Gelatinization Of Starch Granules Research Articles

Molecular and biochemical analysis of the gelatinization temperature characteristics of rice ( Oryza sativa L.) Starch granules

Abstract Through integrated molecular and biochemical investigations and by using a common mutant line in molecular mapping, we have shown that the SSIIa gene, previously reported to be responsible for the starch granule gelatinization temperature (GT) differences between indica and japonica rice varieties, might also control the GT variations among certain indica varieties. This effect is mediated through differences in the amounts of SSIIa protein bound to starch granules leading to differences in the structure of amylopectin molecules synthesized. For the first time it was shown, that the amylopectin type accounted only for the GT differences between varieties with different SSIIa alleles, but not between varieties carrying a common SSIIa allele. In the latter case, another gene, alk2(t) , with a genetic distance of 3.93 cM from the Wx gene, was identified as being responsible for the GT variations. Based on the thermal properties and amylopectin chain length profile characteristics, it is postulated that the SSIIa gene has at least three different alleles, one in japonica rice and two in indica rice varieties, whereas alk2(t) has at least two alleles for either low or high GT. Thus, the rich diversity of the GT character in rice very probably results from various combinations of these alleles.

Gelation characteristics and morphology of corn starch/soy protein concentrate composites during heating

The formation of corn starch (CS) and soy protein concentrate (SPC) composite during heating has been investigated using thermal and rheological analysis. SPC did not exhibit endothermic peak in differential scanning calorimetry (DSC) thermogram. Adding CS at low mass percentage (16.7%) to SPC resulted in a reduction of storage modulus ( G′) from 7.72 to 3.63 kPa at 50 °C. The DSC thermogram showed that the peak temperature was raised to 73.5 °C, compared with 70 °C for CS. The gelatinization of starch granules played an important role on the rheological properties of the composite during heating. Scanning electron microscopy and light microscopy with the aid of histological technique revealed the microstructure of CS/SPC composites. The observation illustrated that starch granules lost integrity and formed a gel with SPC at the temperature of maximum G ′ ( T G max ′ ) . The effect of starch mass percentage on the structural change of the composite was discussed.

The Physical Properties of Micronised Lentils as a Function of Tempering Moisture

Micronisation (infrared heat treatment) following tempering (conditioning) is an effective means of reducing cooking time in grain legumes such as lentils. However, the physical, physico-chemical and chemical changes that bring about this desirable change in the lentils have not been extensively investigated. The objective of this study was to investigate the physical changes occurring in lentils as a result of micronisation at different moisture contents. Lentils were tempered to a range of moisture contents (17–45%) and micronised under an electric microniser to return them to their initial moisture content (13%). Control samples were tempered to the same moisture contents but were air-dried (at 40 °C). Changes in the density and apparent elastic modulus (of a collection of grains) of the processed lentils were measured, as was the diffusion coefficient of moisture into them. Porosity of the micronised lentils increased with increasing tempering moisture, up to approximately 25%, arising from void creation induced by evaporation of moisture. However, porosity decreased at higher tempering moisture contents, presumably due to filling of voids by amylose from partially gelatinised starch granules. Changes in the porosity of air-dried lentils were slight. Apparent elastic modulus of the micronised lentils was essentially unaffected by tempering conditions. The rewetting coefficient of the micronised lentils was significantly greater than that of air-dried lentils, and the difference increased as tempering moisture content was increased. Diffusion coefficients of moisture within the lentils were strongly dependent on tempering moisture content, increasing as tempering moisture increased. The results indicate that rate of hydration of the lentils (a factor in cooking time reduction) depends on the physico-chemical changes brought about by heat and moisture during micronisation as well as on the increase in porosity.

