Summary
The steps for carrying out maturity testing on citrus are:
- Citrus maturity standards may change from time to time so it is advisable to check with Citrus Australia or you local citrus industry body to confirm the current industry standards prior to testing.
- Collect a representative sample of at least 10 fruit for each variety to be tested. Remember that the more fruit you test and the more representative the sample, the more accurate your result will be.
- Determine the percentage juice content of the fruit (juice weight divided by fruit weight multiplied by 100).
- Determine the sugar level using a refractometer (percentage total soluble solids or
°Brix). - Determine the percentage acid by titrating 10mL of juice with 0.1 Normal sodium hydroxide solution and multiplying the result by 0.064.
- Calculate the sugar-acid ratio (°Brix divided by percentage citric acid).
- Calculate the Australian Citrus Standard {°Brix - (%Acid x 4)} x 16.5.
- Compare your test results with the standards you are using. If any standard is not attained, the fruit are not mature and should not be harvested.