ContentsV238LovibondSystem239Gloss239Food Colorants2637.Flavor263Introduction263TasteOdor282291DescriptionofFoodFlavors294Astringency296FlavorandOff-Flavor297FlavorofSomeFoods3118.Texture311Introduction313TextureProfile316ObjectiveMeasurementofTexture320DifferentTypesofBodies328ApplicationtoFoods334TexturalPropertiesofSomeFoods341Microstructure347WaterActivityandTexture9.355Vitamins355Introduction355Fat-SolubleVitamins366Water-SolubleVitamins385VitaminsasFoodIngredients.38910.Enzymes389Introduction389NatureandFunction395Hydrolases413Oxidoreductases423ImmobilizedEnzymesThis page hasbeen reformatted byKnovel toprovideeasier navigation
Contents v This page has been reformatted by Knovel to provide easier navigation. Lovibond System . 238 Gloss . 239 Food Colorants . 239 7. Flavor . 263 Introduction . 263 Taste . 263 Odor . 282 Description of Food Flavors . 291 Astringency . 294 Flavor and Off-Flavor . 296 Flavor of Some Foods . 297 8. Texture . 311 Introduction . 311 Texture Profile . 313 Objective Measurement of Texture . 316 Different Types of Bodies . 320 Application to Foods . 328 Textural Properties of Some Foods . 334 Microstructure . 341 Water Activity and Texture . 347 9. Vitamins . 355 Introduction . 355 Fat-Soluble Vitamins . 355 Water-Soluble Vitamins . 366 Vitamins as Food Ingredients . 385 10. Enzymes . 389 Introduction . 389 Nature and Function . 389 Hydrolases . 395 Oxidoreductases . 413 Immobilized Enzymes . 423
viContents42911.AdditivesandContaminants429Introduction431IntentionalAdditives449IncidentalAdditivesorContaminants12.RegulatoryControlofFoodComposition,Quality,and475Safety475HistoricalOverview477SafetyU.S.FoodLaws479481CanadianFoodLaws482EuropeanUnion(EU)FoodLaws484InternationalFoodLaw:CodexAlimentarius488Harmonization491Appendices491AppendixA.UnitsandConversionFactors495AppendixB.GreekAlphabetIndex497ThispagehasbeenreformattedbyKnoveltoprovideeasiernavigation
vi Contents This page has been reformatted by Knovel to provide easier navigation. 11. Additives and Contaminants . 429 Introduction . 429 Intentional Additives . 431 Incidental Additives or Contaminants . 449 12. Regulatory Control of Food Composition, Quality, and Safety . 475 Historical Overview . 475 Safety . 477 U.S. Food Laws . 479 Canadian Food Laws . 481 European Union (EU) Food Laws . 482 International Food Law: Codex Alimentarius . 484 Harmonization . 488 Appendices . 491 Appendix A. Units and Conversion Factors . 491 Appendix B. Greek Alphabet . 495 Index . 497
1CHAPTERWaterTable1-1TvpicalWaterContentsofSomeWater is an essential constituent of manySelectedFoodsfoods.It may occur as an intracellular orextracellular component in vegetable andProductWater(%)animal products, as a dispersing medium or95solvent in a variety of products, as the dis-Tomato95persed phase in some emulsified productsLettuce92such as butter and margarine, and as a minorCabbage90constituent in other foods. Table 1-1 indi-BeerOrange87cates the wide range of water content in87foods.Apple juiceMilk87Because of the importance of water asaPotato78food constituent, an understanding of itsBanana75properties and behavior is necessary.The70Chickenpresence of water influences the chemical67and microbiological deterioration of foods.Salmon,cannedMeat65Also,removal (drying)or freezing of waterCheese37is essential to some methods of food preser-35vation. Fundamental changes in the productBread, white28Jammay take place in both instances.Honey2016ButterandmargarinePHYSICALPROPERTIESOFWATER12Wheat fiourANDICERice125Some of the physical properties of waterCoffeebeans,roasted4and ice are exceptional, and a list of these isMilkpowder0presentedin Table1-2.Muchof this infor-ShorteningmationwasobtainedfromPerry(1963)andLandolt-Boernstein (1923).The exception-ally high values of the caloric properties ofoperations such as freezing and drying.Thewater are of importance for food processingconsiderable difference in density of water1
