Molecular characterization of acid-thinned wheat, potato and pea starches and correlation to gel properties (original) (raw)
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Molecular Investigation of the Gel Structure of Native Starches
Starch - Stärke, 2018
Starch gels were prepared by varying the starch source (regular potato: PS; regular corn: CS; high amylose (AM) corn: HACS), the disintegration temperature (95 and 140 °C) and the storage time (1 day and 7 days). The mechanical strength was determined and found to be increased with increasing disintegration temperature and storage time. Enhanced AM content of the starch enabled stronger gels under specific preparation conditions. For the purpose of a detailed analysis of the gel composition, a new method was developed separating the system by means of centrifugation in two phases, a liquid (dissolved polymers; supernatant) and a swollen phase (polymers involved in gel network structure; sediment). Most of the starch was found to be involved in the swollen gel network phase. That structure was selectively degraded by means of specific enzyme combinations (pullulanase and α-amylase; pullulanase and β-amylase) to obtain different resistant portions representing the crystalline "junction zones" (α-amylase) and the polymer chains involved in both crystallized areas as well as amorphous intermediary segments (β-amylase), respectively. The portions were subsequently characterized by means of SEC. Within the present study, highest gel strength (HACS; 140 °C) was accompanied by the highest amounts of α-and β-amylase resistant portions (10 and 50 %, respectively), and the regular starches had basically lower gel strength by lower amounts of resistant portions. In general, the starch polymers within the β-amylase resistant portions had higher M w compared to that building the "junction zones", and the M w of the β-amylase resistant portions was higher for HACS compared to the regular starches. The AP-fraction is not supposed to be strongly involved in the gel network structure. Limitations of the analytical method were discussed.
Starch - Stärke, 2019
A matrix of 27 acid-thinned (AT) potato starch (PS) samples is prepared in a laboratory scale in slurry by gradation of the process parameters temperature (30, 40, and 50°C), acid concentration (0.3, 0.6, and 0.9 m HCl) and time (4, 10, and 20 h), and is investigated in terms of functional properties (range of molar mass [M w ] between 17.7 × 10 6 and 1.95 × 10 4 g mol −1). The solubility (S) increased basically with a higher degree of molecular degradation and disintegration temperature, and the viscosity decreased systematically with decreasing M w and increasing disintegration temperature. The existence of a specific M w range of the starch to achieve highest gel strength is proved. However, an impact of the molecular properties on the light transmittance (T gel) can be excluded, since all starch gels are opaque. A correlation between the strength and the specific non-freezable bound water content (w nf) of the gels is found. High gel strength is accompanied by comparatively low w nf. In particular, the viscosity (processing) and the gel strength (final product characteristic), which are important technofunctional properties for the industrial application of AT starches, are found to be directly correlated to the M w of the starch product. Moreover, the latter is controllable by the hydrolysis process parameters.
Cereal Chemistry, 2001
In this study, 3% aqueous high-amylose maize starch (Hylon VII) dispersions were heated to temperatures of 140-165°C. The onset and rate of gel formation was observed using a small-strain oscillation rheometer as a function of temperature from 90 to 25°C. The gel formation clearly began earlier in high-amylose starch paste preheated at lower temperatures, but the rate of gelation was slower and the resulting gel was weaker in comparison with starch pastes preheated at higher temperatures. In addition, the structure of the final gels was studied using large deformation compression measurements. The most rigid gel structure on the basis of small and large deformation tests was obtained for high-amylose starch gel preheated to 150-152°C, depending on the type of measurement. The rate of gelation was also fastest in that temperature range. High-amylose gels heated to higher temperatures lost their rigidity. The molecular weight distribution of starch molecules was measured by size-exclusion chromatography. Heating caused extensive degradation of amylopectin, which had a great effect on amylose gel formation and the final gel properties of high-amylose maize starch. Micrographs of Hylon VII gels showed that phase separation of starch components visible in light microscopy occurred on heating to higher temperatures.
