Food Composition Chapter 9 Food Composition n Food

Food Composition Chapter 9

Food Composition n Food contains chemical molecules Chemical composition may be determined in laboratory Tables of food composition available n n USDA National Nutrient Database http: //www. ars. usda. gov/main/site_main. htm? modecode=12 354500 Introductory Foods, 13 th ed. Bennion and Scheule 2 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Food Composition n Chemical substances found in the largest amounts in food: n Water n n found inside cells in plants and animals Carbohydrates Fats Protein Introductory Foods, 13 th ed. Bennion and Scheule 3 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Water n All foods contain at least some water n Free water n n Held inside cells Maintains properties of free water May be removed by pressure Bound water n n n Is part of molecule structure Reduced mobility Does not retain properties of free water Introductory Foods, 13 th ed. Bennion and Scheule 4 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Water Activity n More bound water, then less water activity n Water activity n n Ratio of the vapor pressure of water in a food at a specified temperature to the vapor pressure of pure water at same temperature Foods more perishable if higher water activity n n Microorganisms need water! To reduce water activity n n n Introductory Foods, 13 th ed. Bennion and Scheule Dry Freeze Add sugar or salt 5 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Uses of Water in Food Prep n n n Universal solvent Heat transfer Freezing Cleansing agent Promotion of chemical changes n n Ionization of salt Baking powder Water and p. H Hydrolysis reactions Introductory Foods, 13 th ed. Bennion and Scheule 6 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Nature of Water n n n H 2 O Two hydrogen atoms bonded with covalent bonds to one oxygen atom Is dipolar n n n Negative on oxygen side Positive on hydrogen sides Oxygen Hydrogen bonds Introductory Foods, 13 th ed. Bennion and Scheule H+ H+ 7 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Water Hardness n Types of hard water n n n Hard water and food preparation n n Temporary Permanent Rehydration and softening of dried beans slowed Alkalinity may affect color of vegetables Promote cloudiness in tea Water may be softened Introductory Foods, 13 th ed. Bennion and Scheule 8 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Carbohydrates n Simple n n Complex n n sugars starch and fiber Made of n n Carbon (C) Hydrogen (H) Oxygen (O) One molecule of H 2 O for each atom of carbon Introductory Foods, 13 th ed. Bennion and Scheule 9 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Chemical Classification n Classified by number of basic sugar units linked together n n Monosaccharide – One unit Disaccharides – Two units Oligosaccharides – 10 or fewer units Polysaccharides – Up to 1000 units Introductory Foods, 13 th ed. Bennion and Scheule 10 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Monosaccharides n Glucose n Fructose n Galactose Introductory Foods, 13 th ed. Bennion and Scheule 11 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Disaccharides n Sucrose n n Lactose n n Glucose + Fructose Glucose + Galactose Maltose n Glucose + Glucose Introductory Foods, 13 th ed. Bennion and Scheule 12 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Oligosaccharides n Raffinose and Stachyose n Not broken down by digestive tract n Found in dried beans Introductory Foods, 13 th ed. Bennion and Scheule 13 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Polysaccharides n Starch n n n Amylose Amylopectin Dextrins n Produced when starch molecules are partially broken down by enzymes, acid, or heat. n Less thickening power than starch n Glycogen n Plant Fiber Components Introductory Foods, 13 th ed. Bennion and Scheule 14 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Plant Fiber Components n Called dietary fiber / roughage / bulk n Cellulose n Hemicellulose n Beta-glucans n n n Pectic substances n n Found in oats and barley Associated with reduced risk of heart disease Pectin forms gels in jams, jellies, and preserves Vegetable gums Introductory Foods, 13 th ed. Bennion and Scheule 15 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Browning of Foods n Carmelization n n Heating of sugars above melting point Maillard Reaction n n Involves carbohydrate Carbonyl group of sugar combines with amino group of a protein with removal of water. After additional reactions brown pigments are formed n i. e. browning of bread during baking Introductory Foods, 13 th ed. Bennion and Scheule 16 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Lipids or Fats n Insoluble in water n Feel “greasy” n Three major groups n n n Triglycerides Phospholipids Sterols Introductory Foods, 13 th