Water is an essential constituent of many foods. It may occur as an intracellular or extracellular component in vegetable and animal products, as a dispersing medium or solvent in a variety of products, as the dispersed phase in some emulsified products such as butter and margarine, and as a minor constituent in other foods. Table 1-1 indicates the wide range of water content in foods. Because of the importance of water as a food constituent, an understanding of its properties and behavior is necessary. The presence of water influences the chemical and microbiological deterioration of foods. Also, removal (drying) or freezing of water is essential to some methods of food preservation. Fundamental changes in the product may take place in both instances. PHYSICAL PROPERTIES OF WATER AND ICE Some of the physical properties of water and ice are exceptional, and a list of these is presented in Table 1-2. Much of this information was obtained from Perry (1963) and Landolt-Boernstein (1923). The exceptionally high values of the caloric properties of water are of importance for food processing Table 1-1 Typical Water Contents of Some Selected Foods Product Water (%) Tomato 95 Lettuce 95 Cabbage 92 Beer 90 Orange 87 Apple juice 87 Milk 87 Potato 78 Banana 75 Chicken 70 Salmon, canned 67 Meat 65 Cheese 37 Bread, white 35 Jam 28 Honey 20 Butter and margarine 16 Wheat flour 12 Rice 12 Coffee beans, roasted 5 Milk powder 4 Shortening O operations such as freezing and drying. The considerable difference in density of water Water CHAPTER 1
2PRINCIPLES OFFOODCHEMISTRYTable1-2SomePhysicalPropertiesofWaterandIceTemperature (℃)040602080Water1004.5817.53Vaporpressure (mmHg)55.32149.4355.2760.0Density (g/cm°)0.99980.99820.99220.98320.97180.95831.00740.99880.99800.99941.00231.0070Specificheat (cal/gC)Heat of vaporization597.2586.0574.7563.3551.3538.9(cal/g)0.4860.5150.5400.5610.5760.585Thermal conductivity(kcal/m2h℃)Surface tension75.6272.7569.5566.1762.6058.84(dynes/cm)1.7921.0020.6530.4660.3550.282Viscosity (centipoises)Refractive index1.33381.33301.33061.32721.32301.318088.080.473.366.760.855.3Dielectric constant2.073.875.386.57Coefficient of thermalexpansion×10-4Temperature (C)0-5-15-2025Ice-10-303.011.951.240.77Vaporpressure (mmHg)4.580.470.2879.8Heatoffusion (cal/g)-666.7Heatof sublimation (cal/g)677.8672.3662.30.91680.91710.9178Density(g/cm3）0.91750.91820.91850.91880.48730.47700.4647Specificheat (cal/gC)0.45049.27.15.54.43.93.63.5Coefficientofthermalexpansion×10-52.06Heatcapacity (joule/g)1.94STRUCTUREOFTHEWATERandicemayresult instructuraldamagetofoods when they are frozen. The density ofMOLECULEice changes with changes in temperature,The reason for the unusual behavior ofresulting in stresses in frozen foods. Sincesolidsaremuchless elasticthan semisolids.water lies in the structure of the water mole-structural damage may result from fluctuat-cule (Figure 1-1) and in the molecule's abil-ing temperatures,even if the fluctuationsityto formhydrogen bonds.In the waterremain belowthefreezingpoint.molecule the atoms are arranged at an angle
and ice may result in structural damage to foods when they are frozen. The density of ice changes with changes in temperature, resulting in stresses in frozen foods. Since solids are much less elastic than semisolids, structural damage may result from fluctuating temperatures, even if the fluctuations remain below the freezing point. STRUCTURE OF THE WATER MOLECULE The reason for the unusual behavior of water lies in the structure of the water molecule (Figure 1-1) and in the molecule's ability to form hydrogen bonds. In the water molecule the atoms are arranged at an angle Table 1-2 Some Physical Properties of Water and Ice Temperature (0C) Water Vapor pressure (mm Hg) Density (g/cm3 ) Specific heat (cal/g°C) Heat of vaporization (cal/g) Thermal conductivity (kcal/m2 h°C) Surface tension (dynes/cm) Viscosity (centipoises) Refractive index Dielectric constant Coefficient of thermal expansion x 1 (T4 O 4.58 0.9998 1.0074 597.2 0.486 75.62 1.792 1 .3338 88.0 20 17.53 0.9982 0.9988 586.0 0.515 72.75 1.002 1 .3330 80.4 2.07 40 55.32 0.9922 0.9980 574.7 0.540 69.55 0.653 1.3306 73.3 3.87 60 149.4 0.9832 0.9994 563.3 0.561 66.17 0.466 1.3272 66.7 5.38 80 355.2 0.9718 1.0023 551.3 0.576 62.60 0.355 1 .3230 60.8 6.57 100 760.0 0.9583 1 .0070 538.9 0.585 58.84 0.282 1.3180 55.3 Temperature (0C) Ice Vapor pressure (mm Hg) Heat of fusion (cal/g) Heat of sublimation (cal/g) Density (g/cm3 ) Specific heat (cal/g 0C) Coefficient of thermal expansion x 1 0~5 Heat capacity (joule/g) O 4.58 79.8 677.8 0.9168 0.4873 9.2 2.06 -5 3.01 0.9171 7.1 -10 1.95 672.3 0.9175 0.4770 5.5 -15 1.24 0.9178 4.4 -20 0.77 666.7 0.9182 0.4647 3.9 1.94 -25 0.47 0.9185 3.6 -30 0.28 662.3 0.9188 0.4504 3.5
