The effect of onion skin powder addition on extrudate properties
The extrusion process is widely used in the industry to obtain different types of products such as breakfast cereals and snacks. The starch based extruded products which are nutritionally poor can be enriched by adding some fruit and vegetable based functional components. The functional components addition not only affects the nutritional value, but also the textural and physical structure of extrudates. In this study, the effects of addition of different levels of onion skin powder (3, 6 and 9%) to the wheat flour extrudates were investigated. Extrusion final zone temperature was kept at 150°C and screw speed was 250 rpm. The extrudate samples were investigated in gelatinization properties, internal structure, antioxidant activity and total phenolic contents. DSC analysis showed that the extruded samples were gelatinized compared to feed samples. The fibrous structure of the onion skin led to the decrease in the diameter and pore size of extrudates. The pores in the 9% onion skin powder added extrudates are much smaller compared to control samples according to the SEM results. Antioxidant activity and total phenolic content increased with the increase in onion skin powder addition.
Tonyali, B. and Sensoy, I. 2017. The effect of onion skin powder addition on extrudate properties. Acta Hort. (ISHS) 1152:393-398
extrusion, antioxidant activity, total phenolic content, gelatinization, SEM