Vol 120 (2007): Proceedings of the Florida State Horticultural Society
Handling & Processing

A new composite coating containing HPMC, beeswax, and Shellac for 'Valencia' oranges and 'Marisol' tangerines

Anne Plotto
USDA
Published December 1, 2007
Keywords
  • Citrus sinensis,
  • edible coatings,
  • storage,
  • flavor,
  • hydroxymethylcellulose

Abstract

Commercial coatings used for citrus fruit include carnauba and shellac waxes or resins, which provide an attractive shine to the fruit, but are not necessarily made of 100% food-grade ingredients. A new food-grade formulation based on beeswax (BW), shellac resin (Sh), hydroxypropylmethylcellulose (HPMC), and glycerol (Gly) was tested, along with an experimental polyethylene-candelilla (PE) wax emulsion, and two commercial citrus coatings (shellac and carnauba based). 'Valencia' oranges from a local grove were washed, hand-coated, dried, and stored 2 weeks at 23 to 25 C. The PE and carnauba coatings provided the best weight loss control, and were preferred for appearance by a sensory taste panel. The HPMC-BW-Sh-based coating exhibited the least shine, and was rated similar to the control for appearance. On the contrary, shellac-coated fruit were the shiniest, but had intermediate appearance preference ratings. Shellaccoated fruit had high levels of CO2, followed by HPMC-BW-Sh-coated fruit. Volatiles analysis showed that ethanol, methanol, ethyl actetae, and hexanal were high in shellac-coated fruit, while uncoated oranges had higher levels of volatile compounds that characterize fresh citrus flavor. The HPMC-containing coating was modified to increase permeability to O2 and CO2 and four formulations were tested on 'Marisol' tangerines from Spain, and stored at 23 C for 1, 2, and 3 weeks. A reduction of the HPMC : glycerol ratio from 18% : 11% to 11% : 18% improved gas permeability and sensory quality of tangerine stored 1 and 2 weeks at 24 C. Increasing solid content (SC) in the composite coating from 5% to 8% reduced weight loss. Therefore, the HPMC : BW:Sh-containing formulation with HPMC : glycerol ratio of 11% : 18% and at 8% SC could be considered an edible coating appropriate for tangerines.