Soluble sugars and polysaccharides

During sourdough fermentation, important changes in the carbohydrate fraction occur due to enzymatic and metabolic reactions of both yeasts and lactic acid bacteria involved in the process. Indeed, the production of several metabolites depends on the availability of soluble carbohydrates either initially present in the flour or resulting from the hydrolysis of starch or other polysaccharides. For the determination of soluble sugars and polysaccharides, enzymatic kits, often based on official methods of analysis, recognized by the scientific community are available. The high specificity of enzymes enables the analysis of complex matrixes without complicated sample preparation techniques and little interferences which, on the contrary, might occur during chromatographic coelution. Nevertheless, although enzymatic assays favor the analysis of several samples in relatively little amount of time, the higher costs of analysis per sample compared to lab-developed methods tip the scale in favor of the latter. Whereas soluble sugars can be easily extracted and separated through high performance liquid chromatography, starch quantification needs to be preempted by its hydrolysis to glucose. As for dietary fibers, the hydrolysis of proteins and starch precedes filtration of insoluble fiber and precipitation of soluble fiber in ethanol. Their content is then evaluated by weighing after drying. In this chapter, the chromatographic method for mono-, di-, and oligosaccharides, the enzymatic hydrolysis of starch, and the analysis of dietary fibers according to official methods will be described.