Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.2
Food Composition Food contains chemical molecules
Chemical composition may be determined in laboratory
Tables of food composition available USDA National Nutrient Database http://www.ars.usda.gov/main/site_main.htm?modecode=12
354500
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.3
Food Composition Chemical substances found in the largest amounts in
food: Water
found inside cells in plants and animals Carbohydrates Fats Protein
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.4
Water All foods contain at least some water
Free water Held inside cells Maintains properties of free water May be removed by pressure
Bound water Is part of molecule structure Reduced mobility Does not retain properties of free water
Introductory Foods, 13th ed.Bennion and Scheule
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Water Activity
More bound water, then less water activity
Water activity 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 Microorganisms need water! To reduce water activity
Dry Freeze Add sugar or salt
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.6
Uses of Water in Food Prep Universal solvent Heat transfer Freezing Cleansing agent Promotion of chemical changes
Ionization of salt Baking powder
Water and pH Hydrolysis reactions
Introductory Foods, 13th ed.Bennion and Scheule
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Nature of Water H2O Two hydrogen atoms bonded
with covalent bonds to one oxygen atom
Is dipolar Negative on oxygen side Positive on hydrogen sides
Hydrogen bonds
H +
Oxygen
H +
Introductory Foods, 13th ed.Bennion and Scheule
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Water Hardness Types of hard water
Temporary Permanent
Hard water and food preparation Rehydration and softening of dried beans slowed Alkalinity may affect color of vegetables Promote cloudiness in tea
Water may be softened
Introductory Foods, 13th ed.Bennion and Scheule
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Carbohydrates Simple
sugars
Complex starch and fiber
Made of Carbon (C) Hydrogen (H) Oxygen (O) One molecule of H2O for each atom of carbon
Introductory Foods, 13th ed.Bennion and Scheule
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Chemical Classification Classified by number of basic sugar units
linked together Monosaccharide – One unit Disaccharides – Two units Oligosaccharides – 10 or fewer units Polysaccharides – Up to 1000 units
Introductory Foods, 13th ed.Bennion and Scheule
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Monosaccharides Glucose
Fructose
Galactose
Introductory Foods, 13th ed.Bennion and Scheule
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Disaccharides Sucrose
Glucose + Fructose
Lactose Glucose + Galactose
Maltose Glucose + Glucose
Introductory Foods, 13th ed.Bennion and Scheule
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Oligosaccharides Raffinose and Stachyose
Not broken down by digestive tract
Found in dried beans
Introductory Foods, 13th ed.Bennion and Scheule
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Polysaccharides Starch
Amylose Amylopectin
Dextrins Produced when starch molecules are partially broken down
by enzymes, acid, or heat. Less thickening power than starch
Glycogen
Plant Fiber Components
Introductory Foods, 13th ed.Bennion and Scheule
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Plant Fiber Components
Called dietary fiber / roughage / bulk
Cellulose
Hemicellulose
Beta-glucans Found in oats and barley Associated with reduced risk of heart disease
Pectic substances Pectin forms gels in jams, jellies, and preserves
Vegetable gums
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.16
Browning of Foods Carmelization
Heating of sugars above melting point
Maillard Reaction Involves carbohydrate Carbonyl group of sugar combines with amino group of a
protein with removal of water. After additional reactions brown pigments are formed
i.e. browning of bread during baking
Introductory Foods, 13th ed.Bennion and Scheule
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Lipids or Fats Insoluble in water
Feel “greasy”
Three major groups Triglycerides Phospholipids Sterols
Introductory Foods, 13th ed.Bennion and Scheule
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Triglycerides Account for 90-95 percent of fatty substances
in food.
Composed of 3 fatty acids
linked atoms of carbon with organic acid group One molecule glycerol
3 carbon atoms and three hydroxyl groups
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.19
Fatty Acids Most fatty acids in foods are combined in
triglycerides.
Fatty acids differ Number of hydrogen atoms attached Length of carbon chain
Carbon chains Usually even numbered
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.20
Types of Fatty Acids Saturated fats
No double bonds between carbon atoms, so no more hydrogen can be added
Unsaturated Double bonds between some of the carbon atoms that can be
broken to add hydrogen Monounsaturated
One double bond
Introductory Foods, 13th ed.Bennion and Scheule
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Omega 3 fatty acids Polyunsaturated fatty acids with double bond
between 3rd and 4th carbon from the left on the structure.
Found in fatty fish
Protective for heart disease
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.22
Linoleic Acid
An essential fatty acid
Cannot be made by the body – must be consumed in food
Introductory Foods, 13th ed.Bennion and Scheule
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Cis – Trans Configuration Cis
Hydrogen atom on both sides of bond
Trans Hydrogen atoms on opposite sides of bond
Introductory Foods, 13th ed.Bennion and Scheule
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Phospholipids Found in food in relatively small amounts
Function as emulsifiers One side of molecule attracts fat One side attracts water
i.e. Lecithin
Introductory Foods, 13th ed.Bennion and Scheule
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Sterols Cholesterol
Widely known sterol Found ONLY in animal foods Is associated with coronary heart disease Our bodies also make cholesterol
Plant sterols Phytosterols Interfere with absorption of cholesterol
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.26
Fat in Food Preparation Tenderizing in baked foods Contribute to leavening
Creaming of fat and sugar Promote moistness Major components of salad dressings May be heated to high temperatures
Frying of foods Contribute flavor
Butter
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Proteins Essential nutrient In food preparation several important roles
Binding water Forming gels Thickening Producing foams Aiding browning
Introductory Foods, 13th ed.Bennion and Scheule
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Protein Contain
Carbon Hydrogen Oxygen Nitrogen Potentially also sulfur, phosphorus, iron
Large molecules Hundreds or thousands of amino acids joined with peptide
linkage
Introductory Foods, 13th ed.Bennion and Scheule
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Protein Structure Primary
Long chains Secondary
Springlike coiling - Alpha helix Tertiary
Folding of coils forming globular shape Quaternary
Combining of globular proteins
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.30
Protein Quality Amino acids used as
building blocks for proteins
Nine amino acids are essential for adult human nutrition
Complete proteins include essential amino acids
Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Histidine
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.31
Food Sources Meats, Fish, and Poultry Eggs and Dairy Nuts Dry legumes Cereal grains – in lesser amounts
Introductory Foods, 13th ed.Bennion and Scheule
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Properties and Reactions Buffering
Denaturation and Coagulation
Enzymes
Introductory Foods, 13th ed.Bennion and Scheule
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Solutions and Dispersions Gas dispersed in liquid
Air in whipped egg white
Liquid dispersed in liquid Oil dispersed in vinegar
Solid dispersed in liquid A protein such as casein dispersed in milk