Pyrodextrin powder production from sorghum beer residue: optimisation of spray drying parameters for improved conservation properties.

Abstract

Pyrodextrins are polysaccharides with the potential to be used as food additives, standing out for their nutritional interest associated with their behaviour as soluble dietary fiber. Being isolated from a gluten-free cereal, it is possible to add them to products suitable for individuals with coeliac disease. In the present study, the impact of the spray drying process of sorghum pyrodextrins obtained by pyroconversion of beer mashing residues, is investigated. The operating conditions for laboratory-scale drying are optimised to produce a stable powdered material for storage. The response surface methodology was used for different drying air inlet temperatures (150-250 °C), feed flow rates (20-80%) and drying airflow rates (20-80%). To characterise the spray-dried sorghum pyrodextrins, their water activity, moisture content, colour, particle size distribution and glass transition temperature were analysed. It was verified that the operational variables evaluated had an impact on the characteristic parameters of sorghum pyrodextrin powders. The optimal drying conditions determined a drying air temperature of 181.9 °C, feed flow rate at 23% and drying airflow rate at 78%, allowing powders with stability suitable for conservation to be obtained. The utilisation of a substantial waste from another process enhances efficiency and contributes to sustainability.