Alberta researcher finds beneficial use for mango pits

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By Elise Stolte, Edmonton Journal

August 14, 2009


Mango lassi going bad? Just add more mango, says a University of Alberta researcher celebrating a breakthrough in her quest to develop natural alternatives to synthetic food preservatives.

PhD student Christina Engels has found a way to extract a bacteria-killing compound from the millions of mango pits tossed or burned around the world daily. She recently published her findings in the Journal of Agricultural and Food Chemistry.

Surrounded by fume hoods and laptops in a lab Thursday, she said "the natural compounds are really concentrated in the pits but they are in the flesh of the mango as well. For centuries, people were eating those in mango flesh and they didn't have any(negative) impact on their bodies. But if we use a chemical preservative, we might not be sure."

The process would also reuse a major byproduct from factories that process mango juice.

Engels spent five months experimenting with different temperatures, times and organic solvents to isolate the specific compound she wanted from the mango pit -- a certain group of tannins, the same group of compounds used in tanning hides and the substance that colours water run-off when it leaches through dead leaves.

Once she had a concentrated amount suspended in water, she tested them on cultures of bacteria, including listeria, the organism responsible for making many Canadians sick last summer after they ate luncheon meat, and on lactic acid bacteria, which is beneficial and found in yogurt and some fruit juices. Even at a small concentration, the tannins killed the listeria and left the lactic acid bacteria alone.

Engels' next steps are to get a food safety specialist to double check that the tannins are safe for human consumption, and also start testing them in food, in fruit smoothies and by adding them to the water used to wash lettuce, "another product that is easily spoiled by bacteria," she said.

Hopefully, people won't be able to notice the taste, she said. "They are said to be bitter, but in my test I found the concentration can be very small."

Mangos are a popular tropical fruit. Juan Torres sold about 21,000 mangos speared on a stick and rolled in lime juice and spices at the recent Heritage Days. He said he could have guessed the fruit would be full of surprises. It's used regularly to treat stomach aches in his home country of Guatemala and is believed to increase men's sexual desire.

"We have mangos the whole year. It cleans up your system. It's very good," he said. "There is so much good in the mango, a lot of people don't even know.

One of Engels' two supervisors, Andreas Schieber, has been studying the properties of mangos for 10 years. "We've always found new things to study. I've stopped counting the number of graduate students who worked on mangos in my group alone," he said.

Doctors in India have been using an extract from the mango seed and the bark of the tree to treat diarrhea and skin infections.

Fats from the mango seed have already been approved in Europe as a substitute for cocoa butter.

It is a fruit that has a high level of antioxidants, Schieber said, which have been tied to decreased risks of cancer and cardiovascular-related diseases.

"There is a lot of potential."



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