Pasting and Thermal Properties of Potato and Bean Starches

Starches from potato (Mainechip, ND651-9 and Commercial) and Navy and Pinto bean were isolated and the pasting and thermal properties examined. Analysis by Rapid Visco-Analyzer (RVA) showed potato starches had lower pasting temperatures, higher peak viscosity, and lower setback than bean starches. High intrinsic viscosity values obtained for the potato starch indicated higher average molecular weight for the potato starches compared to the bean starches. Characterization of thermal (gelatinization and retrogradation) properties of starches by Differential Scanning Calorimetry (DSC) showed that potato starches had sharp, well-defined gelatinization thermograms, while bean starches had broad, shallow thermograms with higher peak temperature (Tp). Potato starches required higher gelatinization enthalpies than bean starches. In comparison with gelatinization, the retrogradation thermograms of starches stored at three different temperatures (23,4 and −10°C) were broader and occurred at the lower temperatures. Compared to potato starches, Navy and pinto bean starches showed a higher retrogradation enthalpy at 4 and 23°C storage temperatures, but a lower enthalpy at −10°C.     

Inhibitory Effects of Green Tea Polyphenols on the Retrogradation of Starches from Different Botanical Sources

This paper aims at investigating the effects of green tea polyphenols (GTPs) on the retrogradation of potato, rice, and maize starches. Starch/GTPs mixing ratios were 2/0, 2/0.1, 2/0.2, and 2/0.3 (w/w) that equated with starch containing 0%, 5%, 10%, and 15% GTPs (based on starch weight), respectively. The analytic samples had a water–starch/GTPs ratio of 2:1. The effects of GTPs on the retrogradation of these starches were analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The analysis of DSC indicates that the temperature and enthalpy of gelatinization of all the tested starches decreased as the GTPs level increased. After storage at 4 °C, retrogradation enthalpy (ΔH _ret) for potato starches with 5%, 10%, and 15% GTPs appeared after 10 days of storage, however ΔH _ret for rice and maize starches with 10% and 15% GTPs did not appear until storage of 20 days, and both the ΔH _ret and degree of retrogradation of the three starches significantly decreased with the increased level of GTPs. After 10 days of storage at 4 °C, the analysis of XRD shows that the intensity of X-ray diffraction peaks of potato starch gradually decreased with the concentration of GTPs increasing, and rice and maize starch gels with 10% and 15% GTPs had almost no recrystallization of the retrogradation. It is concluded that the addition of GTPs considerably inhibits the retrogradation of rice, maize, and potato starches.     

Influence of enzyme active and inactive soy flours on cassava and corn starch properties

The aim of this work was to study the influence of enzyme active and inactive soy flours on the properties of cassava and corn starches. Four starch/soy flour composites were evaluated: cassava/active soy flour (Cas/AS), cassava/inactive soy flour (Cas/IS), corn/active soy flour (Corn/AS) and corn/inactive soy flour (Corn/IS). Starch gelatinization occurred at 58.67°C for Cas and at 64.19°C for corn; gelatinization occurred at higher temperatures when soy flours were present, while ΔH diminished. The presence of AS reduced 80% the retrogradation enthalpy of Cas and 40% that of corn. Cas presented lower pasting temperature than corn starch (67.8 and 76.8°C, respectively) and higher peak viscosity (427.9 and 232.8 BU, respectively). The pasting properties of both starches were drastically reduced by soy flours, and this effect was more noticeable in Cas; AS had higher effect than IS. X‐ray diffraction pattern of retrograded samples showed that both starches recrystallisation (mainly that of Cas) was reduced when AS was added. Tan δ values decreased with AS addition to corn, but they increased when added to Cas. The images obtained using confocal laser scanning microscopy (CLSM) showed that IS was distributed as large aggregates, whereas AS distribution was more homogeneous, especially when incorporated to Cas. These results show that cassava starch interacts specifically with active soy flour (AS, mainly in native state). The delaying effect of AS on cassava starch retrogradation was clearly shown. This finding could be useful in obtaining gluten‐free breads of high quality and low retrogradation rate.     

