Iodine Binding Capacity Research Articles

Effects of water deficit during grain filling on the physicochemical properties of waxy maize starch

The effects of water deficit after pollination on the physicochemical properties of waxy maize starch were clarified, using Suyunuo5 and Yunuo7 as test materials. Pot experiments were conducted in 2012 and 2013; a pool trial was performed in 2014. Results indicated that the starch granule size was decreased by water deficit in both pot and pool experiments. Furthermore, the water deficit reduced the starch crystallinity and peak intensities at different reflection angles. The reduced iodine binding capacity under drought condition indicated that the proportion of long chains in amylopectin was decreased by water deficit. Swelling power was only decreased by drought under pool condition. The structural changes in starch decreased the peak and breakdown viscosities, but increased the retrogradation percentage. The maximum absorption wavelength, blue value, gelatinization enthalpy, pasting and gelatinization temperatures of starch were not affected by the water deficit. Therefore, drought during grain filling deteriorated the pasting viscosities and increased the tendency of retrogradation by reducing the starch granule size, proportion of long-chains in amylopectin, swelling power, and crystallinity.

Effects of waterlogging after pollination on the physicochemical properties of starch from waxy maize

Waterlogging frequently occurs in Southern China in summer and significantly affects waxy maize growth. This study investigated the physicochemical properties of starch from six waxy maize varieties exposed to waterlogging for 1–7days after pollination. Waterlogging decreased the starch granule size. Starch maximum absorption wavelength, iodine-binding capacity, crystallinity, and peak intensities in response to waterlogging depended on varieties. Swelling power and solubility in response to waterlogging increased in Wannuo5 and decreased in the other five varieties. Gelatinization and pasting temperatures were only slightly affected by waterlogging. Gelatinization enthalpy was unaffected in Nongkeyu301, increased in Guangbainuo5, and decreased in the other four varieties. Peak and breakdown viscosities decreased and retrogradation percentage increased when plants were subjected to waterlogging after pollination. In conclusion, waterlogging decreased starch granule size, crystallinity, swelling power, and solubility, resulting in deteriorated starch quality (i.e., low swelling, less sticky and easy to retrograde).

Heat Stress at Different Grain Filling Stages Affects Fresh Waxy Maize Grain Yield and Quality

The effects of heat stress (mean day/night temperatures were 29/18 and 35/18°C for control and heat stress treatments, respectively) at 1–10 or 11–20 days after pollination (DAP) on grain yield and quality of two waxy maize varieties, Suyunuo5 and Yunuo7, were studied. The decrease in grain number and fresh grain yield was more severe when heat stress was introduced early. The responses of grain weight and its components to heat stress were dependent on the variety and heat stress stage. Heat stress increased the starch granule size and volume percentage of diameter larger than 17 μm in both varieties. Crystallinity, iodine binding capacity, and pasting and gelatinization temperatures were increased in both varieties under heat stress at 11–20 DAP; however, the response to early‐stage heat stress was variety dependent. Peak viscosity and retrogradation percentage were increased by heat stress at either stage. These results suggest that heat stress decreases fresh grain yield and accelerates grain filling rate; it increases starch content, starch granule size, crystallinity, and iodine binding capacity as well as decreases the protein content in Yunuo7, thus making the grain less tender and prone to retrogradation. Warm conditions should shorten the time to harvest in fresh waxy maize production.

Effects of shading after pollination on starch physico-chemical properties of waxy maize

Shading stress after pollination is an important abiotic factor affecting waxy maize starch quality. The objective of the current study is to investigate the effects of shading after pollination on starch physico-chemical properties of waxy maize. The shading experiment was conducted in the field in 2011 and 2012, with a waxy maize variety (Suyunuo5) as the test material. Plants were given shading with black polyethylene nets and the light intensity was reduced by 30%, with plants grown under natural light were taken as control. Shading after pollination decreased the starch granule size and iodine binding capacity, and reduced the peak intensities at 2θ=15º, 17º, 18º and 23º. Pasting viscosities were decreased by shading in both the years. The ΔHgel and Tc were not affected, To and Tp were decreased, while ΔHrest and %R were increased by shading. The results indicated that shading deteriorated the pasting and retrogradation properties through reducing the starch granule size, iodine binding capacity and peak intensities.

