Effect of added ingredients on the acrylamide level and quality of extrudates

Thesis Type: Postgraduate

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

Approval Date: 2014

Thesis Language: English


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

Co-Supervisor: Beraat Özçelik


Ingredients which are NaCl, CaCl2, ascorbic acid, citric acid, glycine, cysteine and quercetin were blended at two different concentrations with whole wheat flour, mixed with D-glucose monohydrate (100:5, w/w), and fed to twin screw extruder. Effect of these ingredients on acrylamide level and quality characteristics of extrudates were investigated. Set zone temperatures were 80 ± 2, 90 ± 2, 115 ± 2 and 150 ± 2 oC with 180 rpm screw speed and feed flow rate of 30 g/min during extrusion. Feed moisture content was 18.24 ± 0.48%. Drying process was performed at 150 oC for 15 min after the extrusion process. Lower acrylamide level were observed with added ingredients with differences in degree of reduction. Increasing concentration led to further decrease in acrylamide level for all of the ingredients. Among the ingredients studied highest acrylamide reduction was obtained with 5 g/kg cysteine addition while lowest reduction was obtained with 7.26 g/kg citric acid and 13.36 g/kg ascorbic acid. Highest sectional expansion index (SEI) was obtained with 50 g/kg CaCl2 while the lowest was obtained by 66.80 g/kg ascorbic acid when compared to control. Longitudinal expansion index vi (LEI) reached the highest value at the addition of 66.80 g/kg ascorbic acid while the lowest value was obtained by 10 g/kg CaCl2. 50 g/kg CaCl2 or 36.30 g/kg citric acid addition did not cause any significant change in volume expansion index (VEI) compared to control. The highest bulk density found at the addition of 66.80 g/kg ascorbic acid. Addition of 1 g/kg glycine, 10 g/kg NaCl, 36.30 g/kg citric acid or 50 g/kg CaCl2 did not affect the bulk density when compared to control and gave the lowest values of bulk density in extrudates. In terms of lightness, ascorbic acid addition at the level of 66.80 g/kg gave the highest L* value and lowest browning index in extrudates while the lowest L* value was observed with 5 g/kg glycine addition with the highest browning index. In conclusion, data indicated that added ingredients decreased the acylamide level at a certain level while affecting the quality parameters of the extrudates to some extend.