Wx Starch Research Articles

Selective Adsorption of Essential Oil Compounds by Waxy/Amylose Extender (wx/ae) Double‐Mutant Rice Starch Revealed by Gas Chromatography

The present study describes how waxy/amylose extender (wx/ae) double mutant and waxy (wx) single mutant rice starches adsorb many kinds of chemical compounds in essential oils using dynamic adsorption and gas chromatography. Selectivity in the dynamic adsorption is determined by the functional groups of chemical compounds. Compounds with a hydroxyl group (OH) are easily adsorbed. Compounds with aldehyde (CHO) and ketone ((CO)) groups, or with ester bonds ((CO)O) are also adsorbed if they had a cyclic structure or carbon double bond. Compounds with an ether bond (COC) are adsorbed if they had a carbon double bond. The dynamic adsorption process may be driven mainly by forming hydrogen bonds between hydroxyl groups of starch and these proton acceptor groups of chemical compounds in essential oils. The authors also analyzed the adsorption capacity of the wx/ae and wx starches for several compounds which are adsorbed to these starches in a dynamic process, by static adsorption. The wx/ae starch has greater capacity than wx starch to adsorb chemical compounds, due to its larger surface area and surface pore volume. The adsorption capacity of starch for chemical compounds is also affected by the structural features of the chemical compounds.

Linear and nonlinear rheological behavior of native and debranched waxy rice starch gels

Abstract The rheological behaviours of native (WX) and debranched (DB) waxy rice starch gels in the linear viscoelastic (LVE) regime and non-linear (NL) regime were investigated using small amplitude oscillatory shear (SAOS), and large amplitude oscillatory shear (LAOS), respectively. Our results show that WX starch gels exhibited a wider LVE region than DB starch gels, and a scaling of G′ with frequency given by G’∼ω0.26. The G' and G” scaled nearly linear with concentration and were nearly independent of temperature in the tested range. The Lissajous plots showed a gradual yielding of the gels, followed by softening behavior. These results indicated that the WX gel has the characteristics of a weak particle gel (of non-entangled polymers). In contrast, the DB starch produced gels with a more stiff and brittle behavior. The shear moduli had a very strong concentration dependence (∼C10.30) and temperature dependence. The DB starch gel showed more abrupt yielding and strong softening behavior in the Lissajous curves. Creep measurements showed a lower compliance for these gels, and significant creep ringing. These observations suggest the DB starch gels consist of clusters of stiff polymers.

Extraction and identification of internal granule proteins from waxy wheat starch

AbstractA method is described for extracting and comparing internal granule proteins from a normal commercial soft wheat variety (QAL2000) and related wx starch mutants (QA‐Wx‐59 and QA‐Wx‐1). Our results demonstrate that granule‐bound starch synthase I (GBSS I) was by far the most abundant internal protein of starch granules from QAL2000. Several minor, smaller bands observed in gels were also identified by MS as GBSS I peptides. The GBSS I peptides were detected in only trace amounts in the wx mutants. Proteins corresponding to other starch biosynthetic enzymes were present in QAL2000 and the wx mutants.

Starch–lipid composites containing cinnamaldehyde

AbstractThe formulation of a starch–lipid composite containing cinnamaldehyde as antimicrobial agent has been studied. Cinnamaldehyde was incorporated as an emulsion using acetem 90–50 K as a carrier and Tween 60 as the emulsifier. Oil in water emulsions were prepared by direct emulsification using a high shear mixer or a high pressure homogenizer (Microfluidizer). Oil in water emulsions containing cinnamaldehyde were further used to prepare starch–oil composites by mixing the emulsions with a completely gelatinized starch solution (wx starch, native corn dent starch, and high AM corn starch). Results demonstrated that in the presence of the emulsifier Tween 60, stable composites could be obtained when sufficient amount of AM was present in the sample. Finally, stable composites were tested for their biocidal activity against Listeria monocitogenes; no survivors remained after 1 day of incubation with 0.25% cinnamaldehyde or after 7 days with 0.025% cinnamaldehyde.

