How are mangoes preserved as pickles?
Salt and oil act as preservatives in pickles. The oil layer floating above the pickle, blocks the moisture from any contact with the pickle.
When the jar is filled completely with pickle, negligible amount of air/ moisture is present in the jar. As we use the pickle, the quantity of air in the jar increases, as well as the moisture content. Due to the build up of moisture, the mango loses its freshness, as it absorbs the moisture. Also, the moisture aids in the growth of micro-organisms.
To keep the mango pickles fresh till the next mango season, you may fill them up in small jars and refrigerate. This way, you will be opening a small jar which gets exhausted before absorbing much moisture, and the other jars remain fresh for a longer time as they are not exposed to moisture.