Recipe location: Majuro, Marshall Islands.
We always try our hardest to buy as few packaged foods as we can, and if we do buy pre-made goods we aim for glass, this too through isn't always possible.
We ran out of mustard the other day, and couldn't find any at the store that wasn't packaged in plastic. We decided then that it was better to make our own. It requires few ingredients, little time to prepare (25min for prep, few days for soaking), and is inexpensive.
First, you need some mustard seeds. You can choose between yellow, brown and black seeds, the color affects the 'heat' of the mustard. A dark seed imparts more flavour than the lighter variety, and is what we used in this recipe. The seeds are then soaked in a mixture of water and apple cider vinegar, although you can also use beer and white wine as a base. The water should be room temperature or cold, because using hot liquids denatures the enzymes that create the 'heat' in mustard.
We don't have tools onboard that require electricity, so to grind and crush seeds and herbs we use a heavy ceramic mortar and pestle.
After the mustard is ground, it is stored in a glass jar at room temperature. Because of its antibacterial properties, mustard does not require refrigeration.
The best thing about making it yourself is that you can vary the quantities and base ingredients according to your personal preferences. If you don't like having a strong vinegar taste, you can lessen the amount of apple cider vinegar and add more water instead. You can also add spices and sweeteners. For traditional 'yellow mustard', all you need to do is add turmeric (for color) and a sweetener.