Fluoride indicator that functions in mixed aqueous media: hydrogen bonding effects
A urea-based fluoride anion indicator, 3, that functions in mixed aqueous media is reported. Under these conditions, indicator 3 and the two control systems 1 and 2 are colorless. Addition of fluoride anions produces an easy-to-visualize colorimetric response (colorless to yellow) in the case of 3, but not 1 or 2 as the result of anion-induced Si–O bond cleavage. Most of the colorimetric response is believed to stem from an alteration in the hydrogen bonding network, rather than changes to the p-conjugation pathway per se.
Abstract The objective of this study was to evaluate the chemical and physical characteristics of fresh egg pasta samples obtained by using two different production methodologies: extrusion and lamination. The results of the study demonstrate that products have different characteristics in terms of colour and level of gelatinization, while they do not show significant differences with regard to the amount of absorbed water during the cooking stage. It was evaluated that it is possible to discriminate the two kinds of products by using FT-NIR spectroscopy. FT-NIR analysis results suggest the presence of a different matrix–water association, a diverse level of starch gelatinization and a distinct starch–gluten interaction in the two kinds of pasteurised samples.