Effect of debranching and storage condition on crystallinity and functional properties of cassava and potato starches

Debranching starch by pullulanase is considered to improve the RS content of starch which is widely used to produce the starch‐based foods with high‐health benefit impacts. In this study, the cassava and potato starches were debranched by pullulanase, followed by an autoclave treatment and storage at −18°C, 4°C, or 25°C to investigate their crystallinity and functional properties. After debranching, the potato starch contained significantly higher CL (35.4 glucose units) than did the cassava starch (32.4 glucose units). The debranched cassava and potato starches after retrogradation at the storage temperatures had a typical B‐type crystalline structure although the native cassava and potato starches exhibited the different crystalline forms (A‐ and B‐type, respectively). The RS contents of the debranched cassava and potato starches significantly improved with higher RS content of the debranched potato starch than that of the debranched cassava starch at the same storage condition. The storage temperature significantly affected the RS formation of the debranched starches with the highest RS content at storage temperature of −18°C (35 and 48% for the debranched cassava and potato starches, respectively). The debranched starches had significantly lower viscosities and paste clarities but higher solubilities than did the native starches. As a result, the debranched cassava and potato starches can be considered for use not only in functional foods with enhanced health benefits but also in pharmaceutical and cosmetic industries.     

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.     

Effect of Fiber Degrading Enzymes on Wet Milling and Starch Properties of Different Types of Sorghums an Maize

A factorial experiment (4 × 2 × 2) was carried out to study the effect of a fiber degrading enzyme complex on starch yield, SO₂ steeping time and starch properties of normal red sorghum (RS), heterowaxy (WHWx) and waxy (WWx) white sorghums compared to regular yellow maize (YM). Starch yields and total starch recovery for the sorghums ranged from 53–64% and 70–85%, respectively. Sorghum starch recovery values were significantly lower (p < 0.05) than maize (66% starch yield and 88% recovery). However, the WWx yielded more starch with lower protein and ash contents (P < 0.05) than the RS and WHWx sorghums. In the RS, the fiber degrading enzymes reduced steep time while owing the same starch recovery. The WWx starch required lower temperature to initiate gelatinization and had higher peak viscosities and lower retrogradation than the other starches. The WHWx starch had intermediate viscoamylograph properties between the regular and waxy starches.     

Isolation and characterization of Mexican chayote tuber (Sechium edule Sw.) starch

Starch was isolated from Mexican chayote tubers (Sechium edule Sw.) and the yield, physicochemical, rheological, and molecular characteristics were investigated. Commercial potato was used for comparison. Starch yield was 49% with a purity of 89.1%. AM content of chayote tuber starch was 26.3%. Birefringence was shown in chayote tuber starch and granules had diverse shapes such as spherical, oval, and polygonal, with size between 10 and 25 µm. B‐type XRD pattern was shown by chayote tuber starch. Chayote tuber starch had higher peak viscosity (PV) than potato starch and the maximum PV for chayote tuber starch was obtained at lower temperature. Flow properties of chayote tuber starch showed higher hysteresis than potato at the same concentration. In chayote tuber and potato starches, G′ > G″ at both temperatures. Chayote tuber starch presented slightly lower gelatinization temperatures, but slightly higher enthalpy of gelatinization than potato starch, and similar retrogradation rate (due to the enthalpy value of the phase transition) were found in both tuber starches. Chayote tuber starch presented higher Mw and Rz values than potato starch. Chayote tuber could be an alternative for starch isolation with specific physicochemical and molecular characteristics.     

The physicochemical properties and in vitro digestibility of selected cereals,tubers and legumes grown in China

Digestibility, gelatinization, retrogradation and pasting properties of starch in various cereal, tuber and legume flours were determined. Rapidly and slowly digestible starch and resistant starch were present in 11 selected flours. In general, cereal starches were more digestible than legume starches and tuber starches contained a high amount of resistant starch. Thermal and rheological properties of flours were different depending on the crop source.     

