Pre storage treatments of fruits and vegetables
What are pre-storage treatments?
These are the treatments given to a commodity (fruits and vegetables in present context) generally after harvesting to reduce postharvest losses, enhance storage life and retain quality.
Any examples of pre-storage treatments?
Vapour heat treatment
This is a treatment given to remove adhering dust, dirt, extraneous matter, pathogenic load etc. from the surface of a commodity. Cleaning basically sanitizes the produce and avoid entry of undesirable contents to enter the packaging and storage line.
Cleaning is a broader term and includes, dusting, washing etc.
Methods of cleaning
i. Dry method (Dusting etc.)
ii. Wet method (Washing)
This method is mainly used to remove the adhering soil, etc from commodity i.e. potato, root vegetables, carrot, radish etc.
Dusting helps to shed undesirable load (weight) of the commodity and thus reduce transportation cost.
It also removes pathogenic microorganisms present in the soil from the surface of the vegetables.
This method is used in most fruits and vegetables. Washing is done at the pack house through automated washing system fitted with overhead sprayers and smooth rotating brushes to clean and wash the fruits.
Washing with clean water mixed with a neutral detergent such as Teapol, Sandovit or Indtron at 0.1% (1 ml / litre of water) is effective.
The process of cleaning and washing will take 3-5 minutes. The temperature of water should be at room temperature (270C).
2. Sorting and Grading
This may be done manually or by using a machine. Fruits are graded on the basis of their colour, size and weight and sorted for freeness from damage/ diseases.
At the sorting and grading table, trained workers wearing gloves sort out the oversized and undersized fruits, immature/scarred/blemished fruits, diseased/insect damaged fruits and as well as fruits with sap injury (in mango) under the supervision of quality supervisor.
The segregated fruits in the grader machine kept in plastic crates are removed at the end each working shift from the process area and are distinctly labeled for disposal.
Difference between sorting and Grading
1. Undesirable type of fruits i.e. diseased, damaged, deformed are removed
1. Fruits and vegetables are categorized according to difference in their weight, size, colour, maturity etc.
2. Done primarily to reduce spread of infection to other fruits
2. Done to fetch better price in the market.
3. Waxing / Coating
It is the process of applying wax on the surface of commodity by spraying, dip or immersion, brushing, fogging or foaming.
Some fruits develop natural fruit wax on their surface at the time of maturity. i.e. plum, apple, citrus, grapes etc.
This has its role in reducing water loss fro the commodity and thus reducing shriveling and weight loss. While handling care is taken to touch the fruits as minimum as possible to retain as much of the natural wax (also called bloom) on the fruit.
Advantage of Waxing
Improve appearance of fruit
Reduce moisture loss by 30-50% and retards wilting/ shriveling
Heals minor injuries
Protects fruits from minor infections
Provides modified atmosphere and increase shelf life
Acts a carrier for various chemicals etc