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4 Lipids

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Chemistry and Biochemistry of Food
This chapter is in the book Chemistry and Biochemistry of Food
4 Lipids4.1 Definition and classificationLipids are a heterogeneous family of biomolecules whose common characteristic is alow or null solubility in water and high solubility in non-polar organic solvents suchas chloroform or hexane. This definition includes a wide variety of biological com-pounds that can be classified according to different criteria, such as behavior uponhydrolyzation or chemical structure and composition [1]. According to the first crite-rion, lipids are classified as:–Hydrolysable (saponifiable) lipids. Those that yield fatty acids when subjectedto hydrolysis in the presence of strong acids (soaps in the presence of strongbases such as NaOH or KOH).–Non-hydrolysable (unsaponifiable) lipids. They do not produce fatty acids/soapsupon hydrolysis.Considering chemical structure and composition, food chemists distinguish three clas-ses of lipids:–Simple lipids: esters of fatty acids and biological alcohols like glycerol (propane-1,2,3-triol). This group is of paramount importance due to their abundance infoods, as they include fats and oils.–Compound, complex, or conjugated lipids: lipids linked or associated to othernon-lipid molecules producing substances with amphiphilic properties. Theseinclude phospholipids, glycolipids, and lipoproteins.–Derived lipids. Hydrophobic substances not included in the above groups, such asfree fatty acids, carotenoids, lipophilic vitamins, steroids, or pigments and volatilescents from plants.Similarly to the rest of biomolecules, the backbones of lipids are composed mainlyof carbon, hydrogen, and oxygen although they may contain additional elementssuch as phosphorus, sulfur, and/or nitrogen.Lipids are molecules of hydrophobic nature implicated in important biologicalfunctions:–Energetic. The most energy-dense biomolecules are lipids, containing up to 9kilocalories (kcal, approximately 37.6 kilojoules or kJ) per gram; therefore, theyare the molecules of choice for efficient energy storage in vertebrates and otherspecies [1].–Structural. Phospholipids, glycolipids, and sterols play an essential role in thestructure and function of biological membranes, the complex structure that me-diates the interchange of mass, energy, and information between the cell andits environment [2].https://doi.org/10.1515/9783110595482-004
© 2020 Walter de Gruyter GmbH, Berlin/Munich/Boston

4 Lipids4.1 Definition and classificationLipids are a heterogeneous family of biomolecules whose common characteristic is alow or null solubility in water and high solubility in non-polar organic solvents suchas chloroform or hexane. This definition includes a wide variety of biological com-pounds that can be classified according to different criteria, such as behavior uponhydrolyzation or chemical structure and composition [1]. According to the first crite-rion, lipids are classified as:–Hydrolysable (saponifiable) lipids. Those that yield fatty acids when subjectedto hydrolysis in the presence of strong acids (soaps in the presence of strongbases such as NaOH or KOH).–Non-hydrolysable (unsaponifiable) lipids. They do not produce fatty acids/soapsupon hydrolysis.Considering chemical structure and composition, food chemists distinguish three clas-ses of lipids:–Simple lipids: esters of fatty acids and biological alcohols like glycerol (propane-1,2,3-triol). This group is of paramount importance due to their abundance infoods, as they include fats and oils.–Compound, complex, or conjugated lipids: lipids linked or associated to othernon-lipid molecules producing substances with amphiphilic properties. Theseinclude phospholipids, glycolipids, and lipoproteins.–Derived lipids. Hydrophobic substances not included in the above groups, such asfree fatty acids, carotenoids, lipophilic vitamins, steroids, or pigments and volatilescents from plants.Similarly to the rest of biomolecules, the backbones of lipids are composed mainlyof carbon, hydrogen, and oxygen although they may contain additional elementssuch as phosphorus, sulfur, and/or nitrogen.Lipids are molecules of hydrophobic nature implicated in important biologicalfunctions:–Energetic. The most energy-dense biomolecules are lipids, containing up to 9kilocalories (kcal, approximately 37.6 kilojoules or kJ) per gram; therefore, theyare the molecules of choice for efficient energy storage in vertebrates and otherspecies [1].–Structural. Phospholipids, glycolipids, and sterols play an essential role in thestructure and function of biological membranes, the complex structure that me-diates the interchange of mass, energy, and information between the cell andits environment [2].https://doi.org/10.1515/9783110595482-004
© 2020 Walter de Gruyter GmbH, Berlin/Munich/Boston

Chapters in this book

  1. Frontmatter I
  2. Preface VII
  3. Contents IX
  4. 1 Food, nutrition, and diet 1
  5. 2 Water 13
  6. 3 Carbohydrates 25
  7. 4 Lipids 79
  8. 5 Proteins 131
  9. 6 Vitamins 189
  10. 7 Minerals 253
  11. 8 Oxidative stress and antioxidants in nutrition 329
  12. 9 The biochemistry of flavor perception 363
  13. 10 Food additives 381
  14. 11 Food safety 401
  15. 12 The biochemistry of digestion 415
  16. 13 Absorption of nutrients 447
  17. 14 Energy homeostasis and integration of metabolism 479
  18. 15 The Mediterranean diet 509
  19. 16 The foods of the future 523
  20. Appendix 1: Dietary reference values 545
  21. Appendix 2: Reference intakes (RI) for total fat and carbohydrates and adequate intakes (AIs) for fatty acids, dietary fiber, and water 547
  22. Appendix 3: Summary of average requirement (AR) for energy expressed in kcal/day for different groups of population 548
  23. Appendix 4: Alcohol as a nutrient 551
  24. About the author 555
  25. Index 557
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https://doi.org/10.1515/9783110595482-004

Chapters in this book

  1. Frontmatter I
  2. Preface VII
  3. Contents IX
  4. 1 Food, nutrition, and diet 1
  5. 2 Water 13
  6. 3 Carbohydrates 25
  7. 4 Lipids 79
  8. 5 Proteins 131
  9. 6 Vitamins 189
  10. 7 Minerals 253
  11. 8 Oxidative stress and antioxidants in nutrition 329
  12. 9 The biochemistry of flavor perception 363
  13. 10 Food additives 381
  14. 11 Food safety 401
  15. 12 The biochemistry of digestion 415
  16. 13 Absorption of nutrients 447
  17. 14 Energy homeostasis and integration of metabolism 479
  18. 15 The Mediterranean diet 509
  19. 16 The foods of the future 523
  20. Appendix 1: Dietary reference values 545
  21. Appendix 2: Reference intakes (RI) for total fat and carbohydrates and adequate intakes (AIs) for fatty acids, dietary fiber, and water 547
  22. Appendix 3: Summary of average requirement (AR) for energy expressed in kcal/day for different groups of population 548
  23. Appendix 4: Alcohol as a nutrient 551
  24. About the author 555
  25. Index 557
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