Simultaneous determinations of the molecular weight distributions of amyloses and the fine structures of amylopectins of native starches

Effect of lactobacteria fermentation on structure and physicochemical properties of Chinese yam starch (Dioscorea opposita Thunb.)

Biotransformation is an effective technique to modify the structure and physicochemical properties of carbohydrates. In this work, Chinese yam (Dioscorea opposita Thunb.) starch was fermented by lactobacteria. The effect of fermentation time (6, 12, 30, 42 and 72 h) on structure and physicochemical properties of Chinese yam starch were investigated. The microstructure was destroyed after lactobacteria fermentation for 42 and 72 h. The X-ray diffraction pattern of Chinese yam starch indicated a transformed A to A + V crystalline type. → 4)-α-d-glucose-(1 → from backbone and unreduced terminal α-d-glucose-(1 → 4 from branch were identified by NMR spectra, and free glucose was only detected in fermented starch at 72 h. With the extension of fermentation time, the crystallinity and thermal parameters increased within 42 h and thereafter decreased. M_w, M_w/M_n, long chains of DP25-36 and DP ≥ 37, peak viscosity, trough viscosity, finally viscosity and setback presented a reverse trend.

Transformations and functional role of starch during potato crisp making: A review

Potato chips are a major product in the savory snack market and are consumed worldwide because of their enjoyable and distinctive organoleptic properties. They are conventionally produced by deep-frying thin slices of fresh potato. In contrast, potato crisps are manufactured from dried potato derivatives such as potato flakes (PFs). Their production is reviewed in this manuscript and requires the formation of dough based on hydrated PFs. Expansion of the dough during deep-frying provides the crisps with their desired crunchy texture. As part of an overall trend, the consumer search for calorie-reduced food products has also stimulated research to lower oil uptake during crisp production. However, minimizing oil absorption without losing the characteristic palatability of deep-fried products is challenging and requires fundamental knowledge on factors determining product texture and oil absorption. The transformations and functional role of starch, potato's main constituent, during crisp making are key in this respect and are reviewed here.

Characterization of amylose and amylopectin fractions separated from potato, banana, corn, and cassava starches

Analytical techniques such HPSEC, DSC, and TGA have been employed for amylose determination in starch samples, though spectrophotometry by iodine binding is most commonly used. The vast majority of these techniques require an analytical curve, using amylose and amylopectin standards with physicochemical properties similar to those found in the original starch. The current study aimed to obtain the amylose and amylopectin fractions from potato, banana, corn, and cassava starches, characterize them, and evaluate their behavior via thermogravimetric curves. Blue amylose iodine complex and HPSEC-DRI methods have obtained high purity amylose and amylopectin fractions. All molecular weights of the obtained amylose and amylopectin fractions were similar to those presented in other reports. Different results were obtained by deconvolution of the amylopectin polymodal distribution. All amyloses presented as semi-crystalline V-type polymorphs, while all amylopectin fractions were amorphous. The T_g of all V_amyloses presented were directly proportional to their respective crystalline index. TGA evaluations have shown that selective precipitation of amylose with 1-butanol strongly changes its thermal behavior. Therefore, the separation procedure used was an ineffective pathway for obtaining standards for thermal studies.

The analysis of the different functions of starch-phosphorylating enzymes during the development of Arabidopsis thaliana plants discloses an unexpected role for the cytosolic isoform GWD2

The genome of Arabidopsis thaliana encodes three glucan, water dikinases. Glucan, water dikinase 1 (GWD1; EC 2.7.9.4) and phosphoglucan, water dikinase (PWD; EC 2.7.9.5) are chloroplastic enzymes, while glucan, water dikinase 2 (GWD2) is cytosolic. Both GWDs and PWD catalyze the addition of phosphate groups to amylopectin chains at the surface of starch granules, changing its physicochemical properties. As a result, GWD1 and PWD have a positive effect on transitory starch degradation at night. Because of its cytosolic localization, GWD2 does not have the same effect. Single T-DNA mutants of either GWD1 or PWD or GWD2 have been analyzed during the entire life cycle of A. thaliana. We report that the three dikinases are all important for proper seed development. Seeds from gwd2 mutants are shrunken, with the epidermal cells of the seed coat irregularly shaped. Moreover, gwd2 seeds contain a lower lipid to protein ratio and are impaired in germination. Similar seed phenotypes were observed in pwd and gwd1 mutants, except for the normal morphology of epidermal cells in gwd1 seed coats. The gwd1, pwd and gwd2 mutants were also very similar in growth and flowering time when grown under continuous light and all three behaved differently from wild-type plants. Besides pinpointing a novel role of GWD2 and PWD in seed development, this analysis suggests that the phenotypic features of the dikinase mutants in A. thaliana cannot be explained solely in terms of defects in leaf starch degradation at night.

