Study Guide Food Science test 2 Chapter 4 Covalent bonds Occur when electrons are shared One two or three pairs of electrons can be shared resulting in single double or triple bonds Fats proteins carbs vitamins have covalently bonded carbon atoms they form the backbone of these molecules Hydrogen Bonds a type of covalent bond with unequal rather than equal sharing of electrons resulting in a weak force Intermolecular bonds bonds between two different molecules Occur when elements such as oxygen and nitrogen in one compound come into close proximity with hydrogen from another compound and share the electron of hydrogen Enzymatic reactions Positive tenderization of meat Negative browning of cut fruits and vegetables Enzymes are specialized proteins and serve as biological catalysts cause reactions to speed up of chemical reactions Active Site Location where the substrate joins with the enzyme to form the enzyme substrate complex A three dimensional region that contains amino acids that bind non covalently to the substrate Water Molecule Structure Two hydrogen atoms bonded to one hydrogen Each H atom shares an electron pair with the O Oxygen attracts the shared electron pair more strongly than the hydrogen A Dipole is established where the oxygen is more negatively charged and the hydrogen is more positively charged Like a magnet 1 This results in hydrogen bonding High boiling point and freezing point High vapor pressure High interfacial surface tension Chapter 5 Valence Shell The outermost shell of most atoms become chemically stable when they have 8 electrons Humectant A substance that has an affinity for moisture also referred to as hygroscopic substances This is ultimately related to their ability to form hydrogen bonds with water Sugar is hygroscopic Hydroscopic holds water Oxidation of aldehyde group in sugars causes a loss of sweetness and converts it to an acid Reduction of the carbonyl group of reducing sugars causes the formation of sugar alcohols which are moderately sweet Ex Mannitol and Sorbitol Sweetness sucrose used as reference Fructose sucrose glucose maltose galactose lactose Vegetable gums A broad category of complex polysaccharides that contain a variety of sugars including pentoses and hexoses Gums are derived from a variety of sources including plant seeds guar seaweed carageenans and microorganisms xanthan Triglyceride the predominate chemical structure of lipids Glycerol is a three carbon molecule containing 3 OH alcohol groups Fatty acids are chains of carbon with a carboxyl at one end and a methyl at the other end Conjugated Double Bond When the double bonds occur between every other carbon Methylene interrupted When a carbon without a double bond occurs between two sets of double bonds More typical and more reactive C C C C C Cis and Trans Fats Refers to the geometric configuration around the double bond of unsaturated fatty acids Cis When the hydrogen are on the same side Cis is more common in nature Trans When the hydrogen are on opposite sides Trans configuration occurs when vegetable oil is hydrogenated modify to make trans Smoke Point Characteristic temperature at which fats begin to break down Most fats begin to decompose before their boiling point May spontaneously ignite on the stove if their fumes come in contact with flame Depends on the initial free fatty acid content Amphiphilic A molecule that has polar and nonpolar regions Ex Phospholipids 2 Fractionation splits lipids into higher and lower melting point component parts Hydrogenation the forced addition of hydrogen to unsaturated lipids raising the melting point and increasing stability but produces trans fatty acids Hydrolysis Addition of a water molecule and heat to separate fatty acids from glycerol Causes hydrolytic rancidity which causes the release of short chain fatty acids Acrolein responsible for the aroma of oils at their smoke point When all three fatty acids are lost during heating and the glycerol molecule is further degraded Interestification The rearrangement of fatty acids on the glycerol molecule to create less homogenous triglyceride molecules Causes plastic fats such as lard to have a smoother texture Functional properties of Lipids Aeration creaming of fat crystallization emulsification flavor heat transfer can be heated to higher temperatures than water mouthfeel lipids provide a smooth creamy sensation during the mastication of food plasticity describes the softness of the fat at room temperature tenderization Crystallization all food fats contain very small crystals of fat which are composed of the fat s triglycerides Polymorphism Different crystalline arrangements are possible because of the differences in the fatty acids that make up the triglycerides Includes the classifications prime provide a smooth texture crystals are coarser prime is the most desirable from a functionality standpoint because they Structure of Proteins pleated sheet Primary Linear arrangement of amino acids Secondary The structural arrangement of the amino acids such as the alpha helix and beta Tertiary The overall three dimensional structure Quaternary The arrangement of more than one peptide chain within a single protein molecule Visible light occurs between wavelengths 380nm and 780nm in the electromagnetic spectrum Nonconjugated protein contains only amino acids Conjugated protein combined with other nonprotein substances Chapter 6 Color can be classified according to its hue chroma and intensity Hue actual color name Chroma clarity and purity of color Intensity degree of lightness or darkness Total Reflection White Total Absorption Black 3 Pigment Molecules Color of food is due to pigment molecules Chlorophylls plants Phenolics plants Anthocyanins anthoxanins betalains Carotenoids plants Myoglobin animals can tell if meat has gone bad Iron content storing oxygen in muscle tissue Ultimately responsible for the reddish color of muscle foods Animals can derive pigmented compounds from the plant foods that they eat Globular protein with an iron containing a prosthetic group called heme Responsible for The Color Chemistry of Fruits and Vegetables 3 major groups Phenolics Carotenoids and Clorophylls All contain conjugated double bonds which allows for electron resonance which in turn produces color Resonance electrons are spread across the atoms and their movement across carbon bonds gives color Anthocyanins Water soluble purple to orange red in color flavonoids which contain at least Phenolics