Dry weight of Florida Grown avocados and their relation to quality
I have always wondered who and how determines the oil content in avocados. Seems to me one source quotes the other, No one says "I did the test and this avocado at this time has X percent of oil". High oil content in avocados seem to be a goal, I still say that there is a flavor component to that and in fact reading the literature it is. Researching the subject I came across the information that oil content is not used any more to determine readiness of a cultivar to be picked. For over 20 years or so, the test to determine oil content on avocados has been illegal because the chemical used to do the test is a carcinogen. Instead the method used is the dry weight method. So I have my scale, pitre dish and microwave ready.
In this page I will place a collection of articles dealing with the subject. In another section I will collect the data on dry weight of avocado cultivars that I grow at different time of the growing season.
From University of California Davis
The standard protocol these days for determining maturity of avocados is using DRY WEIGHT not oil. There is a very close relationship between oil and dry matter. The switch for the California industry came in the mid-80’s when the protocol for oil determination, the Hallowax method, was deemed carcinogenic. Most industries now use dry matter although some industries will report in oil content since there is such a close correlation.
It is important to note the minimum dry weight standard for some varieties in California:"The average dry weight at 8% oil (the existing legal standard in California) was 19.4% for 'Bacon', 19.1% for 'Fuerte', 19.8% for 'Hass', 18.9% for 'Pinkerton', and18.4% for 'Zutano' fruit. Dry weight at acceptable taste was 20.0% for 'Bacon', 21.0% for 'Fuerte', 22.8% for 'Hass', 20.0% for 'Pinkerton', and 20.2% for 'Zutano'." The correlation does not mean igual amounts. See table 4 in the Maturity Studies of Avocado.....listed below. Seems like oil ranges between 40-50% of dry weight.
For example the minimum dry weight for Hass in California is 20% but during the growing season the dry weight ranges from 18.88% to 30 %. The range is from early to late in the season. A Hass with 30% dry weight has about 15% oil about 50% of its dry weight.
On the other hand the work of Marisa Wall USDA in Hawaii has a higher percent of oil to dry matter in the range of 55-65% I'm not sure how to reconcile this difference if I have no access to check and verify oil content. According to her chart the Oro Negro that came at 26% dry weight would have 14-16% oil.
In this page I will place a collection of articles dealing with the subject. In another section I will collect the data on dry weight of avocado cultivars that I grow at different time of the growing season.
From University of California Davis
The standard protocol these days for determining maturity of avocados is using DRY WEIGHT not oil. There is a very close relationship between oil and dry matter. The switch for the California industry came in the mid-80’s when the protocol for oil determination, the Hallowax method, was deemed carcinogenic. Most industries now use dry matter although some industries will report in oil content since there is such a close correlation.
It is important to note the minimum dry weight standard for some varieties in California:"The average dry weight at 8% oil (the existing legal standard in California) was 19.4% for 'Bacon', 19.1% for 'Fuerte', 19.8% for 'Hass', 18.9% for 'Pinkerton', and18.4% for 'Zutano' fruit. Dry weight at acceptable taste was 20.0% for 'Bacon', 21.0% for 'Fuerte', 22.8% for 'Hass', 20.0% for 'Pinkerton', and 20.2% for 'Zutano'." The correlation does not mean igual amounts. See table 4 in the Maturity Studies of Avocado.....listed below. Seems like oil ranges between 40-50% of dry weight.
For example the minimum dry weight for Hass in California is 20% but during the growing season the dry weight ranges from 18.88% to 30 %. The range is from early to late in the season. A Hass with 30% dry weight has about 15% oil about 50% of its dry weight.
On the other hand the work of Marisa Wall USDA in Hawaii has a higher percent of oil to dry matter in the range of 55-65% I'm not sure how to reconcile this difference if I have no access to check and verify oil content. According to her chart the Oro Negro that came at 26% dry weight would have 14-16% oil.
Collection of Articles on dry weight and Avocados. These are links to the material. Click on the name.
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University of California Article on dry weight
****** Quality assessment of avocados by means of dry matter content (Israel) by Brett Hickson (good) ******* 
Above: Great Power Point from Marisa Wall USDA Hawaii a few good slides on dry weight and oil correlation.
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Results of dry weight percentages on avocados I grow.
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Oro Negro Avocado. Picked on November 21, 2013 at 19.2 oz and tested next day, this fruit was allowed to turn black in the tree almost 90-95 % Two samples were done and the average dry weight was an incredible 26% This translates to 12-14% oil. This is the mid season range of Hass
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Monroe Avocado. Picked on November 21, 2013 and evaluated it for Dry Weight next day. The avocado season for this variety began on November 4, so it has a few more weeks to go. I would say this is an early Monroe. Two samples were taken and the average dry weight is 19%, very decent 10-11% oil. Probably this has a lot more to go I will check in mid December.
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Just bellow I have the work sheet I use to record and calculate the dry weight measurement. The blue measurements were done with a new more accurate scale. You can download the Excel file.
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