Approaches to optimising surface coatings for fruits

Abstract

A mathematical model predicted that final water vapour permeance in surface-coated fruits would depend upon water permeance of the coating but not the proportion of pores blocked on the fruit surface. In contrast, predicted final oxygen (O 2 ) permeance depended upon numbers of pores blocked but not O 2 permeance of the coating. Predicted variation in internal atmosphere composition caused by coatings that blocked different proportions of pores on the model fruit surface was consistent with data from two experiments on coated apples (Malus domestica Borkh.). A new equation was developed to characterise the relationship between internal carbon dioxide (CO 2 ) and O 2 levels resulting from different coating treatments. Two graphical approaches to assess surface coatings for fresh fruits are presented. In the first, a plot of water vapour permeance against internal O 2 was used to identify the most suitable of three surface coatings for reducing water loss in 'Royal Gala' apples at 20°C. The second method used a plot of internal CO 2 versus internal O 2 in coated fruit to identify the crop's internal lower O 2 limit (LOL i ), which lies just below the optimum internal O 2 level for modified atmosphere effects. Coatings containing different concentrations of carboxymethyl cellulose produced internal O 2 levels ranging from almost H96074

Ripening behaviour, postharvest quality, and physiological disorders of coated pears (Pyrus communis)

“…This observation is consistent with reports of coating effects in other commodities (Hagenmaier & Baker 1993Banks et al 1997). This was the combined result of decreased respiration rate coupled with the selective permeability of surface coatings to these gases (Banks et al 1997;Amarante et al 2001b).…”

“…During the past few years, more attention has been paid to the use of surface coatings to generate a modification of the internal atmosphere of bulky organs to achieve similar beneficial effects of CA/MA storage, as well as to reduce water loss and improve the gloss of the skin (Smith et al 1987;Meheriuk & Lau 1988;Glenn et al 1990;Hagenmaier & Baker 1993Banks et al 1997;Amarante & Banks 2001). Coating materials, by providing differential changes in skin permeance to O 2 and CO 2 , can create different levels of modification of internal O 2 and CO 2 partial pressures, depending on the chemical nature (Hagenmaier & Baker 1993, thickness (Hagenmaier & Baker 1993), and character of surface cover (Amarante et al 2001a).…”

Selection of a surface coating and optimisation of its concentration for use on ‘Hass’ avocado (Persea americanaMill.) fruit

“…Although surface coatings reduce diffusion of water out of fruit, they also hinder the diffusion of other gases such as carbon dioxide (CO2), oxygen (O 2 ), and ethylene (Ben-Yehoshua 1987;BenYehoshua & Cameron 1989;Banks et al 1993;Banks et al 1997). As a result of respiration and limited skin permeance to respiratory gases, the atmosphere inside the fruit is modified, with a lowering of internal O2 partial pressure (p' O2 , Pa) and elevation of internal CO 2 partial pressure (p' co2> ^a) -Thus, surface coatings provide potential for reducing respiration (Meheriuk & Porritt 1972;Smith & Stow 1984;Hagenmaier & Shaw 1992) as well as water loss (Durand et al 1984;Hagenmaier & Shaw 1992;Joyce et al 1995).…”

“…As a result of respiration and limited skin permeance to respiratory gases, the atmosphere inside the fruit is modified, with a lowering of internal O2 partial pressure (p' O2 , Pa) and elevation of internal CO 2 partial pressure (p' co2> ^a) -Thus, surface coatings provide potential for reducing respiration (Meheriuk & Porritt 1972;Smith & Stow 1984;Hagenmaier & Shaw 1992) as well as water loss (Durand et al 1984;Hagenmaier & Shaw 1992;Joyce et al 1995). In addition, surface coatings provide some visual benefits by increasing sheen or perceived depth of colour (Hagenmaier & Baker 1995;Banks et al 1997).…”

“…This problem can be minimised through use of coatings with appropriate permeability characteristics. Some criteria for the optimisation of surface coatings have recently been explored (Banks et al 1997) and were adopted for the purposes of this research.…”