Changes in Starch Granules Trapped and Heated Using Optical Tweezers

A microscopic method to investigate the swelling process of individual starch granules heated in excess water is proposed. A starch granule focused under a light microscope is adjustably trapped using the optical tweezing of a near-infrared laser beam, which simultaneously heats the granule. Using this method, morphological changes in starch granules during heating were continuously recorded and quantitatively analyzed by image-processing techniques. The changes in granules of domestic wheat starches with differing amylose content were investigated under irradiation by the laser beam at constant optical power. The shapes of swollen granules of waxy wheat starches were observed to be distinctly different from those of non-waxy starches. Numerical indicators, specifically the time constant of swelling for the granule and its swelling magnification, were also obtained. These showed little relation to the pasting profiles of the same starches, obtained with a Rapid Visco Analyser.     

Noodle quality affected by different cereal starches

To investigate the effects of starch characteristics on the quality of noodle making, white salted noodles (WSN) made from reconstituted flours, in which the wheat starch was substituted by different cereal starches, including waxy and non-waxy rice starches, waxy wheat starch and waxy corn starch, were prepared. The rheological properties of raw WSN were mainly influenced by the size of starch granules, where the small starch granules, such as for rice starches, exhibited high amounts of water absorption during dough preparation and a dense packing of starch granules inside a thin gluten-strand network. The rheological properties of cooked WSN were mainly dominated by the amylose content and fine structure of the amylopectin, which resulted in the differences in water absorption and cooking time required for cooked WSN.     

Rheological Properties of Mixed Gels using Waxy and Non‐waxy Wheat Starch

Mixed starches with an amylose content of 5, 10, 18, 20, 23, and 25% were prepared by blending starches isolated from waxy and non‐waxy wheat at different ratios. The dynamic viscoelasticity of mixed 30% and 40% starch gels was measured using a rheometer with parallel plate geometry. The change in storage shear modulus (G′) over time at 5 °C was measured, and the rate constant of G′ development was estimated. As the proportion of waxy starch in the mixture increased, starch gels showed lower G′ and higher frequency dependence during 48 h storage at 5 °C. Since the amylopectin of waxy starch granules was solubilized more easily in hot water than that of non‐waxy starch granules, mixed starch containing more waxy starch was more highly solubilized and formed weaker gels. G′ of 30% and 40% starch gels increased steadily during 48 h. 30% starch gel of waxy, non‐waxy and mixed starches showed a slow increase in G′. For 40% starch gels, mixed starch containing more waxy starch showed rapidly developed G′ and had a higher rate constant of starch retrogradation. Waxy starch greatly influenced the rheological properties of mixed starch gels and its proportion in the mixture played a major role in starch gel properties.     

Physicochemical and Biochemical Characterization of Starch Granules Isolated of Pigmented Maize Hybrids

In this study, the morphological and physicochemical of pigmented maizes as well as the initial characterization of the corresponding starch granule enzymes are described. Starch granules were isolated from blue, black, and white maize. They were analyzed using scanning electron microscopy, particle size distribution, pasting characteristics, sorption isotherms, differential scanning calorimetry, and two‐dimensional gel electrophoresis. The morphology of the starch granules of pigmented maizes was different from the granules of white maize; the pattern was related to the endosperm type of these varieties. The average starch granule size was higher for black than for white and blue maizes. The average gelatinization temperature was similar in the three starches, but the pigmented maizes had higher gelatinization enthalpy; black maize starch showed the lowest enthalpy of retrogradation. These results indicated that the starches from the three maizes analyzed had different organization level. Black maize starch showed the highest peak viscosity followed by white and blue maize starches. In the gel electrophoresis three starch granules presented one main spot at pI of 5 and MW of 60 kDa that corresponds to the granule‐bound starch synthase. Blue and white starches presented some spots near 97 kDa at pI of 5.3–5.7 (white maize) and 5.1–5.5 (blue maize), spots that were not observed for black maize starch. The morphological and physicochemical characteristics of maize starch are related to the enzymes involved in its biosynthesis.     

