Tài liệu Tự điển Food Science, Technology And Nutrition - Vần X,Y,Z doc

Most have no vitamin a activity.. Yellow colour on boiling with nitric acid, turns orange on adding ammonia.. xyloascorbic acid Term used for ascorbic acid vitamin c to distinguish from

work See energy.

wormseed See epazote.

wraplings See wuntun.

wuntun (wonton) Chinese; small dough parcels containing meat, boiled or deep fried Also known as chiao-tzu or wraplings.

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XangoldTM Natural source esters of the carotenoids xanthophyll and lutein.

xanthaemia See carotinaemia.

xanthan gum Complex polymer made by bacterial fermentation; stable to wide range of pH and temperatures; used as thickening agent to form gels, increase viscosity in foods.

xanthelasma Yellow fatty plaques on the eyelids, due to hypercholesterolaemia.

xanthine A purine, intermediate in the metabolism of adenine and guanine to uric acid caffeine (in coffee and tea) is 1,3,7- trimethylxanthine; theophylline (in tea) is 1,3-dimethylxan- thine; theobromine (in cocoa) is 3,7-dimethylxanthine.

xanthoma Yellow skin lesion associated with disorders of lipid metabolism, and especially hypercholesterolaemia.

xanthophylls Hydroxylated carotenoids Occur in all green leaves together with chlorophyll and carotene, also present in egg yolk, cape gooseberry, etc Most have no vitamin a activity Include flavoxanthin (E-161a), lutein (161b), cryptoxanthin (E- 161c, is vitamin A precursor), rubixanthin (161e), rhodoxanthin (161f), canthaxanthin (161g).

xanthoproteic reaction Test for proteins (actually for the matic rings of phenylalanine, tyrosine and tryptophan) Yellow colour on boiling with nitric acid, turns orange on adding ammonia.

aro-xanthosis Yellowing of the skin associated with high blood centrations of carotene.

con-XenicalTM See orlistat.

xenobiotic Substances foreign to the body, including drugs and some food additives.

xerophilic See osmophiles.

xerophthalmia Advanced vitamin a deficiency in which the epithelium of the cornea and conjunctiva of the eye deteriorates because of impairment of the tear glands, resulting in dryness then ulceration, leading to blindness.

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xerosis Abnormal dryness of conjunctiva, skin or mucous membranes.

xerostomia Dry mouth, a common side effect of a variety of drugs.

See also ptyalism.

X-ray diffraction Technique for determination of crystal tures (e.g of proteins) by analysis of the diffraction pattern of a beam of X-rays shone through the crystal.

struc-xylanase Mixture of enzymes of fungal or bacterial origin that

β-d-xylosidase (EC 3.2.1.32) Sometimes added to poultry and pig feed to increase the digestibility of cereal non-starch polysaccharides.

xylans Polysaccharides of xylose, not digested, part of starch polysaccharide; a major component of hemicellulose.

non-xylitol A five-carbon sugar alcohol found in raspberries, endive, lettuce; 80–100% of the sweetness of sucrose; used in sugar-free hard sweets and gelatine gums Apart from being of low cario- genicity, xylitol is said to have an effect in suppressing the growth

of some of the bacteria associated with dental caries (see

tooth-friendly sweets).

xyloascorbic acid Term used for ascorbic acid (vitamin c) to

distinguish from isoascorbic acid (see erythorbic acid), which

is araboascorbic acid and has only slight vitamin C activity.

xyloglucan One of the hemicelluloses in plant cell walls, linking cellulose fibres A component of non-starch polysaccharide.

xylose Pentose (five-carbon) sugar found in plant tissues mainly

as polysaccharides (xylans); 40% as sweet as sucrose Also known as wood sugar Mainly excreted unmetabolised, and used

to test carbohydrate absorption.

xylulose Pentose (five-carbon) sugar occurring as a metabolic intermediate in the pentose phosphate pathway.

Y

that can carry large DNA inserts.

YakultTM yogurt containing live Lactobacillus spp which are biotics Originally Japanese name for yoghurt fermented with L.

pro-casei.

of Dioscorea, D rotundala white yam, and D cayenensis, yellow

or Guinea yam, water, trifoliate or Chinese yam A major food

in parts of Africa and also the Far East In USA sweet potatoes

(see potato, sweet) are sometimes called yam.

