Flavonoids

At one time a mixture of flavonoids was shown to decrease capillary permeability and fragility in human beings and was named vitamin P, but later, 1950, when it was found that they are not dietary essentials, the name was dropped.

More recently there has been epidemiological evidence from observations in population groups with a high intake of fruits and vegetables that flavonoids may have a role in protection against some forms of cancer. Some are antioxidants and may help to prevent atherosclerosis; others have weak oestrogen activity (phytoestrogens) and have been associated with lower incidence of breast, uterus and prostate cancer.

Total dietary intake is around 1g per day (650 mg when calculated as aglycones), a large part of which comes from tea, red wine, berries and onions. flavonols Alternative name for flavonoids. flavoproteins Enzymes that contain the vitamin riboflavin, or a derivative such as flavin adenine dinucleotide or riboflavin phosphate, as the prosthetic group. Mainly involved in oxidation reactions in metabolism. flavour See taste; organoleptic.

flavour enhancer A substance that enhances or potentiates the flavours of other substances without itself imparting any characteristic flavour of its own, e.g. monosodium glutamate, ribotide, as well as small quantities of sugar, salt and vinegar.

flavour potentiator See flavour enhancer. flavour profile A method of judging the flavour of foods by examination of a list of the separate factors into which the flavour can be analysed, the so-called character notes. flavour scalping The adsorption of food flavours by packaging materials; may result in undesirable loss of flavour, or may be used to remove unwanted flavours in storage.

See also packaging, active. flavours, biogenetic Flavours naturally present in a food. flavours, synthetic Mostly mixtures of esters, e.g. banana oil is ethyl butyrate and amyl acetate; apple oil is ethyl butyrate, ethyl valerianate, ethyl salicylate, amyl butyrate, glycerol, chloroform and alcohol; pineapple oil is ethyl and amyl butyrates, acetalde-hyde, chloroform, glycerol, alcohol. flavours, thermogenetic Flavours formed by heat treatment during food processing and cooking. Flavr SavrTM The first genetically modified tomato; approved by the US Food and Drug Administration in 1994, but not a commercial success.

flaxseed Seeds of Linum usitatissimum; also called linseed. Grown mainly as an oilseed (and for the fibre for textile use), but the seeds are also a rich source of phytoestrogens.

Composition/100g: water 8.8g, 2060kJ (492kcal), protein 19.5 g, fat 34g (of which 10% saturated, 21% mono-unsaturated, 69% polyunsaturated), carbohydrate 34.3 g (1g sugars), fibre 27.9 g, ash 3.5g, Ca 199mg, Fe 6.2mg, Mg 362mg, P 498mg, K 681 mg, Na 34mg, Zn 4.2mg, Cu 1mg, Mn 3.3mg, Se 5.5|g, 651 |g carotenoids, vitamin E 0.3 mg, B1 0.17mg, B2 0.16 mg, niacin 1.4mg, B6 0.93 mg, folate 278|g, pantothenate 1.5mg, C 1mg. A 10g serving is a source of Mg, Mn, folate. flea seed See psyllium.

fleishig Jewish term for dishes containing meat, which cannot be served with or before milk dishes.

See also milchig; pareve. flint corn See maize. flippers See swells.

floridean starch A branched polysaccharide of glucose obtained from red algae (Florideae spp.). florigens See phytochromes.

flounder Small flatfish, Platichthys spp., also called fluke. flour Most commonly refers to ground wheat, although also used for other cereals and applied to powdered dried matter such as fish flour, potato flour, etc.

See also bread; flour, extraction rate. flour, ageing and bleaching See ageing.

flour, agglomerated A dispersible form, easily wetted, produced by agglomerating the fine particles in steam; particles are greater than 100 |im in diameter, so the flour is dust-free. flour, air classified Sieving cannot separate particles smaller than 80 |im, and for production of flour with more precisely defined particle size it is subjected to centrifugation against an air current.

