Pineapple vinegar

The Kadagaya campus is located in an agricultural region and is surrounded by pineapple plantations. There is often a lot of wasted produce as the fruit needs to be harvested quite ripe. If rain or transport problems delay harvesting, many pineapples are discarded on the side of the road or left to rot in the field. Some chemical processes can be used to promote ripening of the entire crop at the same time to avoid these losses. However, this is an added cost for the farmer and increases the use of synthetic chemicals.

We are experimenting with various ways of using this waste stream. We collect rotting pineapples for feeding our chickens, worms, and adding to the compost, but large quantities are problematic as sweet fruits ferment quickly to produce alcohol in our hot climate. In the future, this waste could be added to our biodigester system to produce methane biogas for cooking. We are also planning to install a dryer to use excess power from the hydroelectric plant, which could be used to dry fruit such as pineapple to allow them to be stored and sold at a more convenient time for the farmer.

We are lucky to be able to eat fresh pineapple most days and often prepare juice, jam, chutneys, tepache (fermented pineapple drink), and vinegar. As we entered quarantine in the middle of March 2020, our neighbours were unable to harvest their pineapples as the connection between Lima and the jungle was greatly restricted. So we had access to an abundant supply of overripe pineapple, which was not good for eating, but perfect for making vinegar. We used a juice extractor to prepare around 15 L of pure juice, which was added to a 20 L bucket with a few litres of water. The juice was stirred well, covered with a cloth, and left to naturally ferment. Naturally occurring yeasts in the air process the sugars in the juice to produce alcohol, which is then converted to acetic acid (vinegar). This is an aerobic process, so the mixture needs to be stirred well every other day to ensure it has adequate oxygen. In our hot climate, the fermentation process is very fast. After about one week, we removed the first batch of vinegar, which was pasteurized by boiling to stop the fermentation process and sterilize the vinegar for storage. When the pH of the vinegar decreases to a certain point (i.e., the acid becomes strong enough), fermentation will naturally stop as the active yeast will be killed.