Separation and Characterization of Five Kinds of Medicinal Starches by Gravitational Field-Flow Fractionation (GrFFF) / 中国药学杂志

OBJECTIVE: To study the large/small granule number ratio, granule morphology, crystal structure, amylopectin and amylose ratio of five kinds of medicinal starches. METHODS: Five kinds of medicinal starches were separated and characterized by self-assembled gravitational field-flow fractionation (GrFFF) instrument and the proportion of large and small starch granules was calculated according to the results. Optical microscopy and scanning electron microscopy were applied to characterize the morphological property of starch. FT-IR and X-ray diffraction were used to obtain the starch crystalline structure and crystallinity. The contents of amylose and amylopectin were determinate by double wavelength method. RESULTS: The large/small granule number ratios of the five kinds of medicinal starches had obvious difference. The size difference was obvious and the shape was different. The change trends of the order and the amorphous structure of different kinds of starches were the same as that of its relative crystallinity; the higher the amylopectin content, the lower the amylopectin/amylopectin was, the better the crystallinity was. CONCLUSION: GrFFF can be used to characterize and separate large and small starch granules, and the results are in agreement with that of other methods.

Introduction of a synthetic Thermococcus-derived α-amlyase gene into barley genome for increased enzyme thermostability in grains

Background: The enzymes utilized in the process of beer production are generally sensitive to higher temperatures. About 60% of them are deactivated in drying the malt that limits the utilization of starting material in the fermentation process. Gene transfer from thermophilic bacteria is a promising tool for producing barley grains harboring thermotolerant enzymes. Results: Gene for α-amylase from hydrothermal Thermococcus, optimally active at 75­85°C and pH between 5.0 and 5.5, was adapted in silico to barley codon usage. The corresponding sequence was put under control of the endosperm-specific promoter 1Dx5 and after synthesis and cloning transferred into barley by biolistics. In addition to model cultivar Golden Promise we transformed three Slovak barley cultivars Pribina, Levan and Nitran, and transgenic plants were obtained. Expression of the ~50 kDa active recombinant enzyme in grains of cvs. Pribina and Nitran resulted in retaining up to 9.39% of enzyme activity upon heating to 75°C, which is more than 4 times higher compared to non-transgenic controls. In the model cv. Golden Promise the grain α-amylase activity upon heating was above 9% either, however, the effects of the introduced enzyme were less pronounced (only 1.22 fold difference compared with non-transgenic barley). Conclusions: Expression of the synthetic gene in barley enhanced the residual α-amylase activity in grains at high temperatures.

Effects of Leached Amylose and Amylopectin in Rice Cooking Liquidon Texture and Structure of Cooked Rice

ABSTRACT Effects of leached amylose (AM) and amylopectin (AP) on textural and morphological properties of cooked rice were investigated separately by replacing cooking liquid with AM and AP separated from pouring cooking liquid. The pouring of cooking water reduced the hardness (from 28.45 to 19.42N) and stickiness (from 1.74 to 1.19N·s) significantly. However, the addition of AM and AP enhanced the hardness (27.63N) and stickiness (1.71N·s).Scanning electron microscopy show that the leached short-chain AM entered the surface hollows in the cooked rice after water evaporation. Meanwhile, the Long-chain AM cross-linked to formed a three-dimensional network structures, which covered on the filled hollows. This distribution led to a harder texture of cooked rice. The leached AP absorbed water and swelledto form masses. Atthe gelatinization temperature,theAPmassesagglomeratedtoformafilmlayer,whichcoveredtheunevenstructure, the thicker and smoother film contributed to the sticky texture.

Estrutura dos grânulos de amido e sua relação com propriedades físico-químicas: [revisão] / Starch granules structure and its regards with physicochemical properties: [review]

Devido aos escassos trabalhos brasileiros sobre a estrutura dos grânulos de amido, o objetivo desta revisão foi demonstrar os avanços atuais na elucidação da arquitetura e da estrutura química desse polímero. Muitas pesquisas sobre a avaliação da relação existente entre a estrutura molecular do amido e seu comportamento em algumas propriedades físico-químicas sugerem que diversas características estruturais, tais como teor de amilose, distribuição de comprimento das cadeias de amilopectina e grau de cristalinidade no grânulo, estejam intimamente relacionadas a eventos associados à gelatinização e retrogradação, como inchamento do grânulo, lixiviação de amilose e/ou amilopectina, perda da estrutura radial (birrefringência), supra-molecular (cristalinidade) e molecular e recristalização. O foco principal desta revisão foi a compilação de estudos a fim de obter melhor entendimento da estrutura e das características dos componentes do amido e sua relação com propriedades físico-químicas, principalmente no que diz respeito à gelatinização e retrogradação, as quais apresentam grande importância nutricional e tecnológica.

Due to poor Brazilians work on the structure of starch granules, the purpose of this review was to demonstrate the advances in current understanding of architecture and chemical structure of this polymer. Many studies evaluating the relationship between the molecular structure of starch and its behavior in some physicochemical properties, suggest that several structural features, such as amylose content, amylopectin chain length distribution and the degree of crystallinity in the granule, are closely related to the events associated with gelatinization and retrogradation as starch granule swelling, amylose and/or amylopectin leaching, loss of radial structure (birefringence), supra-molecular (crystallinity) and molecular order, and recrystallization. The main focus of this review was to make a compiler of studies in order to gain better understanding of the granule structure and characteristics of starch components and physicochemical properties (gelatinization and retrogradation) that could play a significant role in improving the quality of different food products.