Aroma chemicals are compounds which consist of smell and odor. They are also known as aroma, fragrance and odorant among others. Any chemical compound is said to have odor or smell only if it is sufficiently volatile to reach the olfactory system in the upper part of the nose. The molecules that inhibit this property have molecular weight of <300. Both the sense of taste and smell are affected by flavors whereas fragrance affects only smell. Fragrances are synthetic and flavors are naturally occurring compounds. The presence of aroma is found in wine, food, species, fragrance oils, perfumes and essential oils. Many are formed biochemically in the process of ripening of crops and fruits and also form byproducts of fermentation in wines. Odorless substances such as propane, hydrogen and natural gas among others can consist of odorants. Moreover, aroma compounds have a significant role in manufacture of flavorants that are used in the food service industry to improve, flavor and increase the demand of the products. Aroma compounds are classified by structure namely, cyclic terpenes, linear terpenes, aromatics, amines and esters.