Measurement of electrical conductivity,differential scanning calorimetry and viscosity of starch and flour suspensions during gelatinisation process

Electrical conductivity measurements were applied to analyse the gelatinisation process of 12 starch or flour suspensions. The electrical conductivity of starch suspensions was found to increase upon gelatinisation because of the release of ions from starch granules. The initiation temperature of ion release, T_i, correlated well with the onset temperature in the DSC thermogram (R = 0.868), while the completion temperature of ion release, T_f, correlated with the temperature at the start of viscosity increase (R = 0.865). Thus T_i and T_f corresponded to the beginning and ending temperatures of gelatinisation respectively. The electrical conductivity measurement will be used as an on‐line technique to monitor the whole process of starch gelatinisation. © 2001 Society of Chemical Industry     

Effect of Salts and Sugars on Pressure‐induced Gelatinisation of Wheat,Tapioca, and Potato Starches

The impact of a variety of chlorides, sodium salts, potassium salts and low‐molecular sugars on pressure‐induced gelatinisation of wheat, tapioca and potato starches has been investigated. Just as thermal gelatinisation, pressure‐induced gelatinisation is influenced by solutes in the starch suspensions. In general the effects of salts and sugars on starch gelatinisation were comparable for thermal and pressure treatments. For example, the gelatinisation pressure was reduced by sugars whereas the degree of gelatinisation was linearly correlated with the number of equatorial hydroxyl groups. The influence of salts on the gelatinisation pressure varied and the extent of effect on the gelatinisation pressure did not only depend on the solute added but also on the type of starch. At high chloride concentrations (> 2 M) the impact of the salts on starch gelatinisation augmentation followed the order Na⁺<K⁺<Li⁺<Ca²⁺, which corresponds to the order of the lyotropic series. At concentrations above 1 M the effect of potassium salts on starch gelatinisation upon pressurisation also followed the order of the Hofmeister series (Cl⁻<Br⁻<I⁻<SCN⁻).     

Influence of acid hydrolysis on thermal and rheological properties of amaranth starches varying in amylose content

BACKGROUND: The granules of amaranth starch are very small compared with starches from other sources. In the current work, amaranth starches with different amylose contents were treated with hydrochloric acid as a function of time in order to study the effect of acid treatments on starches. Differential scanning calorimetry and dynamic oscillation in shear were employed to analyse the thermal and rheological properties of acid‐modified amaranth starch. RESULTS: Results showed that gelatinisation temperatures and enthalpy change of gelatinisation (ΔH) decreased steeply initially, and had a slight increase with further treatment up to 12 h then decreased, an outcome that reflected distinct resistance to acid with various amylose contents. Rheological parameters of storage and loss moduli during heating, cooling and frequency sweep of modified starches reflected the differential scanning calorimetry results by decreasing in value as the time of acid hydrolysis increased. CONCLUSION: With amylose content increase, the effects of acid hydrolysis on gelatinisation temperatures became less pronounced. Nevertheless, prolonged acid hydrolysis decreased the storage and loss moduli, with the starch pastes becoming more liquid‐like. Copyright © 2012 Society of Chemical Industry     

Effect of gelatinisation on slowly digestible starch and resistant starch of heat-moisture treated and chemically modified canna starches

The effects of gelatinisation on slowly digestible (SDS) and resistant starch (RS) of native and modified canna starches were investigated. Starch slurries (10% w/w) were gelatinised at 100 °C for 5, 10, 20 and 40 min using a rapid visco analyzer (RVA). Significant change in the degree of gelatinisation (DG) values of all starch samples was observed during the initial 10 min of gelatinisation; after that the DG values increased gradually with gelatinisation time. The RS contents in all gelatinised starches decreased with increasing gelatinisation time, while the SDS values fluctuated. Chemical modification affected DG values as well as RS/SDS contents. The RS contents in 10% (w/w) acetylated, hydroxypropylated, octenyl succinylated and cross-linked canna starches gelatinised at 100 °C for 40 min were 26.6%, 32.0%, 45.3% and 19.8%, respectively, which were higher than that of the native starch (12.4%). Canna starch modified by crosslinking had the highest SDS content when gelatinised for 20-40 min. Modification of canna starch by heat-moisture treatment resulted in a lower content of RS for all treated samples. However, the Vt-HMT25 (canna starch containing moisture content of 25% during heat treatment) when gelatinised for 5-20 min contained a higher amount of SDS, compared to unmodified starch. The most effective modification method for RS and SDS formation was octenyl succinylation, where the sum of RS and SDS approached that of Novelose260.     

