Peak Gelatinization Temperature Research Articles

Characterization of arenga starch in comparison with sago starch

The aim of this research was to characterize the composition and physical properties of palm starch obtained from Arenga pinnata in comparison with another palm starch from Metroxylon sago. The amylose contents of both starches were not significantly different. Peak gelatinization temperature was also similar at approximately 67°C, but arenga starch showed a narrower range of gelatinization temperature than sago. The crystallinity and swelling power capacity of arenga starch were lower than those of sago. Arenga and sago starch paste at low concentrations showed shear thinning behavior, and sago formed a more viscous sol/paste than arenga. The sol–gel transition concentration of sago starch paste was found at a lower concentration than arenga starch. At high concentrations, gel from arenga starch was more rigid than that of sago. The breaking properties and texture profile of both starch gels were also clearly different, suggesting that they are suited for different applications.

Synthesis, physicochemical characterization, and functional properties of an esterified starch from an underutilized source in Nigeria

Acha (Digitaria exilis Sta pf), also known as Findi, Hungry rice , Petit mil and White fonio, is a small seeded cereal, indigenous to West Africa, which is generally classified as millet. It grows in various parts of Nigeria, Sierra Leone, Ghana, Guinea Bissau and Benin Republic . That species is the most important of a diverse group of wild and domesticated Digitaria species that are harvested in the savannas of West Africa. It is one of the primary cereals of southern Sudan and Ethiopia in Africa. It has potential to improve human nutrition, boost food security, foster rural development and support sustainable use of lands . In this study, acha starch was subjected to modification by acetylation. The acetylated acha starch with degree of modification 0.78 had reduced foaming capacity and amylose contents. The starches have similar organoleptic properties ranging from white, gritty, non sticky to bland tastes. P hysicochemical indices investigated such as true density, bulk and tapped densities, water absorption capacity, moisture content, total and acid insoluble ash, and pH were reduced by the acetylation of acha starch. The modification resulted in a significant (P < 0.05) increase in the solubility as well as water and oil absorption capacities of the starch. Scanning electron micros copy revealed starch granules that were predominantly polygonal in shape. Acetylation did not alter the granule morphology. X -ray pattern of the native starch was A type, with similar pattern in the acetylated derivative. Fourier transform infrared spectroscopy (FTIR) results revealed a new band at 1728 cm -1. Thermogravimetry revealed 3 phase decomposition of both the native and modified starches. The a cetylation as revealed by Differential scanning calorimetry studies improved the gelation capacity of the native starch and revealed two endothermic peaks and one exothermic peak each for both starches . There was considerable reduction in the peak temperature of gelatinization (Tp) of native starch and a significant (P < 0.05) decrease in the enthalpy of gelatinization (DH) was noticed after acetylation.

Rheological properties of water insoluble date fiber incorporated wheat flour dough

The influence of water insoluble date fiber addition, to standard flour was studied through rheological tests at small and large deformations and at different levels of fiber incorporation (1–10 g/100 g). The added DF increased the water absorption of the dough. An increase in mixing time and stability were recorded upon addition of DF (≤5 g/100 g), and the extensibility decreased at similar condition. The elastic modulus, G′ of the blended doughs increased with fiber concentration in the frequency range of 0.1–10 Hz, and the dough exhibited predominating solid-like behavior. The difference in microstructure between control and fiber incorporated dough samples were characterized by a plot of G′ vs. G″. During non-isothermal heating of doughs from 30 to 95 °C at a heating rate of 2.5 °C/min, the G′ achieved its peak value (TG′max) at a temperature representing the peak gelatinization temperature (Tp). Addition of DF did not significantly affect the Tp of the dough. The dough gelatinization kinetics was described by two rate equations corresponding to upward and downward of gelatinization curve. The upward and downward curves fitted the first-order and the second-order reaction kinetics, respectively. The gelatinization process activation energies ranged between 129 and 194 kJ mol−1.

