Ch.8: Flavorings from Plants

Chapter 8 of the book "On Food and Cooking: The Science and Lore of the Kitchen" by Harold McGee (1984) The Nature of Flavor and Flavorings Chemistry of Herbs and Spices Handling and Storing Herbs and Spices Cooking with Herbs and Spices A Survey of Common Herbs A Survey of Temperate-Climate Spices A Survey of Tropical Spices Tea and Coffee Wood Smoke and Charred Wood

339 flashcards · Other · by lakesare

Part of Public › Books › On Food and Cooking (Harold McGee) · 16 courses

1. [Flavorings from Plants] What is the difference between an herb and a spice?

   An herb is a leaf, fresh or dried. A spice is a dry piece of seed, bark or root. Both are used in tiny amounts and have practically no nutritional value.Example: basil and parsley are herbs; cinnamon (bark), pepper (seed) and ginger (root) are spices.

2. [Flavorings from Plants] Why does wood smoke taste a little like spices?

   Intense heat breaks wood down into some of the same aroma compounds that spices contain. Example: vanillin, the aroma of vanilla, forms when wood burns.

3. [Flavorings from Plants] How did the spice trade lead Europeans to the Americas?

   Portugal and Spain sought a sea route to Asia's spices, around the Turks; Columbus sailed west in 1492. The Turks controlled the land routes and prices. The Americas turned out to be the home of chillis and vanilla.

4. [The Nature of Flavor and Flavorings] Flavor combines taste and smell. Which of the two makes up most of what we experience as flavor?

   Smell. There are only about five tastes (sweet, sour, salty, bitter, savory) but many thousands of smells.Example: with a blocked nose, an apple and a pear are hard to tell apart.

5. [The Nature of Flavor and Flavorings] Herbs and spices mainly add aroma. Which ones add something else?

   The hot ones (chilli, black pepper, ginger, mustard): they irritate nerves in the mouth.

6. [The Nature of Flavor and Flavorings] What does it mean that an aroma chemical is volatile?

   Its molecules are light enough to evaporate from the food into the air, so they can reach the nose.

7. [The Nature of Flavor and Flavorings] Why does heating an herb or spice release more of its aroma?

   Heat makes the aroma molecules evaporate faster.

8. [The Nature of Flavor and Flavorings] What does the word perfume literally mean?

   "Through fire" (Latin). Aromatic plants were burned in sacrificial fires and as incense.

9. [The Nature of Flavor and Flavorings] Why can foods smell of wood, soil, dry grass, flowers or the seashore?

   Smell evolved to tell an animal about its whole surroundings, not only its food. So we can detect smells of the ground, plants, predators and mates, and foods with such notes remind us of places.

10. [The Nature of Flavor and Flavorings] Why might smells bring back memories so strongly?

    Animals learn by linking sensations, smells included, with the situations they occurred in.

11. [The Nature of Flavor and Flavorings] For early human hunter-gatherers, what did sweet, bitter and foul-smelling foods signal?

    Sweet: nourishing sugar. Bitter: toxic alkaloids. Foul: dangerous decay. Their diet probably included several hundred kinds of food.

12. [The Nature of Flavor and Flavorings] How did farming change the variety of the human diet?

    A varied diet became a monotonous one, based on a few bland grains. Wheat, barley, rice and corn were reliable sources of energy and protein. Herbs and spices brought flavor and variety back.

13. [The Nature of Flavor and Flavorings] What do the flavor chemicals of herbs and spices do for the plants that make them?

    They defend the plant: they make it unpleasant to animals and microbes. They are released when the plant is chewed. Chewed on their own, most herbs and spices are harsh, irritating or numbing. Pure oregano and thyme oils are sold with warnings that they damage skin and lungs.

14. [The Nature of Flavor and Flavorings] What does a plant gain from its defensive chemicals being volatile (evaporating into the air)?

    They act at a distance, and their smell warns animals to stay away.

15. [The Nature of Flavor and Flavorings] Herb and spice chemicals are irritating plant defenses. Why are they pleasant in food?

