Sesame - Sesamum indicum!
Sesame is among the most important oil seeds of mankind, and one of its oldest. There are very different kinds of sesame oil available, and some knowledge about their culinary properties is required to make an educated choice. Basically, nearly all seeds contain some kind of stored energy used as a fuel by the young plant in the first phase of its life. Energy is sometimes stored in the form of proteins, e.g. in the bean family (beans, peas, lentils); yet much more common in the use of carbon hydrates (e.g., cereals) or fat to store energy. Oil obtained by pressing such seeds contains besides true fats (lipids) several more constituents: Aroma compounds, which make up for the culinary character of the oil, vitamins, trace elements and more. With respect to lipids, in the plant kingdom nearly pure glycerides, saturated and unsaturated fats are distinguished.
Among the unsaturated fats there are several essential; failure to incorporate enough of them leads to disease. Yet saturated fats are better for cooking, because they can be heated to higher temperatures and have longer shelf life. Also, some aroma compounds decompose at higher temperature, imposing a burnt flavor to the dish. Cold-pressed oils (in more recent literature also called native oils) contain a wealth of aroma compounds and their aroma resembles the plant they were obtained from. They must be heated carefully to preserve their aroma compounds; otherwise, the advantage of cold pressure is lost. Cold-pressed oils are perfect for salads and well-suited for dishes prepared at temperatures not much higher than the boiling point of water. A famous example is extra vergine olive oil; some other examples are walnut oil, poppy oil and rapeseed oil.
The term "cold-pressed" is somewhat confusing, because even "cold-pressed" oils are not obtained at refrigerator or even room temperature; due to friction in the seeds the temperature may rise well up to 40 C. Some oil mills improve the quality of their products by artificial cooling during the extraction procedure. Cooling increases the quality of the oil; it is particularly important for obtaining highest-quality olive oil. A number of oils is obtained from seeds toasted before pressing; typically, these products are very flavorful (pumpkin seed oil, hemp oil, oriental sesame oil). Since the seeds have been exposed to elevated temperatures before pressing, there is no need to keep the temperature low in the following steps: typically, pressing takes place at 60 to 80 C (even higher temperatures would further increase the yield, but lead to development of off-flavors, see below).
Flowering sesame plant (Sesamum radiatum)!
Hot-pressed oils are much more cheaper, since pressing yield increases with the temperature; even the waste from a first pressing may be reprocessed to give more oil at high temperature (above 100 C). Solvent extraction, finally, gives nearly quantitative yield. Yet in the heat, a large number of unpleasant smelling or even toxic compounds form and make hot-pressed oils not suited for human consumption. Thus, a further step called raffination is needed to remove free fatty acids, solvent residues and all aroma compounds, leaving a bland oil consisting purely of lipids. Refined oils are common in the West, on one hand because strong flavors are not popular anyway and on the other hand because they are stable up to high temperatures and are thus perfectly suited for deep frying.
For the taste, it's not of much importance which plant they are obtained from, but their thermal stability and content of multiply unsaturated fatty acids depends on the plant species. The most popular refined oils in Europe are sunflower, corn, sesame and safflower oil and the solid coconut fat. Margarine is made by hydrogenization of vegetable oils, whereby unsaturated fats are converted into saturated fats. Because of loss of the valuable polyunsaturated fatty acids, it is less valuable but, on the other hand, it is a cholesterol-free plant product and thus still bears some dietetic advantages compared to butter. Culinarily, of course, butter is far superior, even if "butter-flavoured" margarines are sold. Sesame oil is traded in any of the forms described above: Refined sesame oil is very common in Europe and the USA; most margarine is made therefrom.
Cold-pressed sesame oil is available in Western health shops. In most Asian countries, different kinds of hot-pressed sesame oil are preferred. For example, a hot-pressed sesame oil is the preferred cooking medium in Southwest India (mainly, the union state Maharashtra) and Burma (see also onion for Burmese curries). A specialty particular worth noting is oriental (dark) sesame oil, which is obtained by toasting the seeds before pressing. Dark sesame oil (Chinese xiang you"fragrant oil", Korean cham girum) is a common flavoring in Korea and in the Chinese province Sichuan (see also sichuan pepper), where it is used drop by drop as a condiment, e.g., for Sichuan hot and sour soup (suanla tang); in parts of China, it is commonly flavored with crushed dried chiles. Dark sesame oil is not suitable as a frying medium, unless it is diluted with bland oil; for example, Japanese tempura is made by deep-frying battered vegetables in a mixture of one part sesame oil and ten parts vegetable oil.
Toasted sesame seeds are a common spice in Eastern Asia; it is often sprinkled over Japanese and Korean dishes. It forms part of shichimi togarashi, an exotic spice blend of Japan (see Sichuan pepper). Chinese sesame paste (zhi ma jiang) is made from toasted sesame seeds and has a very strong flavor. Dried but untoasted sesame seeds are popular in the Near East and occur in the Jordanian spice mixture zahtar (see sumac) and in the Egyptian dukka (see thyme). All over Western Asia, tahini, a paste made from ground dried sesame seeds, is popular and used to thicken and flavor sauces and gravies. Hummus, a bread spread popular in Israel and in the Lebanon, is made from cooked chickpeas, tahini, olive oil, a hint of lemon juice and fresh parsley. Sesame seeds are quite common in Mexican cookery and appear in one of the country's most famous creations: mole rojo or mole poblano, a sophisticated sauce that is usually served to baked turkey.
See also paprika about mole in general and Mexican pepper-leaf about green mole, mole verde. What makes mole Poblano so special is the large number of ingredients that lead to an unsurpassed rich flavor: chicken stock, broiled tomatoes and tomatillos, raisins, three different kinds of paprika (the "holy trinity" of ancho, mulato and pasilla), a handful of tropical spices (cloves, allspice, cinnamon, nutmeg and black pepper), sesame seeds and almonds are combined with a most unusual ingredient, unsweetened chocolate or, even better, toasted cocoa beans. After a long simmering period, the sauce is refried in lard which makes its flavor even more deep and unforgettable. Some Korean cookbooks refer to a flavoring called "wild sesame" (tul-kae). This name, however, does not refer to any sesame variety, but means perilla, a different plant with fragrant leaves.