 3 starches. The swelling power tendency of bracken starch in different temperature intervals was very similar to that of potato starch. The viscosity parameters during gelatinization were the lowest in waxy maize, followed by bracken and potato starches. The contents of 3 nutritional components, that is, rapidly digestible, slowly digestible, and resistant starches in native, gelatinized, and retrograded starch from bracken rhizome presented more similarities with potato starch than waxy maize starch. These finding indicated that physicochemical properties of bracken starch showed more similarities with potato starch than waxy maize starch.     

韧化处理对不同玉米淀粉理化特性的影响

以不同直/支链比例的普通玉米淀粉和蜡质玉米淀粉为材料,在40、50、60℃进行韧化处理,研究韧化处理对玉米淀粉理化特性的影响。结果表明：韧化处理的两种玉米淀粉颗粒形貌有较小变化。韧化处理后,两种淀粉的溶解度和膨胀度随着处理温度的升高而降低;所有韧化处理过的玉米淀粉黏度低于原淀粉,起糊温度高于原淀粉;韧化处理后淀粉的糊化温度升高,热焓变化不大。     

Effect of Ultrasonic Treatment on the Physicochemical Properties of Maize Starches Differing in Amylose Content

Normal maize, waxy maize and amylomaize V starches were treated at a moisture content of 70% by ultrasonic treatment. The results showed that the surface of normal and waxy maize starches was porous after treatment and a fissure could be clearly observed in the surface of amylomaize V starch. Ultrasonic treatment did not change the X‐ray pattern of the three maize starches. The swelling power (amylomaize V (B‐type) > normal maize > waxy maize (A‐type)) and solubility (amylomaize V > normal maize > waxy maize), the syneresis of amylomaize V starch and the gelatinization transition temperatures of the three starches increased on this treatment. Ultrasonic treatment decreased the syneresis of normal and waxy maize starches, the enthalpy of gelatinization (amylomaize V > waxy maize ≈︂ normal maize) and the gelatinization temperature range (amylomaize V > normal maize ≈︂ waxy maize) of all starches. A drop in viscosity of all three starches was observed and the viscosity patterns of three starches remained unchanged after ultrasonic treatment. The data showed that ultrasonic treatment degraded preferentially the amorphous regions and more easily attacked linear amylose than highly branched amylopectin.     

A Study of Starch-Lipid Interactions for Some Native and Modified Maize Starches

Starch-lipid interactions of five maize starches varying in amylose content and chemical modification were investigated by differential scanning calorimetry (DSC). The high-amylose maize starch gave the greatest endotherm due to the amylose-lipid complex in presence of cetyltrimethylammonium bromide (CTAB). This endotherm was decreased in an acetylated high-amylose maize starch, and the waxy varieties did not give rise to such an endotherm. However, when the gelatinization enthalpies were compared it was found that these values decreased also for waxy varieties in the presence of CTAB. Dynamic rheological measurements showed that CTAB increased the storage modulus (G′) for all the starches investigated (normal maize starch, acetylated high-amylose maize starch and crosslinked waxy maize starch), whereas saturated monoglycerides increased G′ for normal maize starch, decreased G′ for the crosslinked waxy maize starch and left acetylated high-amylose maize starch unaffected. Lecithin and soybean oil either decreased G′ or had no effect.     

Effect of hydroxypropyl β-cyclodextrin on physical properties and transition parameters of amylose–lipid complexes of native and acetylated starches

