Nutritional, functional and rheological properties of bunya nut flour as a versatile gluten-free option

Bunya nuts are a starch-rich food that has been consumed by Indigenous communities for thousands of years. In addition to consuming fresh nuts, they were commonly processed into flour. However, their properties as a gluten-free flour are still unknown. In this study, we investigated the nutritional, functional and rheological properties of bunya flour prepared using different methods, as well as the isolated starch, and compared to wheat, rice and chestnut flours. Overall, raw bunya nut flour showed higher fibre (8.4%d.b.), lower protein (4.7%d.b.) and higher fat content (4.4%d.b.) when compared to rice and wheat flours. Its proximate composition was similar to chestnut flour. By altering the preparation method for bunya nut flour we showed that its functional properties can be altered, for example, raw and whole bunya flours showed good foam and emulsion capacity and stability, whereas roasted bunya flour had poor emulsion activity and stability but a high water absorption capacity. Raw and fermented flours showed high peak viscosity when heated in water. Bunya flours, except for the roasted one, showed a slow rate of starch hydrolysis and high resistant starch content compared to wheat and rice flours, especially considering the role of the inner coating when not removed from the nut. Bunya nut flour is a versatile option and can overcome issues found for gluten-free flours such as poor nutritional quality and sensory properties of the resultant products.