We harvested a few pounds of olives with the purpose of trying our hand at curing them. When you start reading about how to cure olives, you quickly realize that there are many methods to do that and many conflicting sets of instructions. An interesting fact that I had never thought about is that olives are actually a fermented food, they become palatable through fermentation. Olives used to be a very important source of nutrition; curing them was also a way of preserving them and making them available year round.
The olives we picked are of a variety called galega, which is Portuguese for Galician. It's a Portuguese variety which is quite small and naturally high in acidity, making it ideal for the curing process that we are going to attempt: the brining. They weren't quite ripe yet, most were half back-half green:
We sorted them, picking the leaves and stalks and discarding any that were short of perfect, ie, any that were bruised or had rotten spots. We then put them in a 3-liter glass Kilner jar, which became full up to the shoulder. Perfect amount, just out of luck. Of course, our harvest was larger, but we gave some away to family so that they could have a go at this as well. We washed the olives carefully inside the jar, avoiding bruising the fruit, and then added a 6% salt solution - ie, 6 grams of coarse sea salt per 100 ml of filtered water. We needed 1.2 liters of brine to cover the olives completely. To make the solution, we put the salt inside a large plastic bottle, added the water, and then vigorous shook the bottle until the salt was completely dissolved. To prevent the olives from coming in contact with oxygen, we put a piece of cling film on top of the brine and made sure that it was fully submerging the olives. The glass lid went on top of the jar, but without the rubber and metallic fastener. The slow fermentation will produce carbon dioxide and alcohol, so it is not a good idea to fully seal the jar unless you release the trapped gas once in a while. The jar is now in our pantry, away from direct light, and we'll wait patiently and monitor how it develops. Anything we do to the olives will be registered here.
Edit 1: as the olives ferment, the cling film will rise with the gases produced. We have to/should press down on the cling film to free that trapped gas and prevent the olives to come in contact with oxygen.
Edit 2: at some point, the jar starts smelling like olives (which is a sign things are working) and the water will become cloudy. We decided at day 20 to strain the olives, clean then with some filtered water in a colander, wash the jar with some dishwasher liquid, and add a fresh 1.2 liter 6% salt solution to the jar with the olives.
