Interesterification of lard

Abstract

The graininess, which develops at 27C (80F) in lard shortening which has not undergone interesterification, is due to large crystal aggregates of disaturated 2-palmitoyloleoylstearin (OPS) of intermediate melting level and existing in a β'-type form of triple-chain-length structure. This β'-3 phase exists in ordinary lard accompanied by the commonly reported β phase which is largely due to trisaturated glycerides. Random interesterification eliminates graininess, not by reducing the disaturated content which remains about the same, but by reducing OPS to its “random” proportion and producing a mixture of disaturated glycerides, which is substantially lower melting than the original OPS. The resulting product crystallizes typically in a β'-2 form, characteristic of hydrogenated vegetable oil shortenings. (Directed interesterification actually reduces disaturated content as well as graininess, while simultaneously creating trisaturated “hardstock.”)