Mango kernels are used for the first time as a source of both starch and starch nanocrystals (SNC) for bionanocomposite films. The starch yield was 38.5%, whereas the SNC yield (from starch) is more than 30%. Bionanocomposite films are produced from mango kernel starch (MKS) and 0-10 wt% SNC, and the corresponding films are also obtained from commercial corn starch. The addition of 5% SNC to MKS films increases their tensile strength and modulus in about 90% and 120% respectively, and reduces their water vapor permeability in about 15%. On the other hand, the film elongation has been reduced to half the one for the unfilled film, and the opacity has been increased. When compared to the corresponding corn starch films, mango kernel starch films exhibited higher overall tensile strength and elastic modulus, as well as increased opacity.
This study was conducted to evaluate color and anthocyanin stability of clarified acerola juice (CAJ) as affected by montmorillonite (Mnt) at different concentrations (0-6 wt%, dry basis). While non-complexed CAJ suffered noticeable color degradation with time and pH variations, the presence of Mnt (especially at 4-6 wt%) not only changed the initial color of CAJ but also made it more stable with time and pH changes. CAJ/Mnt mixtures were ultracentrifuged in order to separate them into supernatants and anthocyanin-complexed Mnt precipitates. The supernatants presented decreasing anthocyanin contents with increasing Mnt concentrations, indicating pigment retention by the precipitates. X-ray diffraction of precipitates showed that Mnt interlayer spacing was increased by increasing anthocyanin/Mnt ratios, corroborating anthocyanin intercalation. FTIR revealed a band at 1530 cm ascribed to formation of anthocyanin-Mnt complexes. Moreover, chromatograms indicated the selective adsorption of two compounds by Mnt, which were identified by LC-MS as cyanidin-3-O-rhamnoside and pelargonidin-3-O-rhamnoside.
Summary
Properties of glycerol‐plasticised cassava starch–carnauba wax emulsion films were studied as functions of carnauba wax/starch (CW/S) ratios. Increases in CW concentrations improved elongation, but impaired tensile strength and elastic modulus, suggesting a plasticising effect by CW and/or the emulsifier. CW reduced water solubility of the films and decreased their water vapour permeability (WVP) up to CW/S ratios of 0.15–0.20, probably because of the decreased water solubility. Higher CW concentrations resulted in increased WVP, possibly due to starch matrix loosening. The opacity imparted by high CW concentrations in films could compromise some applications. The Tg of starch and the expected CW effects on it were not evidenced by DSC thermograms, but CW seems to have affected starch crystallisation, maybe by forming complexes with amylose and/or amylopectin.
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