AMYLOLYSIS OF SORGHUM STARCH AS INFLUENCED BY CULTIVAR,GERMINATION TIME AND GELATINISATION TEMPERATURE

The susceptibility to amylolysis of starches derived from two improved Nigerian sorghum cultivars were evaluated at assay temperatures between 50°C and 75°C. Enhancement of gelatinisation rates at temperatures up to 65°C was not significant inspite of the apparent grain modification due to germination for four days. Greater starch gelatinisation rates (20–22%) were achieved in this study compared to previously reported values, suggesting possible roles for cultivar and malting methods. There was a statistical correlation between starch gelatinisation rates over the temperature range 65°C–75°C and the duration of grain germination (r=0.91 for KSV8 and r=0.5 for SK5912 starches). Gelatinisation rate and temperature were affected significantly by assay pH. The occurrence of two pH related maxima of starch gelatinisation for both cultivera at all temperatures examined indicates the possible presence of two sets of “binding forces” within the starch granules and features of starch retrogradation .     

超高压辅助制备醋酸酯淀粉结构性质研究

以玉米淀粉为原料,乙酸酐为反应试剂,NaCl为反应介质,采用超高压辅助制备醋酸酯淀粉,利用光学显微、X-射线衍射、快速黏度分析技术对醋酸酯淀粉结构性质进行分析。研究表明,颗粒态醋酸酯淀粉结晶类型与原淀粉相同,当处理压力为600 MPa时淀粉糊化,颗粒结构被破坏,A型结晶向V型结晶转换,但糊化并不利于醋酸酯淀粉取代度的增加。适量NaCl的添加有利于超高压处理时淀粉颗粒态的维持,因而有效提高了醋酸酯淀粉的取代度。当NaCl溶液浓度为1.0%、乙酸酐添加量为2.0%、压力为400MPa时,所制备的醋酸酯淀粉取代度达到最大值(0.090),且表现出较高的峰值黏度(400.00cP)。     

电导率和取代度对阳离子淀粉增强作用的影响

自行合成不同取代度的季铵型阳离子淀粉,用氯化钠调节浆料的电导率,探讨不同浆料电导率和阳离子取代度对系统Zeta电位、纸张的环压强度和耐破指数的影响.结果表明,阳离子淀粉的取代度越高,系统的Zeta电位变化越大,纸张环压指数和耐破指数提高幅度越大;电导率对添加低取代度阳离子淀粉的系统Zeta电位影响较大,对添加高取代度阳离子淀粉的Zeta电位影响较小,在取代度相同的情况下,电导率对纸张环压指数和耐破指数的影响不明显.     

Effect of high pressure on binding aroma compounds by maize starches with different amylose content

Hylon VII, waxy maize starch and their mixtures were subjected to high pressure treatment (650 MPa/9 min). To obtain starch-odorants products: (i) the pressurised and native starches were incubated with odorants; and (ii) the native starches mixed with odorants were treated under high pressure (650 MPa/9 min). The sorption capacity of odorants by investigated starches was studied using capillary gas chromatography.The sorption capacity of odorants by native starches was found to stronger depend on hydrophobicity and molecular structure of odorants rather than the starch botanical origin. The highest sorption was observed for polar hydrophobic compounds (hydrocarbons) and for aliphatic esters, whereas the lower one—for guaiacol and methyl anthranilate. The high pressure-treated Hylon VII demonstrated slight changes in melting enthalpy and degree of gelatinisation compared to other starches and it showed the highest sorption capacity of the majority of odorants. The treatment of a starch with odorant under 650 MPa for 9 min resulted in a diminished average sorption of the aroma compounds. However hexanol, guaiacol and methyl antrinilate, that were slightly or not sorbed by native and high pressure-treated starches, demonstrated the highest degree of binding with waxy starch and its mixtures under high pressure conditions.     

