Food Science Final Exam
Dt. Specchio Lipids Food Color Food Prservation
Terms in this set (86)
lipid that is solid at room temperature, usually from animal sources
lipid that is liquid at room temperature, usually from plants
3 compounds in lipid family: triglycerides (fats and oils), phospholipids, & ____________
________ + 3 fatty acids=triglyceride structure
What type of fatty acids are Linoleic acid and Linolenic acid?
Linoleic acid is an omega-_ fatty acid
Linolenic acid is an omega-_ fatty acid
Component of cell membrane; ideal emulsifiers;
found in Egg yolks, liver, soybeans, wheat germ, and peanuts; polar, hydrophillic "head" two nonpolar, hydrophobic "tails"
oil on inside (lipophillic part on inside) and water on outside (hydrophillic part on outside)
water on inside (hydrophillic part on inside )and water on outside (lipophillic part on outside)
Sterols in body
cholesterol, bile, sex hormones (testosterone, estrogen) and adrenal hormone (cortisol), and vitamin D
soybeans, and small amounts in fruits, vegetables, nuts, seeds, legumes
What is used to make bile for digestion?
cholesterol makes a mixture of compounds, made by the liver, stored in the gallbladder, and secreted into the small intestine
functions of fats:
____ ______, shortening/leavening power, flavor/texture
turns liquid oils (e.g., soybean, corn, canola) to solid or semi-solid fats, the process of adding hydrogen to unsaturated fatty acids, making them more saturated and thereby more solid at room temperature
partially hydrogenated oil
Converts healthy fat to an unhealthy fat (change from cis (natural) to trans (unnatural)) turns liquid oils to solid or semi-solid fats
We want to avoid trans fat, by avoiding partially hydrogenated oils
emulsifies lipids to prepare them for enzymatic digestion & helps transports them into intestinal cell walls
Advantages of hydrogenation
Enables higher heating temperatures without smoking & Increases shelf life
Most abundant type of fat replacers; Help retain moisture to maintain the juiciness or creaminess that is lost with fat reduction; Fruit purees, fibers, gums, starches, pectin, cellulose
fat replacers that are cooked & blended to form tiny round particles that trap water to maintain the mouthfeel of fat; made from Whey protein concentrate, egg white proteins, or soy proteins
fat replacers that are either only partially digestible or completely undigestible to prevent absorption of fat; Caprenin, Salatrim, and Olestra
Chemical deterioration of lipids, causing off-flavor and rancid odors, The overall chemical deterioration of fats, which occurs when the triglyceride molecule and/or the fatty acids attached to the glycerol molecule are broken down into smaller units that yield off-flavors and unpleasant odors is called _____.
when water is added to fat, and the lipid breaks down into three fatty acids and a glycerol molecule , breaking of chemical bonds with the addition of water. Lipase may cause the breaking of bonds. The release of short chain fatty acids give flavors and odors
-Butyric acid- 4 carbons (short chain, no double bonds), fatty acid in butter
-Need: water and lipase, free the short chain fatty acid
rancidity that occurs with exposure to oxygen, heat, light, development of off-flavors and odors in Unsaturated Fats
results of the uptake of oxygen and the formation of peroxides, hydroperoxides, etc
Molecules that neutralize free radicals, thereby preventing them from causing damage to cells
preventing oxidative rancidity:
Avoid _______ by using vacuum packs or nitrogen;
Avoid heat & light; keep in cool, dark place
First impression is made based on?
processing Enhance Minimize
4 reasons to color food
1. Offset color loss due to _________
2. ______ colors
3. _______ natural variations
4. Color otherwise colorless food
polyphenotic compounds made of conjugated double bonds whose natural color that is red-purple (grapes, blueberries)
water pH antioxidants
4 facts about anthocyanins
1. ____-soluble pigments
2. color depends on __
3. Powerful _______
red or pink
colors of anthocyanin when pH<7
color of anthocyanin when pH~7
Blue, green or yellow
colors of anthocyanin when pH>7
color of anthocyanin when in very alkaline solution
anthocyanin molecule forms complex with other compounds - brighter, stronger, more stable color
Organic acids attached to the sugar moiety of anthocyanin through covalent acyl linkage ("acylated anthocyanins") - copigments become part of anthocyanin molecule; sandwich stacking; pH 4-5
Phenolic compounds and anthocyanins "stack" on top of each other - overlapping arrangement of the two molecules; H-bonds and hydrophobic interactions are main driving forces; more common in fruits, Are more common fruits. More red color at higher pH level. Greater application range in foods
most abundant pigment
found in chloroplasts
important in photosynthesis - produces glucose, water, and OXYGEN - the only place humans get oxygen
has 3 different states
structurally unique, a chlorophyll has A ________ ion in the center of the ring
pH 5 - chlorophyll
normal vegetable green color
pH < 5 pheophytin
Mg++ is lost and the color changes to the characteristic olive green color
pH >7 chlorophyllin
the methyl and phytyl esters are removed, producing a
olive drab green is also called ________ when heating chlorophyll
loss of Mg++ (pheophytin)
effect of heating on chlorophyll
effects of ________on chlorophyll:
chlorophyllase - removes the phytol group
loses some color
photodegradation - irreversible bleaching
effects of light and oxygen
the addition of _____ and ____ help you maintain green color in canned green vegetables?