Food Hydrocolloids, 2018
The impact of acidification and non-gluten protein fortification (egg-albumin and soy-protein isolate) on thermal transitions of rice, potato and tapioca starches as well as the viscoelastic properties of their gels prepared at two casting temperatures, 90ºC and 120ºC, was investigated. The thermal and rheological behaviour of starches depended on their botanical origin and were significantly influenced by the presence and type of protein added as well as by the pH of the aqueous dispersion. Acidification to pH 4.5 increased the gelatinization temperature of rice starch in the presence of albumin or soy proteins, while reduced it in the case of tapioca starch, regardless of the presence of proteins. Acidification of rice starch dispersions decreased significantly the apparent gelatinization enthalpy; this effect was even greater in the presence of proteins. The addition of proteins brought about a structuring effect on tapioca gels leading to higher viscoelastic moduli and lower tan δ values. In general, acidification led to weaker gel structures, with more pronounced effect for potato starch, most likely related to its higher phosphate content (charge screening). Much weaker gels were obtained at 120ºC compared to those processed at lower temperatures; however, protein incorporation reinforced gel structure, an effect that was not observed in gels formed at 90º, as also revealed by microstructure analysis using confocal scanning laser microscopy. In conclusion, protein addition and pH adjustments of aqueous starch dispersions can provide an effective means to modulate the functional and textural properties of gel-like starch-based gluten-free formulations.
Properties of Starch Subjected to Partial Gelatinization and β-Amylolysis
Journal of Agricultural and Food Chemistry, 2009
The overall objective of this research is to understand the impact of partial gelatinization and -amylase hydrolysis ( -amylolysis) on the physicochemical properties of starch. Three starches (normal corn, waxy corn, and wheat) were chosen as test examples and thermally treated at 40% moisture content to up to 95°C and then subjected to -amylolysis. The enzyme treatment resulted in over 10% maltose yield. Subsequent debranching analysis showed the production of chain stubs as short as having the degree of polymerization of 2 and 3, suggesting a thorough -amylolysis at certain branch locations. For starch samples subjected to partial gelatinization, polarized light microscopy shows reduced intensity of birefringence and differential scanning calorimetry shows reduced enthalpy change associated with gelatinization. Both indicate the reduced chain organization due to the treatment. Further, a substantial transformation of initial A-type crystalline structure to B-and V-types upon treatments is noticed from X-ray powder diffraction measurements. In addition, the rapid viscosity analysis (RVA) indicated a drastic viscosity reduction, increased peak temperature, and improved stability of pasting behavior due to hydrothermal treatments and -amylolysis. Overall, our results point out the possibility of obtaining modified starches having desirable stable pasting behavior by using a combined partial gelatinization and -amylolysis approach.
Gel texture and chain structure of amylomaltase-modified starches compared to gelatin
Food Hydrocolloids, 2008
Amylomaltase (AM) (4-a-D-glucanotransferase; E.C. 2.4.1.25) from Thermus thermophilus was used to modify starches from various botanical sources including potato, high amylose potato (HAP), maize, waxy maize, wheat and pea, as well as a chemical oxidized potato starch (Gelamyl 120). Amylopectin chain length distribution, textural properties of gels and molecular weight of 51 enzyme and 7 nonenzyme-modified starches (parent samples) were analyzed. Textural data were compared with the textural properties of gelatin gels. Modifying starch with AM caused broadening of the amylopectin chain length distribution, creating a unimodal distribution. The increase in longer chains was supposedly a combined effect of amylose to amylopectin chain transfer and transfer of cluster units within the amylopectin molecules.
