L. B. Steyn, J. H. Knoetze



Optimization of an Edible Carnauba Wax Coating by means of a Screening Experimental Design of Experiments

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Carnauba wax, post-harvest industry, screening experimental design, mixture experimental design, optimization


This study aimed to identify and optimize the significant process parameters and formulation of a specific edible anionic Carnauba wax emulsion coating by means of design of experiments.  A D-Optimal Combined screening experimental design was setup to identify the significant process parameter/s of a specific edible Carnauba wax coating. Three additional center points, two replicates and two additional points to estimate lack of fit were included in the design. The experimental runs were performed on a pilot plant that included a 6 liter semi-batch reactor with a stirrer and high shear homogenizer. Formulation parameters were included in the screening experimental design to optimize the specific edible Carnauba wax coating formulation that consists of Carnauba wax, water and a surfactant (Potassium hydroxide, Ammonium hydroxide and Oleic acid in a fixed ratio). The parameters with fixed ranges determined by their capabilities and literature were; Carnauba wax [10-15 wt%], Water [80-85 wt%], Surfactant [5-8 wt%], Stirrer Speed [450-1850 rpm], High Shear Homogenizer (HSH) Speed [3050-8050 rpm], High Shear Time Interval [0-55 min], Cooling Rate [-1,0,1], Inverting Phase Addition Rate [3-4 l/h] and Temperature [100-120 oC]. Particle size and –distribution [um], Roughness [Ra], Gloss [GU], Dynamic Viscosity [mPa.s], pH and Density [kg/m3]. These parameters were analyzed and recorded as responses. Due to the optimized formulation parameter not falling within the formulation ranges, a D-Optimal Mixture design was performed to optimize the formulation. The significant process factors with their optimized settings were identified as the Stirrer Speed [800 rpm], HSH Speed [6800 rpm], High Shear Time Interval [10 min] and Temperature [120oC]. The optimized formulation was identified as; 75.3 wt% Water, 15.8 wt% Carnauba wax, 6.3 wt% Oleic acid, 0.6 wt% Potassium hydroxide and 2 wt% Ammonium hydroxide. By using the identified significant process parameters and optimized edible Carnauba wax coating formulation, a composite experimental design can be used to optimize the process parameters and achieve superior product characteristics. This can aid in the advancement of future applications of edible coatings in the food industry.

Cite this paper

L. B. Steyn, J. H. Knoetze. (2016) Optimization of an Edible Carnauba Wax Coating by means of a Screening Experimental Design of Experiments. Food and Nutrition Science - An International Journal, 1, 32-39