Determination Of Fruit Firmness
The development of sensors to measure fruit internal quality variable is one of the challenges of post – harvest technology. Several variables can currently be measured, including sugar content, firmness and internal disorders. Fruit quality is related to both internal variables (firmness, sugar content, acid content and internal effect) and external variables (shape, size, external defects and damage). Increasing consumer demand for high quality has led to the development of optical, acoustic, and mechanical sensors that determines this quality. Fruit firmness is one of the most important quality variables; it is an indirect measurement of ripeness and its accurate assessment allows appropriate storage periods and optimum transport conditions to be established. Fruits firmness can be estimated by different techniques. There are two types of methods that can be used to determine fruit firmness i.e penetrometer and TAPlus Texture Analyser. The penetrometers are available with dial gauges calibrated in both metric (kg) and imperial (lbs) measurement and can be obtained to cover different ranges of pressure suitable for measuring either soft or harder types of fruit, depending on the variety and the stage of ripeness of the fruit to be tested. There are three detachable plungers available:
1. One of 8 mm (½ cm²) diameter generally suitable for use in testing softer fruit (e.g peaches, nectarines, plums). 2. One of 11 mm (1 cm²) diameter generally suitable for use in testing harder fruit (e.g apples, pears) 3. A pointed plunger for use in testing avocados.
Ideally the penetrometer should be bench – mounted on a fixed, rigid drill stand to ensure that pressure is applied at a steady controlled rate and at a constant angle to the fruit i.e vertically downwards. This is more difficult to achieve when using a hand – held penetrometer. While, Stable Macro System, TA.XTplus texture analyzer measures texture and quantifies the hardness, brittleness, fracturability, adhesiveness, stiffness, elasticity, etc. this equipment is extremely efficient, capable of high speed testing and boasts a very easy to use, comprehensive software package.
Penetrometer, TA.XTplus Texture Analyser, knife, chopping board, and fruit as list below: 1. Green apples
2. Red apples
1. From two opposite sides of the equatorial area of the fruits a disc of peel (only skin depth) of up to 2 cm² (¾ sq. ins) is removed. 2. Where fruits is of mixed color, e.g apple, the test has been carried out where possible between the highest and the lowest colored portion of the surface. 3. The fruit is hold firmly with one hand, and rest on a rigid surface such as a table top or the plate at the base of the stand. 4. The choice of plunger size and scale range used will depend on the type and the variety of the produce being tested and its stage of maturity and ripeness. If the size of plunger is mandatory in marketing standards, the given size has been used. It is recommended that the size of the plunger chosen and the particular scale used should be such as to give readings in the middle range of the scale. 5. The penetrometer is zero and the plunger head against the flesh is placed in the peeled area of the fruit. 6. The plunger is applied downward pressure until it penetrated the flesh of the fruit up to depth mark (half way up) on the plunger. Slow, steady pressure is essential as sharp uneven movements may give unreliable results. The plunger is removed and the reading in the penetrometer dial is recorded to one decimal place. 7. The process is repeated on the opposite side of the same fruit after first zeroing the penetrometer. 8. It is important to conduct all test as uniformly and carefully as possible in order to allow an accurate comparison of results. 9. Data is recorded in Table 1....
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