what color food is rich in beta-carotene?
what color foods contain lutein and zeaxanthin?
chlorophyll degrades and carotene pigments are able to come out
how do you explain leaves changing color in the fall?
Bright red pigment
Found in tomatoes, watermelons, papayas, pink grapefruit
A polyunsaturated hydrocarbon - fat-soluble
11 conjugated double bonds give red color
what gives lycopene its red color?
molecules of vitamin A per molecule of beta cartotene
An accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis
the red pigment in tomatoes and watermelons, has 11 conjugated double bonds. Fat Soluble. It is also an antioxidant, a compound that prevents unwanted oxidation from occurring. Diets containing high levels of antioxidants result in decreased risk of heart disease and cancer.
LUTEIN & ZEAXANTHIN
Hydroxyl carotenoids accumulated in human retina
Fat soluble antioxidant that neutralizes free radicals and helps slow the aging process. It is converted to vitamin A in the body.Two beta rings at both ends of molecule. splitting one molecule of this compound produces two molecules of vitamin A; antioxidant,
Changing raw products into more stable forms that can be stored for longer periods of time.
what is food preservation?
Temperature preservatives Fermentation
6 preservation approaches
Water activity (lower)
4 heat preservation methods
kill 100% pathogenic microorganisms and most nonpathogenic microorganisms, and inactivate enzymes. 161F, 15s
inactivate enzymes within a food product to improve quality, used mainly for vegetables and fruits prior to freezing or canning. Heat the product using boiling water. 212F
MILD heat treatment. Used for jams, jellies, syrups, sauces
Lower pH, water activity, or add preservatives
1. product heated to 180 degrees F
2. filled into container
3. vacuum is formed (anaerobic env.)
destroy both vegetative cells and spores of pathogenic & spoilage microorganisms 241-250F
pH > 4.6
pH < 4.6
the time in minutes at a specified T required to destroy 90% of m.o. in a given population
time/temperature process that will reduce the C. botulinum spore population by 12 log cycles - Required for low acid (pH < 4.6) canned foods
problem with freezing caused by fluctuating temp; ice crystals enlarge with refreezing
problem with freezing caused by dehydration (sublimation of ice); surface of food; solve: moisture-proof freezer wrap
problem with freezing that causes fat to have an off-flavor and enzymatic browning; solve: blanching before freezing
Most bacteria can't grow below aw=
No microbial growth below aw =
• Food paste is applied to a heated drum in a thin layer to cause fast drying
• The dried food is scraped off the drum
• Ex. Dehydrated mashed potatoes
When food is frozen at temperatures above -18°C. This is quite a slow method so water moves while freezing, resulting in large ice crystals forming. During thawing, the large ice crystals dissolve breaking cell walls and releasing vitamins. Slow freezing increases the risk of vitamin loss and effects the texture of food.
Quick method of freezing that causes tiny ice crystals @ -25'C, very little damage to cell walls.
Method of preservation where food is sprayed with or immersed in liquid nitrogen. The food is frozen quickly and results in excellent quality preservation.
Relative humidity of the product/Relative humidity of pure water
Total water content
bound water + free water=
product is sprayed into a large, hot chamber along with hot air, an atomizer form fine droplets that facilitate the dehydration; fluid products like eggs, milk, coffe and tea
product frozen, then put in vacuum chamber, water leaves product via sublimation, goes directly from solid to gas, little or no heat is added and flavor/texture is retained, expensive
Add solutes to the food: (1) ___ "free" water to reduce aw (2) ______ micro
Sugar (e.g., jam), salt (e.g., ham, bacon), etc.
problems associated with drying:
1.Enzymatic reactions - controlled by blanching or adding sulfur compounds before drying
2. Non-enzymatic browning - caramelization or Maillard browning
3. _______ _________
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