Effects of Salts on the Reaction of Normal Corn Starch with Propylene Oxide

The objective of this research was to develop a greater understanding of the mechanism by which salts inhibit gelatinization of starch granules. Using hydroxypropylation of corn starch in the presence of sodium sulfate under conditions employed industrially as the control reaction, reactions with propylene oxide were done with different salts at levels that matched the control reaction in anion molal concentration, cation molal concentration, and total ion molal concentration. Salts used were selected based upon their position in the lyotropic series. Reactions were characterized by determining reaction efficiency and ion concentrations. Sodium and potassium citrates, salts exhibiting a strong lyotropic effect, were extremely effective as gelatinization inhibitors, but resulted in low reaction efficiency. Salts without a strong lyotropic effect (sodium and potassium chlorides) exhibited a weak protective effect, probably at least in part based upon generation of a Donnan potential. In the hydroxypropylation reaction, sodium citrate greatly reduced swelling; sodium chloride was ineffective as a swelling inhibitor, resulting in pasting of granules, and sodium sulfate allowed restricted swelling, most likely as a result of a moderate lyotropic effect and some generation of a Donnan potential. That reaction efficiency parallels granule swelling was confirmed.

Microstructural changes of starch in cooked wheat grains as affected by cooking temperatures and times

The changes of starch microstructure in soft and hard wheat grains after cooking in a pressure cooker were investigated using a scanning electron microscope (SEM) and a light microscope (LM) in conjunction with image analysis. The conditions studied included variation of the cooking times (20–120 min) at the constant temperature (120 °C) and with variable temperatures (110–140 °C) for constant time (40 min). SEM images showed that steam induced changes in the intact starch granules of cooked wheat grains, with the microstructure becoming more in mud-like structure, with increased cooking time or temperature. The swelling and gelatinization of starch granules could contribute to this change. Suspensions of cooked wheat flour were selectively stained with iodine, for observation using the LM. The image analysis software was used for quantitative analysis of the images captured from the LM, providing both the number and area of the starch granules (determined from the dark-blue spots) per fixed image size. With increased cooking time or temperature, the number of starch granules decreased and the area increased as a result from the swelling and melting of starch granules. This study demonstrated the use of SEM and LM for the investigation of starch granules in cooked wheat grains without prior starch isolation.

Modification of Gelatinization Properties of Rice Flour by Heat-Treatment

The effects of autoclave and oven treatments on gelatinization properties of rice flour and on crystallite structures of rice starch in rice flour were studied using dynamic oscillatory measurement, differential scanning calorimetry (DSC), X-ray diffractometry, and scanning electron microscopy (SEM). Autoclave-treated rice flour (ATR) and oven-treated rice flour (OTR) were prepared using an autoclave at 120 °C for 60 min and oven at 160 °C for 60 min. Dynamic oscillatory and DSC measurements demonstrated that autoclave treatment modified the gelatinization properties that delayed gelatinization temperature (TG' and To) and decreased in peak storage modulus (G'p). Autoclave treatment caused formation of amylose-lipid complexes and partial gelatinization of starch granules in ATR studied by DSC and X-ray diffractometry. Autoclave-treatment engendered formation of amylose-lipid complexes and partial gelatinization of starch granules in ATR studied by DSC and X-ray diffractometry. Alteration of gelatinization properties of ATR flour is attributed to changes in rigidity of starch granules during treatment. Similarly to ATR, oven treatment was effective for gelatinization properties. Nevertheless, it was insufficient for rearrangement of starch chains in OTR flour.

