I know that alot of shave ice vendors have had problems regarding syrup shelf life. Regular syrup without preservative roughly have a shelf life of 1-2 weeks depending on your exterior temperature. On hot california summers, my syrup only last for a week at most so I usually just make it fresh every event that I have and approximate I plan to sell. After some research here are some things that I found that help syrup have a better shelf life..
1.) Boil sugar
Boiled sugar kills the bacteria inside the sugar which helps extend shelf life. Unboiled cane sugar is usually the culprit for fast spoilage.

2.) Use filtered water
Depending on the water drinkability in your city, many shave ice vendors use either tap or filtered water. Filtered water is usually cleaner and contain less microbes which can cause spoilage. You may use filtered or boiled water.

3.) Preservative and citric acid
Preservative as the name says help preserve syrup. You usually mix preservative with a bit of citric acid to help extend its shelf life.

4.) Make sure all your bottles/mixing utensils are clean
The cleaner it is, the less microbes and bacteria it contains

5.) Refrigerate
By refrigerating the syrup, it will slow down bacteria growth which helps extend shelf life.


By following the above procedures, I was able to extend the shelf life of my syrup for over 2 month without any flavor loss! If there is anything else t hat helps shelf life, feel free to share!

Thanks for the tips!

Interesting! Excuse my newbie-ness but how can you tell when your syrup has gone bad?

This really depends on the flavor. Flavors such as banana, lemon or light colored flavors are fairly easy to catch. If you see mold floating in the syrup, then that pretty much means it is bad. However for darker flavors, I usually do a taste test. If the flavors taste sour or off, it is usually spoiled.

Capitalist is correct. I just want to add that I try not to taste it yet as much as possible. So I usually smell it and if it produces a bad odor. I usually play it safe than sorry and dump it. If I really am unsure of it's quality. I would do the taste test last.