Comparison of structural and functional properties of maize starch produced with commercial or endogenous enzymes.

To explore an effective and economic method to prepare higher contents of resistant starch (RS), different enzyme treatments including single pullulanase (PUL), commercial α-amylase (AA) or/and ß-amylase (BA) with PUL, and malt endogenous amylase (MA) with PUL were used and the structural, physicochemical properties and digestibility of all modified starches (MS) were compared. All the enzyme-treated starches displayed a mixture of B and V-type diffraction patterns. The MA/PUL-MS showed higher V-type diffraction peak intensity as compared to other modified starches. Compared to the combination of commercial enzyme treatment, the combination of malt enzyme treatment led to higher apparent amylose contents (45.56%), RS content (53.93%) and thermal stability (302 °C), whereas it possessed lower solubility indices and predicted glycaemic index. The apparent viscosity and shear resistance of MA/PUL-MS were lower than that of AA/PUL-MS, whereas that of MA/PUL-MS was higher than that of BA/PUL-MS and BA/AA/PUL-MS. These findings would provide a theoretical and applicative basis to produce foods with lower GI in industrial production.

Preparation, Characterization and Tailoring Properties of Poly(Vinyl Chloride) Composites with the Addition of Functional Halloysite-Lignin Hybrid Materials.

In this article, halloysite-lignin hybrid materials (HL) were designed and obtained. The weak hydrogen bonds found between the components were determined based on Fourier transform infrared spectroscopy (FTIR), proving the achievement of class I hybrid systems. The HL systems were characterized by very good thermal stability and relatively good homogeneity, which increased as the proportion of the inorganic part increased. This was confirmed by analyzing scanning electron microscope (SEM) images and assessing particle size distributions and polydispersity indexes. Processing rigid poly(vinyl chloride) (PVC) with HL systems with a content of up to 10 wt% in a Brabender torque rheometer allowed us to obtain composites with a relatively homogeneous structure confirmed by SEM observations; simultaneously, a reduction in the fusion time was noted. An improvement in PVC thermal stability of approximately 40 °C for composites with HL with a ratio of 1:5 wt/wt was noted. Regardless of the concentration of the HL system, PVC composites exhibited inconsiderably higher Young's modulus, but the incorporation of 2.5 wt% of fillers increased Charpy impact strength by 5-8 kJ/m2 and doubled elongation at break. This study demonstrated that favorable mechanical properties of PVC composites can be achieved, especially with an HL system with a ratio of 5:1 wt/wt.

Synergistic effects of branching enzyme and transglucosidase on the modification of potato starch granules.

Potato starch displayed high viscosity, low hydroscopicity and dispersity, and acid susceptibility leading to the limited application of potato starch. To expand the potato starch utility with appropriate processing characteristics, potato starch granules were modified with branching enzyme (BE) and transglucosidase (TG). The results indicated that the susceptibility of potato starch granules to TG was higher than BE. Moreover, the two enzymes showed the synergistic effect in enzymatic modification of potato starch granules. They cooperatively attacked the external and interior of potato starch granules. The crystal forms of potato starch changed from B to C-type after double enzyme treatments, and enzyme-treated starches exhibited homogeneous crystal distribution. Compared to BE or TG alone, the combined action of BE and TG increased significantly the ratio of α-1,6-glycosidic linkage and the amounts of short chains of potato starch, which led to the significant reduction in degree of crystallinity, viscosity, gelatinization temperature and enthalpy, and a remarkable increase in solubility. Especially, the physicochemical characteristics of modified starch largely depended on the treatment time of TG. Thus, through the combination of BE and TG, the appropriate treatment time of TG may be chosen to improve the physicochemical properties of potato starch in processed starch-based products.

Effect of lactic acid and UV irradiation on the cassava and corn starches

In this work, the effect of lactic acid and UV irradiation on the physicochemical and structural characteristics of cassava and corn starches was evaluated. Only the modified cassava starch presented baking expansion capacity. From RVA, reduction of viscosity values, greater internal stability and none set back for modified cassava starch were observed. Modified corn starch did not show any peak viscosity. There were no significant differences in DSC thermal properties of treated and native starches. Amylopectin and amylose molecules from both the modified starches displayed some degradation. Molecular weight of cassava amylopectin was mostly preserved, whereas corn amylopectin was evenly attacked through the granule. Nevertheless, the B long branched chains of cassava amylopectin, with DP~37, were degraded whereas they were unchanged for corn amylopectin.

Amido de mandioca modificado com ácido lático e radiação ultravioleta antes da secagem artificial têm mostrado boa capacidade de expansão, a exemplo da encontrada para o polvilho azedo. Neste trabalho, os efeitos do ácido lático e radiação UV sobre as características físico-químicas e estruturais de amidos de mandioca e milho foram investigados. Apenas o amido de mandioca modificado apresentou capacidade de expansão durante o forneamento. Do RVA, redução dos valores de viscosidade, boa estabilidade interna e nenhuma tendência a retrogradação para este amido modificado foi observado. O amido de milho não apresentou qualquer pico de viscosidade após modificação. Não foram observadas diferenças significativas nas propriedades térmicas, determinadas em DSC, entre os amidos nativos e modificados de ambas as fontes. As moléculas de amilopectina e amilose de ambos os amidos modificados mostraram alguma degradação. O peso molecular da amilopectina do amido de mandioca foi mais preservado, enquanto a amilopectina do amido de milho foi mais atacada em todo o grânulo. As cadeias ramificadas longas da amilopectina de mandioca, com DP~37, foram degradadas, enquanto as de milho mantiveram-se inalteradas.