Submitted to: Florida State Horticultural Society Meeting
Publication Type: Abstract only
Publication Acceptance Date: 2/11/2007
Publication Date: 5/10/2007
Citation: Navarro-Tarazaga, M.L., Plotto, A., Goodner, K.L., Pérez-Gago, M.B. 2007. Optimization of a HPMC, bee’s wax and shellac edible coating for 'Valencia' oranges and 'Marisol' tangerines. Florida State Horticultural Society Meeting. Abstract No. HP3. Interpretive Summary:
Technical Abstract: Commercial coatings used for citrus fruit include carnauba- and shellac-based waxes or resins, which provide an attractive shine to the fruit, but are not necessarily made of 100% food grade ingredients. A new formulation containing only food grade ingredients was tested, along with an experimental polyethylene-candellila (PE) wax emulsion, and two commercial citrus coatings, one shellac and the other carnauba wax-based. The food-grade formulation contained hydroxypropylmethylcellulose (HPMC), bee’s wax and shellac resin, oleic acid, and glycerol. 'Valencia' oranges were obtained from a local grove in Florida in May 2006. Fruit were washed, hand-coated and dried, and stored 2 weeks at room temperature (25 C). The PE and carnauba based coatings provided the best weight loss control, and were preferred for appearance by a taste panel. The HPMC-based coating provided the least shininess (less than control), and rated similarly to control for appearance preference. On the contrary, shellac coated fruit were the shiniest, but had intermediate appearance preference ratings. Shellac coated fruit had high levels of ethanol and CO2, followed by HPMC-coated fruit. These indicators of anaerobiosis are known to produce off aromas. Volatiles analysis showed that ethanol, methanol, ethyl acetate and hexanal were high in shellac-coated fruit, while uncoated oranges had the most volatile compounds that characterize fresh citrus flavor. The HPMC formulation was modified to increase permeability to O2 and CO2. Formulations with 5% or 8% solids content (SC) and HPMC to glycerol ratios of 2:1 and 1:2 were tested on 'Marisol' tangerines and stored at 23 C for 3 weeks. A reduction of the HPMC:glycerol ratio from 2:1 to 1:2 improved gas permeability and sensory quality of tangerines stored 1 and 2 weeks at room temperature. Increasing SC from 5% to 8% reduced weight loss. Therefore, HPMC formulation with HPMC:glycerol ratio of 1:2 and at 8% SC was retained for further applications with tangerines.