Post Harvest Management of Horticultural Crops

Wax Coating

Fruits and vegetables have a natural waxy layer on the whole surface (excluding under-ground ones). This is partly removed by washing. Waxing is especially important if tiny injuries and scratches on the surface of the fruit or vegetable are present and these can be sealed by wax.
Waxes - are esters of higher fatty acid with monohydric alcohols and hydrocarbons and some free fatty acids.
Waxing generally reduces the respiration and transpiration rates, but other chemicals such as fungicides, growth regulators, preservative can also be incorporated specially for reducing microbial spoilage, sprout inhibition etc. However, it should be remembered that waxing does not improve the quality of any inferior horticulture product but it can be a beneficial in addition to good handling.
A protective edible coat on fruit and vegetable which protect them from transpiration losses and reduce the rate of respiration is called ‘waxing’.

Skin coating (Protective coating)
It is defined as artificial application of a very thin film of wax or oil or other material to the surface of the fruits or vegetables as an addition to or replacement for the natural wax coating.
Advantages of wax application are:

• Improved appearance
• Reduced PLW - reduced moisture losses and retards wilting and shriveling during storage
• Reduced weight loss
• Prevents chilling injury and browning
• Protect produce from bruising
• Reducing respiration rate - by creating diffusion barrier between fruit and surrounding as a result of which it reduces the availability of O2 to the tissues.
• Protects fruits from micro-biological infection
• Considered a cost effective substitute in the reduction of spoilage when refrigerated storage is unaffordable.
• Carrier agent - used as carrier for sprout inhibitors, growth regulators and preservatives.
• Increase in the shelf life
• Mango fruits treated with wax emulsion containing 8 to 12% solids have one or two week’s longer storage life than the untreated ones.
Disadvantage:

• Development of off-flavour if not applied properly. Adverse flavour changes have been attributed to inhibition of O2 and CO2 exchange thus, resulting in anaerobic respiration and elevated ethanol and acetaldehyde contents.Specifications of a desirable wax
• The selected wax material should provide a lasting shine
• Must be manufactured from food grade materials
• It should not develop any off-flavour and resistant to chalking. This can be determined by cooling waxed fruit to 0°C and allowing moisture to condense on fruit on removal from cold room
• It should reduce weight loss of commodity by 30% to 50%
• Rapid drying, competitive price and easy clean up