Tài liệu Tự điển Food Science, Technology And Nutrition - Vần N doc

net dietary protein calories See net dietary protein–energy ratio.. net dietary protein–energy ratio NDpE A way of expressing the protein content of a diet or food taking into account bo

mycotoxins Compounds produced by filamentous fungi (and so exclude mushroom toxins) that may accumulate to harmful levels in foods without any adverse effect on the flavour or appearance of the food; many are acutely or chronically toxic or carcinogenic The most important are: aflatoxins (produced by

Aspergillus spp.), ochratoxins (Aspergillus and Penicillium spp.), monoliformin (Fusarium spp.), patulin (Aspergillus and Penicil-lium spp.) and ergot alkaloids formed by Claviceps purpurea

growing on rye

myenteron Muscle layers of the intestine, a layer of circular muscles inside a layer of longitudinal muscles, responsible for peristalsis

myocardial infarction Damage to heart muscle due to ischaemia (failure of the blood supply from the coronary arteries)

myofibril See muscle.

myoglobin haem-containing oxygen binding protein in muscle Responsible for the red colour of fresh meat, oxidised to brown metmyoglobin as meat ages, or on cooking When meat is cured

(see meat, curing) with nitrite, the myoglobin is converted to the

bright red nitrosomyoglobin

myo-inositol See inositol.

myosin The major protein of muscle, about 40% of the total A globulin, insoluble in water but soluble in salt solution

myristic acid A saturated fatty acid with 14 carbon atoms (C14:0)

myrosinase The enzyme (thioglycosidase, EC 3.2.3.1) in mustard seed and horseradish that hydrolyses myrosin or sinigrin to glucose and allyl isothiocyanate, the pungent principle

Mysore flour A blend of 75% tapioca and 25% peanut flour

mysost See gjetost.

myxoedema Severe hypothyroidism (underactivity of the thyroid

gland, see thyroid hormones) in adults; the name is derived from

puffiness of hands and face due to thickening of skin Signs include coarsening of the skin, intolerance of cold, weight gain and dull mental apathy, as well as reduced basal metabolic rate

myxoxanthin carotenoid pigment in algae with vitamin a activity

N

naartje Afrikaans; a small tangerine; see citrus fruit.

NAASO North American Association for the Study of Obesity, now called the Obesity Society; web site http://www.naaso.org/

NAD, NADP Nicotinamide adenine dinucleotide and nicoti-namide adenine dinucleotide phosphate, the coenzymes derived 324

from niacin Involved as hydrogen acceptors / donors in a wide variety of oxidation and reduction reactions

NAEL See no adverse effect level.

nalidixic acid Quinolone antibiotic used to treat intestinal (and urinary tract) infections

nam pla Thai; salted paste made from shrimps and small fish

nan Indian flat bread, an egg dough prepared with white flour and leavened with sodium bicarbonate, normally baked in a tandoor

(see tandoori).

nanofiltration A membrane process to separate particles with molecular weights from 300–1000 Da, using lower pressures than

reverse osmosis (see osmosis, reverse).

naphthoquinone The chemical ring structure of vitamin k; the various chemical forms of vitamin K can be referred to as sub-stituted naphthoquinones

naringenin See naringin.

naringin A glycoside (trihydroxyflavonone rhamnoglucoside) found in grapefruit, especially in the immature fruit Extremely bitter: dilutions of 1 part in 10 000 parts of water can be detected Sometimes found in canned grapefruit segments as tiny, white beads Hydrolysed to the aglycone, naringenin, which is not bitter

naseberry Alternative name for sapodilla

nashi See pear, nashi.

nasogastric tube Fine plastic tube inserted through the nose and thence into the stomach for enteral nutrition

nasturtium Both the leaves and seeds of Tropaeolum officinalis

can be eaten; they have a hot flavour The seeds can be pickled

as a substitute for capers, and the flowers can be used to deco-rate salads

nata Filipino; thick gelatinous film grown on the surface of coconut, sugarcane or fruit juice by fermentation with the acetic

acid bacterium Acetobacter aceti, which produces an

extracellu-lar cellulose polymer Eaten as a dessert

natamycin (or pimaricin) A polyene antifungal agent, from Strep-tomyces natalensis, used as a coating on the surface of cheeses to

prevent the growth of mould or yeast

national flour See flour, wheatmeal.

natriuretic Any compound that promotes excretion of sodium salts in the urine; most diuretics are natriuretics

natto Japanese; soya bean fermented using Bacillus natto.

