Synthesis of Prebiotic Caramels Catalyzed by Ion-Exchange Resin Particles: Kinetic Model for the Formation of Di-d-fructose Dianhydrides

Accelerated d-Fructose Acid-Catalyzed Reactions in Thin Films Formed by Charged Microdroplets Deposition

Thin films derived by the deposition of charged microdroplets generated in the ESI source of a mass spectrometer act as highly concentrated reaction vessels in which the final products of an ion-molecule reaction can be isolated by their precipitation onto a solid surface under ambient conditions. In this study, the ESI Z-spray source supplied to a Q-TOF Ultima mass spectrometer was used to investigate the d-fructose acid-catalyzed reactions by microdroplets deposition onto a stainless-steel target surface. High conversion ratios of d-fructose into 5-hydroxymethylfuraldehyde (5-HMF), 5-methoxymethylfuraldehyde (5-MMF), and difructrose anhydrides (DFAs) were obtained with HCl and KHSO₄ as metal-free catalysts by using synthetic conditions under which the same products in bulk are not formed. Furthermore, the reaction outcome was found to be highly sensitive to the catalyst and the solvent employed as well as to the ESI source parameters influencing the thin film formation from microdroplets deposition onto the solid surface.

Difructose anhydride III: a 50-year perspective on its production and physiological functions

Production and applications of difructose anhydride III (DFA-III) have attracted considerable attention because of its versatile physiological functions. Recently, large-scale production of DFA-III has been continuously explored, which opens a horizon for applications in the food and pharmaceutical industries. This review updates recent advances involving DFA-III, including: biosynthetic strategies, purification, and large-scale production of DFA-III; physiological functions of DFA-III and related mechanisms; DFA-III safety evaluations; present applications in food systems, existing problems, and further research prospects. Currently, enzymatic synthesis of DFA-III has been conducted both industrially and in academic research. Two biosynthetic strategies for DFA-III production are summarized: single- and double enzyme-mediated. DFA-III purification is achieved via yeast fermentation. Enzyme membrane bioreactors have been applied to meet the large-scale production demands for DFA-III. In addition, the primary physiological functions of DFA-III and their underlying mechanisms have been proposed. However, current applications of DFA-III are limited. Further research regarding DFA-III should focus on commercial production and purification, comprehensive study of physiological properties, extensive investigation of large-scale human experiments, and expansion of industrial applications. It is worthy to dig deep into potential application and commercial value of DFA-III.

Solvent Effects on Degradative Condensation Side Reactions of Fructose in Its Initial Conversion to 5-Hydroxymethylfurfural

The degradative condensation of hexose, which originates from the C-C cleavage of hexose and condensation of degraded hexose fragment, is one of the possible reaction pathways for the formation of humins in hexose dehydration to 5-hydroxymethylfurfural (HMF). Herein, the impacts of several polar aprotic solvents on the degradative condensation of fructose to small-molecule carboxylic acids and oligomers (possible precursors of humins) are reported. In particular, a close relationship between the tautomeric distribution of fructose in solvents and the mechanism of degradative condensation is demonstrated. Typically, α-fructofuranose in 1,4-dioxane and acyclic open-chain fructose in THF favor the conversion of fructose to formic acid and oligomers; α-fructopyranose in γ-valerolactone or N-methylpyrrolidone favors levulinic acid and oligomers, whereas β-fructopyranose in 4-methyl-2-pentanone favors acetic acid and corresponding oligomers. This close correlation highlights a general understanding of the solvent-controlled formation of oligomers, which represents an important step toward the rational design of effective solvent systems for HMF production.