flour enrichment The addition of vitamins and minerals to flour, to contain not less than: (UK) vitamin B1 0.24mg, niacin 1.6 mg, iron 1.65mg, calcium 120mg/100g; (USA) vitamin B1 0.44-0.56mg, vitamin B2 0.2-0.33 mg, niacin 3.6-4.4mg, folic acid 140|g, iron 2.9-3.7mg/100g; calcium not specified. flour, enzyme inactivated Flour in which the enzyme a-AMYLASE has been inactivated by heat to prevent degradation when the flour is used as a thickening agent in gravies, soups, etc. flour, extraction rate The yield of flour obtained from wheat in the milling process. 100% extraction (or straight-run flour) is wholemeal flour containing all of the grain; lower extraction rates are the whiter flours from which progressively more of the bran and germ (and thus B vitamins and iron) have been removed, down to a figure of 72% extraction, which is normal white flour. 'Patent' flours are of lower extraction rate, 30-50%, and so comprise mostly the endosperm of the grain.

Wholemeal, composition/100g: water 10.3g, 1419kJ (339kcal), protein 13.7g, fat 1.9g (of which 23% saturated, 15% mono-unsaturated, 62% polyunsaturated), carbohydrate 72.6g (0.4g sugars), fibre 12.2g, ash 1.6g, Ca 34mg, Fe 3.9mg, Mg 138mg, P 346mg, K 405mg, Na 5mg, Zn 2.9mg, Cu 0.4mg, Mn 3.8mg, Se 70.7 |g, 225 |g carotenoids, E 0.8 mg, K 1.9 mg, B1 0.45 mg, B2 0.22mg, niacin 6.4 mg, B6 0.34mg, folate 44 |g, pantothenate 1mg.

White, composition/100g: water 11.9g, 1524kJ (364kcal), protein 10.3 g, fat 1g, carbohydrate 76.3 g (0.3 g sugars), fibre 2.7 g, ash 0.5 g, Ca 15 mg, Fe 4.6 mg, Mg 22 mg, P 108 mg, K 107mg, Na 2mg, Zn 0.7mg, Cu 0.1 mg, Mn 0.7mg, Se 33.9|g, 18 |g carotenoids, E 0.1 mg, K 0.3 mg, B1 0.79mg, B2 0.49mg, niacin 5.9mg, B6 0.04mg, folate 183 |g (if enriched), pantothenate 0.4mg.

See also bread.

flour, high-ratio Flour of very fine, uniform particle size, treated with chlorine to reduce the gluten strength. Used for making cakes, since it is possible to add up to 140 parts sugar to 100 parts of this flour, whereas only half this quantity of sugar can be incorporated into ordinary flour. See flour strength. flour improvers See ageing. flour, national See flour, wheatmeal. flour, patent See flour, extraction rate.

flour, self-raising Wheat flour to which baking powder has been added to produce carbon dioxide in the presence of water and heat; the dough is thus aerated without prolonged fermentation. Usually 'weaker' flours are used (see flour strength). Legally, self-raising flour must contain not less than 0.4% available carbon dioxide.

flour strength A property of the flour proteins enabling the dough to retain gas during fermentation to give a 'bold' loaf. 'Strong' flour is higher in protein, has greater elasticity and resistance to extension, and greater ability to absorb water. A 'weak' flour gives a loaf that lacks volume.

See also extensometer; farinograph. flour, wheatmeal Name given to 85% extraction flour (see flour, extraction rate) when introduced in the UK in February 1941; later called national flour. The term has been obsolete, and replaced by 'brown', since 1956. flour, wholemeal Flour made from the entire grain of wheat, i.e.

100% extraction rate (see flour, extraction rate). flow, streamline (or laminar) Flow of liquids in layers without significant mixing between layers. fluence Energy imparted to the surface of a material by light. fluid balance See water balance.

fluid bed dryer A bed of solid particles supported on a cushion of hot air jets (fluidised); the material may be conveyed this way, while being dried. The method achieves mixing without mechanical damage; applied to cereals, tableting granules, salt, coffee and dried vegetables. fluke (1) Small flatfish, Platichthys spp., also called flounder.

(2) Parasitic flatworms of the order Trematoda.

flummery Old English pudding made by boiling down the water from soaked oatmeal until it becomes thick and gelatinous. Similar to frumenty. Dutch flummery is made with gelatine or isinglass and egg yolk; Spanish flummery with cream, rice flour and cinnamon.

Fluon See PTFE.

fluorescence The ability to absorb light at one wavelength and emit at another within 10-100 ns.