Composition /100 g: water 55 g, 887 kJ (212 kcal), protein 17.7 g, fat 11 g (of which 16% saturated, 24% mono-unsaturated, 61% polyunsaturated), carbohydrate 14.4 g (3.6 g sugars), fibre 5.4 g, ash 1.9 g, Ca 217 mg, Fe 8.6 mg, Mg 115 mg, P 174 mg, K

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729 mg, Na 7 mg, Zn 3 mg, Cu 0.7 mg, Mn 1.5 mg, Se 8.8µg, vitamin

K 23.1 mg, B1 0.16 mg, B20.19 mg, B6 0.13 mg, folate 8µg, pan-tothenate 0.2 mg, C 13 mg

NatualTM Low cholesterol cheese, prepared by use of cyclodextrin

natural foods A term widely used but with little meaning and sometimes misleading since all foods come from natural sources

No legal definition seems possible but guidelines suggest the term should be applied only to single foods that have been sub-jected only to mild processing, i.e largely by physical methods such as heating, concentrating, freezing, etc., but not chemically

or ‘severely’ processed

natural water See water, mineral.

nature-identical Term applied to food additives, including vita-mins, that are synthesised in the laboratory and are identical to those that occur in nature

N balance (equilibrium) See nitrogen balance.

NCHS standards Tables of height and weight for age used as ref-erence values for the assessment of growth and nutritional status

of children, based on data collected by the US National Center for Health Statistics The most comprehensive such set of data, and used in most countries of the world

N conversion factor See nitrogen conversion factor.

NDGA See nordihydroguaiaretic acid.

NDpCal See net dietary protein–energy ratio.

neat’s foot Ox or calf’s foot used for making soups and jellies Now called cow heels Neat’s foot oil is obtained from the knuckle bones of cattle; used in leather working and for canning sardines

intestine; the human parasite is N americanus.

necrosis Death of cells or tissues in an unprogrammed manner,

in response to toxicity or ischaemia

See also apoptosis.

nectarine Smooth-skinned peach (Prunus persica var nectarina).

Composition /100 g: (edible portion 91%) water 87.6 g, 184 kJ (44 kcal), protein 1.1 g, fat 0.3 g, carbohydrate 10.6 g (7.9 g sugars), fibre 1.7 g, ash 0.5 g, Ca 6 mg, Fe 0.3 mg, Mg 9 mg, P 26 mg, K

201 mg, Zn 0.2 mg, Cu 0.1 mg, Mn 0.1 mg, vitamin A 17µg RE (378µg carotenoids), E 0.8mg, K 2.2mg, B10.03 mg, B20.03 mg, niacin 1.1 mg, B60.03 mg, folate 5µg, pantothenate 0.2mg, C 5mg

A 150 g serving (1 fruit) is a source of Cu, vitamin E, C

Neeld–Pearson reaction See carr–price reaction.

neep Scottish name for root vegetables; now used for turnip (and sometimes for swede in England)

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NEFA Non-esterified fatty acids.

negus Drink made from port or sherry with spices, sugar and hot water

NEL See no effect level.

nematode Any one of a large group of unsegmented worms; most are free-living, but some, including hookworms and pinworms, are intestinal parasites

neohesperidin dihydrochalcone (NEO-DHC) A non-nutritive sweetener, 1000 times as sweet as sucrose; formed by hydro-genation of the naturally occurring flavonoid neohesperidin

neomycin Broad spectrum aminoglycoside antibiotic isolated

from Streptomyces fradii that is poorly absorbed from the

gas-trointestinal tract and is used to treat persistent intestinal bac-terial infections

neonate Literally new-born, used to describe infants in the first four weeks of life

neotame Synthetic intense sweetener, 8000 times as sweet as

sucrose, N-[N-(3,3-dimethylbutyl)-l-α-aspartyl]-l-phenylalanine

1-methyl ester See also aspartame.

nephrocalcinosis Presence of calcium deposits in the kidneys; may result from vitamin d toxicity

neroli oil Prepared from blossoms of the bitter orange by steam distillation Yellowish oil with intense odour of orange blossom

net dietary protein calories See net dietary protein–energy

ratio

net dietary protein–energy ratio (NDpE) A way of expressing the protein content of a diet or food taking into account both the amount of protein (relative to total energy intake) and the protein quality It is protein energy multiplied by net protein utilisation divided by total energy If energy is expressed in kcal and the result expressed as a percentage, this is net dietary protein calories per cent, NDpCal%

See also net protein value.

net protein ratio (NPR), net protein utilisation (NPU) Measures

of protein quality

net protein value A way of expressing the amount and quality of the protein in a food; the product of net protein utilisation and protein content per cent

See also net dietary protein–energy ratio; protein quality

neural tube defect Congenital malformations of the spinal cord caused by failure of the closure of the neural tube in early embry-onic development (before day 28 of gestation) Supplements of folic acid (400µg/day) begun before conception reduce the risk significantly

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neuritis Inflammatory disease of peripheral nerves.

