Storing garlic, ginger and certain other vegetables etc. in oil is a well documented botulism risk if preservatives are not added. As a consequence, I always make my pastes fresh immediately before use. I have considered freezing them, but due to the amount of oil used I am concerned they will not freeze well. I have had reasonable success freezing ginger and garlic pastes made with water, but the taste is obviously very different.
I am due to have guests for a curry evening and it would be helpful if I could do a lot of the preparation beforehand. One of these steps would be the prep of ginger and garlic pastes with rapeseed oil.
Taking into account that the pastes will comprise of pure garlic with oil and ginger with oil (I don't make a combined garlic/ginger paste), what factors other than acidity etc. will eliminate this risk? I don't intend to store the paste more than 24 hours in the refrigerator and the quantities of oil used will be just enough to make a smooth paste. I can potentially add salt, sugar or freshly squeezed lemon juice, but ideally I would prefer to omit the latter which is the only ingredient I assume would change the pH to safe levels.
(For clarification the water and oil are not essential ingredients here, I use them purely so the solid garlic/ginger will process into a smooth paste in my blender).