Morphological and Molecular Studies of Banana Starch

Molecular and morphological characteristics of banana starch were determined by different spectroscopic techniques. Light and scanning electron microscopy showed the molecular order, shape and size of starch granules. Banana starch granules had a lenticular shape with an average size of 39 m. The X-ray diffraction study showed starch granules with a pattern of a mixture between the A- and B-type polymorphs, also referred to as C-type. The absorbance ratio (1045/1022cm 1) measured by infrared spectroscopy was 1.12, suggesting that the crystalline component was higher than the amorphous regions. Gelatinisation temperature assessed by differential scanning calorimetry was 77.6°C with a gelatinisation enthalpy of 23.4J/g. These data stated that banana starch had a high crystallinity level, which might be important in several food applications.

Crystallization and chain reorganization of debranched rice starches in relation to resistant starch formation

The effects of chain distribution, concentration, temperature and hydrothermal treatments on the recrystallization behavior and formation of resistant starch (RS) were investigated. Waxy and normal rice starches were debranched at 10 and 21% w/w solid concentrations, incubated at 25 or 50 °C, and further subjected to annealing or heat moisture treatment (HMT) to enhance RS formation. The crystallization at 25 °C favored the formation of the B-type structure, whereas crystallization at 50 °C led to the A-type structure with a higher melting temperature (100-120 °C) and a higher RS content (52%). All incubated samples showed an increase in RS content after subsequent hydrothermal treatments. The sample incubated at a high temperature contained the highest RS content (74.5%) after HMT with larger/perfect crystallites. These results suggested that the RS formation could be manipulated by crystallization conditions and improved by hydrothermal treatments which are dependent on the initial crystalline perfection.

A hyaluronic acid–pentamidine bioconjugate as a macrophage mediated drug targeting delivery system for the treatment of leishmaniasis

A new HA–Pent bioconjugate was synthetized and proposed as drug targeting delivery system for the treatment of leishmaniasis, exploiting the specific biological recognition of HA by the macrophage.

Bioplastics from Blends of Cassava and Rice Flours: The Effect of Blend Composition

Bioplastics from melt-mixing of cassava flour, rice flour and their blends with compositions of between 0/100 and 100/0 %wt were successfully obtained using twin-screw extrusion and compression molding processes. The influence of blend composition on the bioplastic's properties was studied. It was found that the flour blends were uniformly mixed. The tensile properties and dynamic properties of the flour bioplastics were examined. The tensile strength and storage modulus of compression molded bioplastics based on rice flour was greater than those of the cassava flour, but their flexibility was lower. The tensile strength and storage modulus of the flour blend bioplastics increased with increasing rice flour content. The flour bioplastics showed two glass transitions, one corresponding to glycerol rich phase and the other corresponding to plasticized starch. For plasticized flour blends, the glass transitions were not affected by the blend composition. The improvement in the mechanical properties of the bioplastics produced from the cassava/rice flour blend could be explained by an increase in the crystallinity level resulting from the higher concentration of rice flour. Using flour blends derived from cassava and rice flours, the bioplastics developed in this study offer a greater performance while maintaining environmental compatibility and sustainability, which allows for a substitution of tradition bioplastics from cassava starch.

Structural and thermodynamic properties of rice starches with different genetic background

A combined DSC - HPAEC-PAD approach, gel permeation chromatography and mild long-term acidic hydrolysis were employed to study the effects of amylopectin chain-length distributional and amylose defects on the assembly structures of amylopectin (crystalline lamellae, amylopectin clusters) in A-type polymorphic starches extracted from 11 Thai cultivars of rice with different amylose level. Joint analysis of the data allowed determining the contributions of different populations of amylopectin chains to the thermodynamic melting parameters of crystalline lamellae. It was shown that amylopectin chains with DP 6-12 and 25<DP<36 as well as amylose-lipid complexes or V-type crystalline structures and apparently amylose "tie-chains" could be considered as defects in the assembly structures of rice starches. Contrary to the defects listed above, amylopectin chains with DP 13-24 and >or=37 could be related to chains stabilizing these structures. The total effect of amylose and amylopectin defects can be described by means of Thomson-Gibbs' equation. The increase of defects in the assembly structures is accompanied by rise of the rates of acidic hydrolysis of both amorphous and crystalline parts in starches.

Starch granules: structure and biosynthesis

The emphasis of this review is on starch structure and its biosynthesis. Improvements in understanding have been brought about during the last decade through the development of new physicochemical and biological techniques, leading to real scientific progress. All this literature needs to be kept inside the general literature about biopolymers, despite some confusing results or discrepancies arising from the biological variability of starch. However, a coherent picture of starch over all the different structural levels can be presented, in order to obtain some generalizations about its structure. In this review we will focus first on our present understanding of the structures of amylose and amylopectin and their organization within the granule, and we will then give insights on the biosynthetic mechanisms explaining the biogenesis of starch in plants.