Mutation of the maize sbe1a and ae genes alters morphology and physical behavior of wx-type endosperm starch granules

In maize, three isoforms of starch-branching enzyme, SBEI, SBEIIa, and SBEIIb, are encoded by the Sbe1a, Sbe2a, and Amylose extender ( Ae) genes, respectively. The objective of this research was to explore the effects of null mutations in the Sbe1a and Ae genes alone and in combination in wx background on kernel characteristics and on the morphology and physical behavior of endosperm starch granules. Differences in kernel morphology and weight, starch accumulation, starch granule size and size distribution, starch microstructure, and thermal properties were observed between the ae wx and sbe1a ae wx plants but not between the sbe1a wx mutants when compared to wx. Starch from sbe1a ae wx plants exhibited a larger granule size with a wider gelatinization temperature range and a lower endotherm enthalpy than ae wx. Microscopy shows weaker iodine staining in sbe1a ae wx starch granules. X-ray diffraction revealed A-type crystallinity in wx and sbe1a wx starches and B-type in sbe1a ae wx and ae wx. This study suggests that, while the SBEIIb isoform plays a dominant role in maize endosperm starch synthesis, SBEI also plays a role, which is only observable in the presence of the ae mutation.

Amylopectin Nature and Amylose‐to‐Amylopectin Ratio as Influences on the Behavior of Gels of Dispersed Starch

ABSTRACTThe importance of the nature of the amylopectin and the amylose‐to‐amylopectin ratio in the gelation of high‐amylose maize starch was examined by preparing gels of model systems using amylose (AM) from a high‐amylose maize starch mixed with an amylopectin (AP): either wx starch, acid‐hydrolyzed wx starch (AH‐wx), ae wx starch, or wx β‐limit dextrin. Mixtures of 7.5% starch in 20% dimethyl sulfoxide (DMSO) were examined by differential scanning calorimetry and dynamic oscillatory rheometry. Mixtures of 1.88 or 3.75% AM with the remainder either wx or AH‐wx developed a measurable elastic modulus (G′) within one day, more quickly than for the corresponding AP without AM. Gels of AM with either wx or AH‐wx starch developed a higher retrogradation enthalpy (ΔH) than corresponding AP without AM when the ΔH values were normalized to the amylopectin content. The G′ and ΔH of all gels containing ae wx did not change after one day. During heating of the gels to 80°C, most of the G′ at 25°C was lost, indicating that the initial gel structure was not due to a thermally stable AM network. Gelation is proposed to be due to physical junction zones (PJZ) between AM molecules (AM‐AM), between AM and amylopectin molecules (AM‐AP), and between amylopectin molecules (AP‐AP). For wx, AH‐wx, or ae wx starch, the higher G′ and ΔH of the gels with 3.75% AM compared with the gels with 1.88% AM suggests that AM‐AP PJZ are more important in gel formation when AM makes up half the starch. Gels from the mixture of 3.75% AM and 3.75% ae wx starch behaved most similarly to gels of 7.5% high‐amylose maize starch. The development of a starch gel is affected by both the nature of the amylopectin as well as the amylose‐to‐amylopectin ratio of the gel.

Observations on the α‐Amylolysis Pattern of Some Waxy Maize Starches from Inbred Line Ia453

ABSTRACTMaize starches of the endosperm mutants waxy (wx), dull:waxy (duwx), and amylose‐extender:dull:waxy (aeduwx) from inbred line Ia453 lack amylose. However, in addition to high molecular weight (HMW) amylopectin, the duwx and aeduwx starches contained 40 and 80%, respectively, intermediate branched material of low molecular weight (LMW). As gelatinized, the amylopectin of the wx starch was easily hydrolyzed into small dextrins by the α‐amylase of B. amyloliquefaciens, but components of duwx and aeduwx possessed partial resistance to amylolytic attack. Residual material of intermediate size obtained by a 4‐hr α‐amylolysis could not be separated from LMW dextrins by fractional precipitation in methanol. It is suggested that this material possessed a more regularly branched structure, in which the d‐glucosyl chain segments were too short to allow α‐amylase action. The granular starches of duwx and aeduwx genotypes were initially considerably more resistant than the wx sample to α‐amylase attack. This was possibly due to an altered structure in the amylopectin component or the high content of intermediate material in the former granules.

Physical Properties and Enzymatic Digestibility of Phosphorylated ae, wx, and Normal Maize Starch Prepared at Different pH Levels

ABSTRACTPhosphorylated 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.