The effect of hydroxpropyl β-cyclodextrin (HPβ-CD) on physical properties and digestibility of wheat, potato, waxy maize and high-amylose maize starches before and after acetylation was studied. Effect of HPβ-CD on amylose–lipid complexes in native and acetylated potato starches synthesized using α-lysophosphatidylcholine was also studied. Acetylation increased swelling factor, amylose leaching, peak viscosity and susceptibility to α-amylase hydrolysis, but decreased gelatinization temperature and enthalpy and gel hardness in all starches. HPβ-CD markedly increased swelling factor and amylose leaching in native and acetylated wheat starches but had little or no impact on other starches. Wheat starch gelatinization enthalpy decreased in the presence of HPβ-CD but gelatinization temperature of all the starches was slightly increased. HPβ-CD had no influence on enzymatic hydrolysis. Melting enthalpy of amylose–lipid complex in both native and acetylated wheat starches was decreased by HPβ-CD. Acetylation also decreased the melting enthalpy of amylose–lipid complex in wheat starch. Similar trend of thermal transitions was observed in the presence of HPβ-CD for the amylose–lipid complexes synthesized in potato starch. Acetylation reduces the complex formation ability of the amylose polymer. Similar to gelatinization, acetylation widened the melting temperature range of amylose–lipid complexes while shifting it to a lower temperature. Higher swelling and amylose leaching, and decreased gelatinization temperature and enthalpy resulting from acetylation of wheat starch is consistent with its influence on starch hydration. Similar effects resulting from the inclusion of HPβ-CD were consistent with the disruption of amylose–lipid complex by HPβ-CD which promotes granular hydration.     

Endosperm Structure and Physicochemical Properties of Starches from Normal,Waxy, and Super-Sweet Maize

Maize is a main botanical source used for extraction of starch in the world market. New maize cultivars with different amylose contents and special starch metabolism characteristics have been generated. Three types of maize cultivars, namely, normal maize, waxy maize (wxwx homozygous mutant), and super-sweet maize (sh2sh2 homozygous mutant), were investigated to determine differences in endosperm structures, morphologies, and physicochemical properties of starches. Maize kernels exhibited significantly different contents of total starch, soluble sugar, and amylose. Normal maize kernels contained the largest proportion of floury endosperm, followed by waxy maize and then super-sweet maize. Normal maize starch and waxy maize starch were larger in size than super-sweet maize starch. Normal maize starch and waxy maize starch were spherical and polygonal in floury and vitreous endosperms, respectively. Super-sweet maize starch was spherical both in floury and vitreous endosperms. Waxy maize starch showed the strongest birefringence patterns, the highest crystallinity and the largest proportion of ordered structure in external region of granules, and the largest proportion of double helix components, followed by normal maize starch and then super-sweet maize starch. Waxy maize starch showed the highest peak viscosity, trough viscosity, breakdown viscosity, gelatinization temperatures (i.e., gelatinization conclusion temperature, gelatinization onset temperature, gelatinization peak temperature, and gelatinization enthalpy). By contrast, super-sweet maize starch showed the lowest corresponding values for these parameters.     

Influence of prior acid treatment on physicochemical and structural properties of acetylated sorghum starch

Influence of prior acid treatment on acetylation of starch isolated from an Indian sorghum cultivar was investigated. The starch was acid thinned (AT) using 0.1, 0.5, and 1 M HCl for 1.5 h and then acetylated (Ac) with acetic anhydride (8% w/w). The acid thinning and subsequent acetylation appeared to reduce the percentage acetylation as indicated by degree of substitution. Ac‐AT starches exhibited significantly different physicochemical, thermal, pasting, and gel textural properties from those of AT and Ac starches. Starches after dual modification showed higher solubility, lower AM content, gelatinization temperatures, retrogradation, peak viscosity, and gel hardness than native starch. Enthalpy and range of gelatinization were observed to be higher in dual modified starches than native starch. However, no significant changes in granule morphology or crystalline pattern of Ac‐AT starches were observed compared with native starch.     

几种不同品种淀粉及羟丙基产物糊液性质比较研究

以薯类淀粉(木薯,马铃薯)及禾谷类淀粉(普通玉米、蜡质玉米、高直链玉米及糯米)为原料,以环氧丙烷为醚化剂。制备了羟丙基变性淀粉。反应条件:淀粉乳质量分数40%、反应温度40℃、无水Na_2SO_4添加量12%(以淀粉干基计)、NaOH添加量1.2%、环氧丙烷添加量12%、反应时间18h。分别对原淀粉及在相同的反应条件下制备的羟丙基变性淀粉糊性质做了对比研究。不同品种淀粉糊性质存在很大差别。经过羟丙基改性。淀粉糊液粘度性质、冻融稳定性、透光率、都有不同程度的改善,但凝沉性质不能准确反映羟丙基化对蜡质玉米淀粉和糯米淀粉糊液性质的改善。     