See also neuropathy.

neuropathy Any disease of peripheral nerves, usually causing weakness and numbness

See also neuritis.

neuropeptide Y A peptide neurotransmitter involved in the control of appetite and feeding behaviour, especially in response

to leptin

neutron activation analysis The nuclei of a number of elements will capture a neutron on exposure to a neutron beam, leading

to the formation of unstable (radioactive) isotopes which can then be measured by the radiation emitted as they decay Used for determination of whole body calcium, chlorine and nitrogen

new cocoyam See tannia.

New Zealand process Drying process for meat It is immersed in hot oil under vacuum when it dries to 3% moisture in about 4 h

NFE See nitrogen-free extract.

NFLEA US National Food Labelling and Education Act, 1993, the basis of nutrition labelling of foods and health claims that may be made

nham South-east Asian; semi-dry uncooked pork or beef sausage left to undergo lactic acid bacterial fermentation for 4–5 days

niacin (see p 329) A vitamin; one of the B complex without a

numerical designation Sometimes (incorrectly) referred to as vitamin B3, and formerly vitamin PP (pellagra preventative) Deficiency leads to pellagra, photosensitive dermatitis resem-bling severe sunburn, a depressive psychosis and intestinal dis-orders; fatal if untreated

Niacin is the generic descriptor for two compounds in foods that have the biological activity of the vitamin: nicotinic acid (pyridine carboxylic acid) and nicotinamide (the amide of nico-tinic acid) In the USA niacin is sometimes used specifically to mean nicotinic acid, and niacinamide for nicotinamide

The metabolic function of niacin is in the coenzymes NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), which act as intermediate hydrogen carriers in a wide variety of oxidation and reduction reactions In cereals niacin is largely present as niacytin, which

is not biologically available (see availability); therefore the

pre-formed niacin content of cereals is generally ignored when cal-culating intakes

See also niacin equivalents.

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niacinamide American name for nicotinamide, see niacin.

niacin equivalents Nicotinamide can be formed in the body from the amino acid tryptophan; on average 60 mg dietary tryptophan

is equivalent to 1 mg preformed niacin The total niacin content

of foods is generally expressed as mg niacin equivalents; the sum

of preformed niacin (excluding that in cereals, see niacytin) plus

one-sixtieth of the tryptophan

niacinogens Name given to protein–niacin complexes found in

cereals; see also niacytin.

niacin toxicity High doses of nicotinic acid have been used to treat hypercholesterolaemia; they can cause an acute flushing reaction, with vasodilatation and severe itching (nicotinamide does not have this effect, but is not useful for treatment of hyper-cholesterolaemia) Intakes of niacin above 500 mg/day (the ref-erence intake is 17 mg/day) can cause liver damage over a period

of months; the risk is greater with sustained release preparations

of niacin

niacytin The main form of niacin in cereals Nicotinic acid ester-ified as nicotinoyl-glucose in oligosaccharides and non-starch polysaccharides; susceptible to alkaline hydrolysis and partially susceptible to acid hydrolysis in the stomach However, because

of variable availability, it is conventional to exclude the niacin content of cereals from calculations of intake

See also niacinogens.

nib See chocolate.

nibbler Machine for comminution of dry foods using grating action rather than grinding as in mills

niceritol Penta-erythritol tetranicotinate, a derivative of niacin used as a hypolipidaemic agent

nickel A mineral (see mineral, ultratrace) known to be

essen-tial to experimental animals, although its function is not known There is no information on requirements Metallic nickel is used

as a catalyst in the hydrogenation of fats

nicotinamide (niacinamide) One of the vitamers of niacin

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NIACIN

nicotinamide adenine dinucleotide (phosphate) See nad.

nicotinate, sodium Sodium salt of nicotinic acid; has been used, among other purposes, to preserve the red colour in fresh and processed meats

nicotinic acid (see p 329) One of the vitamers of niacin.