Rheological and thermal properties of thermoplastic starch with high glycerol content

This work is part of a series of papers devoted to the study of LDPE/thermoplastic starch (TPS) blends. In those papers, a starch/glycerol/water suspension was fed to a twin-screw extruder (TSE) and a water-free TPS was prepared in the first half of the TSE. Molten LDPE was added via a single screw extruder added midway on the TSE and the latter half of the TSE was used to prepare the blend. This approach allows for the preparation of TPS with particularly high loadings of glycerol plasticizer. In this paper, the thermal and rheological properties of water-free TPS (glycerol content 29–40%) prepared in the first half of a TSE using the above approach was analyzed. DSC analysis reveals the presence of a glass transition temperature ( T g) below ambient temperature, which indicates the complete gelatinization of starch granules. The T g decreases from −45.6 to −56.2 °C as glycerol content increases from 29 to 40%. Rheological properties in the shear and oscillation mode were determined on-line from the TSE and by using two oscillatory rheometers, respectively. Time sweep measurements demonstrate that TPS has excellent thermal stability at 150 °C, but becomes unstable at temperatures above 180 °C. The studies indicate, however, that TPS stability is maintained for short time periods at temperatures up to 200 °C. These results are important since they indicate that the potential exists to prepare stable TPS materials at high temperature by maintaining short residence times during processing. The shear viscosity of TPS (at γ ̇ ∼130 s −1) decreases by 20% when the glycerol content is increased from 36 to 40%. Similarly, G′ and G″ decrease as glycerol content increases, with a particularly dramatic reduction around 30% glycerol. This suggests the percolation threshold of the well-plasticized glycerol-rich soft regions. These results concerning the plasticization of starch are critical for morphology control protocols. The shear and oscillation viscosities of TPS (40% glycerol, TPS40) were compared with that of LDPE. It is shown that TPS does not follow the Cox-Merz relation, whereas LDPE measured under similar conditions does. The viscosity ratio of the system TPS40/LDPE is greater than 1 if measured in the dynamic mode, while it is less than 1 if determined from steady shear viscosity values. These results are highly relevant considering the importance of viscosity ratio on the prediction of the morphology of immiscible polymer blends.

Effects of the Preheating Treatments of Raw Ginseng in the Model System on the Synthesis of the Maillard Type-Browning Reaction Products of Red Ginseng

During our investigations on the relationship between the browning reaction of ginseng root and two compounds (arginyl-fructosyl-glucose and arginyl-fructose) in the model system of steaming and heat-drying processes for the preparation of red ginseng, the preheating treatment of main roots of raw ginseng at 60∼70<TEX>$^{\circ}C$</TEX> prior to the steaming and heat-drying processes was found to bring about the gelatinization of starch granules. The enzymatic hydrolysis of gelatinized starch to maltose, a marked formation of maltose, and the increase of both free arginine and total amino acids, resulting the acceleration of the Maillard type-browning reaction of ginseng root during the steaming and heat-drying processes, and the rise of brown color intensity of red ginseng. These results show that the preheating treatment may be effective for the decrease of inside white of red ginseng.

Dynamic Rheological and Thermal Properties of Soft Wheat Flour Dough Containing Structured Lipid

ABSTRACT: The effect of substituting canola oil/caprylic acid structured lipid for shortening (at 0%, 25%, 50%, 75%, and 100% levels) on the viscoelastic and thermal properties of soft wheat flour dough (28.4% total lipid, 43% moisture) was determined using dynamic rheological and differential scanning calorimetry tests. Ambient frequency scans produced higher G″ (loss modulus) and G′ (storage modulus) values at increasing frequencies. Temperature scans revealed rapid G″ and G′ increases for dough heated to above 56 °C, apparently because of starch gelatinization. Three differential scanning calorimetry endothermic peaks were observed at 54 °C, 69 °C, and 93 °C, which were attributed to shortening transition and gelatinization of starch granules.

Physical investigations of surface membrane–water relationship of intact and gelatinized wheat–starch systems

Water mobility in intact and dried gelatinized starch was investigated by gravimetric water sorption, scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance (NMR). A multi-component exponential model quantitatively measured different spin–spin relaxation times of two water components, namely bound water ( Ts i ) at 3.16 ms and mobile or free water ( Ts ii ) at 3.23 ms, as a function of water activity ( a w). The starch samples were moistened to 30% moisture content. SEM confirmed the disrupted, absorbent microstructure in dried, gelatinized starch powder and revealed starch granules in an incomplete gelatinized state, as compared to the complete membrane surface of the intact starch granule. Starch granules sorbed significantly differently at low a w, but after a w=0.44, sorption leveled similarly with increasing a w. The presence and role of a surface membrane was concluded, in support of the hypothetical “water sink” properties of intact granules, and was considered to influence in part the sorption behavior of incompletely gelatinized starch granules.

