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<pre>Dear All …

I have just returned from working away and have read the last week or
so of emails. Research is still continuing on the low and high
Manzanilla extraction yields in different areas this season and we
need as much data as we can get to be prepared for the 2001 season.

It seems that during this season, the Manzanilla oil yields have been
very low in the south-east regions (eg reports from Victoria at 1-
5%), higher in the north (eg Queensland 15-18%) and in between in the
central eastern area (eg a single report from the Hunter Valley at 6-
8%). Peter Caird has also quoted results up to 18-19% from
Manzanilla at other processors this season but no location was given.

From Soxhlet laboratory tests we can see that the oil is present in
the Manzanilla fruit but we need to identify the best methods to
extract it with maximum efficiency, thereby reducing the volume of
oil being left in the waste.

Further research on maximising the oil build up in the fruit of all
varieties through various grove management techniques, irrigation
scheduling and the like is also important.

Here's some further thoughts for discussion on the Manzanilla
difficulties in the southern groves.

Fruit Maturity:
While we don't have a lot of data from any particular region this
season, it does seem that the further north we go, the higher the
extractable oil yields from Manzanilla. My understanding at this
stage is that the Manzanilla appears to mature early but relative to
other varieties, the skin colour is not necessarily an accurate
indicator of the oil content of the fruit. It appears that
Manzanilla fruit increase their oil volume until the skin has turned
from purple to fully black, and possibly even beyond this date in
some climates.

Could it be that we need to extend the harvest date of Manzanilla
olives in the southern regions to increase the extractable yields?

Paste Temperature:
Another factor which I think could be playing a major role in these
variable yields from north to south is the paste temperature during
extraction. Let's use an example, if a batch of olives are
processed
on the same day, say April 20th, with 50% of the batch being
processed in Victoria and 50% in Queensland then the Queensland
processor will most likely extract a higher percentage of oil as the
paste will likely be some degrees warmer than the southern location.

However, this scenario is compounded even further by the fact that
being further south, the fruit take longer to mature and during that
time the weather cools even further. This could result in the
southern paste being 10 degrees or more colder than the northern
paste if they are both processed at a given maturity and ambient/room
temperature.

A recent report from New Zealand showed that they were having trouble
extracting Manzanillo oil when the paste was 17 degrees Celsius. A
number of overseas processors recommend up to 35-40 degrees for
efficient oil extraction. Is 35 degrees Celsius still the
internationally accepted maximum processing temperature for Extra
Virgin Olive Oil?

Could it be that the Manzanilla fruit need a slightly warmer paste
than other varieties, to break the emulsion which has formed from
their recorded high moisture contents, and to successfully extract
the oil? There is no need to heat it so high as to `scorch'
the oil
and negate its ability to be labelled "cold pressed" or
"extra
virgin" but maybe this needs to be considered by processors
working
where harvest dates coincide with cooler weather. Most oil factories
I have visited around the world (including the more established ones
in Australia) raise the paste temperature through the use of hot
water jackets on the malaxers or simply by heating the room with a
fire (often fuelled with dry waste cake) or air-conditioning.

Irrigation:
An informative email from Steve Sibbett noted that sustained deficit
irrigation techniques (SDI) used in the June to mid-August period
(Generic November to mid-February in southern hemisphere), helped to
increase their overall percentage extraction rates for Manzanilla.
(Please be careful transferring dates between hemispheres as
Australia is a big country and aspects such as harvest dates could be
up to two months out depending on the comparative climates of the
regions you are transferring the data from and to.)

This SDI method would be worth trialing on Australian groves
regardless of the variety in 2001. SDI saves water and increases the
percentage yield without, according to the research, actually
reducing the overall oil volume. Here's the extract:

"Subsequent studies by Goldhamer (done in case water shortages
occur
and one
has to "parcel out" limited supplies) have identified the period from
early
June through mid-August here as a period when Manzanillo olive can
tolerate
some stress. In those studies, again for two seasons, he applied 50%
of the
water requirement during this period and found no impairment in yield
(tonnage) but he found improved total oil yield, provided trees did
not
suffer for water prior to the stress and were returned to optimal
irrigation
following the mid-summer stress up until harvest. This REGULATED
deficit
irrigation (RDI) strategy should be important to oil producers as it
improves oil yield (fruit % oil at the same tonnage) without
compromising
total yield, thus improving total oil yield (& hopefully revenue) per
acre." Steve Sibbett.

Processing Additives:
There are a number of additives which can be used to make olive oil
extraction more efficient without affecting the final character or
quality of the oil. Has anyone done comparative testing of batches
with and without extraction additives such as enzymes or talc in
Australia? An article on additives has been written by Argentinean
Marcelo Berlanda for the next Australian Olive Grower based on
overseas research.

I am coming near the end of editing the June issue of the Australian
Olive Grower and there are a number of articles dealing with
extraction additives, oil extraction efficiencies, oil extraction
yields in 2000 and comparative laboratory oil yields from 1999 and
2000. There is also a general article on irrigation for olive groves
by Steve Goodchild which will answer more irrigation questions.

I have also included a new section in the June issue
called "Questions Needing Answers" which will include some of
the
questions raised here and elsewhere to over 12,000 readers around the
olive growing world. Hopefully we will get some more answers to our
pressing questions.

We are still needing to collate a lot of data to get a clearer answer
to the specific yield problems this season. As I see it, the main
factors we need to compare across all batches (Manzanilla and others)
processed this season are:

1. Grove location, and source and age of trees
2. Irrigation/rainfall schedule from flowering onwards
3. Harvest date and perceived maturity of fruit
4. Processing method used
5. Temperature of paste when fruit was processed
6. Oil yield result (and the oil percentage remaining in the waste if
recorded)

I am keen to receive any such information from growers and processors
so that we can continue our research and hopefully have some more
conclusive answers before next season. Results can be posted here to
the OliveOil Net or to me directly at jarcher@adra.org.au

Let's continue to work on this issue until it is resolved. The
results will benefit all producers and processors in the years ahead.

Kind regards,
Julian Archer
Olives Australia
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<pre>Mr Archer said:

"A recent report from New Zealand showed that they were having trouble
extracting Manzanillo oil when the paste was 17 degrees Celsius. A number
of overseas processors recommend up to 35-40 degrees for efficient oil
extraction. Is 35 degrees Celsius still the internationally accepted
maximum processing temperature for Extra Virgin Olive Oil?"

In Australian Olive Grower, Nov 1977**, Dr Marco Mugelli said when
discussing the malaxing stage of oil processing:

"During the process the temperature musn't exceed 25 degrees Centigrade:
any higher than that affects the quality of the oil."


Ian Fraser


**Footnote: This issue of the journal described Dr Mugelli as "one of
Italy's foremost oil extraction specialists and head of the Florence Oil
Tasting Panel".
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