Colour changes of extrudates from wheat semolina with added cocoa bean shells

¹ Department of Process engineering, Faculty of Engineering, University of Food Technologies, 4002 Plovdiv, Bulgaria
² Department of Preservation and refrigeration technology, Faculty of Technology, University of Food Technologies, 4002 Plovdiv, Bulgaria
³ Department of Technology of grain, fodder, bakery and confectionary products, Faculty of Technology, University of Food Technologies, 4002 Plovdiv, Bulgaria

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Response surface methodology was employed to evaluate the influence of cocoa bean shells content (5 % and 10 %), moisture content (14 % and 20 %) and temperature of the matrix (160 °C and 180 °C) on the colour characteristics of extruded products from wheat semolina with added cocoa bean shells. The extrusion cooking was performed using a Brabender 20 DN single-screw extruder. A NS800 spectrophotometer was used to determine the lightness (L), redness ( a), yellowness ( b) and total colour difference (∆E) of extrudates. The extrusion process resulted in a noticeable darkening of the samples relative to the non-extruded mixtures. The average values of lightness varied from 60.68 ± 0.81 to 69.04 ± 0.81, redness from 7.11 ± 0.10 to 8.20 ± 0.25, yellowness changed from 15.29 ± 0.19 to 16.92 ± 0.48 and for the total colour difference from 2.26 ± 0.17 to 4.08 ± 0.10, respectively. The moisture content exerted the greatest influence on the total colour difference, followed by the temperature of the matrix, whereas the cocoa bean shells content had no significant effect.