The present invention relates to flameless heating apparatus for food products. In particular, it relates to an improved potentially exothermic mixture/blend for such heaters and to meal packages including foods and heating apparatus. An embodiment of the invention comprises a composite material consisting of a potentially exothermic metallic alloy powder dispersed throughout a porous polyethylene matrix, which releases hydrogen in an exothermic reaction. The present invention seeks to reduce the production of such gas per unit mass, and further seeks to improve the efficiency of the reaction.