Chemical methods

Chemical methods of judging maturity
    1. Juice content
    The juice content of fruit increases as they mature on the tree. By taking representative samples of the fruit, extracting the juice in a standard and specified way and then relating the juice volume to the original mass of the fruit it is possible to specify its maturity.

    Sl No

    Type of citrus fruit

    Minimum juice content (%)

    1

    Navel oranges

    30%

    2

    Other oranges

    35%

    3

    Grape fruit

    35%

    4

    Lemons

    25%

    5

    Mandarins

    33%

    2. Oil content
    Oil content of the fruit may be used to determine the harvest maturity of avocados. At the time of picking and at all times there after shall contain not less than 8% of oil by weight of the avocado excluding the skin and seed. There is good correlation between taste and oil content and dry matter.

    3. Dry matter
    Rate of dry matter accumulation is used to predict optimum harvest time by using instrument hydrometer. Dry matter is also being used to as the maturity standard in processing varieties of potato. Potato dry matter content at the time harvesting should be in the range of 18 - 24.

    4. Sugar
    In climacteric fruit carbohydrates are accumulated during maturation in the form of starch. As the fruit ripens starch is broken down to sugars. In non-climacteric fruits sugars tend to be accumulated during maturation. In both cases it follows that measurement of sugars in the fruit can provide an indication of the stage of ripeness or maturity of that fruits. Sugar is measured in terms of soluble solids using Brix hydrometer or Refractometer.

    Fruit

    TSS (%)

    Fruit

    TSS (%)

    Apple

    11.50 -14.50

    Papaya

    11 - 12

    Citrus

    12 -14

    Pineapple

    13.00

    Grapes

    12-20

    Mango

    12 -18

    Kiwi

    8.00



    Pear

    12.92-12.99



    5. Acidity
    In many citrus fruits and others acidity progressively reduces on maturation and ripening. Extract the juice from the sample and titrating it against a standard alkaline solution gives a measure which can be related to optimum time of harvest. It is important to measure acidity by titration and not the pH of the fruit because of the considerable buffery capacity in fruit juices. This measure gives the brix: acid ratio

Last modified: Tuesday, 5 June 2012, 5:43 PM