NIDDK National Institute of Diabetes and Digestive and Kidney Diseases; web site http://www.niddk.nih.gov/

nigella Peppery seeds of the wild onion, Nigella sativa.

Nigerian berry See serendipity berry.

nigerseed Or nug, Guizotia abyssinica; grown in India and

Ethiopia as food crop

night blindness Nyctalopia Inability to see in dim light as a result

of vitamin a deficiency

See also dark adaptation; vision.

nim leaf Sweet nim, an aromatic Indian herb with an aroma resembling that of truffles

ninhydrin test For proteins and amino acids (actually for the amino group) Pink, purple or blue colour is developed on heating the amino acid or peptide with ninhydrin (triketohy-drindene hydrate)

nip The gap between rollers in a mill or a moulding/forming machine

nisatidine See histamine receptor antagonists.

nisin antibiotic isolated from lactic Streptococcus group N; inhibits some but not all Clostridia; not used clinically The only

antibiotic permitted in the UK to preserve specified foods It is naturally present in cheese, being produced by a number of strains of cheese starter organisms Useful to prolong storage life

of cheese, milk, cream, soups, canned fruits and vegetables, canned fish and milk puddings It also lowers the resistance of

many thermophilic bacteria (see thermophiles) to heat and so

permits a reduction in the time and/or temperature of heating when processing canned vegetables

nitrates The inorganic form of nitrogen used by plants; found in soils and included in inorganic fertiliser Nitrate is a natural con-stituent of crops in amounts sometimes depending on the content

in the soil Also found in drinking water as a result of excessive use of fertilisers Health problems can arise because within a day

or two of harvesting some crop nitrates are converted into nitrites which can react with the haemoglobin (especially fetal haemoglobin) to form methaemoglobin which cannot transport oxygen An upper limit of 45–50 mg nitrate/L drinking water has been recommended for infants Also used, together with nitrite,

for curing meat (see meat, curing).

See also nitrosamines.

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nitric oxide (NO) Synthesised in most mammalian cells by the action of nitric oxide synthetase (EC 1.14.13.39) on arginine It causes vasodilatation and inhibits platelet aggregation (and so has anticoagulant action), acting by cell surface receptors and intracellular guanylate cyclase (EC 4.6.1.2), leading to increased formation of cyclic GMP Before it was identified, NO was known

as the endothelium-derived relaxation factor

nitrites Found in many plant foods, since they are rapidly formed

by the reduction of naturally occurring nitrate Nitrite is the essential agent in preserving meat by pickling, since it inhibits

the growth of Clostridia; it also combines with the myoglobin of

meat to form the characteristic red nitrosomyoglobin

See also nitrosamines.

nitrogen A gas comprising about 80% of the atmosphere; in nutrition the term ‘nitrogen’ is used to refer to ammonium salts and nitrates utilised as plant fertilisers; proteins and amino acids

as animal nutrients; and urea and ammonium salts as excretory products

nitrogenase The enzyme (EC 1.18.6.1 or 1.19.6.1) in nitrogen-fixing micro-organisms that catalyses the reduction of N2 to ammonia Irreversibly inactivated by oxygen

See also leghaemoglobin.

nitrogen balance (N balance) The difference between the dietary intake of nitrogen (mainly protein) and its excretion (as urea and other waste products) Healthy adults excrete the same amount

as is ingested, and so are in nitrogen equilibrium During growth and tissue repair (convalescence) the body is in positive N balance, i.e ingestion is greater than loss and there is an increase

in the total body pool of nitrogen (protein) In fevers, fasting and

wasting diseases (see cachexia) the loss is greater than the intake

and the individual is in negative balance; there is a net loss of nitrogen from the body

nitrogen conversion factor Factor by which total nitrogen content

of a material (measured chemically, e.g by the kjeldahl deter-mination) is multiplied to determine the protein; depends on the amino acid composition of the proteins concerned Wheat and most cereals 5.8, rice 5.95, soya 5.7, most legumes and nuts 5.3, milk 6.38, other foods 6.25 Errors arise if part of the nitrogen is non-protein nitrogen In mixtures of proteins, as in dishes and diets, the factor of 6.25 is used Crude protein is defined as N × 6.25

nitrogen equilibrium See nitrogen balance.

nitrogen-free extract (NFE) In the analysis of foods and animal feedingstuffs, the fraction that contains the sugars and starches plus small amounts of other materials

