Traditional indian methods uses beautiful ways to prevnt food spoiling: pickle-it contain lot of salt which PREVENT microbs growth. Moreover it has layer of oil, prevent contact with oxygen.
Avaleha-sugar,syrup BASED preparations, use hight sugar to check microbes E.g. dried sweet awala candy.
Alcohol can be USED for preservation-asava, arishta formulation.
Use of NATURAL preservatives can improve shelf life. Honey is such wonderful thing in nature with no expiry date!
So in nutshell, not only preparation but packing,storage of food also need to addressed. Till now any one method is seldom used with success for preservation of food.