Physicochemical,crystallinity, pasting and thermal properties of heat‐moisture‐treated pinhão starch

The effect of heat‐moisture treatment (HMT) on the properties of pinhão starches under different moisture and heat conditions was investigated. The starches were adjusted to 15, 20 and 25% moisture levels and heated to 100, 110 and 120°C for 1 h. The X‐ray diffractograms, swelling power, solubility, gel hardness, pasting properties and thermal properties of the native and HMT pinhão starches were evaluated. Compared to native starch, there was an increase in the X‐ray intensity and gel hardness of HMT starches, with the exception of the 25% moisture‐treated and 120°C heat‐treated starch. HMT reduced the swelling power and solubility of the pinhão starches when compared to native starch. There was an increase in the pasting temperature, final viscosity and setback and a decrease in the peak viscosity and breakdown of HMT pinhão starches compared to native starch. HMT increases the gelatinisation temperature of native pinhão starch and reduces gelatinisation enthalpy.     

Gelatinisation Characteristics and Enzyme Susceptibility of Different Types of Barley Starch in the Temperature Range 48–72°C1

The gelatinisation temperatures, pasting characteristics and enzymic susceptibilities in the temperature range 48–72°C of normal, high amylose, low amylose and zero amylose barley starches were determined. Normal starches had the lowest gelatinisation temperatures, but low and zero amylose starches had the lowest pasting temperatures. Normal starches were the most readily soluble in water at 48–60°C in the presence of a mixture of α‐amylase, β‐amylase and limit dextrinase and were most readily broken down to reducing sugars by these enzymes. High amylose starch was the most resistant to enzymic hydrolysis in the temperature range 48–72°C and, hence, produced the lowest level of reducing sugars.     

AMYLOLYSIS OF LARGE STARCH GRANULES FROM BARLEYS IN RELATION TO THEIR GELATINISATION TEMPERATURES

Large starch granules, prepared from a range of barley samples, show considerable variation in their susceptibility to attack by α-amylase at 65°C. Susceptibility is not correlated with their protein content, amylose/amylopectin ratio or gelatinisation temperature as measured by loss of birefringence. It does correlate with gelatinisation as measured by swelling of the granules or their staining with Congo Red. When granular expansion is taken as the measure of gelatinisation, the more resistant starches show gelatinisation curves displaced to higher temperatures.     

Application of high‐pressure treatment in the mashing of white malt in the elaboration process of beer

In this study, high‐pressure treatment (HPT) was applied to the mashing stage of beer production, which involves drying and milling of white malt and subsequent mixing with water. The following parameters were evaluated after pressurisation: β‐glucanase activity, starch gelatinisation and sugar extraction. Evaluation of starch hydrolysis from the malted barley endosperm after HPT was performed by measuring β‐glucanase activity after pressurisation; this enzyme breaks down gums and β‐glucans in wort and is desirable to obtain a good‐quality beer. Soaked malt samples pressurised at 200–600 MPa showed no increase in this activity compared with controls. Conversion of milled malt was evaluated indirectly by measuring the gelatinisation of starch, which began at 400 MPa. Soluble sugars were also measured in pressurised samples from the mashed liquid to investigate saccharification during the mashing stage. After 400 or 600 MPa treatment for 20 min, both the sucrose (g per 100 ml) and extract (l ° kg^?1) values were the same as those found in mashed samples following the standard procedure used in the brewing industry (65 °C,90 min). Starch gelatinisation was analysed at different high pressures (200–600 MPa) and it was shown that gelatinisation began at 400 MPa. The HPT time would have to be shorter to make the process commercially attractive. © 2002 Society of Chemical Industry     

Recent advances in gelatinisation and retrogradation of starch by high hydrostatic pressure

Starch is the major polysaccharide following cellulose, but native starch has limited application due to physicochemical and functional properties. To handle such problems, starch is usually modified with either thermal or more recently by non-thermal technologies such as high hydrostatic pressure (HHP). HHP is a non-thermal technique that can be applied to a variety of food materials with minimum effect on nutritional quality. High-pressure levels can cause physicochemical changes in starch such as partial/completely gelatinisation, reduction in solubility and swelling power, increasing pasting temperature and content of slowly digestible starch (SDS) and retention of retrogradation. These physicochemical changes depend on the starch type, pressurisation level, treatment time and temperature. This review has evaluated and synthesised the current research about the effect of HHP on starch gelatinisation, retrogradation and physicochemical properties of starch.     

