Two-Dimensional Nuclear Magnetic Resonance Studies of Starch and Starch Products

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Production, refining, structural characterization and fermentability of rice husk xylooligosaccharides

Oligosaccharides produced by hydrothermal processing of rice husks (xylooligosaccharides and glucooligosaccharides) were refined by membrane processing (operating in diafiltration and concentration modes), subjected to xylanase treatment to reduce the average molar mass, and subjected to further purification by ultrafiltration (operating in concentration mode) and ion exchange. The purified products were assayed for composition, molar mass distribution and structural characterization by HPLC, HPAEC-PAD, HPSEC, MALDI-TOF-MS and NMR ((1)H and (13)C). The fermentability of the purified product by fecal inocula was assessed on the basis of the time courses of pH and oligosaccharide concentrations. Succinate, lactate, formiate, acetate, propionate and butyrate were the major products resulting from fermentation experiments.

Structure of dicarboxyl malto-oligomers isolated from hypochlorite-oxidised potato starch studied by 1H and 13C NMR spectroscopy

The main oxidised component in hypochlorite-oxidised potato starch was isolated by anion-exchange chromatography after enzymatic hydrolysis. The primary structure of the isolated oligosaccharides was determined by 1H and 13C NMR spectroscopy, using homonuclear and heteronuclear two-dimensional techniques. The isolated pentamer and hexamer contained one glucose unit oxidised to a dicarboxyl residue. As the hypochlorite oxidation has occurred at positions C-2 and C-3 of a glucose unit, the introduced carboxyl groups caused ring cleavage between the carbons C-2 and C-3. The ring-cleaved dicarboxyl residue had glycosidic linkages on both sides, implying that this oxidation pathway does not result in depolymerisation. The vicinal coupling constant between H-4 and H-5 in the ring-cleaved dicarboxyl residue was 3.2 Hz, showing that the gauche orientations are preferred. As a result, a different bending of the starch chain is observed and is probably, therefore, one of the reasons why hypochlorite oxidation reduces the tendency to retrogradation. The pKa values (3.0) were determined from the pH-dependent chemical shifts of H-1, H-4 and H-5 of the dicarboxylic residue.