Effect of different drying methods on the physicochemical and functional properties of Dioscorea opposita Thunb. starch

AbstractThe effect of sulfur fumigation and freeze–drying on the physicochemical and functional properties of Dioscorea opposita Thunb. starch was investigated. Freeze–drying markedly decreased the AM content of starch from 16.68 to 8.59%. Both sulfur fumigation and freeze–drying decreased the protein content but obviously increased the water absorption capacity and swelling power. Sulfur fumigation significantly increased the solubility of starch. Retrogradation tests showed that Chinese yam starch had a poor stability of retrogradation in water, salty, sugar, and acidic medium, but a good stability in alkaline medium. SEM analysis showed that different drying methods had minor effects on the morphological properties of D. opposita cv. Ma starch. Although the pattern of D. opposita cv. Ma starch was C‐type and was not affected by drying methods, sulfur‐fumigation, and freeze–drying increased the crystalline degree of starches from 23.24 to 25.16% and 34.40%, respectively. A minor difference was found in the Fourier transform infrared spectra of native and treatment starches. After sulfur fumigation and freeze–drying, the peak gelatinization temperatures increased from 71.03 to 76.03°C and 83.07°C, respectively, whereas the gelatinization enthalpy and gelatinization range decreased.

Studies on the Gelatinization Temperature of Some Cereal Starches

Gelatinization temperature of starches from different varieties of cereals, deep-red sorghum, red sorghum, white sorghum, mixed sorghum, white fonio (Digitaria exilis), black fonio (Digitaria iburua), Eleusine coracana (tamba), proso millet (p. miliacium), brown top millet (p. ramosum) and finger millet (Eleusine coracana) were determined by electrical conductivity (EC) method. Among the untreated starches, the results showed that tamba recorded the least onset and peak gelatinization temperatures of 53.0oC and 63.0oC respectively while the highest onset gelatinization temperature, 76oC was recorded with proso millet. Proso millet and finger millet had the highest peak gelatinization temperature. deep-red sorghum and red sorghum had the least end gelatinization temperature while proso millet recorded the highest value. The 0.1MKCl treatment of cereals starches produced elevated onset gelatinization temperatures (62.0-78.0oC). Mixed sorghum had the least onset gelatinization temperature while proso millet and finger millet recorded the highest gelatinization temperature. Following the 0.1MKCl treatment, starches from tamba and proso millet recorded the least and highest peak gelatinization temperatures respectively. Deep-red and red sorghum recorded the least end gelatinization temperatures while proso millet, brown top millet and finger millet recorded the highest end gelatinization temperatures. The treatment of the cereals starches with 0.10MKCl significantly (p < 0.05) delayed the onset gelatinization temperature of the starches and narrowed the gelatinization temperature range. The results of the conductivity of both the 0.1MKCl treated and untreated starch showed nonlinearity within the gelatinization range. This finding has important implication on the energy and time requirement to gelatinize the starch for specific industrial use.

Physicochemical Characteristics of Starches in Rice Cultivars of Diverse Amylose Contents

Through the sampling four rice cultivars with differing amylose contents, the relationship between the structural and gelatinization properties of endosperm starches was analyzed. These rice varieties exhibited different chain length distribution ratio within the amylopectin cluster as well as varing amylose levels. The proportion of amylopectin short chains of in Goami cutlivars was higher than the other varieties, whereas the Goami 2 which shows amylose extender mutant properties in the endosperm showed the highest proportion of long chains. In X-ray diffraction analysis of rice starches, the Goami 2 variety displayed a B-type pattern whereas the other varieties were all A-type. Among the cultivars with high and normal rice starch levels, those with the higher amylose contents showed distinctly lower swelling. Goami 2 rice was found to have the highest onset and peak gelatinization temperature from the differential scanning calorimetry results. The four rice cultivars under analysis also showed different rates of hydrolysis by amyloglucosidase. These findings suggest that the composition and chemical structure of the starch content is a major determinant of both the gelatinization and functional properties of rice.

Rheological, thermal properties, and gelatinization kinetics of tapioca starch–trehalose blends studied by non‐isothermal DSC technology

AbstractIn this paper, we studied the effects of trehalose on the rheological and thermal properties of tapioca starch (TS). Temperature sweep experiments showed that trehalose shifted the peak gelatinization temperature (TG′max) to higher value. Rheological features calculated from the power law model indicated that trehalose addition increased the consistency and decreased the thixotropy of TS gels. DSC experiments showed that trehalose retarded the gelatinization of TS–trehalose blends reflected in the increase of gelatinization temperature. The gelatinization kinetics was evaluated by a non‐isothermal technique based on the DSC endotherms. Kinetics analysis showed the addition of trehalose increased the activation energy and decreased the rate constants of TS–trehalose blends, indicating the same sugar effect as the rheological and DSC experiments. The work demonstrated that kinetics analysis could provide new evidences for the influence of trehalose on starch gelatinization.

