From MSNBC:
Chocolate is not widely consumed in the tropics, even though that’s where most of the world’s cocoa is produced. The reason: It’s too hot. High temperatures in countries like Nigeria reduce chocolate into a sticky, gooey mess. Food scientists have been trying to remedy this situation for decades, and now researchers in Nigeria believe they are close to achieving the holy grail among chocolate manufacturers: a heat-resistant chocolate that actually tastes like chocolate. Most brands of chocolate melt at temperatures between 77 and about 91 degrees Fahrenheit (25 to 33 degrees Celsius).
S.O. Ogunwolu and C.O. Jayeola, food scientists at the Cocoa Research Institute of Nigeria, have mixed cornstarch with cocoa to produce a heat-resistant chocolate that they say compares “favorably with conventional milk chocolate in terms of color, taste, smoothness and overall acceptability.” The starch acts as a chocolate thickener and prevents the outflow of cocoa butter — the natural fat of the cocoa bean — when the heat is on. The researchers found that using 10 percent starch was ideal and produced a product that was comparable to milk chocolate in taste tests.
More here.