This small accumulation of liquid on the product is called syneresis. This is not a quality defect but a completely normal process that can occur in some products. Mustard and horseradish are originally solid substances that are suspended in water during processing, meaning they are dispersed as finely as possible. If small bubbles or unevenness appear on the surface of the finished mass, some of the liquid can separate from the solid components and settle apart from the product. Larger temperature fluctuations can also promote the release of liquid. In a jar, the liquid can simply be stirred back in with a spoon; for a mustard squeeze bottle, we recommend shaking the tube vigorously before use. The classic aluminum tube can be gently kneaded before use.