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New Crops News, Spring 1992, vol. 2 no. 1

Basil: Promising New Essential Oil Crop

Sweet basil, a popular culinary herb, is grown in gardens and in roadside markets in Indiana for its flavorful and aromatic leaves for use in pesto and other sauces. While basil has long been prized for its aroma, delicacy as a spice, and its beauty and fragrance as an ornamental, the plant also contains essential oils that are used by the perfume, pharmacy, and food industries. Few realize the multitude of natural chemicals contained in the essential oil that can be extracted and used in perfumery and flavoring.

Through research and development in the New Crops Center, special unique forms or chemotypes of basil that were previously identified at Purdue to contain specific chemical constituents of industrial value, are now being developed for commercialization. A team of researchers including Dr. Jim Simon (new crops specialist), Dr. Denys Charles (biochemist), and Dr. Mario Morales (plant breeder) identifed basil plants that contained high concentrations of methyl cinnamate (35% of the oil) in the essential oil. This compound is of interest to the fragrance and food industries searching for a natural cinnamon flavor. After two years of selection, high yielding plants adapted to Midwestern growing conditions are now available with over 80% methyl cinnamate. Several promising methyl cinnamate lines were successfully grown in semi-commercial field plots at the Pinney Purdue Agricultural Experiment Station, Wanatagh, Indiana in 1991. This study demonstrated both the commercial feasibility of introducing this new crop as well as highlighted some of the production and processing problems that remain to be overcome.

One of the major advantages of growing basil and other aromatic plants for essential oils in Indiana is that the state already has a very strong industrial infrastructure to produce essential oils. There are over 14,000 acres of peppermint and spearmint produced annually in northern Indiana, and the state is the home of several national essential oil processing companies. With a few changes, commercial mint growers could utilize the same production, harvesting, and processing equipment for this new crop. Although potential yields already look promising, a number of problems must be resolved. For example, optimum harvest time and method must be determined. Another problem that now must be overcome is in the actual extraction of the methyl cinnamate. As the concentration of methyl cinnamate sky-rocketed upward in the improved chemotypes, the ability to separate the methyl cinnamate from the distillate water became more difficult. Research is underway to increase methyl cinnamate recovery. The incorporation of a secondary extraction process coupled to the steam disitllation process would permit the redistillation of the distillate water that contains the unseparated methyl cinnamate. Development of such a process would also be useful to mint growers to improve recovery of peppermint oil. Basil appears an ideally suited addition to the state's current peppermint and spearmint growers seeking to diversify their agricultural crop base.

Progress is being made in other types of basil which contain essential oils of industrial value, including methyl chavicol, linalool, camphor, citral, and eugenol. As a spinoff to these studies we have developed a basil with a strong lemon aroma, through several selection cycles, that has potential as a new ornamental culinary herb. The high content of citral (over 65%), which is responsible for the lemon aroma, coupled with the large leaf size also has potential use in the herbal tea trade.

James E. Simon
Department of Horticulture