Rice Starch Diversity: Effects on Structural,Morphological, Thermal,and Physicochemical Properties—A Review

Abstract: Rice starch is one of the major cereal starches with novel functional properties. Significant progress has been made in recent years on the characterization of rice starches separated from different rice cultivars. Studies have revealed that the molecular structure and functional properties are affected by rice germplasm, isolation procedure, climate, agronomic conditions, and grain development. Morphological studies (microscopy and particle size analysis) have reflected significant differences among rice starch granule shapes (polyhedral, irregular) and in granule size (2 to 7 μm). Nonwaxy and long‐grain rice starches show greater variation in granular size than the waxy starches. Rice starch granules are smaller than other cereal starches with amylose contents varying from virtually amylose‐free in waxy to about 35% in nonwaxy and long‐grain rice starches. Amylose content appears to be the major factor controlling almost all physicochemical properties of rice starch due to its influence on pasting, gelatinization, retrogradation, syneresis, and other functional properties. Waxy rice starches have high swelling and solubility parameters, and larger relative crystallinity values than nonwaxy and long‐grain starches. However, nonwaxy rice starches have a higher gelatinization temperature than the waxy and long‐grain starches. The bland taste, nonallergenicity, and smooth, creamy, and spreadable characteristics of rice starch make it unique and valuable in food and pharmaceutical applications. This review provides recent information on the variation in the molecular structure and functional properties of different rice starches.     

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

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.     

Dual Modification of Banana Starch: Partial Characterization

Banana starch was double modified by cross‐linking and substitution, using two different cross‐linking agents, i.e. phosphorus oxychloride (POCl₃) and a mixture of sodium trimetaphosphate/sodium tripolyphosphate. The morphological and physicochemical properties and the absorption capacity for heavy metals of the modified starches were assessed. Double modified starch granules (cross‐linked carboxymethyl starches CCSA and CCSB) presented changes in the surfaces. These starches had a bigger average particle size than unmodified starch due to the swelling of the granules during the chemical modification, also aggregates were formed. The double modified banana starches presented an A‐type X‐ray diffraction pattern with slightly decreased crystallinity compared with the unmodified counterparts. The double modification of banana starch decreases the temperature and enthalpy of gelatinization and the decomposition temperature. These results are related to partial disorganization during the chemical treatment. The double modified banana starch possess sorption capacity for heavy metal ions in the order Cd²⁺ >Pb²⁺>Cu²⁺>Hg²⁺. Due to their physicochemical characteristics and absorption capacity, the double modified banana starches can be used in diverse applications.     

Freeze-Thaw Stability and Refrigerated-Storage Retrogradation of Starches

A method for the evaluation of freeze-thaw stability of starch gels is described and compared with refrigerated-storage retrogradation. Differential scanning calorimetry (DSC) is used to estimate the energy required to break down recrystallized starch molecules after 10 cycles of freezing-thawing or after storage at 4°C for 1 week. Different DSC properties were observed for different starches. Chemical modification decreased all DSC values for gelatinization except the gelatinization range of all modified starches examined. Rice and wheat starches displayed the lowest energies of gelatinization compared with other native starches studied. Most chemical modifications completely inhibited the recrystallization of starches during storage at 4°C or after 10 cycles of freeze-thaw. Mira-Cleer 340® (modified regular maize starch; hydroxypropyl distarch phosphate) had a slight recrystallization value. DSC endotherms for both recrystallization studies occured at considerably lower temperatures than those of the original gelatinization.     