Morphological,Thermal, Pasting,and Rheological Properties of Barley Starch and Their Blends

Native barley starch, as well as its blends with corn, wheat, and rice starch at different ratios of 75:25, 50:50, 25:75 were examined in terms of morphology, thermal, pasting, rheological, and retrogradation properties. Amylose content varied between 10.9–41.4% in rice, corn, wheat, and barley while it ranged from 18.02–38.40% in blends of barley starch with rice, corn, and wheat. A rapid visco analyzer showed that barley starch and its blends having low amylose content exhibited higher peak viscosity, breakdown, and setback than the high-amylose-containing starches and their blends. Amylose content was found to be negatively correlated with swelling power while it exhibited nonlinear relationship with solubility index. The transmittance of starch suspension stored at 4°C decreased during storage up to 6 days. Barley starch granules were largest (<110 μm) in size followed by wheat (<30 μm), corn (<25μm) and rice (<20μm) starches. Gelatinization temperatures (To, Tp, Tc) and enthalpies of gelatinization (ΔHgel) of starches from different sources also differed significantly. Corn and rice starches showed higher transition temperatures in general than those from wheat and barley; however, they showed higher ΔHgel values. Barley starch showed a higher tendency towards retrogradation than the cereal starches. Barley starch showed highest peak G′, G″ and lower tan Ð than corn, rice and wheat starches during the heating cycle. This study showed that the magnitude of changes in their properties during blending depends on the amylase content and morphological characteristics.     

Effect of Fiber Degrading Enzymes on Wet Milling and Starch Properties of Different Types of Sorghums and Maize

A factorial experiment (4 × 2 × 2) was carried out to study the effect of a fiber degrading enzyme complex on starch yield, SO₂ steeping time and starch properties of normal red sorghum (RS), heterowaxy (WHWx) and waxy (WWx) white sorghums compared to regular yellow maize (YM). Starch yields and total starch recovery for the sorg-hums ranged from 53—64 % and 70—85 %, respectively. Sorghum starch recovery values were significantly lower (p < 0.05) than maize (66 % starch yield and 88 % recovery). However, the WWx yielded more starch with lower protein and ash contents (p < 0.05) than the RS and WHWx sorghums. In the RS, the fiber degrading enzymes reduced steep time while producing the same starch recovery. The WWx starch required lower temperature to initiate gelatinization and had higher peak viscosities and lower retrogradation than the other starches. The WHWx starch had intermediate viscoamylograph properties between the regular and waxy starches.     

Starch of diverse Mexican rice cultivars: physicochemical,structural, and nutritional features

Structure‐function relationship of rice starch is scarce in the literature. Starch was isolated from diverse Mexican rice varieties and their swelling power (SP), soluble solids (ss), thermal and pasting properties, XRD pattern, in vitro starch digestibility, and AP chain‐length distribution were evaluated. Rice starches with low SP at 60°C had higher temperature and enthalpy of gelatinization. The peak viscosity of rice starches ranged between 2426 and 3519 cP, and the samples presented high values for setback due to the AM content. Rice starches presented the typical A‐type XRD pattern with crystallinity values between 32.7 and 36.3%. Rice starches presented high amounts of short chains (A and B1), and differences were found among the cultivars. AM content for rice starches ranged between 18.4 and 22.9%, and the main fraction recorded by HPSEC was the Fraction III (short chains) with values around 60%. The uncooked rice starch samples presented high values of slowly digestible starch (SDS) and rapidly digestible starch (RDS), and differences were found among the cultivars. In cooked samples decreased SDS and increased RDS and RS. Onset temperature and enthalpy of gelatinization were correlated with the percentage of A‐chains and an opposite pattern was found with the percentage of B1 chains. AP structural characteristics affect the functional, physicochemical, and digestibility properties of rice starches.     