Effects of cultivar and growth season on the gelatinisation properties of cassava (manihot esculenta) starch

Starch was extracted from the roots of four different cassava cultivars (Munihot esculenta Crantz) grown in Colombia and harvested on four different occasions with a view to determining whether there was any relationship between the physicochemical properties of the starch and the texture of the cooked roots. The organoleptic quality of the cooked roots was evaluated by a trained taste panel and found to vary in terms of both their glassy texture and their hardness. Studies of the gelatinisation behaviour of the starches by DSC and amylography (with a Brabender amylograph), of the pasting properties by viscography and of the viscoelastic characteristics by a Bohlin rheometer demonstrated some differences between the physicochemical properties of the starches but insufficient to account for the pronounced textual differences.     

Influence of the naturally occurring phosphate esters on the crystallinity of potato starch

The gelatinisation enthalpy of native potato starch, as measured by DSC, as observed to decrease ith increased natural phosphorylation of the amylopectin. The phosphate esters bound to the C-6 carbons clearly reduced the gelatinisation enthalpy, hereas the phosphate esters bound to C-3 carbons took little or no part in this reduction. Retrograded starch samples ere also studied, in order to find a corresponding relationship beteen the degree of phosphorylation and the recrystallisation enthalpy. These results ere less convincing, but the phosphate esters did tend to increase the retrogradation enthalpy independent of the phosphorylation site.     

Wet Method for Measuring Starch Gelatinization Temperature Using Electrical Conductivity

ABSTRACT:  The objective of the present study was to develop a method for obtaining the gelatinization temperature of starches by using electrical conductivity. Native starches from corn, rice, potato, and wheat were prepared with different proportions of water and heated from room temperature to 90 °C, in a device especially designed for monitoring the electrical conductivity as a function of temperature. The results showed a linear trend of the electrical conductivity with the temperature until it reaches the onset gelatinization temperature. After that point, the electrical conductivity presented an increment or decrement depending on the water content in the sample and it was related to starch swelling and gelatinization phenomena. At the end gelatinization temperature, the conductivity becomes stable and linear, indicating that there are no more changes of phase. The starch gelatinization parameter, which was evaluated in the 4 types of starches using the electrical conductivity, was compared with those obtained by using differential scanning calorimeter (DSC). The onset temperature at which the electrical conductivity increased or decreased was found to be similar to that obtained by DSC. Also, the final temperature at which the electrical conductivity returned to linearity matched the end gelatinization temperature of the DSC. Further, a wet method for measuring the onset, peak, and end gelatinization temperatures as a function of temperature using the electrical conductivity curves is presented for a starch–water suspension.     

Effects of Growth Temperature on Some Structural Properties of Crystalline Lamellae in Starches Extracted from Sweet Potatoes (Sunnyred and Ayamurasaki)

Thermodynamic characteristics defining gelatinisation (modelled as ‘melting’) processes for starches extracted from two sweet potato cultivars (Ayamurasaki and Sunnyred) grown in soil at different temperatures (15, 21, 27 or 33 °C) were studied using high sensitivity differential scanning calorimetry (DSC). The gelatinisation temperatures for all starches were elevated significantly with increasing growth temperature. A linear correlation between growth temperature and gelatinisation temperature of extracted starches was found for both cultivars. The increase of gelatinisation temperatures was associated with almost constant or slightly increased enthalpy (Ayamurasaki) but with moderate elevation of crystalline lamellae thickness (Sunnyred). Elevation of gelatinisation temperatures by 8‐9 °C by DSC for starches heated in 1.5 M aqueous KCl were found in comparison with aqueous starch dispersions. The crystalline polymorphic form was confirmed as A‐type using wide angle X‐ray scattering (WAXS). The values of the thermodynamic surface parameters characterising the faces of crystalline lamellae of these starches were calculated. Two endothermic peaks were observed by DSC for starches grown at 15 °C when suspended in 1.5 M KCl solution. The first peak was ascribed to the melting of B‐type structure while the second one was attributed to the melting of A‐type structure. As a conclusion it was suggested that these starches contain C‐type polymorphic structures.     