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

AbstractThe 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%.

Role of Starch Granule Characteristics (volume fraction, rigidity, and fractal dimension) on Rheology of Starch Dispersions With and Without Amylose

ABSTRACTThe link between rheological behavior and morphological‐structural characteristics of gelatinized starch granules has been studied in two starch dispersions (SDs): a cross‐linked waxy maize (CLWM), and tapioca starch, a tuber starch with 19.3 % amylose. Based on the power law relationship between the elastic modulus and volume fraction of the granules predicted by scaling theory, fractal dimension values were obtained for CLWM starch D = 2.81, and tapioca starch D = 2.79, suggesting that both starch granules have highly convoluted surfaces. However, the preexponential coefficient (G′⊘=1) for CLWM SDs was an order of magnitude greater than that for tapioca SDs, in the same range of volume fractions. The G′⊘=1 was mainly dependent on the granule rigidity, and the amylose content in the continuous phase played only a minor role in the rheological behavior.

Partial Leaching of Granule-Associated Proteins from Rice Starch during Alkaline Extraction and Subsequent Gelatinization

Starch granule-associated proteins, including granule-bound starch synthase (GBSS), were found to be partially lost during alkaline extraction of rice starch. Variability in amount of loss of GBSS and other granule proteins was found among different rice lines. Also, part of the GBSS and other granule proteins leached out during gelatinization of the alkali-extracted rice starch. Confocal laser scanning microscopy revealed that some protein still existed in gelatinized starch granules prepared from starch isolated using alkaline extraction. The starch that retained more GBSS and other granule proteins after alkaline extraction tended to have more protein in the isolated gelatinized starch granules, indicating that proteins resistant to alkaline extraction also tended to resist leaching during gelatinization. The study suggests that leaching of granule-associated proteins may contribute to variations in paste properties of alkali-extracted starches.

Phase transitions in the starch-water system studied by adiabatic scanning calorimetry.

We report high-precision measurements of phase transitions in the starch-water system by using for the first time adiabatic scanning calorimetry (ASC). Potato starch and nixtamalized corn flours were studied by this technique as a function of the moisture content. We calculated the percentage of gelatinized starch granules, as a function of the temperature, for both flours. For bi-phasic behavior in potato starch, at intermediate water contents, we propose an explanation based on previous hypotheses and on the experimental behavior as deduced from ASC measurements. ASC results suggest, in the case of nixtamalized corn flour, that uniform moisture is present in corn starch granules for all the considered moistures. A shift to higher temperatures of the peak temperature is observed when comparing the c(p)(T) curves with the classical DSC endotherms as measured for this flour. For both flours we estimated from the ASC results the melting temperatures of the starch granules, at zero moisture content, by using Flory's equation.

Granular Cold Water Gelling Starch Prepared from Chickpea Starch Using Liquid Ammonia and Ethanol

ABSTRACTGranular cold water gelling (GCWG) starch was obtained by treatment of native chickpea starch with liquid ammonia at low temperature and atmospheric pressure. A free‐flowing powder of the gelatinized starch granules was produced by adding ethanol to the mixture of starch and liquid ammonia. Four ratios of liquid ammonia to starch (A/S) (2:1, 4:1, 6:1 and 8:1) and four ratios of starch ethanol (S/E) (1:1, 1:2, 1:3 and 1:4) were tested for production of GCWG starch. Homogenous mixtures of liquid ammonia and starch granules appeared when the A/S ratio was &gt;4:1. Treating starch with a 4:1:3 ammonia‐starch‐ethanol (A/S/E) ratio on a w/w/v basis resulted in a free‐flowing powder of gelatinized starch, that formed a gel on addition of water at 23°C. Differential scanning calorimetry (DSC) thermograms of the GCWG starch, regardless of A/S/E ratio, displayed enthalpy values of 2.2–3.1 J/g compared with 15.5 J/g for native starch, indicating disappearance of crystallinity due to modification.

