In a method of thermally processing a low acid, heat sensitive foodstuff in a container, said foodstuff being susceptible to heat degradation when thermally processed, which comprises:
- (a) combining the foodstuff in a container with a hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof in an amount sufficient to lower the equilibrium pH to 4.6 or less,
- (b) hermetically sealing the combined foodstuff in said container, and
- (c) subjecting the combined foodstuff to a thermal process at a reduced time-temperature parameter sufficient to achieve commercial sterilization;
- said parameter being lower than the higher commercial sterilization parameter needed when said hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof is not employed, the improvement which comprises:
- prior to placing the foodstuff in the container, combining it with a first portion of said hydrolysis mixture or precursor thereof in an amount sufficient to control discoloration of said foodstuff but insufficient to lower the pH to 4.6 and thereafter;
- but, prior to thermally processing combining the said foodstuff in the container with a second portion of said hydrolysis mixture or precursor thereof in an amount sufficient to lower the equilibrium pH to 4.6 or less, and then conducting Steps (b) and (c).