Effects of high temperature after pollination on physicochemical properties of waxy maize flour during grain development

Waxy maize is grown in South China, where high temperatures frequently prevail. The effect of high-temperature stress on grain development of waxy maize is not known. High temperature decreased the grain fresh weight and volume, and lowered the grain dry weight and water content after 22 days after pollination (DAP). Plants exposed to high temperature had low starch content, and high protein and soluble sugar contents at maturity. Starch iodine binding capacity and granule size were increased by heat stress at all grain-filling stages. The former parameter decreased, while the latter parameter increased gradually with grain development. High temperature increased the peak and breakdown viscosity before 30 DAP, but the value decreased at maturity. Pasting and gelatinization temperatures at different stages were increased by heat stress and gradually decreased with grain development under both high-temperature and control conditions. Gelatinization enthalpy increased initially but decreased after peaking at 22 DAP under both control and heat stress conditions. High temperature decreased gelatinization enthalpy after 10 DAP. Retrogradation percentage value increased with high temperature throughout grain development. High temperature after pollination changes the dynamics of grain filling of waxy maize, which may underlie the observed changes in its pasting and thermal properties.

Effect of Shading During Grain Filling on the Physicochemical Properties of Fresh Waxy Maize

Grain physicochemical properties determine the table quality of fresh waxy maize. Two waxy maize varieties, Suyunuo 5 (shading tolerant) and FHN003 (shading sensitive), were used to estimate the effect of shading (plants received 30% less radiation than control) during grain filling (from 0 d to 23 d after pollination) on physicochemical properties of fresh waxy maize grain. Shading decreased the grain fresh weight of Suyunuo 5 and FHN003 by 8.4 and 19.1%, respectively. Shading increased the grain water content of FHN003, whereas that of Suyunuo 5 was not affected. In both varieties for shading treatment, soluble sugar, starch and protein contents were decreased, whereas zein content was increased. The changes in globulin, albumin and glutenin contents under shading were variety dependent. In both varieties, shading decreased λmax, iodine binding capacity and the percentage of large starch granules (diameter >17 μm) but increased crystallinity. The results of rapid visco analysis showed that the viscosity characteristics (except for pasting temperature) of both varieties were decreased by shading; however, FHN003 was more severely affected than Suyunuo 5. Under shading, ΔHret and %R were decreased in both varieties, whereas the changes in ΔHgel and transition temperatures were variety dependent. Hardness, cohesiveness and chewiness were decreased in both varieties. Significant differences in physicochemical characteristics were observed between the two varieties.

Effects of high temperature during grain filling under control conditions on the physicochemical properties of waxy maize flour

The effects of high temperature during different grain filling stages (1–15d and 16–30d after pollination) on the physicochemical properties of four varieties of waxy maize grain were studied. Heat stress during grain filling decreased grain weight and starch deposition, while it increased protein content, starch granule size, abnormal granule numbers and iodine binding capacity. These effects were more severe when heat stress was introduced at early development stage than at late grain filling stage. The peak intensities and crystallinities were decreased when plants were exposed to high temperature at early development stage. By contrast, responses to high temperature at late development stage were variety-dependent. High temperature during grain filling decreased the peak and breakdown viscosities and increased the gelatinization temperature and enthalpy, and retrogradation percentage of flours, especially during early development stage. In conclusion, high temperature during grain filling changed the grain proximate and starch structure, resulting in the deterioration of pasting and thermal properties.

Effect of iodine in semolina matrices

The effect of starch-protein interactions on the ability of linear starch chains to bind iodine was investigated in 4 types of semolina. Based on K/S (absorption/scattering coefficient) spectra, obtained after equilibration above K2SO4 and exposure to iodine vapor, and X-ray diffraction, semolina samples showed differences in chain mobility, iodine-binding capacity and crystalline order. After removing protein from the samples, starch exhibited a higher iodine-binding capacity, suggesting greater starch chain mobility, and low crystalline order. The results suggest that protein and/or starch-protein affect the packing arrangement of starch polymers within the granule.

