ReviewEffect of extrusion on the anti-nutritional factors of food products: An overview

•ANFs in edible seeds affect the bioavailability status of minerals when consumed.•Extrusion processing is effective in reducing ANFs and improves the nutritional quality of seed-based foods.•ANFs can be reduced at varying degree, depending on the applied process conditions during extrusion.

Edible plant seeds such as cereals, legumes and nuts contain substantial amounts of nutrients including proteins, carbohydrates, minerals, vitamins, and dietary fibers. However, the bioavailability of these nutrients in humans or animals is relatively low, particularly when they are consumed in their unprocessed or raw form. One of the major factors that contribute to a lower nutritional value of legumes and cereals is the presence of naturally-occurring anti-nutritional factors (ANFs, e.g. phytate, tannins and enzyme inhibitors) that indirectly decreasing the bioavailability status of minerals. Fortunately, these ANFs can be modified or reduced through different processing methods, namely heating, enzymes application, soaking, sprouting, irradiation, fermentation, mechanical methods such as dehulling and milling, or even by means of other techniques such as high pressure processing, microwave heating and extrusion. The aim of this review is to highlight the effectiveness of extrusion processing in reducing various ANFs of legumes and cereals. Compared with the traditional processing methods, extrusion processing, a combined thermo-mechanical treatment (which involved careful control on process conditions of the feed composition and moisture content, the cooking temperature along the extruder and the die and screw speed), is a quicker and more consistent way to cause thermal/chemical breakdown of ANFs and at the same time could alter the physical, chemical and nutritional nature of nutrients in a desirable manner. Thus, there is an immense opportunity to apply this versatile processing technique to produce highly nutritious seed-based foods for human consumption as well as products for animal feeds.