    Dilution: a few milligrams spread through a pound of food stimulate without overwhelming. Example: a whole peppercorn bitten alone overwhelms; the same chemicals spread through a dish add flavors that grains and meats lack.

16. [Chemistry of Herbs and Spices] Why is the flavor of an herb or spice called its essential oil?

    Its aroma chemicals resemble fats, so they dissolve better in oil than in water. That is why cooks extract flavors with oil rather than water.

17. [Chemistry of Herbs and Spices] Why do vinegar and alcohol extract more aroma from herbs than plain water does?

    Alcohol and acetic acid are small chemical relatives of fats, so they help dissolve the fat-like aromas.

18. [Chemistry of Herbs and Spices] Where in the plant do herbs and spices keep their aroma chemicals?

    In special storage cells, glands or channels, apart from the working cells. The defensive chemicals would also damage the plant's own cells. In herbs the glands are often on the leaf surface.

19. [Chemistry of Herbs and Spices] How much of a dry spice's weight is aroma oil, compared with an herb?

    Spices: often 5 to 10%, up to 15%. Herbs: around 1%. Fresh herbs contain much more water; dried herbs have lost aroma chemicals in drying.

20. [Chemistry of Herbs and Spices] Is the flavor of a single herb or spice due to one compound?

    No: always to a mixture of several aroma compounds. Sometimes one dominates (clove, cinnamon, anise, thyme). A mixed flavor lets a spice link different ingredients of a dish.Example: coriander seed smells of both flowers and lemon.

21. [Chemistry of Herbs and Spices] In perfumery, what are the top notes, mid-notes and bottom notes of an aroma?

    Top notes Noticed first, light, quick to fade. Mid-notes The main flavors. Bottom notes Slow to develop, and long-lasting.

22. [Chemistry of Herbs and Spices] What is the basic building block of the terpenes, a big family of plant aroma molecules?

    A zigzag chain of five carbon atoms. Plants join and modify these units into tens of thousands of molecules. Limonene (citrus), menthol (mint), myrcene (resinous); dots are carbon atoms.

23. [Chemistry of Herbs and Spices] What kinds of smell do terpenes typically give herbs and spices?

    Pine, citrus, floral and leafy "fresh" notes. Terpene smells are often rather generic.

24. [Chemistry of Herbs and Spices] Why do the fresh, light notes of an herb vanish with even brief cooking?

    They come from terpenes, which evaporate and react very easily. To bring them back, add a little fresh herb just before serving.

25. [Chemistry of Herbs and Spices] What is the basic structure of a phenolic compound?

    A ring of six carbon atoms carrying at least one OH group. OH: an oxygen-hydrogen pair, a fragment of a water molecule. Linked rings give polyphenolics such as anthocyanin pigments. Eugenol (clove), cinnamaldehyde (cinnamon), vanillin (vanilla).

26. [Chemistry of Herbs and Spices] How do phenolic aromas (clove, cinnamon, vanilla) differ from terpene aromas?

    They are more distinctive, and they last longer in food and in the mouth. The OH group makes phenolics somewhat more water-soluble. The burning compounds of chilli, black pepper and ginger are also built on a phenolic base.

27. [Chemistry of Herbs and Spices] Which aromas do these terpenes give?

    Cineole Eucalyptus. Geraniol Roses. Limonene, citral Citrus fruits. Menthol Peppermint. Pinenes Pine needles. Linalool Lily of the valley.

28. [Chemistry of Herbs and Spices] Which aromas do these phenolic compounds give?

    Anethole Anise. Carvacrol Oregano. Cinnamaldehyde Cinnamon. Estragole Tarragon. Eugenol Clove. Thymol Thyme. Vanillin Vanilla.

29. [Chemistry of Herbs and Spices] L-carvone and D-carvone are mirror-image forms of one molecule. What does each smell of?

    L-carvone: spearmint. D-carvone: caraway.

30. [Chemistry of Herbs and Spices] What is pungency (the "heat" of chilli or mustard)?