Complex formation, thermal properties, and in-vitro digestibility of gelatinized potato starch–fatty acid mixtures

Effects of the type and amount of fatty acid (0–2.0 mmol/g-starch of lauric, myristic, palmitic, stearic, oleic, and linoleic acids) on the complex formation, thermal properties, and in-vitro digestibility of gelatinized potato starch–fatty acid mixtures were investigated. Complex index (CI) evaluated by the reduction in the iodine binding capacity of starch increased with an increase in the amount of fatty acids, and reached a plateau depending on the type of fatty acid. The maximum CI value was higher in the order of lauric (49.9%), linoleic (47.6%), myristic (42.4%), oleic (36.7%), stearic (35.3%), and palmitic acid (30.9%). From the calorimetric study, it was demonstrated that melting temperature of the complexes was higher in the order of stearic (96.7 °C) > lauric, myristic, palmitic, and oleic (89.6–92.1 °C) > linoleic acid (78.3 °C). Melting enthalpy for complexes was roughly related to the CI value ( R 2 = 0.667). From the in-vitro digestibility measurement, it was found that a certain amount of fatty acid reduced the starch content hydrolyzed at a given condition. Among them, 0.50 mmol/g-starch lauric and oleic acid samples showed the largest reduction in the hydrolyzed starch content. This result was related to the extent of complex formation characterized by CI value and its helical order characterized by melting temperature. In addition, there was a possibility of the complex formation between amylose and unsaturated fatty acid during the hydrolysis of gelatinized starch.

Characterizing starch structure in a gluten‐free pasta by using iodine vapor as a tool

AbstractThe suitability of starch–iodine complex to highlight differences in chain mobility and crystallinity of starch in rice pasta was investigated. Two pasta samples were produced starting from the same rice flour (RF) and using a conventional extrusion process without (Process A) and with (Process B) a preliminary extrusion‐cooking step. Based on the absorption/scattering coefficient (K/S) spectra (obtained after equilibration above K2SO4 and exposure to iodine vapor), Pasta A showed a behavior similar to RF. Process B exhibited a greater iodine binding capacity suggesting greater starch chain mobility. Moreover, the extrusion‐cooking conditions seem to favor the loss of starch crystallinity and the formation of larger amorphous regions. The organization of starch polymers observed in Pasta B could account for its higher capacity to water absorption during cooking.

Understanding starch organisation in gluten-free pasta from rice flour

Starches extracted from parboiled rice flour and pasta samples produced by two extrusion processes – a conventional method carried out at 50 °C and an extrusion-cooking process at 115 °C – were evaluated by differential scanning calorimetry (DSC) and size exclusion chromatography (SEC) analysis. Molecular changes induced by both pasta-making process and following cooking in boiling water were also investigated using iodine absorption properties of samples expressed as the ratio of absorption to scattering spectra (K/S) and X-ray diffraction. A decrease in polymer chain mobility and iodine binding capacity were observed after pasta-making process. While the characteristic A-type crystalline pattern remained, the exposure to iodine vapor changed the peak intensity of starch samples, especially at 0.97 a w. The higher melting temperature of pasta samples in comparison with parboiled rice flour reflected the decrease in mobility of the amorphous regions detected by K/S spectral analysis. The pasta making-process also affected the molecular size distribution of starch samples. In particular, the elution peak shifted toward lower fraction numbers with increasing extrusion temperature, showing a higher molecular size for starch after the extrusion-cooking. All the differences detected between starch samples according to extrusion conditions were deleted during cooking. Compared to the uncooked samples, starch from cooked pasta showed higher K/S value at all wavelengths, highlighting the increase in mobility of the amorphous region. Moreover, beside the increase in melting temperature, a decrease in endothermic enthalpy was detected, confirming the loss of order observed by X-ray diffraction.

Addressing the Dilemmas of Measuring Amylose in Rice

ABSTRACTAmylose content is a parameter that correlates with the cooking behavior of rice. It is measured at the earliest possible stages of rice improvement programs to enable breeders to build the foundations of appropriate grain quality during cultivar development. Amylose is usually quantified by absorbance of the amylose‐iodine complex. The International Network for Quality Rice (INQR) conducted a survey to determine ways that amylose is measured, reproducibility between laboratories, and sources of variation. Each laboratory measured the amylose content of a set of 17 cultivars of rice. The study shows that five different versions of the iodine binding method are in use. The data show that repeatability was high within laboratories but reproducibility between laboratories was low. The major sources of variability were the way the standard curve was constructed and the iodine binding capacity of the potato amylose used to produce the standard. Reproducibility is much lower between laboratories using a standard curve of potato amylose alone compared with those using calibrated rice cultivars. This study highlights the need to standardize the way amylose is measured, and presents research avenues for doing so.