Multi‐scale structural and digestion properties of wheat starches with different amylose contents

The physicochemical and digestion properties of three wheat starches with different amylose contents were studied. Scanning electron microscopy (SEM) showed they displayed a spherical disc‐like form, a lenticular shape and an irregular morphology, respectively. Compared with waxy and normal wheat starches, high‐amylose wheat starch (HAWS) was characterised by the presence of lower molecular weight amylose fraction, and its granules demonstrated the highest resistance to the cooking. The changes in the IR ratio 1022/999–1047/1022 cm^?1 following the gel storage suggested the molecules of HAWS are more readily to re‐associate and re‐organise into a more organised status than other two starches. The determination of glucose release showed that HAWS had the lowest digestion kinetics (P < 0.001), and this difference in the digestion properties between HAWS and the other two starches might imply that starch molecular structure, in particular amylose structure is another key factor for manipulating starch digestion property rather than amylose content alone.     

Effects of microwave heat-moisture treatment on properties of waxy and non-waxy rice starches

Waxy and non-waxy rice starches adjusted to 20% moisture (wet basis, w.b.) were heat-moisture treated in a microwave oven to determine the effects of the microwave heating characteristics on digestibility, pasting, and morphological properties of the heated starches. Microwave heating produced only minimal changes in digestibility as well as the physical characteristics of heated starches. Significant changes in viscosity properties after microwave heat treatment were observed for both waxy and non-waxy starches heat-treated in a microwave oven, relative to non-treated samples. Non-waxy starch heated in microwave oven showed an increase in breakdown viscosity from 29.8 RVU (non-treated starch) to 35.8 RVU after heating for 60 min. However, for waxy starch, breakdown viscosity decreased from 112.7 to 35.9 RVU after 60 min of microwave heat treatment, reflecting an increased stability of microwave heat-treated starch under cooking. The data obtained in this study indicate that there was much higher re-aggregation of starch granules in waxy starch after microwave heat treatment than occurred in non-waxy starch, suggesting a re-association of amylopectin branch chains in the heat-treated waxy starch.     

In vitro Digestibility of Hydroxypropylated and Cross-linked Waxy and Non-waxy Rice Starches

In vitro digestibility of hydroxypropylated and cross-linked waxy and non-waxy rice starches was investigated to find the proper resistant starch (RS) assaying method for chemically modified starches. RS and total dietary fiber (TDF) content of hydroxypropylated and cross-linked waxy and non-waxy rice starches were measured using the approved AOAC RS assay procedure (AOAC method 2002.02) and the AOAC TDF assay procedure (AOAC method 985.29). Hydroxypropylation did not alter the RS content of waxy and non-waxy rice starches (less than 1% of RS). Cross-linking also did not change the RS content of waxy and non-waxy rice starches (less than 1% of RS). It is interesting to note that non-RS content decreased with increasing hydroxypropylation (97-80%) and cross-linking (99-95%) in both waxy and non-waxy rice starches. This indicates that some fraction of RS in hydroxypropylated and cross-linked waxy and non-waxy rice starches cannot be measured using approved AOAC RS and TDF assay procedures. Therefore, the RS and TDF assay procedures performed in this study are not appropriate to determine the RS content of chemically modified starch. Further investigation is needed to develop a method to determine the RS content of chemically modified starch.     

