The microstructure of the starch from the underutilized seed of jaboticaba (Plinia cauliflora).

This work presents a starch extracted from jaboticaba seeds. The extraction yielded 22.65 ± 0.63% of a slightly beige powder (a* 1.92 ± 0.03, b* 10.82 ± 0.17 and L* 92.27 ± 0.24). The starch presented low protein content (1.19% ± 0.11) and phenolic compounds (0.58 ± 0.02 GAE. g) as contaminants. The starch granules showed small, smooth, irregular shapes and sizes between 6.1 and 9.6 µm. The starch presented a high content of amylose (34.50%±0.90) and a predominance of intermediate chain length (B1-chains 51%), followed by A-chains (26%) in the amylopectin. The SEC-MALS-DRI showed the starch had a low molecular weight (5.3·106 g·mol-1) and amylose/amylopectin content compatible with a Cc-type starch, confirmed in the X-ray diffractogram. Thermal studies showed a low onset temperature (T0 = 66.4 ± 0.46 °C) and gelatinization enthalpy (ΔH = 9.1 ± 1.19 J g-1) but a high-temperature range (ΔT = 14.1 ± 0.52 °C). The jaboticaba starch proved to be a promising material for food and non-food applications.

Influence of Levan on the Thermally Induced Gel Formation of ß-Lactoglobulin.

In this study, the influence of levan on the phase behavior and the thermally induced gelation of the mixed ß-lactoglobulin-levan gels as a function of polymer content, molecular weight and ionic strength was characterized. For this purpose, rheology was used to study the mechanical properties of the gels and the water binding of the network structure was investigated by time domain nuclear magnetic resonance. Phase behavior and network type were analyzed by optical observation and electron microscopy. Levan enhanced the aggregation and gel formation of ß-lg due to segregative forces between the polymer species. Segregation was caused by the excluded volume effect and was more pronounced at lower ionic strength, higher levan contents and higher levan molecular weights. The presence of levan increased the water binding of the gel networks. However, this effect decreased with increasing levan content. At high ionic strength and high levan content, phase separated gels were formed. While segregative forces enhanced network formation, and therefore, increased the gel strength of mixed gels at low ionic strength, levan had also antagonistic effects on the network formation at high ionic strength and high polymer contents.

Size-Dependent Variability in Flow and Viscoelastic Behavior of Levan Produced by Gluconobacter albidus TMW 2.1191.

Levan is a fructan-type exopolysaccharide which is produced by many microbes from sucrose via extracellular levansucrases. The hydrocolloid properties of levan depend on its molecular weight, while it is unknown why and to what extent levan is functionally diverse depending on its size. The aim of our study was to gain deeper insight into the size-dependent functional variability of levan. For this purpose, levans of different sizes were produced using the water kefir isolate Gluconobacter albidus TMW 2.1191 and subsequently rheologically characterized. Three levan types could be identified, which are similarly branched, but differ significantly in their molecular size and rheological properties. The smallest levan (<107 Da), produced without adjustment of the pH, exhibited Newton-like flow behavior up to a specific concentration of 25% (w/v). By contrast, larger levans (>108 Da) produced at pH ≥ 4.5 were shear-thinning, and the levan produced at pH 5.0 showed a gel-like behavior at 5% (w/v). A third (intermediate) levan variant was obtained through production in buffers at pH 4.0 and exhibited the properties of a viscoelastic fluid up to concentrations of 15% (w/v). Our study reveals that the rheological properties of levan are determined by its size and polydispersity, rather than by the amount of levan used or the structural composition.