The effect of induced yellowing on the physicochemical properties of specialty rice

Postharvest yellowing (PHY) of rice kernels can be a major problem in the rice industry. This is especially true with high-valued specialty rice, because profit loss will be greater. The objective of this work was to determine whether a significant change occurs in the physicochemical properties (apparent amylose and protein concentrations, viscosity profile and gelatinisation temperature) as a result of induced PHY. In this study, four specialty rices (Basmati, Jasmine, Arborio and Sushi) were yellowed using a laboratory method. PHY increased apparent amylose concentration. It also significantly increased onset and peak gelatinisation temperatures. However, peak, breakdown and setback Rapid ViscoAnalyzer viscosities were decreased by PHY. Trough viscosity for Basmati and Jasmine decreased, whereas it increased for Arborio. Moisture and protein concentrations were unchanged by the yellowing process. Attempts to rehydrate the kernels after induced PHY caused them to fracture, thus making them unsuitable for their intended purpose. This study indicates that rice that has been subjected to PHY shows a reduction not only in appearance but also in cooking and processing quality, decreasing its value. However, the changes differed for each rice type, with Jasmine being affected the least.

Immersion mode material pocket dynamic mechanical analysis (IMP-DMA): A novel tool to study gelatinisation of purified starches and starch-containing plant materials

There is a clear need for improved methods for the study of the physical changes that occur in slurries and sol–gel systems that have significant water content. In this paper a novel immersion mode material pocket form of dynamic mechanical analysis (IMP-DMA) has been designed, combining material pocket technology to provide physical support to a powdered sample within an immersion bath. IMP-DMA allows the mechanical response of a powder during heating to be monitored in excess water. IMP-DMA was evaluated using a range of starch samples loaded as a slurry into a solid steel pocket, the mechanical responses of these samples were monitored as a function of temperature, and values for modulus and tanδ peaks were found to correspond well with events occurring at both the onset and peak gelatinisation temperatures as measured by differential scanning calorimetry (DSC) (e.g. wheat starch has an onset and peak DSC temperature of 49.3°C and 57.2°C, respectively, and shows a peak in tanδ at 52.8°C and a modulus peak at 57.7°C). Some limitations were found in the ability of DMA to detect transitions in starches with low or high amylose contents. IMP-DMA was shown to be an effective tool for monitoring the changes in starch structure that occur during gelatinisation, both in purified starches and in more complex starch-containing food materials. Thus, a new hyphenated form of DMA is now available that permits the thermally induced transitions of particle water dispersions to be characterised.

The effect of rice aging on the freeze–thaw stability of rice flour gels

This study investigated the effect of aging rice on the freeze–thaw stability of rice flour gels since repeated freeze–thaw cycles can lead to reduced food quality. A rice grain cultivar called ‘Khoa Dawk Mali 105’ was aged for three different time periods, ranging from 0 to 12 months. Rice gels made from the aged rice were then freeze–thawed for up to 5 cycles. Repeated freeze–thaw cycles lead to an increase in syneresis values and hardness with increasing rice aging. Differential scanning calorimetry showed an increase in the enthalpy of melting of the amylose–lipid complex after 5 freeze–thaw cycles and an increase in peak gelatinization temperature and gelatinization enthalpy with longer rice aging. Moreover, aging length of the rice correlated significantly with a decrease in peak viscosity and breakdown but also an increase in final viscosity and setback. These results demonstrate that aging the rice reduced the freeze–thaw stability of the rice flour gels.