Morphological,thermal and rheological properties of starches separated from rice cultivars grown in India

Morphological, thermal and rheological properties of starches separated from five rice cultivars (PR-106, PR-114, IR-8, PR-103 and PR-113), varying in amylose content, were studied. Amylose contents of starches separated from PR-103, IR-8, PR-106, PR-114 and PR-113 were 7.83, 15.62, 16.05, 16.13 and 18.86%, respectively. The granular size, measured using a Scanning Electron Microscope, varied from 2.4 to 5.4 μm in all rice starches. PR-103 starch, with lowest average granular size, amylose content and solubility, had the highest swelling power, while PR-113 starch, with the highest average granular size and amylose content had the lowest swelling power. PR-103 starch showed highest transition temperatures, enthalpies of gelatinization, peak height index, range and enthalpies of retrogradation. The retrogradation (%) was observed to be highest in PR-113 starch and lowest in PR-103 starch. The changes in rheological parameters of rice starches during heating were measured using a Dynamic rheometer. PR-113 rice starch showed the highest G′, G″ and breakdown in G′ values, whereas PR-103 starch showed the lowest values for these parameters. Turbidity value of gelatinized pastes from all rice starches progressively increased up to the 3rd day during refrigerated storage, PR-103 starch paste showed the lowest turbidity value and PR-113 starch showed the highest value. The syneresis (%) of starch pastes, from different rice cultivars during storage at 4 °C, was also measured. The syneresis of starch pastes from all rice cultivars, except PR-103, increased with storage. PR-103 starch paste showed negligible syneresis during storage.     

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.     

Viscosity and Gelatinization Characteristics of Hydroxyethyl Starch

Viscosity and gelatinization characteristics of corn and potato starches as well as their hydroxyethyl derivatives were investigated. The inherent viscosity increased from 164 in native corn starch to 209 in etherified one of DS 0.18. The etherified corn starch gelatinized at lower temperature than native corn starch due to their increase of DS. Maximum viscosity decreased from 93°C to 69°C for the modified corn starch. The retrogradation of starch was minimized by etherification as retrogradation ability of corn starch from its solution decrease from 22% to 6%. This is of great importance when starch is used as blood plasma volume expander. Variable results were obtained with etherified potato starch which might be due to its high contents of phosphorus.     

Effect of Acetylation on Some Properties of Corn and Potato Starches

Corn starch and starches separated from different potato cultivars were acetylated to evaluate the effect of plant source on the physicochemical, morphological, thermal, rheological, textural and retrogradation properties of the starches. Corn starch showed a lower degree of acetylation than potato starches under similar experimental conditions. The degree of acetylation for different potato starches also differed significantly. Morphological examination revealed that the granules of acetylated Kufri Chandermukhi and Kufri Sindhuri starches tended to appear as fused and less smooth than native starch granules. Acetylation of corn and potato starches decreased the transition temperatures and enthalpy of gelatinization and increased swelling power and light transmittance. However, the change in these was greater in the potato starches with higher percentage of small sized granules. Acetylated starches showed higher peak G', G'' and lower tan δ than their counterpart native starches during heating. Among the starches from different cultivars, the change in the rheological parameters after acetylation differed to a significant extent. The retrogradation was observed to be negligible in the acetylated cooked starch pastes. Results implied that the change in functional properties of starches with acetylation depends on source and granule morphology of native starch.     

Thermal characteristics of ohmically heated rice starch and rice flours

ABSTRACT:  Thermal properties of conventionally and ohmically heated rice starch and rice flours at various frequencies and voltages were studied. There was an increase in gelatinization temperature for conventionally heated rice starches since they were pregelatinized and became more rigid due to starch–chain interactions. In addition, there was a decrease in enthalpy (energy needed) for conventionally and ohmically heated starches during gelatinization; thus, the samples required less energy for gelatinization during DSC analysis. Ohmically heated commercial starch showed the greatest decrease in enthalpy probably because of the greatest extent of pregelatinization through ohmic heating. Brown rice flour showed the greatest gelatinization temperature resulting from the delay of starch granule swelling by lipid and protein. Enthalpy of ohmically heated starches at 20 V/cm was the lowest, which was most likely due to the lower voltage resulting in a more complete pregelatinization from a longer heating time required to reach 100 °C. Ohmic treatment at 70 V/cm decreased onset gelatinization temperature of white flour; therefore, it produced rice flour that swelled faster, whereas the conventionally heated sample showed a better thermal resistance.     

