Glucose – a Reducing Sugar? Reducing Properties of Sugars in Beverages and Food

The properties of reducing sugars are interesting for the shelf life of beverages, particularly beer, and for human nutrition. For the brewing process the different reducing potentials and the mode of action of fermentable sugars are vitally important, especially during wort boiling where the reactions of sugars are accelerated. Additionally, several breweries use non-fermentable sugars in the brewing process to imbue the beer with unique flavour, body and mouthfeel.

An optimised method to ascertain the reduction potential of sugars against Fe₃₊ at low pH was developed in this work.

Sugars behave differently at low pH compared to the generally known behaviour described by Fehling when using NaOH. At low pH conditions, the formation of the open chain aldehyde structure of glucose is inhibited. Fructose has a higher ability to generate the open structure, resulting in stronger reducing properties. The results show at pH 4.3 the strongest reduction potential results from isomaltulose (Palatinose^TM), followed by fructose, Vitalose® and maltotriose. The higher reduction potential of the “non-reducing” sucrose compared to glucose can be explained by the invert sugar’s acid hydrolysation. Additional investigations give further evidence about the behaviour of fermentable sugars during the brewing process. Thereby is beside the described mode of action of glucose, fructose and sucrose, the detected stronger reduction potential of maltotriose versus maltose remarkable.

The optimised Chapon method can be used to support the investigation of the complex reaction mechanism of the different sugars in beverages like juice, wine and beer as well as during the brewing process and during storage.

BrewingScience - Monatsschrift für Brauwissenschaft, 64 (July/August 2011), pp. 61-67