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Mr Fernandez, known to friends and colleagues as Super Mario Coffee Taster, comes from a Mexican family with a 180-year history of coffee growing, processing and exporting, and he is the only certified "cupping instructor" - a person who teaches the art of coffee tasting - in Australia and New Zealand.
Mr Fernandez said it was important to slurp because it sent the coffee right to the back of the palate.
Like wine tasters, coffee tasters look for fragrance, aroma, flavour, after-taste, acidity, cup balance and body.
"It's very similar to wine tasting, but coffee is more complex.
"We look for more attributes in coffee than wine tasters do."
One important aspect of coffee tasting is the use of a silver spoon to ladle the liquid from the cup.
"Silver dissipates heat better than stainless steel.
"Your tongue is your tool so you don't want to burn it."
Other hazards of the job are headaches from coffee deprivation and sleepless nights.
"I do get headaches if I don't have coffee for a few days.
"But I do sleep well because, like wine tasters, we spit the coffee out when we have finished tasting it.
"Otherwise, it's just too much coffee for the human body."
His experience comes from studying food technology in Puebla, Mexico, and a master's degree in food science at Montpellier 2 University in France.
For 17 years he has honed his skills in many roles, including miller and exporter, roaster and retailer, technical director of the Cafe Veracruz Regulatory Board, and university lecturer.
Mr Fernandez is undertaking food science doctoral research on the formation of flavour in natural coffees at the University of Otago and will share some of his coffee knowledge as part of the New Zealand International Science Festival in Dunedin from June 30-July 8.
He will give presentations on July 4 and 6 (7.30pm-9pm) at Technique Restaurant and a free demonstration at Wall Street mall on July 6 (noon-1pm).