In low-income countries, malnutrition is often most severe among infants of six to twenty-four months. They need higher-density foods than the family diet, but density is a credence attribute. We hypothesize that the premium now paid for heavily advertised brands reflects demand for quality assurance, which could be provided at lower cost to competing firms through third-party certification. We use a new market experiment to find that mothers' average willingness-to-pay for certification is about $1.75/kg, or four times its cost, so that total economic-surplus gains from introducing certification to Mali would be on the order of $1 million annually.