WICHITA, Kan. — The smiling, blissful and confused-looking emojis dotting the electronic landscape may hold the key to ferreting out grade-school children’s true feelings about foods, Kansas researchers say, and could help schools across the nation cut down on lunchroom food waste. Most school lunch programs in the U.S. already do taste tests, but their efforts pale in comparison to the scope of the research project at the Sensory and Consumer Research Center at Kansas State University Olathe, which is developing a scientific methodology to measure children’s face-emoji responses to food.