See also fluorimetry.

fluorescence immunoassay Sensitive and specific analytical technique for determination of analytes present at very low concentrations in biological samples; the antibody is labelled with a substrate that yields a fluorescent product, but in such a way that it does not act as a substrate for the enzyme when the antigen (analyte) is bound. Therefore only free antibody will yield the fluorescent product when the enzyme is added. Unlike radioimmunoassay, does not require separation of bound and free antigen.

See also elisa.

fluoridation The addition of fluoride to drinking water.

fluoride The ion of the element fluorine. Although it occurs in small amounts in plants and animals, and has effects on the formation of dental enamel and bones, it is not considered to be a dietary essential and no deficiency signs are known.

Drinking water containing about 1 part per million of fluoride protects teeth from decay, and in some areas fluoride is added to drinking water to achieve this level. Naturally, the fluoride content of water ranges between 0.05 and 14ppm.

Water containing more than about 12ppm fluoride can lead to chalky white patches on the surface of the teeth, known as mottled enamel. At higher levels there is strong brown mottling of the teeth and inappropriate deposition of fluoride in bones, fluorosis.

fluorimetry (fluorometry) Sensitive and relatively specific analytical technique dependent on emission of light more or less immediately (within 10-100 ns) after absorption of light by a compound in solution. Both the exciting and emitted wavelengths are characteristic of the analyte, and the intensity of fluorescence is proportional to the concentration of analyte present.

fluorodinitrobenzene (FDNB, dinitrofluorobenzene) Reacts with free amino groups; commonly used to determine free e-amino groups of lysine (and hence available lysine) in proteins.

fluorosis Damage to teeth (brown mottling of the enamel) and bones caused by an excessive intake of fluoride.

fluoxetine An antidepressant acting to stimulate serotoninergic activity (a sEROTONiN-specific reuptake inhibitor); also has anorectic activity, and is used in treatment of obesity and bulimia nervosa. Trade name Prozac. FMN See flavin mononucleotide.

FNIC Food and Nutrition Information Center, located at the National Agricultural Library, part of the US Department of Agriculture; web site http://www.nal.usda.gov/fnic/. FOAD Fetal origins of adult disease, see epigenetics; programming.

foam Colloidal suspension (see colloid) of gas bubbles in a liquid or semi-liquid phase. Most so-called aerosol foams (e.g. whipped cream) are correctly foams, since an aerosol is a colloidal suspension of liquid droplets in a gas phase. Formation of foams can be a problem in manufacturing processes, and can be prevented by use of antifoaming agents or mechanical means of eliminating the foam, such as heating, centrifuging, spraying or ultrasonic vibration. foam cells Macrophages that have accumulated very large amounts of cholesterol and other lipids as a result of uptake of (chemically modified) low-density lipoprotein. They infiltrate the arterial wall and lead to the development of fatty streaks, and eventually atherosclerosis. foam-mat drying A method of drying food. The liquid concentrate is whipped to a foam with the aid of a foaming agent, spread on a tray and dried in a stream of warm air. It can be reconstituted very rapidly with water because of the fine structure of the foam. foie gras (French, fat liver). The liver of goose or duck that has been force fed and fattened; may be cooked whole or used as the basis of pâté de foie gras, the most highly prized of the pâtés. folacin, folate See folic acid. folate equivalents See dietary folate equivalents. folic acid A vitamin that functions as a carrier of one-carbon units in a variety of metabolic reactions. Essential for the synthesis of purines and pyrimidines (and so for nucleic acid synthesis and hence cell division); the principal deficiency disease is mega-loblastic anaemia, due to failure of the normal maturation of red blood cells, with release into the circulation of immature precursors of red blood cells.

Occurs in foods as a variety of one-carbon substituted derivatives, and with a varying number of y-glutamyl residues. Mixed food folate is about 50% as biologically active as synthetic tetrahydrofolic acid used in enrichment and supplements.

Supplements of 400 |j.g free folic acid/day begun before conception reduce the incidence of spina bifida and other neural tube defects in babies; it is unlikely that ordinary foods could provide this much folate, so supplements are advised. In many countries flour is fortified with folate.

See also dietary folate equivalents; dump suppression test; figlu test; homocysteine; methylene tetrahydrofolate reductase.

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