Effect of microfluidized onion skin addition on the quality of extrudates

Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Food Engineering, Turkey

Approval Date: 2016

Thesis Language: English


Principal Supervisor (For Co-Supervisor Theses): Ilkay Şensoy

Co-Supervisor: Behiç Mert


The objective of the study was to investigate the effect of microfluidized onion skin addition on the features of expansion characteristics, water absorption index, water solubility index, color, texture and sensory of extruded products. In addition, addition of microfluidized and non – microfluidized onion skins to extruded products were compared. Increasing microfluidized onion skin content in the samples caused a reduction in sectional expansion index (SEI), volumetric expansion index (VEI) and porosity of extruded samples while causing an increase in bulk density of extruded samples. Increasing microfluidized onion skin content in the extrudates did not cause any significant change in water absorption index (WAI) and water solubility index (WSI) values. Addition of microfluidized onion skin to feed decreased lightness while increased redness and yellowness of extrudates. Addition of microfludizied onion skin increased maximum stress, hardness, and brittleness. After 2% microfluidized onion skin addition, lower scores were observed in sensory data of extrudates. SEI, VEI, porosity, bulk density, WAI, WSI, lightness values, maximum stress, hardness, fracturability and sensory data of extrudates with, microfluidized and nonmicrofluidized onion skin added samples at 6% indicated no significant difference. However, there was significant difference between microfluidized and nonmicrofluidized onion skins added samples in redness and yellowness values. The results indicate that microfluidized onion skins at low concentration can be added to feed samples to increase the fiber content of the extrudates.