I'm planning to grind my own beef patties, but I don't plan to use them until the next day, or perhaps the day after. What is the best way to store them until the day of? Would sticking them in the fridge do, or do I have to put them in the freezer?
Store them as you would the unground beef. If it will be still be in date after a few days, store it in the fridge, otherwise, freeze them (separating the patties with a sheet of greaseproof paper).
Since forming patties takes very little time, I would minimize issues of sticking together or deforming by storing the ground meat as a lump (in a plastic bag well sealed for a day or two should be no problem) and then shaping it into patties as you use it.
A good answer is said to provide sufficient academic reference. I am not providing much references, but providing what my experiences have been. Experience you would have to take with a pinch of salt (pun intended).
I guess your utmost concerns are
To me, it seems strange that you would not consider marinating them first and exploit the preservative features of the marinate.
The reasons I would marinate it first are
Frozen meat would take about eight hours to thaw in the refrigerator. Therefore I find it helpful to freeze my meat for two hours to four hours and then remember to place it into the refrigerator non-freezer compartment no later than 10 hours before I actually would use it.
I buy icecream by the gallon, which comes in cuboid plastic boxes, with a sufficiently tight cover. I use those boxes (after the icecream is finished) to store my veggies and thaw my meat in the refrigerator. That prevents contamination of food by uncooked meat.
I read that sesame oil is an effective preservative. By my experience it has proven to be true.
Have you tried marinating with a mix of salt, spices and sesame oil?
Oregano is a known bacteria inhibitor.
Here is a web page on using spices to prevent bacterial deterioration of meat: http://www.hccfl.edu/media/44231/1025_lab_10_spices_and_food_preservation.pdf, which lists vinegar, salt, garlic, cinnamon, cloves, oregano in the first section.
Sugar is also said to be a preservative. Most people say it is because it dehydrates the food and sucks away water content to prevent bacterial action. What most people do not mention is the oxidating action of sugar. An oxidizing reaction obviously kills bacteria.
But somehow I have not found sugar to be effective, which in fact made it worse. I guess sugar is usable only when you want to soak the food (normally fruits) completely in saturated sugar solution.
Otherwise than that, I found that the sugar provides fermentation material for bacteria, which actually creates the preserving vinegar. Therefore leave out the sugar - just use the vinegar. Because, I found that I did not like the taste of meat on which fermentation of sugar had occurred. That's just me, perhaps other people may like the taste I find strange and yucky.
Effects on taste
These are my experience, but taste is highly subjective effect.
Sesame oil provides a strong pleasant aroma. But I've had people tell me they find its scent too pungent.
Vinegar with Garlic if not overly abundant, provides that luscious Chinese food scent, when food is cooked with them.
Ground nutmeg is meant to enhance/balance the taste of the food being laced with preservative spices. I found that I should not use too much nutmeg. It has a strong biting taste. To me, nutmeg seems to mask and compensate the flavour of spices. I have a suspicion that it has been used in excess to mask the taste of slightly spoiled meat. I don't think it is an effective preservative.
I find the mixture of cinnamon, garlic, cloves, anise, oregano and a little bit of cumin powder provides a pleasant scent and taste to meat.
A little tint of lemongrass oil might also enhance flavour. However, I find the effects of lemongrass similar to nutmeg - a strong biting taste and smell when used too much. I use lemongrass oil as insecticide, but I don't know if it kills bacteria as well as it does insects. Perhaps having lemongrass oil on your raw meat might prevent it from attracting flies and rodents, but then you would have to have sufficient amount, an amount that might affect the taste of the meat too much. If you don't mind Thai curry scent, you wouldn't mind too much lemongrass. If you google "cooking with lemongrass" you would find a lot of people loving its scent I find excessive.