Some physicochemical properties of acha (digitaria exilis stapf) and iburu (Digitaria iburua stapf) grains

Some physicochemical properties of two cultivated species of Digitaria (D exilis and D iburua) were studied. Physical properties such as 1000-kernel weight, kernel size and water absorption rate of the grains were determined. Water absorption by both cereals reached a maximum after 24 h steeping. The starch from both cereals exhibited a two-stage pattern of swelling and solubility properties similar to other non-waxy cereal starches. Starch from acha swelled less than iburu, 7·3 compared with 7·8 for iburu. Chemical constituents such as protein, oil, crude fibre, ash, nitrogen-free extract and amylose were also determined. An amylose content of 280 g kg^?1 was obtained for both cereal starches. Brabender amylograms obtained from starch and flour were typical of most normal, non-waxy cereals. Maize starch had relatively higher hot-paste and cold-paste viscosities than starches of the two Digitaria species.     

糯小麦粉配粉对小麦加工品质的影响(Ⅰ)对理化特性的影响

通过对2种糯小麦和3种非糯小麦理化特性进行比较研究,并利用其中1种糯小麦与非糯小麦配粉,研究其对配粉理化特性的影响。结果表明:糯小麦制粉过程中产生的破损淀粉含量更高,具有极高的吸水能力;在RVA糊化过程中具有较短的峰值时间,低的回生值和低谷黏度,以及较高的衰减值;在DSC测试中还表现出较高的热力学转变温度和糊化焓。糯小麦粉的添加对配粉理化特性的影响因基础粉的不同而有较大差异。配粉的RVA曲线表现为双峰,回生值显著降低;一定比例的添加能够提高峰值黏度低的基础粉的峰值黏度;添加糯小麦粉对弱筋小麦粉的筋力影响较小,其粉力甚至因为面团延伸性的改善而得到增强;对于筋力较强的小麦粉,超过15%的添加量则会使稳定时间降低,但是对粉力的影响不大;添加韧性和延伸性都较低的糯小麦粉,能够提高配粉的吹泡延伸性而不降低其韧性,其原因有待于进一步研究。     

Structure and Physicochemical Properties of Endosperm Starches of a Waxy Allelic Series and Their Respective Normal Counterparts in the Inbred Oh43 Maize Background

Research over the past three decades has greatly increased our understanding of the biochemical genetics of various waxy (wx) alleles of maize, but our knowledge about the structure and physicochemical properties of endosperm starches obtained from the wx alleles is still incomplete. We further investigated the structure and physicochemical properties of endosperm starches from a wx allelic series and their normal counterparts in the Oh43 inbred background. Starch granules were prepared from mature kernels of wx mutant alleles; wx-C31, wx-R, wx-90, wx-a, wx-B3, wx-m-1, wx-m-8, and wx-S5, and their respective normal counterparts in the inbred Oh43 maize background. Measurements of absorption spectra of starch-iodine complexes and by gel permeation chromatography of Pseudomonasisoamylase-debranched starches showed that all of the starches from the wx allelic series were uniquely waxy type in characteristics, and their normal counterparts were characteristically normal type. Pasting characteristics of starch granules and retrograded starches of the wx allelic series and their respective normal counterparts were investigated by differential scanning calorimetry (DSC). The peak temperature (Tp) and conclusion temperature (Tc) values from starches of the wx allelic series were slightly higher than those of their respective normal counterparts and the ΔHs of starches of the wx allelic series were greater than those of their respective normal counterparts. The onset temperature (To), Tp, and Tc of all retrograded starches were very similar, however, the ΔHs of the retrograded starches of the wx allelic series were greate than those of their respective normal counterpart. Starch granules of the wx allelic series were hydrolyzed more rapidly than those of their respective normal counterparts.     

