Check for the "use-by" date on the packaging of vanillin.
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Vanillin is an inorganic compound which is a phenolic aldehyde(a derivative of phenol, an aromatic compound). It is in the form of white crystalline solid, soluble in water. It is a primary component of the extract of the vanilla bean and has a sweet, balsamic, pleasant aroma. It is considered as a synthetic alternative for natural vanilla extract. It can be used as a flavoring agent in food and beverages.