Physicochemical characterization of chemically modified corn starches related to rheological behavior,retrogradation and film forming capacity

An integral approach of chemical modification effects on physicochemical and functional properties of corn starch was performed using different and complementary techniques. Acetylated, acetylated crosslinked, hydroxypropylated crosslinked, and acid modified corn starches were analyzed. Substitution and dual modification reduced significantly amylose concentration. Chemical modification decreased granules crystallinity degree. A significant increase in swelling power was observed in substituted and dual modified starches at 90 °C, besides these treatments decreased gelatinization temperature and enthalpy. Acid modified starch pastes showed a Newtonian behavior while substituted and dual modified ones exhibited a viscoelastic response. Dynamic rheological properties of modified starch pastes were not affected by post gelatinization time while native starch pastes developed a more rigid structure during storage. Retrogradation of substituted starch pastes after 12 days at 4 °C was reduced, since syneresis degree and hardness increase were significantly lower than those of native pastes. It was demonstrated that only substituted and native starches exhibited film forming capacity.     

In vitro Digestibility of Hydroxypropyl Maize,Waxy Maize and High Amylose Maize Starches

Hydroxypropyl derivatives of maize, waxy maize and high amylose maize starches were prepared and characterized. The in vitro digestibility of the raw and gelatinized starches and their derivatives was compared using porcine pancreatic α-amylase. Digestibility of the unmodified starches decreased in the order waxy maize > maize > high amylose maize. Increasing molar substitution (MS) caused a decrease in digestibility for all starch types after gelatinization. Raw maize and high amylose maize starch derivatives showed an initial decrease in digestibility followed by increases at higher MS levels. The digestibility of the raw waxy maize starch derivatives showed a continuing drop as MS increased.     

Physicochemical and Functional Properties of Tetraploid and Hexaploid Waxy Wheat Starch

Waxy wheats possess unique starch functional properties that may be useful in specific end‐uses. To assess the physicochemical, thermal, and pasting properties, starches from seven waxy genotypes originating from two wheat classes, tetraploid durum and hexaploid hard red spring (HRS), were evaluated and compared with their counterpart non‐waxy wild types. The amylose content ranged from 2.3% to 2.6% in waxy durum lines, compared to 29.2% in normal durum control, and 2.1% to 2.4% in waxy HRS, compared with 26.0% in normal HRS control. Significant differences in the degree of crystallinity were observed between the waxy and control starches, despite similar A‐type X‐ray patterns, although differences between the two wheat classes were non‐significant. Both, control and waxy starches displayed an X‐ray peak corresponding to the amylose‐lipid complex, but the intensity of the peak was markedly lower in the waxy starches. The waxy durum starches exhibited the highest transition temperatures as measured by Differential Scanning Calorimetry (DSC), whereas, the enthalpy of gelatinization of most waxy genotypes was statistically higher than that of the controls. All waxy starches displayed high peak viscosity, high breakdown, and low setback profile as measured by the Rapid Visco Analyser (RVA). Texture analysis of RVA gels revealed significant differences between waxy and non‐waxy wheats, as well as between waxy tetraploid and hexaploid wheats, confirming that the nature and class of wheat starch would play a significant role when using waxy wheat blends in different wheat‐based products.     

Characterization of Acetylated Waxy Maize Starches Prepared under Catalysis by Different Alkali and Alkaline‐Earth Hydroxides

The effects of the catalyst used in acetylation, including sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)₂), on the chemical and physicochemical properties of acetylated waxy maize starch were investigated. The Ca(OH)₂‐catalyzed acetylated starch exhibited a slightly higher pasting temperature and a lower β‐amylolysis limit compared with acetylated starch prepared under NaOH or KOH catalysis, but no difference was observed for their thermal properties. The carbohydrate profiles of isoamylase‐debranched acetylated starches and their β‐limit dextrins were characterized by high‐performance size‐exclusion chromatography. The Ca(OH)₂‐catalyzed acetylated starch showed a elution profile that was different from those of the other two acetylated starches with a greater proportion of saccharides eluted at a longer retention time. However, the differences in pasting temperature, β‐amylolysis limit, and carbohydrate profile among the acetylated starches diminished when ethylenediaminetetraacetic acid (EDTA) was added. The results suggest that calcium might induce intermolecular crosslinking through chelation with oxygen of the anhydroglucose units and this type of crosslinking was promoted in acetylation catalyzed by Ca(OH)₂.     

