Robert D. Hagenmaier

Formulation of zein coatings for apples (Malus domestica Borkh)

High gloss coatings are used to improve apple fruit (Malus domestica , Borkh) appearance and sales. The industry standard has been shellac-based formulations, which have problems with whitening, low gas permeability, and association with non-food uses. Zein, a natural corn protein, was used to formulate alternative, shiny coatings by dissolving zein in aqueous alcohol with propylene glycol (PG). Gloss levels on ‘Gala’ apple surfaces varied due to zein and PG content in coating formulations from that of controls to levels observed for shellac-coated fruit. At least 4% (by weight) PG was necessary for adequate gloss. However, increasing levels of both compounds resulted in increased gloss. Whitening, which occurred on the coated fruit surface upon wetting, was reduced by decreasing zein content to less than 11%. Permeability to CO2 ,O 2, and water vapor was strongly dependent on the zein content in the coating. Internal CO2 and O2 in zein-coated ‘Gala’ fruit ranged 4 � /11 and 19 � /6 kPa, respectively, by increasing zein content in the coatings. An optimum formulation with 10% zein and 10% PG was developed, applied to ‘Gala’ apple, and was found to maintain overall fruit quality comparable to a commercial shellac coating. # 2002 Published by Elsevier Science B.V.

Evaluation of a polyethylene-candelilla coating for 'Valencia' oranges

Abstract An experimental polyethylene–candelilla-wax coating formulation was evaluated in comparison to a high-gloss, shellac and wood resin citrus coating for storage of ‘Valencia’ oranges at 15–25°C. Oranges with the wax coating had relatively high flavor scores (8.9–10.4) even after 9–16 days storage at 15–25°C. By contrast, the high-gloss coating, shown to be typical of such citrus coatings, resulted in flavor scores as low as 3.7–4.1 after 9–16 days at 25°C or 16 days at 21°C. Flavor was especially low for fruit with internal O2

A survey of the microbial population and ethanol content of bagged salad

Five nationally and regionally distributed brands of ready-to-eat salads in sealed bags were sampled from major supermarket chains. At time of purchase, product temperature was 4 to 7 degrees C; the mean mesophilic microbial population was 1.0 x 10(7) CFU/g; the yeast population was 210 CFU/g; the mean headspace O2 and CO2 concentrations were 1.2 and 12%, respectively; and the ethanol content was 700 ppm. For samples analyzed on the expiration date (14 to 16 days after packaging) the mean mesophilic microbial population was 6 x 10(7) CFU/g; ethanol content was 1,500 ppm; and the headspace gas had not markedly changed from time of purchase.

Shellac Formulations To Reduce Epiphytic Survival of Coliform Bacteria on Citrus Fruit Postharvest

Survival of the coliform bacteria Enterobacter aerogenes and Escherichia coli was monitored in a neutral carboxymethylcellulose formulation and in shellac formulations with various pH and concentrations of ethanol and the preservative paraben; populations were subsequently measured from the surface of citrus fruit coated with these formulations. Numbers of the two bacteria increased over 24 h from 10(6) CFU/ml to approximately 10(8) CFU/ml in the carboxymethylcellulose solution, but over this time numbers remained little changed in the neutral solution of shellac. The Enterobacter was more tolerant of alcohol over a 3-h period: although its numbers in a shellac solution with 10% ethanol dropped from more than 10(6) CFU/ml to just over 10(3) CFU/ml. E. coli and a third species. Klebsiella pneunoniae, declined toward the limit of detection (5 CFU/ ml) during this time. The addition of morpholine to increase the formulation pH to 9.0 caused numbers of bacteria to plummet to an undetectable level within 30 to 60 min. On Ruby Red grapefruit and Valencia oranges in storage at 13 degrees C numbers of E. aerogenes and E. coli declined over 2 weeks from 10(5) CFU/cm2 to less than 2.5 x 10(1), but most of the loss in numbers occurred within 1 day. Numbers remained significantly less on shellacked fruit compared with those applied in the carboxymethylcellulose coating, and a shellac coating prepared from a pH 9 solution was more toxic to these species than one in which 12% ethanol had been added to the neutral formulation. The addition of the preservative paraben in the basic shellac was further inhibitory.

Quality of fresh citrus fruit.

Fresh citrus fruit, comprising oranges, grapefruit, mandarins, limes, lemons and minor varieties, are among the most popular fruits. With increasing year round competition from other fruits, maintaining this market position will require that fresh fruit quality be optimal. Determinants of fruit quality can be divided into those affecting external quality and those defining internal quality. Both of these are critical, since external quality influences initial purchasing decision, while internal quality determines consumption and repeat sale.