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Ask Mario Fernandez Alduenda what makes a good coffee and you'll get a fascinatingly informative reply that is perhaps not what you were expecting. Charmian Smith talks to the Mexican coffee expert who's living in Dunedin.
Mario Fernandez's ancestors have been growing coffee in the Veracruz state of Mexico since 1830 and his family still grows, roasts and exports coffee, so it's no surprise he has also spent his professional life dealing with coffee.
After studying coffee flavour and sensory analysis at universities in Mexico and France and working with his father, he became technical director for the Café Veracruz Regulatory Board, then owned a coffee shop and consulted around the world on coffee quality.
Now he's at the University of Otago, completing his doctorate on flavour in coffee.
A Kiwi friend persuaded him and his family to come to New Zealand, he said.
The 1000-year-old natural process of fermenting and drying coffee cherries to turn them into coffee beans can produce some wonderful and interesting aromas and flavours, but these are often not repeatable so other forms of processing were developed in the past couple of centuries.
In these the flesh, and in some processes the mucilage as well, is washed off the beans before fermentation to produce a more consistent product.
But with a growing market and appreciation for specialty coffee there's a new interest in naturally processed coffee and its myriad possible flavours, so Fernandez is researching how and why these flavours form, he explains.
But how do you tell if a coffee is good?
Quality in coffee can be judged only on the basis of flavour, he says.
Coffee is assessed by cupping, a method used to determine the price of coffee.
Like assessing tea or wine, it's as rigorous as it can be.
A precise weight of beans - 8.25g beans per 150ml water or 13.8g per 250ml cup - are ground separately for each cup.
The dry grounds are assessed for aroma then water at 92degC is poured on the grounds and allowed to steep for three minutes.
Then the cupper assesses the aroma again as he or she breaks the crust of coffee grounds floating on the top.
The grounds sink and the crema, the tawny froth, is skimmed off the top.
The crema is mostly composed of oils and is desirable for the enjoyment of coffee but they stick to your tongue and make cupping harder, Fernandez says.
Cuppers then wait for the brewed coffee to cool enough to taste, and use a spoon to slurp the coffee, spray it over the tongue, assess the flavours, body, sweetness, texture, acidity and balance.
It's tasted again as it cools, because a good coffee will get better as it cools.
Coffee cuppers, like professional wine and tea tasters, usually spit out the coffee to enable them to assess several samples.
Finally each cupper's notes and scores are discussed and compared.
To achieve a rating as a speciality coffee it has to score more than 80/100.
But isn't this a long way from choosing a flat white at your nearest cafe?
What makes a good coffee?
''As a coffee expert I'm biased and maybe my recommendation won't suit your taste.
"It happens to me a lot in New Zealand because I prefer coffee simply brewed and black,'' he says.
He makes his coffee in a plunger as it's the closest brewing method to making a cupping brew and allows the characteristics of the beans to be showcased easily.
''New Zealand is the only country I know where the plunger is underrated.
"In New Zealand a plunger is synonymous with boring coffee or simply not good coffee but the truth is, the plunger is just another brewing method and brewing methods complicate things.
''If you make yourself a plunger the proper way and you don't like the coffee, chances are it's not a good coffee, so if people look down on the plunger it may be because of the beans rather than the brewing method,'' he said.
''When you say a coffee is good, what are you referring to? The origin of the beans? Maybe the brewing method?
"To complicate it even further there are the fancy preparations with milk we have in New Zealand which are good by themselves but are a problem if what you want to get is the flavour of the bean,'' he said.
In most New Zealand cafes coffee is used to flavour milk and the fat and protein in milk conceal or obscure the flavour of the beans.
If you add sugar as well you can have no idea what the beans taste like, he explains.
New Zealand imports some high-quality beans but most are roasted darkly so the flavour will carry through the milk to give you a nicely flavoured flat white as opposed to a nicely flavoured black coffee, which a coffee connoisseur might appreciate.
''We are talking about two completely different animals here, and that's probably the reason nobody likes the plunger here.
"If I go to the the cafe and get a bag of coffee, the same coffee they use for flat whites and I go home and use that coffee in a plunger, the coffee is going to be terribly bitter and burnt-tasting.
"If I add milk to that plunger coffee it will be drinkable because the roasts and blends here are designed for flavouring milk.''
When Fernandez first arrived in Dunedin he looked around for beans to suit his taste and decided he was better off roasting them himself, he said.
''If you want to enjoy your milk with a nice coffee flavour, then by all means go for a dark roasted espresso.
"Most New Zealand roasters are very good at doing that. They are doing the right thing for their market.''
Lighter roasts enhance the original features, good or bad, of the particular beans and require more expertise from the roaster, whereas darker roasts tend to equalise quality and origins, until you get to a point where they all taste burnt and bitter, not that many New Zealand roasters go that far, he quickly adds.
''It's easier to do darker roasts.
"I have always thought that's a pity here in New Zealand because it's a country that buys really good beans but they don't get the chance to show their individual origins.''
• Fernandez leads me through a cupping session of two coffees from Colombia that he has roasted himself.
One smells fruity and has a bright, slightly sweet nutty flavour, with a medium body and nice fresh acidity.
It's well balanced and becomes more floral as it cools. He chooses to drink this one as we chat after the cupping session.
It certainly opened my eyes to how delicious good coffee simply brewed could be.
It's a far cry from an espresso.
The other sample has a sort of cardboardy aroma, the result of the beans not being as fresh as they could be, even though he roasted them both recently.
It was slightly rougher and the acidity was unbalanced.
It was probably a fine coffee once, but is no longer fresh, he says.
There are many different toys for brewing coffee that are becoming fashionable, although they haven't yet made much impact in Dunedin.
Each can yield a different flavour even from the same roast, and so can the water you use.
Water for coffee needs a certain amount of hardness as the soluble solids are important in flavour.
So if you make your coffee using the same method and beans in different parts of the city, they may taste different because the water is different.
In Dunedin he has gathered a group of interested people and taught them how to cup coffee.
They help back up his own cupping for research in a more objective way, he says.
There's a logistical problem to studying coffee flavour in Dunedin as there are no local coffee farms.
He knows of two coffee trees here, one in the butterfly house in Otago Museum and the other in the glasshouses in the Dunedin Botanic Garden, but in the three years he has been here he hasn't seen either of them flower or fruit.
Instead, he has his contacts send him samples of natural coffee for his research and he spent some time back in Mexico doing experiments on his father's farm, he said.
However, apart from the lack of local coffee growers, he says Otago is a good university at which to do his research.
The food science department is supportive and the flavour experts understand flavours regardless of the product.
He is transferring that knowledge, much of which has been developed in research on wine flavours, to coffee.
''It's excellent teamwork.
"I am the one who knows coffee and they know all about flavour, how to deal with it, how to analyse it, how to understand it, and I think it's been really fine and productive.''
He aims to finish his thesis about the end of the year or early next year, he says.