Effects of moisture content and different gelatinization heating temperatures on retrogradation of waxy-type maize starches

The effect of moisture content on retrogradation of wx, du wx, ae wx, and su2 wx maize starches was studied by differential scanning calorimetry (DSC). All starches showed maximum retrogradation enthalpy at an intermediate moisture content, but the precise relationship between moisture content and retrogradation enthalpy varied for each starch. The ae wx starch was least affected by moisture content, showing measurable retrogradation (2–3 J/g) after only 1 day for the 95% moisture sample. Retrogradation of the su2 wx starch was exceptionally slow even at intermediate moisture contents, and the retrogradation enthalpy was particularly sensitive to moisture content. The effect of varied moisture content was also investigated in combination with initial heating to a wide range of temperatures. Retrogradation of wx, du wx, and su2 wx starches, but not ae wx starch, was strongly influenced by both initial heating temperature and moisture content, with development of enthalpy consistently in the order of du wx> wx> su2 wx. The chain length profiles for the four starches were unique. The exceptionally rapid retrogradation and relatively small concentration dependence of ae wx starch may be related to a greater proportion of longer chains, whereas the very slow retrogradation of su2 wx starch may be related to a population of exceptionally short chains. The more rapid retrogradation of du wx starch than wx starch may be related to the high number and concentration of branch points in a cluster.

Retrogradation of du wx and su2 wx Maize Starches After Different Gelatinization Heat Treatments

ABSTRACTRetrogradation of du wx and su2 wx starches after different gelatinization heat treatments was studied by differential scanning calorimetry. Suspensions of 30% (w/w) starch were initially heated to final temperatures of 55–180°C. Gelatinized starch was cooled and stored at 4°C. Starch retrogradation in the storage period was influenced by initial heat treatments. Retrogradation of du wx starch was rapid: when initially heated to 80–105°C, retrogradation enthalpy was ≈10 J/g after one day at 4°C. The retrogradation enthalpy was ≈15 J/g after 22 days of storage, and reached a maximum of 16.2 J/g after 40 days of storage. For du wx starch, application of the Avrami equation to increases in retrogradation enthalpy suggests retrogradation kinetics vary with initial heating temperature. Furthermore, starch retrogradation may not fit simple Avrami theory for initial heating ≤140°C. Retrogradation of su2 wx starch was slow. After 30 days of storage at 4°C, the maximum retrogradation enthalpy for all initial heating temperatures tested was 7.0 J/g, for the initial heating to 80°C. This work indicates that gelatinization heat treatment in these starches is an important factor in amylopectin retrogradation, and that the effect of initial heat treatment varies according to the genotype.

Rheological and Thermal Properties of Aged Starch Pastes from Three Waxy Maize Genotypes

ABSTRACTThe rheological and thermal properties of aged starch gels (15:85 starch‐water) from three waxy maize genotypes (wx, wx sh1, and du wx) during storage (4°C for up to 25 days) were studied. After storage, changes of storage modulus (G′) and phase angle (δ) of the gels as a function of temperature were measured using oscillatory rheometry. For the du wx samples, G′ at 25°C increased rapidly during the first four days of storage at 4°C, compared to the gradual increases over the 25‐day storage period for the wx and wx sh1 samples. A peak in G′ at 45°C was observed during heating for the du wx samples after 10 days of storage and for the wx sample stored for 25 days. The G′ peak may have been due to syneresis in the gels. Retrogradation of amylopectin of the aged starch samples was examined using differential scanning calorimetry. The du wx starch had greater retrogradation enthalpies than the other two samples (which showed similar retrogradation behavior) throughout the storage. The retrogradation enthalpy of the du wx samples increased rapidly during the first seven days, followed by a slower increase through the rest of storage. For the wx and wx sh1 samples, no endotherm was observed during the first four days of storage, after which the enthalpy increased steadily as a function of storage time. Addition of sucrose delayed the formation of gel networks for all three starches. The greater tendency for gelling and retrogradation of the du wx starch might be attributed to the greater proportion of DP20–30 chains of the amylopectin.

Retrogradation of Maize Starch After Thermal Treatment Within and Above the Gelatinization Temperature Range

ABSTRACTStudies of starch retrogradation have not considered the initial thermal treatment. In this article, we explore the effect of heating to temperatures within and above the gelatinization range on maize starch retrogradation. In the first experiment, 30% suspensions of waxy (wx) starch were initially heated to final temperatures ranging from 54 to 72°C and held for 20 min. On reheating in the differential scanning calorimeter immediately after cooling, the residual gelatinization endotherm peak temperature increased, the endotherm narrowed, and enthalpy decreased. Samples stored for seven days at 4°C showed additional amylopectin retrogradation endotherms. Retrogradation increased dramatically as initial holding temperature increased from 60 to 72°C. In a second experiment, wx starch was initially heated to final temperatures from 54 to 180°C and rapidly cooled, followed by immediate reheating or storage at 4°C. Maximum amylopectin retrogradation enthalpy after storage was observed for initial heating to 82°C. Above 82°C, retrogradation enthalpy decreased as initial heating temperature increased. A similar effect for ae wx starch was observed, except that retrogradation occurred more rapidly than for wx starch. These experiments show that heating to various temperatures above the range of gelatinization may profoundly affect amylopectin retrogradation, perhaps due to varying extents of residual molecular order in starch materials that are commonly presumed to be fully gelatinized. This article shows that studies of starch retrogradation should take into account the thermal history of the samples even for temperatures above the gelatinization temperature range.