    Neither a taste nor a smell, but an irritation close to pain. Pungent spices: chilli, black pepper, ginger, mustard, horseradish, wasabi.

31. [Chemistry of Herbs and Spices] Which are the two most popular spices in the world?

    Chilli and black pepper, both pungent.

32. [Chemistry of Herbs and Spices] When do the pungent compounds of mustard, horseradish and wasabi form?

    Only when the plant's cells are damaged, e.g. by grating or chewing. These compounds are called thiocyanates.

33. [Chemistry of Herbs and Spices] Why does wasabi or mustard sting the nose?

    Its pungent compounds are small, light molecules that evaporate easily into the nose. Thiocyanates: 12 to 24 atoms. In the nose they stimulate pain-sensing nerve endings.

34. [Chemistry of Herbs and Spices] Why does the burn of chilli and black pepper stay in the mouth?

    Their pungent compounds are large molecules, so they barely evaporate. Capsaicin and piperine (alkyl-amides): 40 to 50 atoms. Ginger and Sichuan pepper owe their pungency to the same family. Capsaicin (chilli) and piperine (black pepper).

35. [Chemistry of Herbs and Spices] How does capsaicin, the burning compound of chilli, cause pain?

    It makes pain-sensing nerves oversensitive, so ordinary sensations register as burning. It binds to receptors on those nerves. Black pepper's piperine and mustard's compounds seem to act in a similar way.

36. [Chemistry of Herbs and Spices] Capsaicin (chilli) and piperine (black pepper): how many times more pungent is capsaicin?

    150 to 300 times. Gingerol (fresh ginger) is about as pungent as piperine. A spice's actual heat also depends on how much of the compound it contains.

37. [Chemistry of Herbs and Spices] What happens to the pungent compound of ginger in old ginger, and in cooked ginger?

    Old ginger: it becomes stronger (shogaol). Cooked ginger: it becomes milder (zingerone). Relative to black pepper's piperine at 1: fresh gingerol 0.8, shogaol 1.5, zingerone 0.5.

38. [Chemistry of Herbs and Spices] Why might people enjoy the pain of chilli?

    Safe thrill, like a rollercoaster ride; and the brain releases its own painkillers. Both explanations were proposed by the psychologist Paul Rozin. The painkillers leave a pleasant glow when the burning fades.

39. [Chemistry of Herbs and Spices] Besides burning, what does chilli or pepper do to the mouth?

    It makes the mouth more sensitive to touch, temperature, salt, acid and fizz. The irritation causes a temporary inflammation. Example: in Chinese hot and sour soup, the pepper makes the sourness and saltiness stronger; even breathing in feels cool.

40. [Chemistry of Herbs and Spices] What does strong pungency do to our perception of other tastes and aromas?

    It dulls them, partly by taking up the brain's attention.

41. [Chemistry of Herbs and Spices] Why can regular chilli eaters handle hotter dishes than occasional ones?

    Eating pungent compounds makes us less sensitive to them for 2 to 4 days.

42. [Chemistry of Herbs and Spices] Which three helpful health effects do herbs and spices tend to have?

    Antioxidant Mainly the phenolics: they protect DNA and other body materials, and slow flavor deterioration in foods. Example: some of the strongest are oregano, bay leaf, dill, rosemary and turmeric. Anticancer Mainly the terpenes: they reduce the body's production of DNA-damaging molecules and help control tumor growth. Anti-inflammatory Some phenolics and terpenes calm the body's overreaction to cell damage, which contributes to heart disease and cancer. Whether eating herbs and spices actual…

43. [Chemistry of Herbs and Spices] Do spices make food safer from food-poisoning microbes?

    Mostly not: many spices carry millions of microbes per pinch. A few (garlic, cinnamon, cloves, oregano, thyme) do kill microbes fairly well. Black pepper and other spices dried for days in the tropics may carry Salmonella and other germs, so they are fumigated, steamed or irradiated.

44. [Handling and Storing Herbs and Spices] What spoils the aroma of stored herbs and spices?

    Evaporation, oxygen, moisture, heat and light.

45. [Handling and Storing Herbs and Spices] What is the best way to store dried herbs and spices?