Functional and Microstructural Aspects of Soluble Corn Starch in Pastes and Gels

Soluble starch plays an important role in the rheology of starch pastes and gels. However, some functional aspects and the microstructural basis of its contribution are still not clear. In this study, commercial corn starch was pasted in a Rapid Visco Analyzer to peak viscosity, and separated into soluble starch (clear of granules and primarily amylose) and insoluble starch (gelatinized starch granules and primarily amylopectin). When the insoluble starch was reconstituted at different levels with soluble starch, paste viscosity profiles in the Rapid Visco Amylgram decreased with addition of increasing amounts of soluble starch. Cold stage scanning electron microscopy (SEM) of pastes revealed a continuous cellular structure of the sample without soluble starch and a denser fibrous structure of the one with soluble starch. Texture analysis of gels formed from pastes showed that the firmness of the gel increased, while gel stickiness decreased, with increasing amounts of added soluble starch. Cold stage SEM of gels revealed a fibrous structure of the gels with the addition of soluble starch and a cellular structure of the gels consisting of insoluble starch alone. Decrease in gel stickiness with addition of the amylose-rich soluble portion implies a large contribution by amylopectin or starch remnants to sticky gel texture. The microstructural comparison of pastes and gels with and without soluble starch provides a structural explanation for the function of soluble starch in pastes and gels.

Morphological Changes of Granules of Different Starches by Surface Gelatinization with Calcium Chloride

ABSTRACTNative starch granules of 11 selected cultivars (potato, waxy potato, sweet potato, normal maize, high‐amylose maize, waxy maize, wheat, normal barley, high‐amylose barley, waxy barley, and rice) were treated with a calcium chloride solution (4M) for surface gelatinization. The surface‐gelatinized starch granules were investigated using light microscopy and scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). In general, those starches with larger granule sizes required longer treatment time to complete the gelatinization. The salt solution treatment of starch was monitored by light microscopy and stopped when the outer layer of the granule was gelatinized. The surface gelatinized starch granules were studied using scanning electron microscopy. On the basis of the gelatinization pattern from calcium chloride treatments, the starches could be divided into three groups: 1) starches with evenly gelatinized granule surface, such as normal potato, waxy potato, sweet potato, maize, and high‐amylose maize; 2) starches with salt gelatinization concentrated on specific sites of the granule (i.e., equatorial groove), such as wheat, barley, and high‐amylose barley; and 3) starches that, after surface gelatinization, can no longer be separated to individual granules for SEM studies, such as waxy barley, waxy maize, and normal rice. The morphology of the surface gelatinized starch resembled that of enzyme‐hydrolyzed starch granules.

Effect of Polished-graded Flour Substitution to Commonly Milled Wheat Flour on the Properties of Dough and Bread.

