When He ate that what Catholics call a sacrament that He instituted at the Last Supper (the first communion), did it at that time turn into the literal body and blood of Christ?
In terms of the Holy Eucharist, the bread and wine became the consecrated host.
I’m going to assume you were taught what this means when you were catechized.
I should also correct the formulation of your question by referring to the words of institution. IIt was words of the Savior by which He instituted the Sacrament.