Lecture 1 Water H20 required in many processes in the body nutrient waste carrier chemical reaction texture of food has hydrogen bonding which is why it has a high boiling point and low freezing point Hydrophobic interaction hydrophobic molecules such as oil will join together in water to become more thermodynamic and touch less water hydrophobic amino acids will fold together to have less surface area of a protein touching water Interactions between molecules in order of strength 1 Covalent 2 Hydrogen bond 3 Electrostatic 4 Hydrophobic 5 Van der Waals interaction dipole dipole pH equations pH log10 H3O pOH log10 OH pH pOH 14 H30 OH 10 14 Acids proton H donors Bases proton H acceptors pH meter first invented to measure acidity of citrus juice Organic acids citrus are weaker in acidity than inorganic acids HCl but are more sour because the release protons slower and do not flood the taste buds Buffers a mixture of weak acid and its conjugate base that resist pH change by strong acids or bases pKa when pKa of a weak acid and base is given the buffering range is normally or 1 that number Weak acid partial dissociation HA H2O H3O A Lecture 2 Henderson Hasselbalch equation pH pKa log10 A HA Molality moles of solute in 1kg solvent Molarity moles of solute in 1L solvent Normality molarity valence valence number of H or OH in a molecule Lecture 3 Aw p partial pressure of water above the sample p0 partial pressure of pure water Capacitance hygrometer uses electric charges to measure water activity Dew point hygrometer uses temperature when dew point occurs to get vapor pressure of water then water activity Intermediate moisture food IMF less energy intensive ready to eat foods long shelf life water activity between 6 8 low retains nutrients and quality addition of humectants lower water activity with retained moistness Cupcake problem with moisture If the icing of a cupcake has 13 moisture content and the cake has 9 what will happen over time Moisture moves from high to low concentration True solutions stable particle size 1nm nanometer scatters light kinetic energy example water Colloids relatively stable particle size 1nm 1 um does not scatter light kinetic and potential energy factors that stabilize colloids 1 Brownian movement 2 Electrostatic repulsion 3 Water hydration 4 BET multilayer adsorption example milk Suspension unstable particle size 1um example tomato juice Isotropic solution uniform properties throughout completely dissolved solute in water Anisotropic solution different properties in different directions solute does not completely dissolve Lecture 4 Van t Hoff factor n number of dissociated species to get n know that molecules without a charge have n 1 Those that do have a charge you count the number of charge sucrose n 1 NaCl n 2 CaCl2 n 3 Colligative properties ratio of solute in a volume of solvent when van t hoff factor increases when solute increases 1 Boiling point increases 2 Osmotic pressure increases 3 Freezing point decreases 4 Vapor pressure decreases freezing is faster than thawing because thermal conductivity of ice is higher meaning it transfers heat cold better than water freeze fast to get small intracellular ice crystals Gels macromolecules that entrap liquid three stage theory 1 Denaturation 2 Cross linking 3 Gel network Two types of gels 1 Reversible gel melts with heating strengthen with cooling matrix sustained by hydrogen bonds ordered network and translucent example pectin gels 2 Irreversible gels strengthened with heating matrix sustained by hydrophobic interactions and covalent bonds random network and opaque example egg white Emulsions mixture of two or more liquids that are immiscible dispersed phase in continuous phase xanthan gum is not an emulsifier 1 Oil in water example light cream 20 fat 2 Water in oil example butter 80 fat Hydrophilic lipophilic balance HLB emulsifier are generally more effective if they are soluble in the continuous phase HLB greater than 7 oil in water emulsions HLB less than 7 water in oil emulsions Foams gas bubbles in a continuous liquid semisolid formed by whipping factors affecting foaming 1 pH and salts at pI foaming capacity decreases and foaming stability increases best to use a low pI protein and high pI protein at the same time 2 Sugar increases foaming stability if added after foam increases viscosity 3 Lipid impair foaming 4 Temperature too hot or cold can affect capacity and stability Lecture 5 Difference testing tests that compare at least 2 samples with each other example asking people to say which glass has coke in it by a blind taste test single stimulus 50 chance of guessing correct paired test 50 chance of guessing correct given two samples asked if they are the same or different duo trio 50 chance of guessing correct given one sample then have to say out of two other samples which is the same triangle 33 chance of guessing correct which one sample is different than the two others Preference testing 1 Hedonic uses smiley faces to collect results 2 Scoring USDA uses it for meat and eggs CIE color uses XyY color L a b color uses XYZ coordinates x y z 1 comes from CIE color anything else with this Followed are the L A B values for an anthocyanin solution at different pHs Which one is likely to have the highest pH 76 8 13 5 34 3 74 2 24 7 18 9 70 2 30 1 11 6 A L 76 8 A 13 5 B 34 3 Ask about how to do this don t send exact question Spectrophotometry quantitative measurement of transmission properties of a material by wavelength Lambert Beers law A l c A absorbance Hydrolyzable tannins gallic acids are the basic unit and can be hydrolyzed into tannic acid dilute acid alkali can hydrolyze them Condensed tannins polymers of proanthocyanindins Anthocyanin acidic pH red color basic pH blue color betalains is another pigment with the same color that will not be in a plant if anthocyanin is there M 1 cm 1 l light path cm c concentration M Lecture 6 Carotenoids orange red color 1 Beta carotene in carrots vitamin A 2 Lycopene processed tomatoes have a better source of lycopene than fresh red color Dyes all colorants must be listed certified and exempt Lecture 7 there are no specific areas on the tongue for taste receptors sweet and umami taste receptors are similar in structure sucrose is the standard for sweetness with a relative sweetness of 1 Cyclamate banned from US FDA Neotame most potent sweetener permitted in food Sweet proteins Monellin from an African shrub Dioscoreophyllum cumensii slow onset sweetness