Granule Sizes of Canna (Canna edulis) Starches and their Reactivity Toward Hydration,Enzyme Hydrolysis and Chemical Substitution

Small and large granule fractions were isolated from canna starch (Canna edulis, green leaf cultivar), and their morphology, physicochemical properties, susceptibility towards granular starch hydrolyzing enzymes and chemical reaction with propylene oxide were investigated. Canna starch consisted of a mixed population of large, medium and small granules; the mean of granule diameter was 47.4 μm. The small granules presented round and polygonal shapes, whereas the large granules had oval and elliptical shapes. Significant variations in digestibility of the various granules size by granular starch hydrolyzing enzymes were observed. During the first 24 h, the hydrolysis rate of small granules was higher than that of native and large granule starches. After 72 h, however, the degree of hydrolysis of small granule, large granule and native starches had reached the extent of 19.6%, 32.0% and 27.2%, respectively. The larger the granule size, the higher the MS obtained when modified with propylene oxide, which was due to the higher swelling power of the large granules. The results obtained from this study suggest that small granules had lower water and chemical affinity when compared with the bigger ones. The difference in the reactivity of small and large granules could be presumably attributed to the starch components (amylose and amylopectin) and their organization of glucan chains in ordered and/or less ordered structure of these two fractions.     

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.     

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.     

微波对板栗淀粉结构和理化性质的影响

为探讨微波辐照对板栗淀粉颗粒结构和理化性质的影响,采用微波辐照板栗淀粉,通过扫描电镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、差示扫描量热仪(DSC)等研究微波处理不同时间后板栗淀粉的颗粒结构和理化特性。研究表明:与原淀粉相比,微波处理后板栗淀粉的微观形貌发生明显变化,但淀粉颗粒仍为C型晶体。随着微波处理时间的增加,直链淀粉含量增大,淀粉颗粒表面出现裂纹、孔洞和黏结越显著,淀粉颗粒的相对结晶度降低、红外光谱(1 047/1 022)cm~(-1)峰强度比值降低;淀粉膨胀度和透光率也随微波处理时间的增加而降低。DSC分析表明,微波处理80 s的淀粉相转变温度(T_o和T_p)降低、糊化焓(ΔH)减少。表明微波辐照对板栗淀粉的颗粒结构和理化特征均有显著影响。     

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.     

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.     

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.     

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.     

韧化处理对板栗淀粉特性的影响

以燕山板栗淀粉为材料,在30、40和50℃分别进行韧化处理。采用扫描电子显微镜(SEM)、X-射线衍射分析(XRD)、差示扫描量热分析(DSC)及体外消化法等方法,研究了韧化处理对板栗淀粉颗粒结构、理化特性和体外消化性的影响。研究表明:与原淀粉相比,韧化处理后2种板栗淀粉的直链淀粉含量降低,淀粉颗粒破损率增大,但淀粉仍为C型晶体。随着韧化温度的升高,淀粉颗粒表面出现凹坑和损伤越显著,膨胀度随着处理温度的升高而降低。DSC分析表明,韧化处理使淀粉的糊化温度升高,热焓变化不大。不同的韧化处理温度对板栗淀粉体外消化性有不同的影响,韧化处理使淀粉的快消化淀粉(RDS)含量减少,慢消化淀粉(SDS)含量增大。     

Structural and Physical Properties of Starches Isolated from Six Varieties of Millet Grown in China

This study investigated the structural and physical properties of starches extracted from six varieties of millet mainly grown in China. The amylose content of millet starches ranged from 17.6 to 28.4 g/100 g (dry weight basis, db), and a variety of waxy proso millet starch (0.38 g/100 g, db) was identified. These starches exhibited a majority of large polygonal granules with several indentations, few small spherical granules, and A-type crystallinity. Proso millet starch showed prominent paste clarity and freeze-thaw stability, whereas finger millet starch exhibited the highest solubility. Moreover, barnyard millet starch had the lowest sediment volume. The gelatinization enthalpy of proso millet starch was the highest (5.16 J/g). For non-waxy millet starch, the ratio of retrogradation (R%) was positively correlated with amylose content. Among all starches, the storage modulus (G′) was higher than the loss modulus (G″) during heating and cooling. The G′ and G″ of proso millet starch and barnyard millet starch pastes were significantly lower than other starches during cooling. The pasting properties of six millet starches significantly differed, had positive correlation with amylose content, and were affected by NaCl, sucrose, and pH values.