    In closed, opaque glass jars in the freezer.

46. [Handling and Storing Herbs and Spices] Why should a jar of frozen spices warm to room temperature before it is opened?

    Otherwise moisture from the air condenses on the cold spices.

47. [Handling and Storing Herbs and Spices] At room temperature, how long do whole and ground spices keep their aroma?

    Whole: about a year. Ground: a few months. Fine particles have a large surface and lose aroma to the air fast; whole spices keep it sealed inside intact cells.

48. [Handling and Storing Herbs and Spices] Why should fresh herbs be refrigerated in a partly open bag rather than a closed one?

    Cut stems give off ethylene gas, which would build up in a closed bag and speed decay.

49. [Handling and Storing Herbs and Spices] Why are fresh herbs wrapped in paper or cloth before refrigerating them?

    The wrapping soaks up moisture; on wet leaves microbes grow fast.

50. [Handling and Storing Herbs and Spices] Which two common fresh herbs should not be refrigerated?

    Basil and perilla (shiso). They come from warm climates and are damaged by the cold. Keep them at room temperature with their stems in water.

51. [Handling and Storing Herbs and Spices] What happens to fresh herbs that are frozen?

    The flavor keeps well, but the leaves turn dark and limp when thawed. Ice crystals damage the tissue.

52. [Handling and Storing Herbs and Spices] Why does covering fresh herbs with oil preserve their flavor?

    The oil keeps oxygen away from them. It works for a few weeks; after that much of the flavor has moved into the oil.

53. [Handling and Storing Herbs and Spices] Why must fresh herbs kept under oil be refrigerated?

    Without oxygen, botulism bacteria can grow; the cold stops them.

54. [Handling and Storing Herbs and Spices] Why do most herbs lose their flavor when dried?

    Many aroma chemicals evaporate more easily than water, so they leave along with it. Fresh herbs can be over 90% water. Many dried herbs therefore have a generic, hay-like aroma.

55. [Handling and Storing Herbs and Spices] Which herbs keep their aroma well when dried, and why?

    Oregano, thyme, rosemary and bay: they come from hot, dry places, so their aromas withstand drying.

56. [Handling and Storing Herbs and Spices] Which way of drying herbs at home keeps the most flavor?

    Air-drying in the shade over a few days. A low oven or dehydrator keeps less, because it is hotter. Sun-drying keeps the least: heat plus light damage the aromas.

57. [Handling and Storing Herbs and Spices] Why does a microwave oven dry small amounts of herbs fairly well?

    Microwaves heat the water but hardly the oils, so the water boils off within seconds. The herbs dry in a few minutes, with smaller flavor losses than in an ordinary oven.

58. [Cooking with Herbs and Spices] What share of a dish's weight do herbs and spices usually make up?

    1% or less. Exceptions: pesto and some sauces are made largely of herbs.

59. [Cooking with Herbs and Spices] How does grinding a spice finer change how it flavors a dish?

    Finer particles have more surface, so the flavor passes into the dish faster.

60. [Cooking with Herbs and Spices] When are whole spices or coarse pieces better than finely ground ones?

    In long-cooked dishes and in pickles. In long cooking, slow release keeps the flavor fresher, since released aromas react and change. In pickles, whole spices don't cloud the liquid.

61. [Cooking with Herbs and Spices] When should vanilla extract or another flavor extract go into a dish?

    Near the end of cooking. Its aromas are already dissolved and spread at once, so cooking can only change or evaporate them.

62. [Cooking with Herbs and Spices] Why chill a spice and its grinder before grinding?

    Grinding makes heat, which drives off aromas; cold keeps them in.

63. [Cooking with Herbs and Spices] What is the best tool for cutting fresh herbs while keeping their flavor fresh?

    A sharp knife: it damages only the cells at the cut edges. A dull knife crushes and bruises the leaves, which can turn brown-black. A food processor beats in air, and oxygen alters the aroma. A mortar crushes but adds little air.

64. [Cooking with Herbs and Spices] Can exposure to air ever improve ground spices?

