No abstract

The objectives of this research were to investigate the capability of a new hydrolyzing enzyme to hydrolyze native and cross‐linked starches in the granular state and to examine the influence of cross‐linking on hydrolysis. Corn, tapioca, and sweet potato starches were chemically modified by cross‐linking with 1% epichlorohydrin. The native and cross‐linked starches were subjected to hydrolysis using a new commercial enzyme, STARGEN™ 001 (a blend of α‐amylase and glucoamylase), at 35°C for 24 h, and the physicochemical properties of the starches were determined at different time points. After hydrolysis, the dextrose equivalent (DE) values of corn and tapioca starch decreased significantly after being cross‐linked (from 52.5 to 48.8% and from 35.7 to 27.9%, respectively). However, the sweet potato starch underwent a minimal reduction in DE value (from 27.3 to 26.8%). Scanning electron micrographs revealed that all cross‐linked starches had less porous granules compared to native starches after being hydrolyzed. Enzymatic erosion occurred mainly on the surface of starch granules, and the pores deepened into the interior part of the granules. The swelling power and solubility of all three cross‐linked starch decreased significantly after hydrolysis. Cross‐linking had a greater effect on pasting properties but little influence on the gelatinization properties of starch. The pasting temperature of cross‐linked tapioca starch was undetectable due to high degree of cross‐linking (92.4%). This study showed that cross‐linking had a considerable impact on the hydrolysis of corn and tapioca starch in particular by reducing the swelling power and solubility of its granules.

The stability of lutein nanodispersions was evaluated during storage and when exposed to different environmental conditions. Lutein nanodispersions were prepared using Tween 80, sodium dodecyl sulfate (SDS), sodium caseinate (SC) and SDS-Tween 80 as the emulsifiers. During eight weeks of storage, all samples showed remarkable physical stability. However, only the SC-stabilized nanodispersion showed excellent chemical stability. Under different environmental conditions, the nanodispersions exhibited a varied degree of stability. All nanodispersions showed constant particle sizes at temperatures between 30 and 60°C. However, at pH 2-8, only the SC-stabilized nanodispersion was physically unstable. The addition of NaCl (300-400 mM) only caused flocculation in nanodispersion stabilized by SDS-Tween 80. All nanodispersions were physically stable when subjected to different centrifugation speeds. Only Tween 80-stabilized nanodispersion was stable against the effect of freeze-thaw cycles (no phase separation observed). In this study, there was no particular emulsifier that was effective against all of the environmental conditions tested.

In this study, we prepared a series of lutein nanodispersions via the solvent displacement method, by using surfactants with different stabilizing mechanisms. The surfactants used include Tween 80 (steric stabilization), sodium dodecyl sulfate (SDS; electrostatic stabilization), sodium caseinate (electrosteric stabilization) and SDS-Tween 80 (electrostatic-steric stabilization). We then characterized the resulting lutein nanodispersions in terms of their particle size, particle size distribution, zeta potential, lutein content, flow behavior, apparent viscosity, transmittance, color, morphological properties and their effects on cell viability and cellular uptake. The type of surfactant used significantly (p < 0.05) affected the physical properties of the nanodispersions, but the chemical properties (lutein content) remained unaffected. Transmission electron microscopy (TEM) images obtained from this study demonstrated that the solvent displacement method was capable of producing lutein nanodispersions containing spherical particles with sizes ranging from 66.20-125.25 nm, depending on the type of surfactant used. SDS and SDS-Tween 80 surfactants negatively affected the viability of the HT-29 cells used in this study. Thus, for the cellular uptake determination, only Tween 80 and sodium caseinate surfactants were used. The cellular uptake of the lutein nanodispersion stabilized by sodium caseinate was higher than that which was stabilized by Tween 80. All things considered, the type of surfactant with different stabilizing mechanisms did produce lutein nanodispersions with different characteristics. These findings would aid in future selection of surfactants in order to produce nanodispersions with desirable properties.

A solvent displacement method was used to prepare lutein nanodispersions. The effects of processing parameters (addition method, addition rate, stirring time and stirring speed) and emulsifiers with different stabilizing mechanisms (steric, electrostatic, electrosteric and combined electrostatic-steric) on the particle size and particle size distribution (PSD) of the nanodispersions were investigated. Among the processing parameters, only the addition method and stirring time had significant effects (p<0.05) on the particle size and PSD. For steric emulsifiers, Tween 20, 40, 60 and 80 were used to produce nanodispersions successfully with particle sizes below 100nm. Tween 80 (steric) was then chosen for further comparison against sodium dodecyl sulfate (SDS) (electrostatic), sodium caseinate (electrosteric) and SDS-Tween 80 (combined electrostatic-steric) emulsifiers. At the lowest emulsifier concentration of 0.1%, all the emulsifiers invariably produced stable nanodispersions with small particle sizes (72.88-142.85nm) and narrow PSDs (polydispersity index<0.40).