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North Otago’s limestone caves may hold the secret to creating a truly Kiwi blue cheese, Rebecca Fox discovers.
Mouldy-looking growths covered in tiny droplets of water make cheese-makers Simon Berry and Chris Moran smile.
Excited exclamations of ''over here'' or ''look at this one'' ring out through the surprisingly clear air of the disused water race, which was used to bring water from the Waitaki River to Oamaru.
These days, the old tunnel is used for stock water, but the water level is only ankle deep as the cheese-makers and farmer Allister Cadler wade through to take a closer look at the rock walls.
Moran dons his headset torch and digs out sample kits from his backpack as Berry uses the torch on his phone to scan the walls of the cave.
When they see a likely looking patch of mould or moisture, Moran takes a sample.
They are searching for the Penicillium roqueforti bacteria - the bacteria which creates those rich blue veins in blue cheese.
Until recently Berry and his team at Whitestone Cheese have made their award-winning blue cheeses with a roqueforti imported from France and developed by their own cheese-makers.
The roqueforti comes from the roqueforti limestone caves where it was originally discovered.
''We were learning about blue moulds and thought 'we have very similar limestone caves here','' Berry said.
So when Moran came to him with the suggestion that they search Oamaru's limestone caves for the blue mould, Berry thought ''Why not?''.
''We spoke to the limestone people and they said the style of rock in North Otago is rare and similar to that in northern Europe.''
The pair set about ''bio prospecting'', knocking on farmer's doors where they knew there were limestone caves and asking if they could swab them for mould.
''We got some raised eye brows when we knocked on doors, but people are intrigued by it.''
The mould thrives in the alkaline environment of caves where there is plenty of water and oxygen.
''We tried a number of sites with no luck.''
But they eventually found a keen scientist who tested mould regularly and was prepared to keep an eye out for the P. roqueforti when he tested other samples.
Then a suspicious-looking mould was found in haylage from Shenley Station. Farmer Rit Fisher, who said the mould was pure white and didn't smell like a ''sumo wrestler's armpit'', was concerned that if he fed the haylage to his in-calf heifers they might lose their calves, sent it in for testing.
Then he got a phone call from the lab asking if they could pass Fisher's name on to a third party - Berry.
''We thought it was pretty exciting to have found such a pure form of P. roqueforti.
''What a delight. What is one man's bad luck is another's gold.''
That was especially true for Berry, as the haylage had not been sprayed.
''The lab rang us to say they've isolated a strain, it's non-toxic roqueforti penicillin.''
Moran used the strain to make a trial cheese at home - so they did not risk contaminating the original P. roqueforti they use in the factory.
All strains are slightly different, so they had no idea what sort of cheese the bacteria found in the haylage would produce.
The excitement was subdued as the strain still had to be sent to Germany for it to be formally identified and typed and then go through the required Ministry for Primary Industries testing to ensure it was safe to be introduced into the food chain.
They eventually got a green light and the test blue was ready to be tasted.
They discovered a mild, creamy blue with mushroom flavours.
''It grows quickly and is not a super dark blue. We used a different recipe and it's a different size and shape.''
On a recent trip to France to look at cheese production, they ran it past a cheese-maker there who gave it the thumbs up, as did Berry's father Bob, who started Whitestone Cheese in 1987.
Fisher, not a huge blue cheese fan, has also tasted the cheese and declared it ''outstanding''.
''I adore the stuff. It's a delight to know we had some part in finding New Zealand's own P. roqueforti. I hope they do really well.''
Berry said the first commercial production of the cheese was made after testing to ensure the new and old strains could ''live together'' in the same factory.
The new cheese, to be called Shenley Station Blue, was ''maturing nicely'' on the shelves of the factory and should be ready next month.
''It's really exciting. To acknowledge where the P. roqueforti was found we have called it [the mould] 45 South Blue.''
Berry hopes producing a ''new world'' blue will be a winner at the Wisconsin World Cheese Show in March.
''It's a great point of difference.''
Unfortunately, the search in the Ardgowan water race did not uncover any P. rocqueforti.
''We had some promise initially with some plate growth. However, [they] proved to be false alarms, so the search is continuing.''