Apple pomace pretreated with hydrochloric acid exhibited better adherence with the corn starch during extrusion expansion

Abstract

Apple pomace (AP) was pretreated with hydrochloric acid (HCl) to evaluate its effectiveness in improving interactions between starch and pomace during extrusion. Cellulose, hemicellulose, and lignin contents were reduced, and the sugar content increased after the HCl treatment. Four levels (5, 10, 15, and 20 g/100 g) of AP and modified apple pomace (MAP) were extruded with 17 g/100 g feed moisture, feeding rate of 60 g/min, barrel temperature of 140°C, screw speeds (200 and 250 rpm), and die diameter of 3.15 mm. MAP extrudates at 5 g/100 g had the highest expansion ratio of 3.87, followed by 3.75 for 5 g/100 g AP. Fourier Transform-Infrared (FTIR) Spectroscopy was used to identify the interactions between starch-pomace during extrusion. The FTIR spectra showed significant changes in the 1035 cm−1 moiety, representing the C-O bonds between cellulose and lignin present in extrudates with low ER.

Keywords

• extrusion
• expansion
• molecular interactions
• chemical treatment
• pomace