Thermal Properties of Starch from Selected Maize (Zea mays L.) Mutants During Development

ABSTRACTThe changes in thermal properties of maize starches during five stages of kernel maturity, (12, 18, 24, 30, and 36 days after pollination [DAP]), from three mutant genotypes, amylose extender (ae), sugary‐2 (su2), and waxy (wx) in an OH43 background, and the OH43 genotype were studied using differential scanning calorimetry (DSC). Within a genotype, DSC values of starches at 24, 30, and 36 DAP were similar to each other and often were significantly different (P < 0.05) from the values at 12 DAP, indicating possible differences in the fine structure of starch during endosperm development. For su2 starches, the gelatinization onset temperature (ToG) significantly decreased after 12 DAP and remained low throughout the study. The gelatinization range (RG) had a similar pattern. For wx starches, ToG at 18 DAP was significantly lower than at 12 DAP but tended to increase after 18 DAP. The RG increased significantly after 12 DAP and significantly decreased after 30 DAP. Thus, thermal properties of starches during early development were different from those of their mature counterparts, and differences among the mutant genotypes and the normal starch originated from the earliest endosperm development stage studied (12 DAP).

Fine structure of maize starches from four wx-containing genotypes of the W64A inbred line in relation to gelatinization and retrogradation

Maize starches from four wx-containing genotypes ( wx, du wx, ae wx, and ae du wx) of the W64A inbred line were examined to determine their gelatinization and retrogradation properties and the fine structure of their amylopectins (AP). Chain-length distribution profiles of the APs showed distinct patterns according to genotype. The wx and du wx starches had a large proportion of short chains and showed A-type X-ray patterns, whereas the ae wx and ae du wx starches had a large proportion of long chains and showed B-type X-ray patterns. The ae wx starch had the highest values of onset melting temperature ( T o) and heat uptake (Δ H), both for gelatinization and after retrogradation, which were attributed to a greater proportion of long chains (degree of polymerization > 16) in the AP. Debranching of β-limit dextrins also revealed that the interior chain-length distribution of AP from the ae wx genotype constituted a large proportion of long chains. The extent of retrogradation increased in the order wx, du wx, ae wx and ae du wx starches and appeared to be proportional to the level of unit chains with DP 16–30 and inversely proportional to the level of short chains with DP 6–11.

遺伝的要因が澱粉の特性に及ぼす影響

1. Starch granules were prepared from mature kernels of several single mutants, double- and triple-mutant combinations of waxy (wx) gene with other endosperm genes, and their normal counterpart in the inbred 0h43 maize (Zea mays L.) background. Starches of the mutants containing the wx gene comprised almost 100% amylopectin. jS-Amylase limit dextrins prepared from the starches were successively debranched by isoamylase and pullulanase, and followed by quantitative gel-filtration on Toyopearl HW54SF. The unit chain-length distribution of amylopectins of the normal and wx starches were similar. Amylopectin of the amylose-extender ; waxy (ae ; wx) mutant had an increased proportion of long B chains and a decreased proportion of short B chains, compared with wx amylopectin, whereas amylopectin of dull ; waxy (du ; wx) mutant had a decreased proportion of long B chains and an increased proportion of short B chains. Therefore, the ae ; wx and du ; wx amylopectins were novel. Amylopectin of the ae ; du; wx mutant belonged to the du ; wx type instead of the ae ; wx type. 2. Starch granules were prepared from rice (Oryza sativa L.) endosperms of dull (du), sugary (sug), and high-amylose (ae) mutants. The amylose content of the du starch was half as low as that of the nonmutant (normal) one. The sug starch contained more amylose than the normal starch. The starch in the ae mutants was characterized by a higher content of amylose and loosely branched amylopectin with longer chains compared with the normal starch.

