Pears do not ripen successfully on the tree, and therefore need to be picked when they are 'mature' but un-ripe. It is important that pears are picked at their optimal maturity. This will depend on the variety and also the intended storage period of the fruit.  If pears are picked immature or overmature it can result in a number of storage disorders and undesirable characteristics.

Maturity Indicators for European Pears

Steps for Maturity Testing 

Other Useful Measures

Maturity Standards for the Australian Industry

Further Information

References

Maturity Indicators for European Pears

There are various indicators that can be used to determine pear maturity. Using a combination of methods usually can give the most accurate results.

The two most commonly used indicators in the Australian industry are flesh firmness and total soluble solids (TSS) and standards have been developed to guide growers for 'Williams', 'Buerre Bosc' and 'Packham's.' Starch content can also be used to determine maturity but is less common in the industry.

Flesh Firmness

Flesh firmness is often considered the most reliable measure of maturity. As fruit matures, flesh firmness drops. Flesh firmness is measured through testing the pressure of the pears using a penetrometer with an 8mm plunger.

Figure 1: Penetrometer with an 8mm head, used to test flesh firmness  

Total Soluble Solids (TSS)

The juice of pears contains compounds such as sugars, other carbohydrates, acids, salts and amino acids. These are referred to as the total soluble solids. As pears mature the sugars become the main component of the total soluble solids and their concentration can be estimated using a refractometer (Little and Holmes 2000). TSS is measured as ^oBrix  

TSS is not considered as reliable an indicator as flesh firmness. It is however a good measure of eating quality.

Figure 2: Hand held Refractometer used to test TSS

Starch

Measuring the amount of starch in fruit has worked well for apples but is not so common in pears. As fruit matures, starch is converted into sugars. Starch is measured through an iodine test where a cut surface of the fruit is dipped in an iodine solution. Iodine stains the starch a blue-black colour.

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Steps for maturity testing (firmness and TSS only)

The following are suggested steps for carrying out maturity testing on pears.

Sampling fruit

It is best that growers take a number of fruit samples from different trees in a block to determine an average maturity level for the block. It is best to start maturity testing a few weeks before the 'traditional' harvest time, as maturity can vary each year.

The size of the sample is up to the grower, but consistency is the key. Each time a maturity test is done, the procedure should remain consistent.

The recommended procedure from Little and Holmes (2000) is for growers to select five typical trees spread through a block from which four fruit of typical size are chosen at shoulder height. This would mean a sample size of 20.

Fruit should be sampled at the same time of day to ensure consistency.  

Measuring flesh firmness

1. Each piece of fruit should be tested twice on opposite sides using a penetrometer with an 8mm plunger (do not test bruised/russetted areas as this will distort results).
2. A strip of skin should be removed using a vegetable peeler from each side to be tested.
3. Fruit should be placed against a solid object, such as a bench and held firmly.
4. Penetrometer should be placed on the cut area and pushed into the fruit with an even pressure until it has reached the mark on the plunger.
5. Record the firmness to the nearest 0.25kgs.
6. Average all of the readings

Important note

The penetrometer should be calibrated regularly. Calibration can be done by firstly working the plunger in and out a number of times. The penetrometer should then be held vertically with the tip of the plunger against the pan of a set of scales. Press the penetrometer down slowly until it registers a weight close to the desired firmness levels. The penetrometer should register a similar reading to the scales. The instrument may need to be adjusted according to equipment instructions

Measuring TSS

This procedure outlines how to measure TSS using a hand held refractometer.

1. Using a sharp knife, slice a thin piece of flesh from the pear (on a side not tested with the penetrometer)
2. Extract the juice from the flesh using a clean, dry household garlic press
3. Place enough juice to cover the refractometer prism
4. Read TSS level to the closest 0.2^oBrix and average.

Important Note

The refractometer should also be calibrated before use. It can be zeroed using distilled water and then checked against standard solutions of a known Brix value.

Records

It is important to keep records of maturity tests each season. This can become a useful tool for assessing the changes in maturity dates between seasons and also assessing the affect of harvest time on storage quality.

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Other Useful Measures

There are other measures that can be useful to record whem maturity testing. Size is one of these. Whilst size does not indicate maturity, it is an important parameter to know, particularly for market requirements.

When samples are taken for maturity, growers should also measure the circumference of each and average. This can be done using digital callipers, size rings or a Cranston guage.

Figure 3: Cranston gauge, used to measure fruit size

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Maturity Standards for the Australian Industry

Harvest maturity standards have been determined for Australian grown pears. The following standards have been developed for Williams, Packhams and Buerre Bosc.

Table 1: Maturity standards for pears

           Source: Goulburn Valley Harvest Maturity Committee and Little and Holmes (2000)

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Further Information

These Australian and international sites may be useful for growers. However they are intended as an information source only. Any specific chemical or management recommendations may be outdated or irrelevant for Australian conditions and growers should seek local advice.

Please note: By electing to visit sites linking from this page you will be leaving the intensivepear.com website.

Australian Resources

• Little, C.R., and Holmes, R.J. (2000). 'Storage Technology for Apples and Pears'. Department of Natural Resources and Environment, Victoria.  Contact the DPI Customer Service Centre to find out how to purchase this book (external link).

International Resources

•  Washington State University Post Harvest Information Network contains a wide range of information regarding pear harvest maturity (external link).

References

Little, C.R., and Holmes, R.J. (2000). 'Storage Technology for Apples and Pears'. Department of Natural Resources and Environment, Victoria.  

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