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

Maria-Llanos Navarro-Tarazaga, Maria-Bernadita Perez-Gago, Kevin Goodner, Anne Plotto

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.

Keywords


Citrus sinensis; edible coatings; storage; flavor; hydroxymethylcellulose

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283