Thermal Characterization of Native and Modified White Sorghum (Sorghum Bicolor) Starch

Gelatinization and retrogradation characteristics of native and modified white sorghum (Sorghum bicolor) starches were studied using differential scanning calorimetry. The biopolymer was modified through acetylation, oxidation, and acid thinning reactions to prepare single- and dual-modified white sorghum starches. The results revealed that peak gelatinization temperature (Tp) of AWSS (acetylated white sorghum starch) and AOWSS (acetylated-oxidized white sorghum starch) was less than that of NWSS (native white sorghum starch), while oxidation and acid thinning significantly increased the peak gelatinization temperature. Gelatinization enthalpy (ΔH) of ATWSS (acid-thinned white sorghum starch) was the least among both native and modified starches, which indicates weakening of starch granules after acid modification. Rate of retrogradation was lower in AWSS, OWSS, and AOWSS than NWSS, whereas acid thinning increased the rate of retrogradation. After 12 days of refrigerated storage at 4°C, percent retrogradation was in the order ATWSS > NWSS > AWSS∼AOWSS > OWSS. However, percent increment in retrogradation enthalpy was the least in AWSS.

PHYSICOCHEMICAL PROPERTIES AND SALTED NOODLE-MAKING QUALITY OF PURPLE SWEET POTATO FLOUR AND WHEAT FLOUR BLENDS

The physicochemical properties of purple sweet potato flour (PSPF)-wheat flour blends and their effects on salted noodle-making quality were investigated. PSPF was substituted at levels of 5, 10, 15, 20, 25 and 30% for wheat flour. Addition of PSPF increased the gelatinization peak temperatures from 66.45 to 67.73C, but decreased paste viscosities at all substitution levels. Texture analysis showed that hardness of flour gels decreased as the amount of PSPF increased, while springiness reached the maximum value with 10% PSPF substitution. Farinographic tests indicated that dough stability decreased from 18.0 to 7.8 min with the increasing levels of PSPF up to 30%. PSPF had a weakening influence on cooking and texture properties of noodles, but could be added to wheat flour under the level of 15% without drastically affecting salted noodle-making quality. PRACTICAL APPLICATIONS Purple sweet potato flour (PSPF) could be served as a substitute for cereal flours, which enhanced products through color and nutrient. Salted noodles made by partially replacing wheat flour with 15% PSPF appeared the attractive color of pink redness and favorable cooking properties, which provided a basis to develop novel colored foods with good antioxidant capacity.

Structural Properties of Hydrolyzed High-Amylose Rice Starch by α-Amylase from Bacillus licheniformis

High-amylose cereal starch has a great benefit on human health through its resistant starch (RS) content. Enzyme hydrolysis of native starch is very helpful in understanding the structure of starch granules and utilizing them. In this paper, native starch granules were isolated from a transgenic rice line (TRS) enriched with amylose and RS and hydrolyzed by α-amylase. Structural properties of hydrolyzed TRS starches were studied by X-ray powder diffraction, Fourier transform infrared, and differential scanning calorimetry. The A-type polymorph of TRS C-type starch was hydrolyzed faster than the B-type polymorph, but the crystallinity did not significantly change during enzyme hydrolysis. The degree of order in the external region of starch granule increased with increasing enzyme hydrolysis time. The amylose content decreased at first and then went back up during enzyme hydrolysis. The hydrolyzed starches exhibited increased onset and peak gelatinization temperatures and decreased gelatinization enthalpy on hydrolysis. These results suggested that the B-type polymorph and high amylose that formed the double helices and amylose-lipid complex increased the resistance to BAA hydrolysis. Furthermore, the spectrum results of RS from TRS native starch digested by pancreatic α-amylase and amyloglucosidase also supported the above conclusion.

Rheometric non-isothermal gelatinization kinetics of mung bean starch slurry: Effect of salt and sugar – Part 1

Gelatinization of mung bean starch (MBS) was studied by oscillatory rheological measurement. The effect of sodium chloride (5% and 10% w/w), sucrose (5% and 10% w/w) and sodium chloride–sucrose blend (5%+5%) was also studied and compared during non-isothermal heating from 40 to 95°C. The addition of sodium chloride and sucrose shifted the peak gelatinization temperature (TGmax′) to higher value. The starch gelatinization kinetics was evaluated by a non-isothermal technique as function of elastic modulus (G′) and G′ vs. time (t) data up to the gelatinization peak Gmax′ value were considered for rate estimation. A 1st-order reaction kinetics described well the gelatinization process of MBS individually and sample incorporated with 10% sodium chloride and 10% sucrose. Interestingly, addition of 5% sodium chloride, 5% sucrose and a blend of sodium chloride and sucrose (5%+5%) followed 2nd-order gelatinization kinetics. The process activation energy ranged from 19.7 to 84.9kJ/mol. The work demonstrated that non-isothermal rheological measurement could be applied adequately to characterize the gelatinization process and to evaluate reaction kinetics pertaining to gelatinization.