ed. Bennion and Scheule 17 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Triglycerides n n Account for 90 -95 percent of fatty substances in food. Composed of n 3 fatty acids n n linked atoms of carbon with organic acid group One molecule glycerol n 3 carbon atoms and three hydroxyl groups Introductory Foods, 13 th ed. Bennion and Scheule 18 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Fatty Acids n Most fatty acids in foods are combined in triglycerides. n Fatty acids differ n n n Number of hydrogen atoms attached Length of carbon chain Carbon chains n Usually even numbered Introductory Foods, 13 th ed. Bennion and Scheule 19 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Types of Fatty Acids n Saturated fats n n Unsaturated n n No double bonds between carbon atoms, so no more hydrogen can be added Double bonds between some of the carbon atoms that can be broken to add hydrogen Monounsaturated n One double bond Introductory Foods, 13 th ed. Bennion and Scheule 20 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Omega 3 fatty acids n Polyunsaturated fatty acids with double bond between 3 rd and 4 th carbon from the left on the structure. n Found in fatty fish n Protective for heart disease Introductory Foods, 13 th ed. Bennion and Scheule 21 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Linoleic Acid n n An essential fatty acid Cannot be made by the body – must be consumed in food Introductory Foods, 13 th ed. Bennion and Scheule 22 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Cis – Trans Configuration n Cis n n Hydrogen atom on both sides of bond Trans n Hydrogen atoms on opposite sides of bond Introductory Foods, 13 th ed. Bennion and Scheule 23 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Phospholipids n Found in food in relatively small amounts n Function as emulsifiers n n One side of molecule attracts fat One side attracts water n i. e. Lecithin Introductory Foods, 13 th ed. Bennion and Scheule 24 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Sterols n Cholesterol n n n Widely known sterol Found ONLY in animal foods Is associated with coronary heart disease Our bodies also make cholesterol Plant sterols n n Phytosterols Interfere with absorption of cholesterol Introductory Foods, 13 th ed. Bennion and Scheule 25 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Fat in Food Preparation n n Tenderizing in baked foods Contribute to leavening n n Promote moistness Major components of salad dressings May be heated to high temperatures n n Creaming of fat and sugar Frying of foods Contribute flavor n Butter Introductory Foods, 13 th ed. Bennion and Scheule 26 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Proteins n n Essential nutrient In food preparation several important roles n n n Binding water Forming gels Thickening Producing foams Aiding browning Introductory Foods, 13 th ed. Bennion and Scheule 27 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Protein n Contain n n n Carbon Hydrogen Oxygen Nitrogen Potentially also sulfur, phosphorus, iron Large molecules n Hundreds or thousands of amino acids joined with peptide linkage Introductory Foods, 13 th ed. Bennion and Scheule 28 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Protein Structure n Primary n n Secondary n n Springlike coiling - Alpha helix Tertiary n n Long chains Folding of coils forming globular shape Quaternary n Combining of globular proteins Introductory Foods, 13 th ed. Bennion and Scheule 29 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Protein Quality n Amino acids used as building blocks for proteins n n n Nine amino acids are essential for adult human nutrition n n n Complete proteins include essential amino acids Introductory Foods, 13 th ed. Bennion and Scheule 30 Isoleucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Histidine © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Food Sources n n n Meats, Fish, and Poultry Eggs and Dairy Nuts Dry legumes Cereal grains – in lesser amounts Introductory Foods, 13 th ed. Bennion and Scheule 31 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Properties and Reactions n Buffering n Denaturation and Coagulation n Enzymes Introductory Foods, 13 th ed. Bennion and Scheule 32 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Solutions and Dispersions n Gas dispersed in liquid n n Liquid dispersed in liquid n n Air in whipped egg white Oil dispersed in vinegar Solid dispersed in liquid n A protein such as casein dispersed in milk Introductory Foods, 13 th ed. Bennion and Scheule 33 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Solutions and Dispersions n Solutions n Colloidal solutions n n n Sol Gel Foams Emulsions Suspensions Introductory Foods, 13 th ed. Bennion and Scheule 34 © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.