natural polymers made from combos of 20 different amino acids
What is the structure of an amino acid?
How do proteins form?
amino acids form peptide bonds through condensation reactions; form chains
What is a saturated fatty acid?
carboxylic acid chain with only single C-C bonds
What is a unsaturated fatty acid?
carboxylic acid chain with one double C=C bond
What is a polyunsaturated fatty acid?
carboxylic acid chain with more than one double C=C bond
Why do some fatty acids have a "kink(s)"?
because of the double bond(s); only unsat/polyunsat have them
Which fatty acids have the lowest melting point? Why?
the ones with the most double C=C bonds because it creates more separation between the chains and makes it easier to break apart
What is a cis unsaturated fat?
the form of a molecule where both hydrogen atoms are on the same side of the double C=C bond
What is a trans unsaturated fat?
the form of a molecule where the hydrogen atoms are on different sides of the double C=C bond
Does a cis fat or a trans fat have a lower melting point?
cis isomer because they can't arrange themselves side by side in order to solidify, makes them easier to break apart
Which one leads to heart disease?
trans isomer because they produce LDL cholesterol
What is rancidity?
when lipids break down and change their physical properties
What are the physical properties of rancidity?
disagreeable smell, taste, texture, or appearance
What is auto-oxidation?
the oxidation of unsaturated fats by oxygen (occurs in the air without the help of enzymes)
What are antioxidants?
substances that delay the rate of oxidation; ex. selenium vitamins A, C, and E, and beta-carotene
What foods in selenium found in?
fish, red meats, eggs
What foods is vitamin C found in?
citrus fruits, green leafy vegetables
What is another way oxidation can be delayed?
What is hydrogenation?
when hydrogen is added to lipids across the double C=C bond in order to decrease the level of unsaturation (ie make it saturated/no more double C=C bonds)
What are the advantages of hydrogenation?
decreases the rate of oxidation and increases hardness
What are the disadvantages of hydrogenation?
saturated fats are unhealthier, trans fatty acids are hard to metabolize and can accumulate in fatty tissue
What is shelf life?
our perception of how long a food can stay fresh
What happens when a food is past its shelf life?
no longer maintains the expected quality desired by us because of changes in flavor, smell, texture, color, mass, or microbial spoilage
What is autolysis?
breakdown of food by the enzymes present in the food, causes the release of nutrients
What is microbial spoilage?
when microorganisms use those nutrients (instead of them staying in the food's cells) and render the food unacceptable to eat
What are the chemical factors that decrease shelf life?
changes in water content, pH, light, temperature
What are additives?
chemical compounds that slow down the rate of food deterioration
What are examples of synthetic antioxidants?
BHA and BHT
What is a pigment?
a naturally occurring color found in the cells of plants and animals
What are the main groups of pigments?
porphyrins, carotenoids, and anthocyanins
What are the structural features of porphyrins?
ring shaped molecules with a metal atom in the middle; ex. chlorophyll a and b
What are the structural features of carotenoids?
fat soluble, long chain hydrocarbon molecules
What is special about carotenoids?
they are also antioxidants because they can be converted to vitamin a (share many properties)
What are the structural features of anthocyanins?
water soluble, three ring structure with double C=C bonds
What is an example of each category of pigment?
porphyrins = chlorophyll a and b; carotenoids = butter/grass; anthocyanins = lobster
What is a dye?
water soluble substances that are added to food to improve their color (can be synthetic or from another organic source)
What things can impact pigments?
temperature, pH changes, oxidation
What is enzymatic browning?
chemical process in fruits and veggies that uses an enzyme to create brown pigments and decreases the quality of the food
What is caramelization?
a form of non-enzymatic browning that creates brown pigments but does not decrease quality; involves sugar and the breakdown of sugar molecules at high temperatures
What is Maillard browning?
another form of non-enzymatic browning that creates brown pigments but does not decrease quality; complex series of reactions between amino acids and reducing sugars; involves condensation and fragmentation reactions
Give examples of caramelization.
bakery goods, coffee, soft drinks, beer, peanuts
Give examples of Maillard browning.
heating sugar and cream to make toffees, caramels, fudges, milk chocolate
What are genetically modified foods?
foods whose DNA has been changed to improve certain qualities or traits
What are some benefits of genetically modified foods?
improved flavor, texture, and nutritional value; longer shelf life; more resistant to disease and pests; increased crop yields
What are some concerns about genetically modified foods?
potential increased allergies; risk of altering the balanced diet; genetically modified pollen contaminating other fields
What is a dispersed system?
kinetically stable mixture of one phase in another largely immiscible phase, separates into components w/ different densities but slowly
What is an emulsifier?
substance that helps the mixing of two phases (oil in water and water in oil)
What is the polarity of an emulsifier?
polar hydrophilic head and a nonpolar hydrophobic tail
Give an example of an emulsifier.
Give examples of things that need to be emulsified.
milk, salad dressing, butter
What are stabilizers?
substances that are added to prevent the emulsions from separating into different phases
What are the types of dispersed systems?
aerosol, foam, emulsion, suspension, and gel
Give an example of each type of dispersed system.
aerosol = mist/smoke; foam = whipped cream/beer; emulsion = milk/butter; suspension = molten chocolate; gel = jam