The essential oil is obtained mainly of caraway fruits by steam or hydrodistillation. A good overlook about different distillation facilities is given by Lawrence (). The oil is colourless or slightly yellowish and toxic to humans even in relatively low amounts. Amounts of 4g can already cause health disturbances for adults (). Carvone may also cause allergic effects ().
Instead of distillation of the ripe whole caraway fruit, it is also possible to chaff the umbels directly from the field into a container which is afterwards directly connected on a distillation unit. The essential oil yield gained in such a way was in the experiments of Hannig et al. () about 481/ha. The early harvest had no negative influence on the oil composition (60% carvone in biannual caraway). Average essential oil yield (assessed on laboratory scale by Dachler et al. () in variety tests) was around 70kg/ha, with top yields of 160kg/ha. In the contrary to earlier reported carvone contents () they observed only 30–48% carvone in the tested biannual varieties.
Bazata et al. () found, that during the distillation process the relation of carvone and limonene changed. At the beginning of the distillation the essential oil had higher amounts of carvone whereas at the end limonene predominated. The reason is that carvone as oxygen containing compound is several times more soluble in water than limonene.
The essential oil can be used in the food and cosmetics industries and has to a certain extent an antimicrobial and antioxidative effect.
Since long time human beings used herbs and spices for preventing food deterioration and pathogenic diseases. In general, plants from the Liliaceae family followed by Myrtaceae, Cruciferae and Labiatae showed the highest antimicrobial activity. While usually the antimicrobial effect of caraway is expected to be low, Morris et al. () reports that together with essential oils of other botanicals the oil of caraway showed considerable effect.
Salzer () examined six different spice extracts for their antibacterial properties. The effect of caraway oil was the lowest (pepper > nutmeg > maces > ginger > celery seeds > caraway). Caraway extract had some inhibitory effects against Salmonella typhi murium but even increased growth of Bacillus cereus. Against other germs caraway extract was rather indifferent ().
Generally, gram-positive bacteria were more sensitive to the antimicrobial compounds in spices than Gram-negative ones, as the results of Farag et al. () show. The oil of caraway exhibited moderate effect against bacteria, whereas the oils from clove and thyme were highly active.
Antifungal Effects of Caraway Oil
The constituents of caraway oil are showing only little effects against pests. It has been reported that merely limonene showed fungicide effects against Lenzites saepiaria, Boletus variegatus and Trichoderma viride ().
Antioxidative Effects of the Oil and Oleoresins
Lipid peroxidation, a radical chain oxidation of unsaturated acids, causes various damage not only in living organisms but also in foods. Beside some chemicals it is well known that herbs and spices are proper materials to reduce or to inactivate rancidity in oils and fats. The antioxidative activity depends on the substrate of the oxidation, the preparation procedure and the oxidation test. As pointed out by Nakatani (), rosemary and sage as ground spices are remarkably effective, whereas caraway showed no real effectiveness.
Lee and Widmer () compared the antioxidative capacity from some oleoresins such as rosemary, anise, dill and caraway as antioxidant for limonene oxidation. Rosemary oleoresins were most effective in inhibiting oxidation of limonene, whereas oleoresins from anise and caraway did exert a weak protective effect up to early stage of oxidation. Oleoresins from dill were nearly inactive against limonene oxidation.
Essential Oil in Food
Caraway oil is used in all major categories of foods including alcoholic and non-alcoholic beverages, frozen dairy desserts, candy, baked goods, gelatines and puddings, meat and meat products, condiments and relishes and others. Highest average maximum use level is reported to be about 0.02% in baked goods ().
Essential Oil Used in Cosmetics
Essential oil is also used as a fragrance component in cosmetic preparations including toothpaste, mouth wash, soaps, creams, lotions, and perfumes, with maximum use level of 0.4% reported in perfumes ().
Use of Essential Oil as Animal Food-additive
Vogt and Rauch () evaluated the effect of essential oils as food additives for chicken. Neither with caraway oil nor with coriander, thyme, garlic or onion oils in different doses they found any significant influence on weight or feed efficiency. When checked at the end of the experiment in the organoleptic test, they did not found any typical taste or smell of the meat resembling to the corresponding essential oil in either of the cases.
It is described in elderly publications, that caraway plants may be used as animal food (pasture) for milking cows and sheep (). Nowadays such a use is rather uncommon.
Selections from the book: “Caraway. The Genus Carum”. Edited by Éva Németh. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 1998.