    Yes: ground spice blends mellow when aged for days or weeks.

65. [Cooking with Herbs and Spices] Fat and alcohol both extract aromas well. How do they differ as we eat?

    Fat holds on to aromas and releases them slowly; alcohol evaporates and releases them fast.

66. [Cooking with Herbs and Spices] How does steaming food over herbs flavor it?

    Aroma molecules rise with the steam and condense on the cooler food.

67. [Cooking with Herbs and Spices] Why do marinades and rubs flavor little more than the surface of meat?

    Most aroma molecules dissolve in fat, and meat is 75% water. A salty marinade helps a little: it loosens the meat tissue so slightly water-soluble aromas get in.

68. [Cooking with Herbs and Spices] How can you get marinade flavor deep into a piece of meat?

    Inject small amounts of it in many places with a cooking syringe.

69. [Cooking with Herbs and Spices] Besides flavor, what does a crust of herbs and spices do for roasted or grilled meat?

    It shields the meat from the direct heat, so the outside stays moister. Some oil in the coating makes the crust fry instead of just drying out.

70. [Cooking with Herbs and Spices] Why bruise an herb before infusing it in oil, vinegar or syrup?

    Damaged cells let the liquid in and the aromas out. Flowers can flavor a syrup in under an hour; leaves and seeds take weeks.

71. [Cooking with Herbs and Spices] Why heat the oil, vinegar or syrup before infusing an herb in it?

    To kill bacteria, and to help the liquid get into the herb. The liquid is then cooled, so the heat does not change the flavor.

72. [Cooking with Herbs and Spices] Why are homemade herb-infused oils a botulism risk?

    Oil shuts out air, and botulism spores sprout without air. The spores survive brief boiling. Garlic gives the bacteria enough nutrients. Make and keep infused oils in the refrigerator. Alcohol, vinegar and sugar syrup infusions are safe: they stop bacteria from growing.

73. [Cooking with Herbs and Spices] Why do cheap synthetic flavorings (e.g. imitation vanilla) taste flat and harsh?

    They contain only one or a few chemicals that copy the main note. The real herb or spice contains many aroma compounds. The synthetic version's advantage is its low price.

74. [Cooking with Herbs and Spices] What happens to the aroma of a spice during long cooking?

    Its sharp notes soften, and the overall flavor becomes more complex. The aroma compounds react with other ingredients, oxygen and heat.

75. [Cooking with Herbs and Spices] What does toasting whole cumin or coriander seeds add to their flavor?

    Roasted, nutty notes from browning reactions. The seeds' sugars and amino acids react to form pyrazines.

76. [Cooking with Herbs and Spices] Why do Indian cooks fry ground spices in oil or ghee before adding the other ingredients?

    The heat makes the spices' aromas react with each other, so they blend into one flavor. Example: turmeric, cumin and coriander. Dry-toasting whole seeds instead mellows each spice but keeps its own identity.

77. [Cooking with Herbs and Spices] How do Indian cooks perfume a finished dish with spice smoke?

    They set a live coal inside the covered pot, sprinkle ghee and spices on it, and let the smoke fill the pot. The coal sits in a small bowl or hollowed onion. The technique is called dhungar.

78. [Cooking with Herbs and Spices] Why does a fresh herb puree such as pesto hold its oil in a stable emulsion?

    The herb's many cell walls and membranes coat the oil droplets. The puree is thick because the herb's water is already bound to its cell materials.

79. [Cooking with Herbs and Spices] How do chillis thicken sauces?

    Their pectin-rich cell walls cook down into a smooth, thick puree. Example: Mexican sauces made from rehydrated dried chillis; Hungarian paprikash thickened with paprika.

80. [Cooking with Herbs and Spices] How does each of these spices thicken a dish: coriander seed, ginger, filé powder, fenugreek?

    Ground coriander Its thick, dry husk absorbs a lot of water. Ginger (also turmeric, galangal) Starchy roots: during long simmering the starch dissolves into long tangled chains. Filé powder Ground dried sassafras leaves; thickens Louisiana gumbo. Fenugreek Soaked ground seeds release a slimy carbohydrate.

