Drying and color kinetics of decorticated queen pineapple (Ananas comosus Linn.) fiber bleached with hydrogen peroxide solution

Abstract

The drying and colour kinetics of H2O2-bleached pineapple fibres were studied to determine an optimum drying condition and appropriate drying and colour kinetic models. The experiments were conducted under drying air temperatures of 40, 50 and 60 ºC, air velocities of 0.27, 0.38 and 0.42 m×s-1 and hydrogen peroxide (H2O2) concentrations of 1, 3 and 5% by volume arranged in a three-factor factorial experimental design. Colour values were quantified by the CIELab system where L* is the lightness value, a* is redness/greenness and b* is yellowness/blueness. Total colour difference (ΔE), chroma, hue angle, browning index (BI) and whiteness index (WI) were calculated. The L* value, a* value, b* value, WI, BI, hue angle, and chroma were significantly affected by the interaction of the three factors. A non-parametric test was conducted for the drying rate data and showed that the drying rate was influenced by different treatments. Tensile strength was not affected by any of the factors. The optimum drying condition was determined to be 57 ºC, at an air velocity of 0.345 m.s-1, and H2O2 concentration of 4.8%. The exponential model adequately described drying data. Zero-order kinetic equation described ΔE while L*, a*, b*, chroma, hue angle, WI and BI were satisfactorily described by the first-order kinetic equation.

Keywords

• browning index
• cielab colour system
• fiber bleaching
• chroma
• hue angle
• whiteness index