Stabilization of wholegrain sorghum flour and consequent potential improvement of food product sensory quality by microwave treatment of the kernels

Abstract

Wholegrain sorghum flour (WGF) is sensitive to rancid off-flavour development during storage. Microwave treatment of whole grain kernels (WGK) at 36 and 90 kJ/100 g using a pilot-scale commercial microwave oven was investigated as a flour stabilization technology. WGF from the microwaved and untreated WGK was then subjected to an accelerated storage test at 50 °C for 6 weeks. The effects of microwaving WGK on various quality parameters of the stored flour and the texture, colour and descriptive sensory characteristics of porridge prepared from flour were investigated. Both microwave energy levels resulted in a substantial reduction in the flour fat acidity and anisidine value throughout storage; the higher level being more effective. Sensory indications of porridge rancidity were identified less intensely and much later during flour storage for microwave-treated samples. These data indicate that the microwave treatment partially inactivated the flour lipases and consequently retarded free fatty acid oxidation. The WGK microwave treatment had no substantial adverse effects on other flour and porridge attributes. Microwave treatment of WGK could thus be an effective, practical technology to stabilize WGF and thereby enhance its food product quality.