Effect of several shiny coatings on the internal gases and quality of apple fruit
2000
Bai, Jinhe | Baldwin, Elizabeth A. | Hagenmaier, Robert H.
Zein, starch, polyvinyl acetate (PVA), carnauba, and carnauba-polysaccharide (CPS) coatings were applied post controlled atmosphere storage to 'Red Delicious' apples for comparison to a commercial shellac coating. Coated apples were stored in air at 2°C for two weeks and then removed to 21°C for an additional two week simulated marketing period. Gloss, internal gases, weight loss, flesh firmness, sugars and acid content were measured. Starch and carnauba coated apples showed high initial gloss, which were comparable to the shellac coating. Other coatings showed moderate initial gloss. Gloss decreased during storage to similar levels for all coatings after the 4 week experimental period, although all of the coated fruits remained significantly glossier than uncoated controls. For uncoated apples, the difference in internal O₂ and CO₂ concentrations at ambient atmosphere was 1 to 2 percent at 2°C and increased one more percent after transfer to 21°C. Fruits coated with shellac and starch showed higher than 10 percent internal CO₂, and lower than 10 percent O₂ at 21°C. Zein-, PVA- and carnauba-coated apples showed moderate internal gases (6-7% CO₂, 11-15% O₂). There was an inverse relationship between internal O₂ and CO₂ for most coatings, except for the CPS coating, for which levels of both CO₂ and O₂ were low. Coated fruits exhibited less weight loss than uncoated except for those treated with the CPS coating. The carnauba coating was the most effective water barrier of the coatings tested, but lost this property when the polysaccharide was added. Starch-, shellac-, and CPS-coated fruit were firmer than those from other coating treatments, and all coated fruits were firmer than uncoated controls. Titratable acidity was higher in the fruits coated with CPS, starch, and shellac than in uncoated controls.
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