RESUMO
The aim of this work was to study the impact of the methodology of in vitro gastric digestion (i.e., in terms of motility exerted and presence of gastric emptying) and gel structure on the degree of intestinal proteolysis and lipolysis of emulsion gels stabilized by whey protein isolate. Emulsions were prepared at pH 4.0 and 7.0 using two homogenization pressures (500 and 1000 bar) and then the emulsions were gelled by heat treatment. These gels were characterized in terms of texture analysis, and then were subjected to one of the following gastric digestion methods: in vitro mechanical gastric system (IMGS) or in vitro gastric digestion in a stirred beaker (SBg). After gastric digestion, the samples were subjected to in vitro intestinal digestion in a stirred beaker (SBi). Hardness, cohesiveness, and chewiness were significantly higher in gels at pH 7.0. The degree of proteolysis was higher in samples digested by IMGS-SBi (7-21%) than SBg-SBi (3-5%), regardless of the gel's pH. For SBg-SBi, the degree of proteolysis was not affected by pH, but when operating the IMGS, higher hydrolysis values were obtained for gels at pH 7.0 (15-21%) than pH 4.0 (7-13%). Additionally, the percentage of free fatty acids (%FFA) released was reduced by 47.9% in samples digested in the IMGS-SBi. For the methodology SBg-SBi, the %FFA was not affected by the pH, but in the IMGS, higher values were obtained for gels at pH 4.0 (28-30%) than pH 7.0 (15-19%). Our findings demonstrate the importance of choosing representative methods to simulate food digestion in the human gastrointestinal tract and their subsequent impact on nutrient bioaccessibility.
RESUMO
Cyanide is one of the main reagents used in gold mining that can be recovered to reduce operational costs. Gas membrane technology is an attractive method for intensifying both the stripping and absorption processes of valuable compounds, such as cyanide. However, scaling-up this technology from laboratory to industry is an unsolved challenge because it requires the improvement of the experimental methodologies that replicate lab-scale results at a larger scale. With this purpose in mind, this study compares the performance of three different hollow fiber membrane contactor modules (1.7 × 5.5 Mini Module, 1.7 × 10 Mini Module, and 2.5 × 8 Extra Flow). These are used for recovering cyanide from aqueous solutions at laboratory scale, using identical operational conditions. For each experimental set-up, mass-transfer correlations at the ranges of feed flows assayed were determined. The modules with the smallest and largest area of mass transfer reached similar cyanide recoveries (>95% at 60 min), which demonstrate the impact of module configuration on their operating performance. The results obtained here are limited for scaling-up the membrane module performance only because operating modules with the largest area results in a low Re number. This fact limits the extrapolation of results from the mass-transfer correlation.