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nitrogen, metabolic Nitrogen in the faeces derived from internal

or endogenous sources, as distinct from nitrogen-containing dietary sources (exogenous nitrogen) This nitrogen consists of unabsorbed digestive juices, mucus, shed intestinal mucosal cells and intestinal bacteria, and continues to be excreted on a protein-free diet

nitrogen trichloride See agene.

nitro-keg beer conditioned in kegs under nitrogen, to give a smoother, creamier beverage than traditional conditioning under carbon dioxide

nitrosamines N-Nitroso derivatives of amines Found in trace

amounts in mushrooms, fermented fish meal and smoked fish, and in pickled foods, where they are formed by reaction between nitrite and amines They cause cancer in experimental animals, but it is not known whether the small amounts in foods affect human beings They are also found in human gastric juice, possi-bly as a result of reaction between dietary amines and nitrites or nitrates

nitrosomyoglobin The red colour of cured meat, formed by the reaction of nitrite with myoglobin Fades in light to yellow-brown metmyoglobin

nitrous oxide N2O, a gas used as a propellant in pressurised containers, e.g to eject cream or salad dressing from containers

nivalenol Trichothecene mycotoxin produced when cereals are

infected with Fusarium spp.

nixtamal The paste produced by steeping maize in calcium hydroxide solution to make tortillas and tacos; the process is nixtamalisation

N-liteTM fat replacer made from starch

NMR Nuclear magnetic resonance

NO See nitric oxide.

no adverse effect level (NAEL) Highest dose or intake of a com-pound at which no adverse effect can be detected

See also ld50; minimum lethal dose

noble rot White grapes affected by the fungus Botrytis cinerea It

spoils the grapes if they are damaged by rain, but if they are ripe and healthy, and the weather is sunny, it causes them to shrivel and concentrates the sugar, so that top-quality sweet wines can

be made

See also wine classification, germany.

No Effect Level (NEL) With respect to food additives, the maximum dose of an additive that has no detectable adverse effects

See also acceptable daily intake.

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noggin Traditional measure of liquor = 1/4 pint (140 mL); also known as a quartern

N-oilTM fat replacer made from starch

nominal freezing time The time between the surface of the food reaching 0 °C and the thermal centre reaching 10 °C below the temperature of the first ice formation

non-essential amino acids Those amino acids that can be synthesised in the body and therefore are not dietary essentials

non-esterified fatty acids (NEFA) See fatty acids, free.

non-hygroscopic foods Foods that have a constant water vapour pressure at different moisture contents, and so do not take up moisture from the atmosphere

noni (Indian mulberry) Fruit of the south Pacific evergreen shrub

Morinda citrifolia, with an unpleasant odour; the juice is claimed

to have healing properties and to be beneficial in treatment of diabetes, heart disease and cancer

non-Newtonian fluid See shear rate.

non-nutritive sweeteners See sweeteners, intense.

non-saponified The water-insoluble material remaining in a fat or oil after saponification; mainly sterols, higher alcohols, hydro-carbons and pigments

non-starch polysaccharides (NSP) (see p 334) Those

polysac-charides (complex carbohydrates) found in foods other than

starches They are the major part of dietary fibre (see fibre,

dietary) and can be measured more precisely than total dietary fibre; include cellulose, pectins, glucans, gums, mucilages, inulin and chitin (and exclude lignin) The NSP in wheat, maize and rice are mainly insoluble and have a laxative effect, while those in oats, barley, rye and beans are mainly soluble and have a blood cholesterol-lowering effect In vegetables the pro-portions of soluble to insoluble are roughly equal but vary in fruits

noodles pasta made with flour from various grains (e.g rice, wheat, buckwheat, mung bean starch) and water; may have egg added

nopales Stems or pads of the prickly pear cactus (Opuntia

spp.)

Composition/100 g: (edible portion 96%) water 94.1 g, 67 kJ (16 kcal), protein 1.3 g, fat 0.1 g, carbohydrate 3.3 g (1.1 g sugars), fibre 2.2 g, ash 1.1 g, Ca 164 mg, Fe 0.6 mg, Mg 52 mg, P 16 mg, K

257 mg, Na 21 mg, Zn 0.3 mg, Cu 0.1 mg, Mn 0.5 mg, Se 0.7µg, vitamin A 23µg RE (298µg carotenoids), K 5.3mg, B10.01 mg,

B2 0.04 mg, niacin 0.4 mg, B60.07 mg, folate 3µg, pantothenate 0.2 mg, C 9 mg

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