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Composition/100 g: (edible portion 86%) water 70 g, 494 kJ (118 kcal), protein 1.5 g, fat 0.2 g, carbohydrate 27.9 g (0.5 g sugars), fibre 4.1 g, ash 0.8 g, Ca 17 mg, Fe 0.5 mg, Mg 21 mg, P

55 mg, K 816 mg, Na 9 mg, Zn 0.2 mg, Cu 0.2 mg, Mn 0.4 mg, Se

pan-tothenate 0.3 mg, C 17 mg A 130 g serving is a source of vitamin

yang See macrobiotic diet.

Yarmouth bloater See red herrings.

yautia See tannia.

yeast Unicellular organisms, sometimes grouped with the fungi; eukaryotic organisms with more complex subcellular organisa- tion than bacteria Some types are of major importance in the

food industry Saccharomyces cerevisiae and S carlsbergensis are

used in brewing, wine-making and baking.

Yeasts such as Candida utilis (formerly Torula utilis) are grown

on carbohydrate or hydrocarbon media as animal feed and potential human food, since they contain about 50% protein (dry weight) and are very rich in B vitamins.

Some yeasts are pathogenic (especially Candida spp., which

cause thrush); many are used in biotechnology for production of

hormones (see hormones, human) and other proteins.

yeast extract A preparation of the water-soluble fraction of ysed brewers’ yeast, valuable both as a source of B vitamins and for its strong savoury flavour; used as a drink or a breadspread Composition/100 g: water 37 g, 661 kJ (158 kcal), protein 27.8 g, fat 0 g, carbohydrate 11.8 g, fibre 3 g, ash 23.4 g, Ca 86 mg, Fe 3.7

autol-mg, Mg 180 autol-mg, P 104 autol-mg, K 2600 autol-mg, Na 3600 autol-mg, Zn 2.1 autol-mg, Cu

yeast fermentation, bottom Or deep fermentation; fermentation during the manufacture of beer with a yeast that sinks to the bottom of the tank Most beers are produced this way; ale, porter and stout being the principal beers produced by top fermentation.

YeastrelTM, YeatexTM See yeast extract.

yeheb A nut, fruit of Cordeauxia edulis, originally from the Horn

of Africa.

yellow fats See spread, fat.

yerba dulce The leaves of the Paraguayan shrub, Stevia

rebaudi-ana, the source of stevioside and rebaudioside.

yerba maté See maté.

Yersinia enterocolitica Food poisoning organism that invades

3–5 days; duration weeks; TX 4.1.3.1.

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YestaminTM A variety of preparations of dried debittered

brewers’ yeast (Saccharomyces spp.) used to enrich foods.

yield Weight of food after processing as a percentage of unprocessed material.

yin See macrobiotic diet.

ylang-ylang oil Aromatic oil from flowers of Philippine tree

Cananga odorata used as a flavouring in soft drinks,

confec-tionery and baked goods.

devel-oped by Cadbury to replace lecithin as an emulsifying agent in chocolate manufacture.

yogurt Milk (from a variety of animals but usually cows)

coagu-lated and fermented with two types of bacteria, Streptococcus

thermophilus and Lactobacillus bulgaricus The two organisms

are symbiotic; each produces compounds that promote the growth of the other Both act to precipitate and gel proteins; main flavour development is from the slower formation of d-

lactic acid by L bulgaricus, although S thermophilus has a

greater capacity to metabolise lactose to l-lactate Stirred yogurt is prepared in bulk; set yogurt is fermented in the plastic containers in which it will be sold Strained (Greek style) yogurt is prepared by removing some of the whey by straining through a cloth or by centrifugation Drinking yogurt is a low- viscosity drink made by blending yogurt with fruit juice and sugar.

May be pasteurised, when most of the bacteria are destroyed,

otherwise termed live yogurt Bioyogurts also contain

Lacto-bacillus acidophilus (see milk, acidophilus) and Bifidobacterium bifidum, which are claimed to enhance the growth of beneficial

bacteria in the intestine.

