When General Mills Inc. and Kellogg Co. couldn’t beat the startups appearing on store shelves next to their Yoplait yogurt and Froot Loops cereal, they decided to invest in them.

Food giants are starting venture capital funds to invest in startups focused on healthier and less-processed foods, betting the younger companies can teach them to be more entrepreneurial and innovative. Slow to recognize consumers’ shift toward those products, global titans have found themselves stuck in a rut.

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