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Victorine Alleyne and Robert D. Hagenmaier

An experimental candelilla-shellac formulation for coating apples (Malus ×domestica Borkh.) was developed and compared with commercial shellac-based and carnauba-shellac-based coatings on `Gala' and `Delicious' apples by determining effects on quality attributes, respiration, and internal atmospheres. Fruit were stored at 5 °C for 7 days followed by storage at 21 °C for 14 days. Gloss of `Delicious' apples coated with candelilla-shellac formulations containing 7% to 34% shellac increased with increasing shellac concentrations. `Gala' and `Delicious' apples coated with a candelilla formulation containing 34% shellac maintained quality similar to those coated with commercial carnauba-shellac-based coatings, as indicated by gloss, firmness, internal CO2, O2 and ethanol levels, steady-state respiration rate, weight loss, and flavor. By comparison, shellac-coated fruit maintained the highest gloss throughout the experimental period. Shellac-coated apples were also firmer, contained more ethanol, and received higher flavor scores than did apples receiving other coating treatments. Gloss of all coated fruit decreased with time, although shellac-coated fruit lost less gloss over the 21-day storage period. Analysis of gloss, firmness, fruit respiration, ethanol, weight loss, and flavor demonstrate that the candelilla formulation containing 34% shellac is competitive with current commercial carnauba-based apple-coating products.

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Robert D. Hagenmaier and Robert A. Baker

The shrinkage rate of `Marsh' grapefruit (Citrus paradisi Macf.), `Ambersweet' hybrid [(C. reticulata Blanco × C. paradisi Macf. × C. reticulata) × C. sinensis (L.) Osb.] and `Valencia' oranges [C. sinensis (L.) Osb.] was increased 50 % to 150% by washing the fruit with rotary brushes, but was not changed by hand-washing the fruit with cellulose sponges. Internal CO2 increased using both washing methods. Waxed fruit obtained from five Florida packinghouses and cleaned with rotary brushes and waxed had shrinkage rates the same as those of nonwashed controls. Thus, controlling the washing process is important to minimize shrinkage of fresh citrus fruit.

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Robert D. Hagenmaier and Robert A. Baker

Valencia oranges [Citrus sinensis (L.) Osbeck cv. Valencia] and Marsh grapefruit [Citrus paradisi Macf.] were treated with single or double layers of coating. In cases where two coatings were applied, the first coating was a moisture-barrier wax; the second was either polyethylene wax or a mixture of shellac and resin ester. The inner coating reduced weight loss, and the outer coating imparted gloss. Fruit gloss, as measured by reflectometer, decreased more rapidly during 1 week at 20C with a single glossy coating than with the same coating applied as a second layer over a wax-based first coating. For citrus fruit, using resin ester or shellac as a high-gloss second coating tended to overly restrict the exchange of O2 and CO2; however, two layers of wax did not.

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Robert D. Hagenmaier and Philip E. Shaw

The permeability to O2, CO2, C2H4, and water vapor was determined for 19 commercial fruit wax coatings, four ingredients thereof, and one shrink-wrap film. For the commercial coatings, the O2permeability at 50% relative humidity and 30C ranged from 470 to 22,000 ml (STP) × mil/(m2 × day × atm) (1 mil = 0.0254 mm) with CO)2. permeability two to eight times as high. Permeability to noncondensable gases tended to be higher for coatings made from carnauba wax than for those made from shellac and rosin. Commercial fruit wax had sufficiently low noncondensable gas permeability to account for large reductions in the respiration rate of coated fruit. Wax coatings could be improved if permeability were controlled:

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Xiuxiu Sun, Elizabeth Baldwin, Mark Ritenour, Robert Hagenmaier and Jinhe Bai

In Florida, early season citrus fruits usually reach full maturity in terms of internal quality while their peel often does not turn to orange color after degreening due to insufficient buildup of carotenoids. For huanglongbing (HLB)-affected orange trees, the fruit may never turn orange during the entire harvest season, despite any cold weather. Improvement of early season citrus peel color is important to the citrus industry to better meet consumer expectations. Occasionally, packinghouses apply a dye, Citrus Red No. 2 (CR2), to improve the surface color of oranges, temples, and tangelos before applying a fruit wax to impart shine, retain moisture, and slow fruit senescence. In a previous report, we determined that paprika and annatto extracts are comparable to CR2 as natural colorant alternatives. In this research, the goal was to formulate a natural colorant [annatto, paprika, or paprika oleoresin (PO)]-containing carnauba wax coating. The coatings were first evaluated for color, shine, moisture retention, respiration rate, ethylene production, and internal gas content. Control fruit were coated with carnauba wax alone, or dyed with CR2 then coated with carnauba wax. The effects were assessed under different temperature and light exposure conditions to simulate commercial storage and marketing. The results showed that a one-step application of paprika-containing carnauba wax was comparable to the two-step (“CR2 then wax”) applications in improving fruit appearance and modification of internal gas composition.

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Jinhe Bai, Elizabeth A. Baldwin and Robert H. Hagenmaier

Zein, starch, polyvinyl acetate (PVA), carnauba, and carnauba-polysaccharide (CPS) coatings were compared with a commercial shellac coating using controlled atmosphere stored 'Delicious' apples (Malus ×domestica Borkh). Coated apples were stored in air at 2 °C for 2 weeks and then removed to 21 °C for an additional two weeks to simulate marketing conditions. Gloss, internal O2 and CO2 partial pressures, weight loss, flesh firmness, and contents of sugars, acids and volatiles were measured on 0, 2, and 4 weeks after coating treatment. Starch- and carnauba-coated apples had high initial gloss, similar to that found for shellac-coated fruit. Gloss of all coated fruit decreased similarly during the 4-week evaluation period, although all of the coated fruit were glossier than uncoated controls. For uncoated apples, the differences of O2 and CO2 partial pressure between internal and ambient atmosphere were ≈1 kPa at 2 °C, and these increased by a further 2 kPa after transfer to 21 °C. Fruit coated with shellac and starch had >10 kPa CO2, and <10 kPa O2 at 21 °C. Zein-, PVA- and carnauba-coated apples showed a less modified internal atmosphere (6-7 kPa CO2, 11-15 kPa O2). Internal partial pressures of O2 and CO2 were inversely related for most coatings, except for the CPS coating, for which partial pressures of both CO2 and O2 were low. Carnauba-, PVA-, and shellac-coated fruit lost less weight than uncoated fruit. Starch-, shellac-, and CPS-coated fruit were firmer than those from other coating treatments, and all coated fruit were firmer than uncoated control. Titratable acidity was higher in the fruit coated with CPS, starch, and shellac than in uncoated control. Ethyl alcohol and ethyl esters accumulated in starch-, shellac-, and CPS-coated fruit kept at 2 °C, but, levels of these volatiles decreased after transfer of fruit to 21 °C. Carnauba, PVA and zein coatings compared favorably to shellac for gloss and other quality characteristics.