α-Amylolysis of native potato and corn starches – SEM, AFM, nitrogen and iodine sorption investigations

Scanning electron microscopy (SEM), atomic force microscopy (AFM), as well as iodine and nitrogen sorption measurements were applied to investigate potato and corn starch granules surface after an action of Bacillus subtilis α-amylase. The SEM images revealed holes and pits (corn starch) or scratches (potato starch) on the surface of modified granules. These results were confirmed by AFM investigation which showed the presence of depressions of approximately 121 nm in diameter. Structure of the surface was not uniform. It consisted of small particles, amylopectin blocklets, of approximately 20 nm in diameter. They became more distinctive after α-amylolysis. Values of iodine binding capacity (IBC) obtained for hydrolyzed granules were lower than for native ones which indicated that the amylose and amylopectin chains building their surface were shortened. Specific surface area, volume and average diameter of mesopores increased for both starches after α-amylolysis.

Characterization of starch nanoparticles

Nanomaterials already attract great interest because of their potential applications in technology, food science and medicine. Biomaterials are biodegradable and quite abundant in nature, so they are favoured over synthetic polymer based materials. Starch as a nontoxic, cheap and renewable raw material is particularly suitable for preparation of nanoparticles. In the paper, the structure and some physicochemical properties of potato and cassava starch particles of the size between 50 to 100 nm, obtained by mechanical treatment of native starch, were presented. We demonstrated, with the aim of the Scanning Electron Microscopy (SEM) and the non-contact Atomic Force Microscopy (nc-AFM), that the shape and dimensions of the obtained nanoparticles both potato and cassava starch fit the blocklets – previously proposed as basic structural features of native starch granules. This observation was supported by aqueous solubility and swelling power of the particles as well as their iodine binding capacity similar to those for amylopectin-type short branched polysaccharide species. Obtained results indicated that glycosidic bonds of the branch linkage points in the granule amorphous lamellae might be broken during the applied mechanical treatment. Thus the released amylopectin clusters could escape out of the granules. The starch nanoparticles, for their properties qualitatively different from those of native starch granules, could be utilized in new applications.

Properties of Starches Modified by Different Acids

Starches from wheat, maize, finger millet, tapioca, green gram, chick pea, and potato were acid modified using 0.5N HCl, HNO3, H2SO4, and H3PO4 at 50°C for 1.5 h. Alkali Fluidity Number (AFN) for native starches was very low (0.3–2.5) and increased upon modification. HCl and HNO3 produced the highest AFN followed by H2SO4 and H3PO4 . For each acid, cereal and millet starches showed the highest AFN, followed by root, pulse and tuber starches. The extent of hydrolysis was proportional to number average molecular weight (), of the native starch in the case of HCl and HNO3 but not in other acids. Intrinsic viscosity [η] of native starches showed positive correlation to their ,. However, the [η] of the modified starches, particularly those produced by HCl and HNO3 , showed no proportionality with their , indicating diverse structural differences in the hydrolsed products. Special behavior of finger millet starch is clear from [η] values of these four acid modified starches. The iodine binding capacity (IBC) of starches, although decreased (2 to 36%) upon modification, did not follow any particular pattern. About 0.01 to 0.94% starch got solubilized during modification—highest being in case of HCl and lowest for H3PO4 . Their and IBC were considerably lower in all cases except potato, which showed same IBC for the solubilized, as well as granular modified starch.

Starch Retrogradation in Cassava Flour From Cooked Parenchyma

AbstractStarch changes in cassava flours made from parenchyma (peeled root) cooked either in steam or in boiling water and stored at 5ºC or −20ºC for 24 h were studied using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction and iodine binding capacity. The storage temperature of cooked parenchyma did not have a significant effect on starch retrogradation. For storage at 5ºC, flour from steam‐cooked parenchyma presented a slightly higher melting enthalpy of retrograded starch and crystallinity compared to that of parenchyma cooked in boiling water. When stored at −20ºC, the cooking procedure had no significant effect on the melting enthalpy of retrograded starch, crystallinity and blue value index (BVI). The water content in cooked parenchyma stored at 5ºC influenced the extent of retrogradation. The cooking method and the storage temperature are important parameters that might influence the physicochemical and functional properties of cassava flours.