Water3that water has unusually high values for cer-tain physical constants, such as meltingpoint, boiling point, heat capacity, latent heatof fusion, latent heat of vaporization, surfacetension, and dielectric constant. Some ofthese values are listed in Table 1-3.Watermayinfluence the conformation ofmacromolecules if it has an effect on anyofthe noncovalent bonds that stabilize the con-Figure 1-1 Structure of the Water Moleculeformation of the large molecule (Klotz1965).Thesenoncovalentbonds maybeoneof three kinds: hydrogen bonds,ionic bonds.of 105 degrees, and the distance between theor apolar bonds.In proteins,competitionnucleiof hydrogen and oxygen is 0.0957nm.exists between interamide hydrogen bondsThe water molecule can be considered aand water-amidehydrogen bonds.Accordingspherical quadrupole with a diameter ofto Klotz (1965), the binding energy of such0.276nm,wheretheoxygennucleus formsbonds can be measured by changesin thethe center of the quadrupole. The two nega-near-infraredspectraofsolutionsinN-methtive and two positive charges form the anglesylacetamide.The greater the hydrogen bond-of a regular tetrahedron.Because of the sepa-ing ability of the solvent, the weaker theC=O...H-N bond. In aqueous solvents theration of charges in a water molecule, theheat of formation or disruption of this bondattraction between neighboring molecules isis zero.This means that a C-O...H-N hydro-higherthan isnormal with van der Waalsforces.gen bond cannot provide stabilization inaqueous solutions.The competitive hydro-gen bonding by H,O lessens the thermody-namic tendency toward the formation ofinteramidehydrogenbondsThe water molecules around an apolar solHutebecomemore ordered,leading to a lossIn ice, everyH,O molecule is bound by fourin entropy. As a result, separated apolarsuch bridges to each neighbor. The bindinggroups in an aqueous environment tend toenergy of the hydrogen bond in ice amountsto 5 kcal per mole (Pauling 1960).SimilarTable1-3PhysicalPropertiesofSomestrong interactions occur between OH andHydridesNH and between small, strongly electronega-MeltingBoilingMolarHeatoftive atoms such as O and N. This is the rea-Sub-PointPointVaporizationson for the strong association in alcohols,(℃)(℃)stance(cal/mole)fatty acids, and amines and their great affin-CH4-1841612,200ity to water. A comparison of the propertiesNH378335,550of water with those of the hydrides of ele-HFments near oxygen in the Periodic Table- 92+197,220H,00(CH4,NH3,HF, DH3,H,S,HCl)indicates+1009,750
Figure 1-1 Structure of the Water Molecule of 105 degrees, and the distance between the nuclei of hydrogen and oxygen is 0.0957 nm. The water molecule can be considered a spherical quadrupole with a diameter of 0.276 nm, where the oxygen nucleus forms the center of the quadrupole. The two negative and two positive charges form the angles of a regular tetrahedron. Because of the separation of charges in a water molecule, the attraction between neighboring molecules is higher than is normal with van der Waals' forces. that water has unusually high values for certain physical constants, such as melting point, boiling point, heat capacity, latent heat of fusion, latent heat of vaporization, surface tension, and dielectric constant. Some of these values are listed in Table 1-3. Water may influence the conformation of macromolecules if it has an effect on any of the noncovalent bonds that stabilize the conformation of the large molecule (Klotz 1965). These noncovalent bonds may be one of three kinds: hydrogen bonds, ionic bonds, or apolar bonds. In proteins, competition exists between interamide hydrogen bonds and water-amide hydrogen bonds. According to Klotz (1965), the binding energy of such bonds can be measured by changes in the near-infrared spectra of solutions in TV-methylacetamide. The greater the hydrogen bonding ability of the solvent, the weaker the C=O-H-N bond. In aqueous solvents the heat of formation or disruption of this bond is zero. This means that a C=O-H-N hydrogen bond cannot provide stabilization in aqueous solutions. The competitive hydrogen bonding by H2O lessens the thermodynamic tendency toward the formation of interamide hydrogen bonds. The water molecules around an apolar solute become more ordered, leading to a loss in entropy. As a result, separated apolar groups in an aqueous environment tend to Table 1-3 Physical Properties of Some Hydrides In ice, every H2O molecule is bound by four such bridges to each neighbor. The binding energy of the hydrogen bond in ice amounts to 5 kcal per mole (Pauling 1960). Similar strong interactions occur between OH and NH and between small, strongly electronegative atoms such as O and N. This is the reason for the strong association in alcohols, fatty acids, and amines and their great affinity to water. A comparison of the properties of water with those of the hydrides of elements near oxygen in the Periodic Table (CH4, NH3, HF, DH3, H2S, HCl) indicates Substance CH4 NH3 HF H2O Melting Point ( 0C) -184 -78 -92 O Boiling Point ( 0C) -161 -33 + 19 +100 Molar Heat of Vaporization (cal/mole) 2,200 5,550 7,220 9,750