Effects of high pressure and temperature on buckwheat starch characteristics

Pressure-induced gelatinisation of buckwheat starch suspensions (25% w/w) was studied and compared to heat-induced gelatinisation. Starch suspensions were treated at increased pressure (200–600 MPa) or temperature (60–95 °C) for 10 min. The degree of gelatinisation and the temperature and pressure ranges of gelatinisation were determined using differential scanning calorimetry, changes in birefringence and pasting behaviour. Furthermore, the structural changes during gelatinisation were investigated using microscopy. The pressure-induced as well as the temperature-induced gelatinisation curves were sigmoid shaped. Gelatinisation occurred between 300 and 500 MPa or between 60 and 70 °C. Scanning electron microscopy images showed retention of the granular structure after treatment with 600 MPa. However, when heated at temperatures above 65 °C, the formation of a “sponge-like” structure was observed. Better preservation of the granular structure for pressure treatment compared to temperature treatment resulted in stronger gels for the former. Pre-treatment with pressure as well as temperature made the buckwheat starch granules more resistant to swelling and disintegration under the influence of additional heat.     

Effect of temperature on the synthesis,composition and physical properties of potato microtuber starch

Potato microtubers (cv Maris Piper) were grown at 10, 16 and 24°C in total darkness for 28 days. Soluble and insoluble starch synthase, ADPglucose pyrophosphorylase, sucrose synthase and fructokinase were assayed in extracts of the microtubers and, in the case of soluble and insoluble starch synthase, activity was found to be particularly sensitive to increasing growth temperature. The starch content of the microtubers increased slightly with increasing growth temperature, but with little effect on the number of granules per microtuber and a small increase in the average granule size. The microtuber starch granules were much smaller than those found in commercial potato starch (c 8–9 μm modal diameter compared to c 21 μm). Although the amylose content of the microtuber starches tended to increase with increasing growth temperature, the phosphorus content was variable. Gel permeation chromatographic elution profiles of native and debranched microtuber and a commercial potato starch showed that no differences could be detected in either amylose or amylopectin molecular size, polydispersity or unit chain distribution of amylopectin (which contained two major unit chain fractions at DP 21 and 56). The onset, peak and conclusion temperatures of the DSC gelatinisation endotherm increased linearly as a function of growth temperature whilst the enthalpy of gelatinisation decreased. It is suggested that elevated temperature during starch biosynthesis facilitates ordering of amylopectin double helices into crystalline domains. © 1998 SCI.     

Effect of instant controlled pressure drop process on some physicochemical and nutritional properties of snacks produced from chickpea and wheat

The chickpea and wheat seeds were processed using laboratory‐scale equipment of instant controlled pressure drop process (DIC) to produce nutritious snack products. In this study, we present the results concerning the effect of various DIC‐processing variables, moisture content, steam pressure and processing time on some physicochemical (water absorption (WAI) and water solubility (WSI) indices) and nutritional properties (total phenolic and phytic acid contents, starch gelatinisation and digestibility values). Among the DIC‐processing conditions, processing pressure and time had the highest significance rather than the moisture content. DIC process increased the total phenolic content of chickpea by approximately twofold, whereas it usually decreased in that of wheat. Severe processing conditions such as long processing time and high steam pressures generally led to an increase in WAI, WSI and starch gelatinisation as well as phenolic content, but a decrease in the antinutritional factor of phytic acid content within the working limit of the study. DIC treatment significantly increased the level of starch gelatinisation and digestibility of snack products.