Vegetables have low taste intensities, which might contribute to low acceptance. The aim of this study was to investigate the effect of taste (sweetness, sourness, bitterness, umami, and saltiness) and fattiness enhancement on consumer acceptance of cucumber and green capsicum purees. Three concentrations of sugar, citric acid, caffeine, mono-sodium glutamate, NaCl, and sunflower oil were added to pureed cucumber and green capsicum. Subjects (n = 66,35.6 ± 17.7 y) rated taste and fattiness intensity. Different subjects (n = 100, 33.2 ± 16.5 years) evaluated acceptance of all pureed vegetables. Taste intensities of vegetable purees were significantly different (P < 0.05) between the three tastant concentrations except for umami in both vegetable purees, sourness in green capsicum puree, and fattiness in cucumber puree. Only enhancement of sweetness significantly (P < 0.05) increased acceptance of both vegetable purees compared to unmodified purees. In cucumber purees, relatively small amounts of added sucrose (2%) increased acceptance already significantly, whereas in green capsicum acceptance increased significantly only with addition of 5% sucrose. Enhancement of other taste modalities did not significantly increase acceptance of both vegetable purees. Enhancing saltiness and bitterness significantly decreased acceptance of both vegetable purees. We conclude that the effect of taste enhancement on acceptance of vegetable purees differs between tastants and depends on tastant concentration and vegetable type. With the exception of sweetness, taste enhancement of taste modalities such as sourness, bitterness, umami, and saltiness was insufficient to increase acceptance of vegetable purees. We suggest that more complex taste, flavor, or texture modifications are required to enhance acceptance of vegetables.
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This research concerning the experience and future of zoos was carried out from 2011-2012 and takes regional ideas concerning Zoo Emmen as well as global visions into account. The research focuses partly on Zoo Emmen, its present attractions and visitors while also comparing and contrasting visions on the future in relationship to other international zoos in the world. In this way, remarkable experiences and ideas will be identified and in the light of them, it can serve as inspiration for stakeholders of zoos at large. The main research subject is a look at the future zoos in view of: The Zoo Experience – an international experience benchmark; The Zoo of the Future – a Scenario Planning approach towards the future; The virtual zoo - zoo’s in the internet domain.
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Penicillin acylase (PA) from Escherichia coli can catalyze the coupling of an acyl group to penicillin- and cephalosporin-derived beta-lactam nuclei, a conversion that can be used for the industrial synthesis of beta-lactam antibiotics. The modest synthetic properties of the wild-type enzyme make it desirable to engineer improved mutants. Analysis of the crystal structure of PA has shown that residues alphaR145 and alphaF146 undergo extensive repositioning upon binding of large ligands to the active site, suggesting that these residues may be good targets for mutagenesis aimed at improving the catalytic performance of PA. Therefore, site-saturation mutagenesis was performed on both positions and a complete set of all 38 variants was subjected to rapid HPLC screening for improved ampicillin synthesis. Not less than 33 mutants showed improved synthesis, indicating the importance of the mutated residues in PA-catalyzed acyl transfer kinetics. In several mutants at low substrate concentrations, the maximum level of ampicillin production was increased up to 1.5-fold, and the ratio of the synthetic rate over the hydrolytic rate was increased 5-15-fold. Moreover, due to increased tendency of the acyl-enzyme intermediate to react with beta-lactam nucleophile instead of water, mutants alphaR145G, alphaR145S and alphaR145L demonstrated an enhanced synthetic yield over wild-type PA at high substrate concentrations. This was accompanied by an increased conversion of 6-APA to ampicillin as well as a decreased undesirable hydrolysis of the acyl donor. Therefore, these mutants are interesting candidates for the enzymatic production of semi-synthetic beta-lactam antibiotics.
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