Effect of physico‐chemical properties of tropical starches and hydrocolloids on rice gels texture and noodles water retention ability

The links between the physico‐chemical properties of rice flour (RF), cassava (CS), sago (SS), canna (CaS), sweet potato (SPS), and mung bean (MS) starches, and the gelling properties of rice flour blends with these starches in different proportions (0, 20, 40, 60, 80, and 100% pure starches) and with xanthan (XG) and carrageenan (CG) gums were studied. Water retention ability of starches and hydrocolloids blends in noodle systems during drying at 40°C was also investigated. The mean granule diameter and AM content values of RF, CS, SPS, SS, CaS, and MS were in the range of 12.8–41.0 µm and 21.9–39.4%, respectively. Thermal properties showed significant differences (p < 0.05) between the starches in terms of gelatinization temperature and enthalpy, as well as retrogradation tendency. Different starches produced gels with a wide range of textural properties. Results confirmed the role of AM content in determining the gel strength, and indicated a possible role of retrogradation in increasing the dissipation of mechanical energy during compression and relaxation tests, which can have an effect on mouth feel. Blends of RF with other starches and hydrocolloids generally improved the characteristics of RF‐based gels, by increasing gel strength. In particular, the use of MS markedly increased the strength of RF‐based gels. Addition of hydrocolloids significantly reduced the drying rate of noodles, although overall water retention ability was reduced only to a limited extent. This may be used to produce starch‐based products, especially noodles, in a range of desired characteristics.     

Physicochemical Properties of Sweet Potato Flour and Starch as Affected by Blanching and Processing

The effects of blanching on physicochemical properties of flours and starches prepared from two varieties of sweet potatoes (Mun‐Kai and Negro) were studied and compared. The pasting temperature and peak viscosity of starches, respectively, were 74 and 80 °C and 381 and 433 RVU. The pasting temperature (74.0‐94.8 °C) of flours was greater than that of starch, depending on the variety and blanching process. However, the peak viscosity (ca. 103‐120 RVU) of flours was lower than that of the corresponding starches. Partial gelatinization of starch granules was observed as a result of a 1‐min blanching. Composition of starch and flour was found to affect swelling power and solubility. The starch content of starches, flours from unblanched sweet potato and flours from 1‐min blanched sweet potatoes were 97; 66.3 and 74.9; as well as 36.6 and 40.4%, respectively. Amylose content of flours and starches varied from 17.2‐20.8%.     

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。     

Gelatinisation and Retrogradation Behaviour of Some Starch Mixtures

Differential scanning calorimetry (DSC) and dynamic rheological measurements were used to characterise the behaviour of potato‐waxy maize, potato‐barley and waxy maize‐barley starch mixtures. Gelatinisation and retrogradation were studied at two starch concentrations, 20% (w/w) and 50% (w/w). In the DSC gelatinisation thermograms of the mixtures it was possible to recognise features of the thermograms of the individual components, indicating that each starch gelatinised independently of the other starch in the mixture. The retrogradation enthalpy was measured in the DSC after four and seven days of storage at 6 °C. The lowest values of retrogradation enthalpy for the mixtures were found for the waxy maize‐barley and potato‐barley mixtures, particularly at 20% starch concentrations and in the ratios 25:75 and 50:50, correspondingly. The retrogradation enthalpy measured for most starch mixtures corresponded to the calculated value, assuming that each starch contributed to the enthalpy according to its proportion in the mixture. Storage and loss moduli were measured for gelatinised starch suspensions during cooling from 90 to 6 °C, and then during a holding period at 6 °C for up to 6 h. The moduli for the mixtures were in most cases in between the values obtained for the individual starches.