Comparison of Endosperm Starch Granule Development and Physicochemical Properties of Starches from Waxy and Non-Waxy Wheat

Starch granule development and physicochemical properties of starches in waxy wheat and non-waxy wheat were investigated in this article. Starch granules in waxy wheat endosperm showed an early developmental process. Compared with non-waxy wheat starch granules (round-shaped), waxy wheat starch granules (ellipse-shaped) were larger and contained more B-type granules. According to the granule size, starch granules were divided into two groups in waxy wheat, but were divided into three groups in non-waxy wheat. Compared with non-waxy wheat starch, waxy wheat starch had higher swelling power, gelatinization temperatures (To, Tp, Tc), and relative degree of crystallinity. They showed similar ordered structures on external regions of starch granules. Additionally, waxy wheat starch had a higher proportion of double-helical components and a lower proportion of single-helical components than non-waxy wheat starch. Based on the previous results, it was concluded: (1) waxy wheat and non-waxy wheat not only differed in starch granule development, but also in physicochemical properties of starches; (2) waxy wheat had more potential value for producing traditional products than non-waxy wheat.     

Effects of Granule Sizes on Physicochemical Properties of Cross‐linked and Acetylated Wheat Starches

Large and small wheat starch granules were used for cross‐linking and acetylation to determine effects of granule sizes on physicochemical properties of the modified starches. The native and cross‐linked starches from the small granules showed higher phosphorus contents than did those from the large granules. However, the level of phosphate substituents in the modified starches was not significantly different between the large and small granules under the same conditions. In contrast, the large granules had a higher reactivity with acetic anhydride than did the small granules. The phosphate group cross‐linked starch (CS), acetylated starch (AS) and acetylated cross‐linked starch (ACS) from the large granules had lower gelatinization temperatures and higher enthalpies than those from the small granules. The paste viscosities of the CSs from the large granules decreased rapidly, whereas those of the AS or ACS increased significantly as compared with those from the small granules. The pastes of cross‐linked starches from the small granules were more stable than those from the large granules, whereas the pastes of AS and ACS from the large and small granules had similar resistance to freeze‐thaw treatment. Scanning electron microscopy (SEM) also showed that the small granules were less damaged after modification than the large ones. Thus, the different granule sizes resulted in different physicochemical properties of starch after modification.     

Physicochemical Characteristics of Starches from Unripe Fruits of Mango and Banana

Mango and banana starches were isolated from unripe fruits and their morphology; thermal and pasting properties; molar mass and chain length distribution were determined. Mango starch granules were spherical or dome‐shaped and split, while banana starch had elongated granules with a lenticular shape. Amylopectin of both fruit starches had a lower molar mass than maize starch amylopectin; however, mango amylopectin had the highest gyration radius. Banana amylopectin showed the lowest percentage of short chains [degree of polymerization (DP) 6–12] and the highest level of long chains (DP ≥ 37); mango amylopectin presented the highest fraction of short chains, but the level of longest chains was intermediate between those of banana and maize amylopectins. Banana starch presented the highest average gelatinization temperature followed by mango starch and maize starch had the lowest value; a similar pattern was found for the gelatinization enthalpy. The two fruit starches had a lower pasting temperature than maize starch, but the former samples showed higher peak and final viscosities than maize starch. Structural differences identified in the fruit starches explain their physicochemical characteristics such as thermal and pasting behavior.     

Application of Differential Scanning Calorimetry to Starch Gelatinization. II. Effect of Heating Rate and Moisture Level

The influence of heating rate on the gelatinization of wheat starch and starch/water ratio on the gelatinization of wheat, maize, waxy maize and amylomaize starches was examined. More rapid heating resulted in a lowering of the onset temperature of gelatinization for wheat starch from 52 °C at 8°C/min to 46 °C at 32 °C/min. A linear relationship was observed between moisture content and gelatinization energy for starch/water ratios between 1 :2 and 2:1. This allowed calculation of the minimum level of water necessary to initiate gelatinization of each starch. These levels were in excess of the water binding capacity for each starch and were 0.45, 0.45, 0.47 and 0.52 g water/g of wheat, maize, waxy maize and amylomaize starches respectively.