Answer
Cakes were not preserved by Appert's method because they contain a high amount of sugar, which inhibits the growth of microorganisms but also prevents the formation of a vacuum seal necessary for successful preservation. Appert's method, developed by Nicolas Appert, involved heating food in sealed glass jars to kill microorganisms and create a vacuum seal. This method was effective for preserving low-sugar foods such as vegetables, fruits, and meats.