Natural and Applied Wax Coatings on Oranges

Abstract

Scanning electron microscopy was used to examine the wax coating on oranges. The natural wax platelets are irregular in shape and size, have a rough surface and increase in numbers as the orange matures. Most natural platelets can be removed by dipping the orange in a chloroform‐methanol solution and rubbing the surface. Store‐bought oranges have natural wax platelets 1–2 microns thick covered with a 2–5 micron layer of commercial wax. Wax applied over platelets may be ineffective if the platelets break off in handling and expose the orange's surface. Removal of natural wax platelets prior to commercial waxing allows uniform wax application and consequently better storage life. Drying with air at 2.5 m/s produced uneven wax thickness while 14 m/s air produced a complete, uniform wax layer.

Dependence of Coating Thickness on Viscosity of Coating Solution Applied to Fruits and Vegetables by Dipping Method

“…Calculated, average dry film thickness in our study, were in the range of 0.15 to 2.1m and 0.08 to 0.92 m for HPMC E-50 and HPMC E-5, respectively. Coating thickness has been reported to be in the range of 1 to 5m (Trout and others 1953;Brusewitz and Singh 1985;Elson and Hayes 1985;Hagenmeier and Shaw 1992) and 4.5 to 13m (Park and others 1994b).…”

Reduction in gas exchange of citrus fruit by wax coatings

“…Coating formulations from four commercial suppliers, applied per manufacturer recommendations, would have given coatings of mean weight 0.22 mg/cm2, equivalent to 0.08-µ thickness, near the middle values of Table IV, far below the 20 µ reportedly necessary to completely cover stomatal pores (Brusewitz and Singh, 1985).…”

Internal Modified Atmospheres of Coated Fresh Fruits and Vegetables: Understanding Relative Humidity Effects

“…Film thickness has been related to coating solution concentration others 1994a, 1994b) and will probably be influenced by physicochemical properties of the coating solution. Coating thickness has been reported to range from 1 to 5 m (Trout and others 1953;Brusewitz and Singh 1985;Elson and others 1985;Hagenmeier and Shaw 1992) and from 4.5 to 13 m (Park and others 1994a). Our model predictions may partly explain the variability observed in the past when studying coated fruit systems.…”