Abstract
Heat treatment is used as a pre-processing step to beneficially change the starch properties of wheat flour to enhance its utilisation in the food industry. Heat-treated wheat flour may provide improved eating qualities in final wheat-based products since flour properties predominantly determine the texture and mouthfeel. Dry heat treatment of wheat kernels or milled wheat products involves heat transfer through means of air, a fluidising medium, or radiation—often resulting in moisture loss. Heat treatment leads to changes in the chemical, structural and functional properties of starch in wheat flour by inducing starch damage, altering its molecular order (which influences its crystallinity), pasting properties as well as its retrogradation and staling behaviour. Heat treatment also induces changes in gluten proteins, which may alter the rheological properties of wheat flour. Understanding the relationship between heat transfer, the thermal properties of wheat and the functionality of the resultant flour is of critical importance to obtain the desired extent of alteration of wheat starch properties and enhanced utilisation of the flour. This review paper introduces dry heat treatment methods followed by a critical review of the latest published research on heat-induced changes observed in wheat flour starch chemistry, structure and functionality.
Highlights
Wheat (Triticum aestivum L.) is a staple crop that provides energy, proteins, dietary fibre, vitamins, minerals and phytochemicals that are essential dietary components for many individuals daily [1,2]
This review focuses on dry thermal treatment only and on its use as a pre-processing method for whole wheat kernels and flour
Dry heat treatment of wheat generally results in the partial gelatinisation of starch due to modifications in its structural properties
Summary
Wheat (Triticum aestivum L.) is a staple crop that provides energy, proteins, dietary fibre, vitamins, minerals and phytochemicals that are essential dietary components for many individuals daily [1,2]. A number of studies have recently investigated thermal techniques as pre-processing methods, applied to whole wheat kernels or flour, to improve the properties of wheat flour and enhance its utilisation in breadmaking [6,7,8]. Wheat bran contains significant amounts of vitamins, minerals, fibres and antioxidants including carotenoids, phenolic acids and tocopherol [13] Consumption of these compounds reduces inflammation and contributes to the prevention of heart diseases and cancer. Heat treatment of wheat grains is a promising pre-processing treatment technique to improve the bioavailability of such compounds [15] It reduces the microbial load, mycotoxin concentration and enzymatic activity by lowering the water activity, ensuring an extended shelf life [12,16,17]. The application of the different dry heat treatments as pre-processing methods is reviewed, followed by the effect of these treatments on starch chemistry, structure and functionality as tested in dry heat-treated flour and flour produced from heat-treated wheat kernels
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