Processing of Horticultural Crops (1+2)

Exercise

Practical 2 - Estimation of fruit firmness

Aim: To estimate the fruit firmness.

Apparatus/machineries/equipments required:

• Magness–Taylor Pressure Tester
• Penetrometer

Theory and principle: Fruit firmness is an important feature of maturity. During ripening, fruits may soften and become too soft at the overripe stage. The changes are detected by touching or by using devices like texture analyzers and pressure testers to measure texture of fruits and vegetable.

For measurement of pressure, maximum force required to rupture the sample is measured by pushing a cylindrical metal probe into the sample to a given depth. The Magness-Taylor pressure tester can be used to determine the softening of fruits during maturity. In this instrument 10 lb or 30 lb force springs are used. Each of them is provided with one or two punches of 5/16 or 7/16 inch in diameter. The plunger of larger diameter is used on softer material, while the smaller one is used for firmer material.

Procedure for estimation

1. Select the pressure tester knob according to type of fruit
2. Remove a thin portion of the skin in case of waxy fruits
3. Hold the plunger against the surface of the fruit and forced into the fruit with a steady pressure to attain the force necessary for breaking the flesh
4. The force (lb/inch2 or kg/cm2) recorded on the pressure tester is used to interpret the maturity of fruits.

Observations and results

Sample No.	Pressure lb/ inch
1
2
3
Mean

Inferences

• The unripe fruits have more firmness than that of ripe fruits.
• With the increase in the ripeness of the fruit, the firmness of the fruit decreases.
• The unit for measuring the firmness are: lb/inch and kg/inch