The effect of processing conditions and pulse type on flake properties

Pulses such as chickpeas and Faba beans are a healthy and sustainable food source of global significance, and are gaining popularity with Australian farmers. Despite this, pulse producers face volatile international markets and limited domestic processing opportunities. In developed countries such as Australia, pulse consumption is well below the recommended daily intake, and traditional pulse dishes in developing nations are being replaced by ‘ready-to-eat’ cereal products. It is therefore important that new ways to increase pulse consumption are explored, especially in the processed ready-to-eat market. The production of pulse flakes could be one means of increasing pulse consumption, however to address the challenges of pulse processing, food manufacturers need more knowledge related to the impact of the high protein content, physical size, structural weakness and long cooking times of pulses.
This research investigated the influence of industry-relevant processing conditions on the flaking quality of Australian chickpea and Faba bean splits. Two types of chickpea—the Desi and Kabuli, which have similar compositions but are different sizes—were selected. The Kabuli was in the whole form with hull; the Desi was in the common dehulled and split form. The third pulse selected was a medium-sized Faba bean similar in size and form to the Desi chickpea, but with different chemical composition and higher protein content.
The flake process consisted of first conditioning the pulse splits using different steam injection times (one, three, five or thirty minutes). Second, the softened splits were flaked between two rollers at flake thickness of 0.6±0.2 mm or 1.0±0.3 mm. Finally, the rolled pulse flakes were rapidly dried using a fluidised bed dryer at either 150 °C or 200 °C.
This study was successful in processing Australian pulses to produce flakes with different flake properties such as how much it has been cooked, the appearance, mechanical texture and whole flake durability during transport. New knowledge of flake formation gained includes the low degree of starch gelatinisation and protein denaturation achieved with short steam times and the effects of this on flake attributes. The degree of starch gelatinisation and protein denaturation was dependent primarily on the size of the pulse grit. The ratio of grit thickness to roller gap width determined the pulse flake shape, durability and degree of puffing after drying. A narrower roller gap (0.6-0.9mm), short steam times (less than five-minutes) and higher drying temperatures (200°C) improved flake flour viscosity, and the bowl life of flakes was highest with steam times of one to five minutes for flakes formed using the wider roller gap. Longer steam times when producing thin flakes decreased the middle lamella adhesion between cells, reducing flake durability. In contrast, longer steam times (greater than five-minutes) with thick flakes dried at 150 °C increased flake durability, possibly with formation of a low temperature (less than 150°C) starch-protein matrix melt structure.
The information gained about pulse flake attributes and their processing will provide direction to future ready-to-eat pulse research and the development of innovative products meeting commercial requirements. For example, by improving durability (e.g., small grits, steamed for more than five-minutes, rolled into thick flakes and dried at 150°C) may improve the processing viability of pulse flakes. By further optimising processing conditions, it may be possible to produce pulse flakes that offer new healthy, value-added, ready to eat pulse foods.