See also milk, fermented.

yolk index Index of freshness of an egg; ratio between height and diameter of yolk under defined conditions As the egg deterio- rates, the yolk index decreases.

youngberry Cross between blackberry and dewberry.

yukwa Korean; snack food made by deep frying dried dough pared by steeping waxy rice for 1–2 weeks.

pre-yusho disease Caused by leakage of polychlorinated biphenyls which contaminated edible oil on the Japanese island of Kyushu

in 1968.

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zabaglione (zabaione) Italian; frothy dessert made from egg yolks, sugar and wine (usually marsala) whisked over gentle heat until thick French sabayon is similar.

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ZAG Zinc α2 glycoprotein, secreted by various tumours; vates lipolysis and contributes to loss of adipose tissue in cachexia.

acti-zampone Italian; pork sausage in which meat is stuffed into a boned pig’s trotter instead of casing.

zearalenone Trichothecene mycotoxin produced when cereals

are infected with Fusarium spp.

zeaxanthin One of the carotenoid pigments in maize, egg yolk

and Physalis (cape gooseberry); has no vitamin A activity; used

as a colouring.

See also lutein.

zébrine Variety of aubergine with purple and white stripes.

zedoary root Root of the Indian plant Curcuma zedoaria, a

member of the ginger family Used in the manufacture of flavours and bitters.

kawal.

poor in lysine and tryptophan.

Z-enzyme Enzyme ( β-1,3-glucosidase, EC 3.2.1.58) found

amylose to maltose; it requires the presence of the Z-enzyme for complete conversion.

ZeocarbTM An ion-exchange resin.

of a large number of enzymes, and the nuclear receptor proteins for steroid and thyroid hormones and vitamins a and d Deficiency results in hypogonadism and delayed puberty, small stature and mild anaemia; it occurs mainly in subtropical regions where a great deal of zinc is lost in sweat, and the diet is largely based on unleavened wholemeal bread, in which much of the zinc is unavailable because of the high content of phytic acid Intestinal absorption of zinc requires an (as yet unidentified) organic zinc binding ligand secreted in pancre- atic juice Deficiency may also lead to functional vitamin A deficiency because of impaired synthesis of retinol binding protein.

zitoni See pasta.

zizanie See rice, wild.

zNoseTM A surface acoustic wave-based sensor that permits extremely rapid gas chromatography with very high sensitivity –

an ‘electronic nose’.

See also eNose.

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Zollinger–Ellison syndrome Excessive secretion of gastric acid due to high levels of circulating gastrin secreted by a pancreatic tumour.

zomotherapy Treatment of convalescents with raw meat or meat juice, long since discontinued.

zoopherin Obsolete name for vitamin b12.

zooplankton See plankton.

zucchini Italian variety of marrow developed to be harvested when small American and Australian name for courgette.

Zucker rat A genetically obese strain of rat used in research.

z value See decimal reduction time.

zwieback German; twice-baked bread or rusk.

zwitterions An ionised molecule with both positive and negative charges, e.g the amino acids.

Zygosaccharomyces Yeasts that grow in high concentrations of sugar (osmophilic) that cause spoilage of honey, jams, and syrups.

zymase Obsolete name for the mixture of enzymes in yeast which

is responsible for fermentation.

zymogens The inactive form in which some enzymes, especially the protein digestive enzymes, are secreted, being activated after secretion Also called proenzymes, or enzyme precursors.

zymotachygraph An instrument that measures the gas produced

in a fermenting dough and the amount escaping from the dough,

as an index of bread-making properties.

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Appendix

Table 1 Units of physical quantities and multiples and submultiples of units

Electric potential difference volt V J A−1s−1

temperature

−273.15KTemperature (thermodynamic) kelvin K SI base unit

Table 2 Labelling reference values for foods

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Table 7 Food additives permitted in the EU

Colours

Yellow and orange colours

E101 (i) Riboflavin, (ii) Riboflavin-5′-phosphate (vitamin B2)

E102 Tartrazine (= FD&C Yellow no 5)

E104 Quinoline yellow

E110 Sunset Yellow FCF; Orange Yellow S (= FD&C Yellow no 6)Red colours

E120 Cochineal; Carminic acid; Carmines

E122 Azorubine; Carmoisine

E124 Ponceau 4R; Cochineal Red A

E127 Erythrosine (= FD&C Red no 3)