The optimum conditions for breadmaking composed of various amounts of polished-graded flour and commonly milled soft-type wheat cultivar ‘Norm 61’ (N61) were studied. The viscoelastic properties of the doughs were also tested. When 30 or 50% of N61 was substituted with the 70-40% graded flour (Fraction B) of the whole wheat grain, the loaf volume and softness of bread crumbs increased with optimum amounts of water of 75 and 85%, respectively. Moreover, the addition of pentosanase (PEN) or cellulase (CEL) to the substituted N61 distinctly improved the loaf volume and retarded the retrogradation of bread crumbs as compared with those of N61 alone. Especially, the addition of PEN or CEL to the 50% graded-flour-substituted N61 having 85% water clearly increased viscoelastic parameters, such as the modulus of elasticity (y) and viscosity coefficient (v), as compared with those of N61 alone. In Farinograph data, 50% graded-flour-substituted N61 also decreased the arrival and development times, but increased the stability time. For the DSC result, 50% substitution tended to decrease gelatinization enthalpy with the addition of PEN or CEL. Microscopic observation of the 50% graded-flour-substituted N61 containing PEN showed that most of the starch granules were covered with extensible gluten and expanded still more during fermentation. In the case of the dough with the optimum water content, the gluten matrix was more fibrous and continuous, followed by sufficient gelatinization of starch granules as compared with N61 alone. Therefore, in the case of substituted N61 flour with graded flour, the optimum amount of water and hydrolysis of pentosan or cellulose in the endosperm and bran by PEN or CEL were needed to make good dough and baking properties.

Enzymatic Hydrolysis of Barley Starch Lipids

ABSTRACTThe efficiency of phospholipase and lipase preparations in the hydrolysis of lysophospholipids of native and gelatinized barley starch was examined. The degree of hydrolysis was analyzed by determination of the amount of released fatty acids by an enzymatic method. Thermal and structural properties of the enzyme‐treated starch were studied by differential scanning calorimetry and light microscopy. Lysophospholipids of the gelatinized barley starch were easily hydrolyzed, in contrast to the lipids of the granular starch. The maximum degree of hydrolysis achieved for the gelatinized starch was 80% and for the native starch ≈20%. Gelatinization enthalpies and micrographs indicated that even though the amount of the released fatty acids from the native starch was small, formation of free fatty acids inhibited swelling and gelatinization of starch granules.

Microstructure of the processing of black beans (Phaseolus vulgaris L.) from purée to drum‐dried flakes

AbstractBlack bean purée and drum‐dried flake microstructures were studied and compared with raw bean by light and scanning electron microscopies. Results illustrate the value of microscopy as a tool for evaluating physical and chemical changes in bean components due to processing. Microscopy was employed to follow the microstructural changes during the processing of black beans by looking at the intermediate product (the purée) and the end product (the flake). The consequences of processing on storage components such as starch, proteins, lipids, and cell walls were elucidated. The bean purée contained starch granules within intact cells and seed coat fragments throughout the product. The drum‐dried flakes had a rough exterior, and starch granules were also found within intact cells. Both starch granules and seed coat fragments were found in the drum‐dried flake matrices. Protein bodies, occurring in the raw bean, were present (but less obvious than in the raw bean) in both the bean purée and the drum‐dried flake. Cell contents that no longer occurred in intact cells consisted of fused protein bodies in both products. The seed coat did not change significantly during processing, and pieces of seed coat were easily differentiated throughout the bean purée and the drum‐dried flakes. The endosperm, which is closely adherent to the inner portion of the seed coat in the intact bean, was no longer evident in the processed samples, presumably because the endosperm tissue had completely solubilized following the addition of water. Lipids occurred as small droplets and were located throughout both the bean purée and the drum‐dried flakes. The bean purée consisted mostly of clumps of intact cotyledon cells with very few broken cells. The cotyledon cells contained intact starch granules with no evidence of starch gelatinization [i.e., the irreversible breakdown of the granule structure (Dengate 1984)]. Free starch granules in the purée, resulting from broken cells, were slightly swollen and had begun to gelatinize. Protein bodies were still evident in the purée, but no longer stained as in the raw, mature bean. The drum‐dried flakes contained intact and broken cotyledon cells. Intact cells contained protein bodies that were difficult to detect and appeared to be a rather continuous protein matrix. The cotyledon cells also contained partially gelatinized starch granules that remained mostly distinct but were beginning to fuse. Starch granules interspersed between intact cells were fused and completely gelatinized. The drum‐dried flake matrix consisted of a continuous mixture of protein, starch, and cell wall material.