Fine structural characteristics related to digestion properties of acid‐treated fruit starches

AbstractStarches from unripe fruits (mango, banana, and plantain) were acid modified to form different degrees of lintners with the objective to increase the slowly digestible starch (SDS) and RS contents. Molecular, thermal, and structural characteristics were evaluated. Mango starch showed higher susceptibility to acid hydrolysis than banana and plantain starches. The peak temperature of gelatinization (Tp) showed a decrease at low hydrolysis percentage, but at higher hydrolysis percentage the Tp increased. However, the enthalpy of gelatinization presented an increase with the hydrolysis percentage, but was not higher than its native counterpart. In general, the peak temperature and enthalpy of retrogradation increased with hydrolysis percentage due to formation of linear chains during the modification that promoted retrogradation. High performance size exclusion chromatography (HPSEC) analysis demonstrated the presence of multiple‐branches (DP = 96–109), single branched (DP = 28–31), and linear (DP = 16–18) polymers in the fruit starch lintners. The acid treatment (lintnerization) of mango starch had no effect on the SDS fraction, while for plantain and banana starches, the SDS content increased (6.14–35.4%) at low hydrolysis percentage (0–50%) followed by a decrease at higher days of hydrolysis. At higher hydrolysis percentage (70–80%) the RS content increased for the three fruit lintners.

Impact of down-regulation of starch branching enzyme IIb in rice by artificial microRNA- and hairpin RNA-mediated RNA silencing.

The inactivation of starch branching IIb (SBEIIb) in rice is traditionally associated with elevated apparent amylose content, increased peak gelatinization temperature, and a decreased proportion of short amylopectin branches. To elucidate further the structural and functional role of this enzyme, the phenotypic effects of down-regulating SBEIIb expression in rice endosperm were characterized by artificial microRNA (amiRNA) and hairpin RNA (hp-RNA) gene silencing. The results showed that RNA silencing of SBEIIb expression in rice grains did not affect the expression of other major isoforms of starch branching enzymes or starch synthases. Structural analyses of debranched starch showed that the doubling of apparent amylose content was not due to an increase in the relative proportion of amylose chains but instead was due to significantly elevated levels of long amylopectin and intermediate chains. Rices altered by the amiRNA technique produced a more extreme starch phenotype than those modified using the hp-RNA technique, with a greater increase in the proportion of long amylopectin and intermediate chains. The more pronounced starch structural modifications produced in the amiRNA lines led to more severe alterations in starch granule morphology and crystallinity as well as digestibility of freshly cooked grains. The potential role of attenuating SBEIIb expression in generating starch with elevated levels of resistant starch and lower glycaemic index is discussed.

Effect of genotype and environment on the concentrations of starch and protein in, and the physicochemical properties of starch from, field pea and fababean.

The effects of genotype and environment and their interaction on the concentrations of starch and protein in, and the amylose content and thermal and pasting properties of starch from, pea and fababean are not well known. Differences due to genotype were observed in the concentrations of starch and protein in pea and fababean, in the onset temperature (To) and peak temperature (Tp) of gelatinization of fababean starch, and in the pasting, trough, cooling and final viscosities of pea starch and fababean starch. Significant two-way interactions (location × genotype) were observed for the concentration of starch in fababean and the amylose content, To, endothermic enthalpy of gelatinization (ΔH) and trough viscosity of fababean starch. Significant three-way interactions (location × year × genotype) were observed for the concentration of starch in pea and the pasting, trough, cooling and final viscosities of pea starch. Differences observed in the concentrations of starch and protein in pea and fababean were sufficient to be of practical significance to end-users, but the relatively small differences in amylose content and physicochemical properties of starch from pea and fababean were not.