Analysis of complexes between lipids and wheat starch

Starch–lipid complexes were formed by mixing wheat starch and various fatty acids and monopalmitin in a rapid visco analyser (RVA). The inclusion of the lipids in the starch pastes decreased the holding viscosity, whereas the final viscosity was increased. The changes in RVA parameters were correlated with the loss of iodine-binding capacity of the starch pastes, which was consistent with the formation of starch–lipid complexes. Mixtures of wheat starch with caprylic acid (C8:0), lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1 Δ9), linoleic acid (C18:2 Δ9,11), linolenic acid (C18:3 Δ9,11,13), and monopalmitin showed that maximal complex formation occurred at a different concentration for each lipid, which was related to the water solubility and critical micellar concentration of the lipid. Above a certain concentration, some of the lipids tended to self associate in preference to forming starch–lipid complexes.

Starch transformation and structure development in production and reconstitution of potato flakes

Changes of parenchymous tissue structure and transformations of starch in the production and reconstitution of drum-dried potato flakes as instant mashed potatoes were investigated by light microscopy, iodine binding capacity, thermal analysis, wide-angle X-ray powder diffraction and rheology. Instant mashed potatoes are suspensions which are formed by separating whole potato tissue into individual cells. Mechanical stress during mashing and the subsequent steps also lead to undesirable cell disruption and extracellular starch. The stabilizing effect on starch by gelatinization and retrogradation in the preheating and cooling step was found to be far less important than mentioned in literature. While amylopectin does not retrograde, amylose crystallizes de novo during preheating, probably further aggregates during the cooling step and the ageing of mashed potatoes and melts fully during drum drying. The total amount of cells and the proportion of single cells to cell clusters as dispersed phase determine product flow properties as much as the amount of extracellular starch in the continuous fluid phase. Therefore, the iodine binding value of extracellular starch cannot serve as only measure to judge texture of mashed potato products.

Physicochemical properties of waxy corn starch and corn amylopectin illuminated with linearly polarised visible light

Aqueous suspensions (30%) of either waxy corn starch or corn amylopectin were illuminated with visible linearly polarised light ( λ>500 nm) for 5–50 h. Pasting profiles, thermal properties, iodine binding capacity and intrinsic viscosity (in DMSO/water, 90:10) were taken for them after illumination. The illumination for 5, 15, and 25 h was not reflected in overall paste viscosities. Prolonged illumination (50 h) led to significant decrease in the peak and final viscosities. Illumination for 5 h (6.76 J/g), 15 h (7.74 J/g), 25 h. (7.95 J/g), and 50 h (2.85 J/g) decreased the melting enthalpies which for original waxy corn starch was 9.67 J/g. Decrease in intrinsic viscosity, [ η], as compared to that of native waxy corn starch (7.9 dl/g) was observed for the sample illuminated for 15 h (5.9 dl/g). Further illumination led to increase in [ η] values after 25 h (6.6 dl/g) and 50 h (8.0 dl/g). Blue value (BV) measured for the sample illuminated for 5 h (0.106) was higher than for waxy corn starch (0.076). Gradual decrease in BV was observed for samples illuminated for 15 (0.086), 25 (0.071) and 50 h (0.030). No changes in intrinsic viscosity and BV were found in the case of corn amylopectin irrespective of the illumination time. Findings indicate that polarised light induced depolymerisation of starch polysaccharide only if molecules were organised in crystal structures in same manner as in starch granule.

Physicochemical properties of potato starch illuminated with visible polarised light

Suspensions (30%, w/w) of potato starch in pure water were illuminated for 5–50 h by linearly polarised visible light (λ>500 nm) under stream of nitrogen. Effects of the illumination on the transition enthalpy, melting temperature, the pasting viscosity profiles, and iodine binding capacity of illuminated starch were examined. Starch illuminated in water for 50 h showed lower melting temperature T p (60.57 °C) and transition enthalpy Δ H (10.01 J/g) than original potato starch soaked in water for the same period. After 25 h illumination in water the peak paste viscosity, P v, of starch decreased in order to raise after 50 h illumination. Illumination in water initially degraded starch but prolonged illumination resulted in crosslinking into material of higher molecular weight.