Gelatinization Characteristics of Starch from du, wx, ae, and ae wx Endosperm of Sweet Corn Inbred la5125

AbstractStarch gelatinization in excess water was studied by differential scanning calorimetry for the mutants dull (du), waxy (wx), and amylose extender (ae), and the double mutant amylose‐extender, waxy (ae wx) from the Ia5125 sweet corn inbred background. Onset temperature (To), peak temperature (Tmax), and enthalpy (ΔH) were determined. For du and wx starches Tmax was within 1°C of the value for the normal starch (Tmax = 69.4°C). For starches from ae and ae wx mutants, Tmax was 7–8°C higher than the normal starch. The highest enthalpies were observed for wx (3.26 cal/g) and ae wx (3.39 cal/g) starches; ae (2.93 cal/g) and normal (2.52 cal/g) starches were intermediate, and du (2.32 cal/g) starch had the lowest enthalpy. The endotherm of the ae starch was completed at just above 100°C, in distinction to reports for ae mutants from dent lines. Although the ae wx endotherm occurred at a higher temperature than the wx, the endotherm was sharpened relative to the ae endotherm, and was complete at 90°C.

Starch characteristics in cultures of normal and mutant maize endosperm

Vigorously growing suspension cultures of 'normal', amylose-extender (ae) and waxy (wx) maize endosperm were established from near isogenic lines of maize inbred A636. The recovery of the ability to produce vigorous cultures of ae and wx endosperm by backcrossing demonstrate the genetic control of endosperm growth in vitro. Phenotypic expression of the endosperm mutants in culture was studied by examining the properties of starch accumulated in endosperm cultures and starch from developing and mature kernels of the same genotype. After 9 months in culture, the amylose contents of the starch in normal callus tissue and normal endosperm tissue were not significantly different, 28.2% and 31.7%, respectively. Starch granules from normal cultures and endosperm stained blue-black with iodine and were round to polygonal in shape. The starches of wx endosperm and callus cultures contained no amylose, and wx starch granules stained brown-orange with iodine. Although, wx starch granules were primarily round, a few granules with "jagged edges" were observed in starch samples isolated from cultures and kernels. The percent amylose in starch from ae callus was significantly lower than the amylose content of starch from ae endosperm tissue, 39.9% and 67.7%, respectively. Starch granules from ae endosperm and cultures were smaller than normal and wx starch granules. Irregular starch granules which are typical of ae endosperm were present in ae callus tissue, but were less frequently observed. We conclude that specific endosperm mutant phenotypes are expressed in vitro.

Susceptibility of Starch Granules from Maize Endosperm Mutants to Amylases1

Abstract Starch granules were extracted from maize (Zea mays L.) endosperm of mature F2 kernels of IA5125 × IA453 normal, amylose-extender (ae), dull (du) waxy (wx), and ae du wx and from ae du wx F2 kernels harvested at the fresh market stage of development. Samples were digested for 1.5 hours with hog pancreatic α- amylase and Rhizopus II amyloglucosidase. The mature and immature ae du wx samples were usually digested significantly more than the other 4 genotypes, while ae was digested significantly less than the others. Digestion of starch granules from mature and immature ae du wx kernels did not differ. The sweet corn background used had little effect, since our observations of the single mutant genotypes were similar to those in a dent background. Clearly, ae du wx starch granules do not reflect the reduced digestibility associated with ae, and thus cultivars homozygous for ae du wx are not inferior with respect to their ability to supply carbohydrates to the diet.

The Interaction of the Amylose‐Extender and Waxy Mutants of Maize (Zea Mays L.) Fine Structure of Amylose‐Extender Waxy Starch

AbstractInvestigations into the nature of the effect of the amylose‐extender (ae) mutant of maize (Zea mays L.) on amylopectin structure were conducted by studying the fine structure of amylose‐extender waxy (ae wx) starch. Approximately 59.6% of the starch from ae wx endosperms was converted to maltose by β‐amylase. This starch contained 21% apparent amylose and had a λmax of 580 for the iodine‐starch complex. Fractionation of ae wx starch on Sepharose 4B‐200 gave an elution profile with a single peak characteristic of amylopectin. From these observations we concluded that ae wx starch consisted of an altered amylopectin, with iodine binding properties such that an apparent amylose content of 21% was measured.The fine structures of ae wx and waxy (wx) starches were determined. Pullulanase‐debranched chains of whole starches and β‐limit dextrins were fractionated by gel permeation. The amylopectin of ae wx was shown to be a loosely branched amylopectin with an average internal chain length of 52 glucose units compared with a length of 30 glucose units for wx. The ae wx outer chains were longer than those of wx and fewer in number per mg of starch. These characterizations demonstrate that ae wx starch has a unique structure which is similar to the anomalous amylopectin reported in ae starch.