Comparative Study on Functional Properties of Starch Extracted from Various Sources
International Journal of Current Microbiology and Applied Sciences, 2021
Starch is one of the important carbohydrates that is available in many food materials. It is a great source of energy for man. Starch in its pure form is odorless, tasteless, soft, and looks white. It is highly soluble in hot water but insoluble in alcohol and cold water. Starch can be simplified into two forms: one is the linear and helical polymer amylose and the other is the branched polymer amylopectin. Food having higher amylopectin content shows great swelling and gelatinization properties (Tao et al., 2019). While food containing higher amylose content shows properties of amorphous materials. Also, food having higher amylopectin, or food having lower amylose, shows a higher rate of digestion (Martens et al., 2018). Due to the presence of amylose and amylopectin, starch has unique functional and physicochemical properties, and these International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 10 Number 01 (2021) Journal homepage: http://www.ijcmas.com
Journal of Food Science and Technology, 2018
A comparison between structural, morphological, functional and digestibility studies of starches from cereals i.e. wheat (WS), corn (CS), low amylose corn (LACS) and rice (RS), tubers i.e. potato (PS) and sweet potato (SP), and legumes i.e. kidney bean (KB) were investigated. The shape of granules varied from oval to elliptical or spherical according to the source. Distribution of iso-amylase debranched materials revealed that long and short side chains fractions of amylopectin ranged from 12.6 to 33.1% and 40.5 to 52.5% respectively. KB starch showed the highest amylose content (49.50%) while RS showed the lowest (8.51%). Starches with greater granule size (PS, SP and KB) showed higher proportion of long side chains of amylopectin (AP) (Fr.II) than short side chains of AP (Fr.III). Peak viscosity (PV), breakdown viscosity (BV) and final viscosity (FV) showed significant positive relationship with Fr. II and negative with apparent amylose content (AAC) and Fr.III. Tuber starches showed greater paste viscosities followed by legume starches. Tuber and legume starches with higher apparent amylose content and Fr. II showed greater crystallinity. Gel hardness and gelatinization temperatures showed inverse relationship with RS starch having higher proportion of smaller granules (0-10 lm). KB with higher amylose content showed maximum rapidly digestible starch (RDS) content while SP showed the highest resistant starch. Above observations would be utilized in modifying properties of native starches and help in improving texture, moisture retention capacity and gel firmness of starch and its products. Keywords Starch Á Fine structure Á Scanning electron microscopy Á X-ray diffraction Á Fourier-transform infrared spectroscopy Á In vitro digestibility
Food Hydrocolloids, 2021
Starch performance along digestion is becoming of utmost importance owing to the extensive presence of starch in foods and its association to the foods glycaemic index. However, scarce information exists on the relationship between the digestibility of starch gels and their microstructure. The aim of the study was to identify the rate and degree of digestion of starch gels from different botanical sources and the impact of gels microstructure with the in vitro starch digestibility (IVSD) by fitting the hydrolysis kinetics. Starch gels from cereals, tubers, and pulses were structurally analyzed and subjected to a standardized oro-gastrointestinal IVSD. The gel microstructure was significantly different among starches. Cereal gels had thinner walls than tuber and pulses gels, and this discrimination was not evident in the area of the gel cavities. Starches hydrolysis was well fitted to a first-order kinetics model, except for rice starch gel. Potato and chickpea gels showed the slowest digestion, and in the case of potato gel some starch remained undigested at the end of the digestion. The amylose content of gels was correlated with starch hydrolysis rate. Moreover, starch gels with thinner walls and/or bigger cavities seems to facilitate the enzyme action, and therefore, the starch digestibility.
Influence of lipids on the thermal and mechanical properties of concentrated starch gels
Journal of Agricultural and Food Chemistry, 1991
Interactions between lipids [sodium dodecyl sulfate (SDS); glycerol monostearate; cetyltrimethylammonium bromide; L-a-lysophosphatidylcholine (LPC)] and starches (wheat, rice, pea, and garbanzo bean) were studied in thermoset gel networks of high starch concentrations 120-3576 w/w) by small amplitude oscillatory shear measurements and differential scanning calorimetry. All lipids reduced the apparent gelatinization enthalpies of the granular starches, suggesting complexation with the starch molecules upon heating; granule structure destabilization effects were shown only with SDS. Although rice and wheat starch gels exhibited higher storage modulus (G' ) values when lipids were included, smaller changes in the viscoelastic properties were observed for the legume starches; the higher amylose content of pea and garbanzo bean starches appears to dominate the rheological behavior of their composite gels. Among the lipids examined, LPC exerted the greatest effect in increasing the G' and decreasing the tan 6 (G"/G' ) of rice and wheat starch gels. Kinetic experiments on the evolution of modulus (G' ) and the development of the staling endotherm during storage of gels (35% w/w, 8 "C) indicated that lipids retard both processes. At concentrations between 8 and 40% (w/w) of rice and garbanzo bean starch gels, the dependence of storage modulus on starch concentration (C) followed power law relationships; G' varied as C2.1-2*9.