After harvesting, fruits are dipped or sprayed with a range of materials inorder to improve their appearance or delay deterioration. Few of them are disucssed here
Tal Prolong consists of sucrose esters of fatty acids and carboxymethylcellulose. It has been effective in delaying the ripening of banana. This effect is due to the restriction of gas exchange between the fruit and its surrounding atmosphere. Due to this concentration of CO2 is increased and that of O2 is decresaed thus causing an effect achieved in controlled atmosphere storage.
Ir is similar to Tal Prolong, and guava coated with semperfresh and stored for 2 months at 10 ºC were in better condition than untreated fruit. It is reported that coating fruit with palm oil was more effective, and cheaper, than Semperfresh. Banana crowns coated with Semperfresh also showed delayed development of crown rot. The control of crown rot can be enhanced by the inclusion of organic acids in the coating material.
N,O-Carboxymethylchitosan films are used for coating fruit that are selectively permeable to gases such as CO2, O2 and ethylene. It has been reported that Golden Delicious apples coated with this chemical were kept in storage at 0ºC for 6 months and were of superior quality to those stored without coating. Chitosan has also been effective in reducing the water loss and maintaining the qulaity of coated peppers and cucumbers.
Vapor Gard is an anti-transpirant and its 1.3% solution has been found to be effective in reducing the postharvest water loss of mango. It also retard firmness decrease, reduce the decrease in ascorbic acid content, inhibit malic enzyme activity and increase polygalacturonase activity compared with untreated fruit.
Biofresh is a sucrose fatty acid ester and its 1% solution coating on Apples for 20 second and stored for 3 months resulted in firmer, reduced weight loss and ethylene production, retained titratable acidity and a lower respiration rate than the untreated fruits.
Trehalose is a disaccharide made up of two glucose molecules making it very stable reducing sugar and almost inert and biologically non-toxic. These properties make it a useful preservative for biological molecules and food.
It helps in reducing ethylene production thus increasing the shelf life of harvested produce. The amount of ethylene synthesized can also depend on harvest maturity, handling method, storage temperatures and gaseous content around the fruit or vegetables.
Salicylic acid (2 hydrobenzoic acid) is extracted from the willow and also occurs in the fruits of Ribes and Rubus. Its 0.01g/l solution was effective in delaying the the peak of ethylene production a reduction in polyphenol oxidase activity of peach