81. [A Survey of Common Herbs] Which two plant families give most of the herbs of traditional European cooking?

    The mint family and the carrot family. Mint family: basil, oregano, thyme, rosemary, sage. Carrot family: parsley, dill, fennel, coriander.

82. [A Survey of Common Herbs] When are herbs best harvested, and why?

    As the plants begin to flower, when they hold the most aroma oil.

83. [A Survey of Common Herbs] Why does the mint family give us more kitchen herbs than any other family?

    Harsh, dry homes made them strongly defended, with big oil glands and huge chemical variety. Each species makes many aromatics, and species interbreed readily. McGee: they are "both promiscuous chemists and promiscuous breeders".The oil glands sit on the leaf surface and can make up 10% of the leaf's weight. Oregano leaf: oil glands on the surface.

84. [A Survey of Common Herbs] Which basil leaves are most aromatic, young or old?

    Young leaves: they can hold up to five times more aroma compounds.

85. [A Survey of Common Herbs] What gives lavender its scent?

    Flowery linalool and linalyl acetate, plus eucalyptus-like cineole. Its name comes from the Latin for "wash".

86. [A Survey of Common Herbs] How does marjoram taste compared with oregano?

    Milder: fresh, green and floral, without oregano's sharp bite. Botanically, marjoram is a species of oregano.

87. [A Survey of Common Herbs] How is peppermint related to spearmint?

    Peppermint is an ancient cross of spearmint and watermint.

88. [A Survey of Common Herbs] Which compound makes peppermint taste cool, unlike spearmint?

    Menthol. Spearmint's aroma comes instead from L-carvone, with little or no menthol.

89. [A Survey of Common Herbs] How does menthol make the mouth feel cool?

    It triggers the nerves that sense cold, so they report a cooler mouth than it is. The mouth feels 7 to 13°F/4 to 7°C cooler.

90. [A Survey of Common Herbs] Why is peppermint usually not cooked?

    Its menthol breaks down quickly when heated.

91. [A Survey of Common Herbs] Which peppermint leaves taste more cooling, young or old?

    Old leaves: menthol builds up with age.

92. [A Survey of Common Herbs] What do hot, dry growing conditions do to peppermint?

    They turn its menthol into pulegone, a harsh compound that does not cool. Pulegone is the main aroma of pennyroyal.

93. [A Survey of Common Herbs] What gives oregano its sharp, penetrating taste?

    Carvacrol, a phenolic compound. The name comes from Greek for "joy of the mountains". In the US oregano became common with pizza after World War II.

94. [A Survey of Common Herbs] Why is Italian oregano milder than Greek oregano?

    It has less carvacrol, and more of the gentler thymol (the thyme compound).

95. [A Survey of Common Herbs] Is Mexican oregano a true oregano?

    No: it comes from a different plant family (the verbena family). It seems stronger, with 3 to 4% aroma oil in the dry leaf against about 1% in true oregano.

96. [A Survey of Common Herbs] Which compound gives perilla (shiso) its distinctive aroma?

    Perillaldehyde, a terpene: fatty, herbal, spicy. A red variety colors and flavors Japanese pickled plums (umeboshi).

97. [A Survey of Common Herbs] Why should garden sage be only an occasional flavoring?

    It is rich in thujone and camphor, which are toxic to the nervous system. Thujone gives sage its warm, penetrating note. The genus name Salvia comes from Latin for "health".

98. [A Survey of Common Herbs] Why is "rubbed" sage better than finely ground sage?

    Coarsely crumbled leaves lose their aroma more slowly.

99. [A Survey of Common Herbs] Why does savory taste like a mix of oregano and thyme?

    It contains both carvacrol (oregano's compound) and thymol (thyme's compound).

100. [A Survey of Common Herbs] Thymol (thyme) tastes gentler than carvacrol (oregano). Is it weaker against microbes?

     No: thymol is just as powerful chemically. So thyme oil is used as an antimicrobial in mouthwashes and skin creams.