The applications of fluidized bed drying to pulse proteins: experiments, mathematical modelling, and techno economic analysis

Abstract

This thesis investigates the application of fluidized bed drying (FBD) to the processing of pulses, specifically chickpeas and dehulled faba beans, with a focus on reducing anti-nutritional factors (ANFs) and improving nutritional quality. It begins with an introduction and literature review to establish the research context and identify gaps in the current knowledge.

This study addresses the challenge of preserving protein structure and removing antinutritional factors during the fluidized bed drying of chickpeas. By using a drying schedule, the denaturation of the pulse protein secondary structure was reduced. 86% of the trypsin inhibitor was also removed at the target moisture content.

Technico-economic analysis for the costs of dryng chickpeas has been studied in this thesis. The processing cost per unit mass of chickpeas is predicted to decrease with increasing recycle ratio, from over A$1.32/kg of chickpeas with no recycle down to A$0.0885/kg of chickpeas at a ratio of 99%.

In parallel, the processing of dehulled faba beans has been examined, with an emphasis on phytic acid reduction through a combination of soaking, microwaving, and FBD techniques. Phytic acid is thermally stable, and drying did not lead to any significant reduction in concentration. This thesis addresses the challenge of removing phytic acid, which is one of the major anti-nutritional factors present in faba beans.

A comprehensive techno-economic analysis evaluates the implications of these processes on the cost of drying faba beans, focusing on the comparison between boiling and microwave-based processing. These findings suggest that implementing an air recycle system in fluidized bed drying can lead to significant cost savings in pulse protein processing while maintaining process efficiency, and that boiling with air recycling used in drying is an optimal processing technique to remove phytic acid from dehulled faba beans.