Physicochemical, crystalline, and thermal properties of native, oxidized, acid, and enzyme hydrolyzed Chinese yam (Dioscorea opposite Thunb) starch

AbstractNative yam starch was modified by oxidation (with sodium hypochlorite), acid, and enzyme (with gluco‐amylase), respectively. Ash content, fat content, protein, and AM contents were reduced following modifications. All the modifications reduced swelling capacity whereas improved the solubility. The SEM of the native starch showed the presence of large oval or spherical to small irregular‐shaped granules, however, oxidation and hydrolysis caused collapse of the granules. From the XRD, the typical C‐type XRD pattern of the native starch changed to the typical A‐type XRD pattern of the three modified starches. The above results also demonstrated that amorphous region of yam starch granules was preferentially degraded than crystalline region of granules. DSC showed that oxidation and acid/enzyme hydrolysis reduced peak temperature of gelatinization (Tp) of native starch significantly. Enthalpy of gelatinization (ΔH) of oxidation and enzyme starch was reduced but it has no obviously change following acid modification.

CHEMICAL COMPOSITION, THERMAL AND VISCOELASTIC CHARACTERIZATION OF TUBER STARCHES GROWING IN THE YUCATAN PENINSULA OF MEXICO

ABSTRACT Optical microscopy, proximate analysis, differential scanning calorimetry and rheological oscillatory tests were done to evaluate the physical, thermal and rheological properties of starches isolated from the tubers makal (Xanthosoma yucatanensis), sweet potato (Ipomea batata), cassava (Manihot esculenta) and sago (Marantha arundinacea). Mean starch granule size ranged from 10.6 to 16.5 µm. Makal and sweet potato starch granules were spherical, cassava starch granules were spherical‐truncated and sago starch granules were polygonal. The proximate composition showed that overall, the starches studied were within the group of the normal ones, with low fat and protein content (&lt;7%) and amylose content &lt;30%. Gelatinization peak temperature range was 61.3 to 78.4C and enthalpy (ΔH) range was 9.2 to 14.9 J/g. The rheological profiles of all tuber starches exhibited viscoelastic gel‐like behavior with G′ (storage modulus) &gt; G″ (loss modulus) at the tested amplitude and frequency ranges. Makal and sago starches are potentially useful in the manufacture of products requiring high processing temperatures. Sweet potato starch may have applications in food systems as a thickening and gelling agent, while cassava starch could be used to stabilize low viscosity foods.PRACTICAL APPLICATIONSStarch is a fundamental element of human diets and is used extensively as a functional ingredient. However, despite a global production of 48.5 million tons/annum, part of the worldwide demand remains unmet, meaning new starch isolation sources are needed (FAOSTAT 2001). With worldwide cultivation of approximately fifty million hectares (CIAT 1997), roots and tubers play a significant role in the global food system and are a vital caloric source for people in many developing countries. In Mexico, the most common cultivated roots and tubers are cassava, potato, makal, sweet potato, sago and yam bean, all most frequently eaten in the country's southeastern states (Burgos‐Perez 2005), with scarce information available about its properties. When determining the potential uses of a starch in food systems, the chemical, thermal and rheological behaviors of its pastes and gels (Wang and White 1994) are most important. Thus, results of this study may decide specific application (thickening, flow and gelling agent) of local starches in the food industry.

Effect of fertiliser on functional properties of flour from four rice varieties grown in Sri Lanka

Fertiliser is an essential agro-chemical input in modern rice farming. Fertiliser affects the grain quality and yield of rice. Although much research has been carried out to investigate the influence of fertiliser (recommended NPK addition) on yield and quality of rice grain, little is known about the effect of fertiliser on thermal, pasting, gelling and retrogradation properties of rice flour. The aim of this study was to investigate the influence of recommended fertilisation on functional properties of rice flour from four popular high yielding rice varieties grown in Sri Lanka. Fertiliser (recommended NPK addition) increased the protein content but reduced the apparent amylose content in rice flour except in BG 357. Swelling power and amylose leaching were decreased by fertilizer. [corrected] Pasting onset temperature, cold paste viscosity and setback were increased but peak viscosity and granular breakdown decreased. In response to the fertiliser application, gelatinisation peak temperature was reduced in all varieties except BG 300. However, compared to pasting properties, gelatinisation parameters were not much affected by fertilisation. The extent of amylopectin retrogradation was decreased by fertiliser in BG 305 and BG 352 but unchanged in the other two varieties. Except in BG 305, fertiliser reduced the gel hardness of rice flour but increased the gel cohesiveness. It is apparent that the increased protein and reduced amylose content caused by fertiliser affect the functional properties of rice flour.