E129 Allura Red AC (= FD&C Red no 40)

Blue colours

E131 Patent Blue V

E132 lndigotine; Indigo Carmine (= FD&C Blue no 2)

E133 Brilliant Blue FCF (= FD&C Blue no 1)

Green colours

E140 Chlorophylls and chlorophyllins (the natural green colour of leaves)E141 Copper complexes of chlorophyll and chlorophyllins

Brown and black colours

E150a Plain caramel

E150b Caustic sulphite caramel

E150c Ammonia caramel

E150d Sulphite ammonia caramel

E151 Brilliant Black BN; Black PN

E153 Vegetable carbon

Derivatives of carotene

E160a Carotenes

E160b Annatto; Bixin; Norbixin

E160c Paprika extract; Capsanthian; Capsorubin

E160d Lycopene

E160e Beta-apo-8′-carotenal (C30)

E160f Ethyl ester of beta-apo-8′-carotenoic acid (C30)

Other plant colours

E161g Canthaxanthin

E162 Beetroot Red; Betanin

E163 Anthocyanins

Other compounds used as colours

E170 Calcium carbonate

E171 Titanium dioxide

E172 Iron oxides and hydroxides

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Sorbic acid and its salts

E200 Sorbic acid

E202 Potassium sorbate

E203 Calcium sorbate

Benzoic acid and its salts

E210 Benzoic acid

E211 Sodium benzoate

E212 Potassium benzoate

E213 Calcium benzoate

E214 Ethyl p-hydroxybenzoate

E215 Sodium ethyl p-hydroxybenzoate

E216 Propyl p-hydroxybenzoate

E217 Sodium propyl p-hydroxybenzoate

E218 Methyl p-hydroxybenzoate

E219 Sodium methyl p-hydroxybenzoate

Sulphur dioxide and its salts

E220 Sulphur dioxide

E221 Sodium sulphite

E222 Sodium hydrogen sulphite

E223 Sodium metabisulphite

E224 Potassium metabisulphite

E226 Calcium sulphite

E227 Calcium hydrogen sulphite

E228 Potassium hydrogen sulphite

Biphenyl and its derivatives

E230 Biphenyl; diphenyl (for surface treatment of citrus fruits)

E231 Orthophenyl phenol (for surface treatment of citrus fruits)

E232 Sodium orthophenyl phenol (sodium biphenyl-2-yl oxide)

Other preservatives

E235 Natamycin (NATA, for surface treatment of cheeses and dried cured

sausages)

E239 Hexamethylene tetramine (hexamine)

E242 Dimethyl dicarbonate

E1105 Lysozyme (an antibacterial enzyme found in tears)

Pickling salts

E249 Potassium nitrite

E250 Sodium nitrite

E251 Sodium nitrate

E252 Potassium nitrate (saltpetre)

Acids and their salts

E280 Propionic acid

E281 Sodium propionate

E282 Calcium propionate

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Table 7 (continued)

E283 Potassium propionate

E284 Boric acid

E285 Sodium tetraborate; borax

Antioxidants

Vitamin C

E300 Ascorbic acid

E301 Sodium ascorbate

E302 Calcium ascorbate

E304 Fatty acid esters of ascorbic acid (a lipid-soluble derivative of the

E310 Propyl gallate

E311 Octyl gallate

E312 Dodecyl gallate

E315 Erythorbic acid (the d-isomer of vitamin C, little vitamin activity)E316 Sodium erythorbate

E320 Butylated hydroxyanisole (BHA)

E321 Butylated hydroxytoluene (BHT)

Sweeteners

Sugar alcohols used as bulk sweeteners

E420 (i) Sorbitol, (ii) Sorbitol syrup

E952 Cyclamic acid and its Na and Ca salts

E954 Saccharin and its Na, K and Ca salts

E959 Neohesperidine DC

Emulsifiers, stabilisers, thickeners and gelling agents

E322 Lecithins (found especially in egg yolk and soya bean)

Alginates

E400 Alginic acid

E401 Sodium alginate

E402 Potassium alginate

E403 Ammonium alginate

E404 Calcium alginate

E405 Propane-1,2-diol alginate

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