Acids, Water and Bases – Flashcards
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Unlock answersBoiling point of water |
100 degrees C |
Freezing point of water |
0 degrees C |
Free water in food |
non-chemically bound, loosely entrapped, can be easily pressed out of/dried from foods; dispersing agent |
Absorbed water in food |
structural water, held by weak hydrogen bonds |
Bound water in food |
water of hydration, tightly held by chemical bonds (water-ion, water-water dipole interactions) as in crystals |
Moisture Sorption Isotherm |
relationship (plot) between moisture content and water activity for a food at constant temperature; influences food quality and microbial stability |
Water activity, Aw |
RH/100, important in food systems; measure of ability of water molecules to be reactive |
Aw .95 |
Microbes: Pseudomonas, Escherichia, Proteus, Shigella, Klebsiella, Bacillus, Clostridium perfringens, some yeasts Food ex.: Highly perishable foods (fresh and canned fruits, vegetables, meat, fish), milk, cooked sausages, breads, foods with up to 4 oz sucros or 7% NaCl |
Aw .90 * |
Microbes: Salmonella, Vibrio parabaemolyticus, C. botulinum, Lactobacillus, some molds
Food ex: Cheddar, Swiss, Provolone, cured meat, fruit juice concentrates with 55% sucrose or 12 NaCl |
Aw .87 |
Microbes: Many yeasts, Candida, Torulopsis, Hansenula, micrococcus Food ex: Fermented sausage, sponge cakes, dry cheese, margarine, foods with 65% sucrose or 15%NaCl |
Aw .80 * |
Microbes: Most molds, most Saccharomyces spp., Debaryomyces, Stphylococcus aureus Food Ex: Most fruit juice concentrates, condensed milk, syrup, flour, high-sugar cakes, pulses containing 15-17% moisture |
Aw .75 |
Microbes: Most halophilic bacteria, Mycotoxigenic aspergilli Food Ex: Jam, marmalade, glace fruits, marzipan, marshmallows |
Aw .65 |
Microbes: Xerophilic molds, Saccharomyces bisporus Food ex: Rolled oats with 10% moisture, jelly, molasses, nuts |
Aw .60 * |
Microbes: Osmophilic yeasts, few molds Food ex: Dried fruits with 15-20% moisture, caramel, toffee, honey |
Aw .50-.03 |
No microbial proliferation
Food ex: .50: Noodles with 12% moisture, spices with 10% moisture .40: Whole egg powder with 5% moisture .30: Cookies, crackers, bread crusts with 3-5% moisture .03: whole milk powder with 2-3% moisture, dehydrated soups, potato chips |
Halophiles |
Organisms that thrive in very high salt concentrations ex. the Great Salt Lake in Utah |
Xerophiles |
Organisms that survive in low moisture conditions ex. molds and yeast such as mold growth on bread |
Osmophiles |
Organisms that grow best in relatively high sugar or salt environments ex. organisms that ferment jams and jellies |
Thermophiles |
Organisms that grow best in relatively high temperature (~80c). Not relevant in food systems/production but useful in biotechnology. |
Aw under .5% |
Dried Foods |
Aw <0.9 |
unfavorable to bacterial growth |
Aw < 0.8 |
unfavorable for mold, yeast growth |
Aw < 0.85 |
inactivation of most enzymes |
Aw <0.7 |
inactivation of most fungi |
Aw <0.60 |
inactivation of microorganisms |
Emulsions formation |
(either dispersed or continuous phase) in development of foods ex. sausage, salad dressings |
Heat Transfer promotion |
(thermal energy conduction) promotes cooking |
Ingredient |
serves to influence flavor, texture, quality of food |
Plastisizer effect |
lowers glass transition temperature, affecting mouthfeel/texture of food |
Solvent |
disperses heat, other ingredients, promotes reactions (hydrolysis) |
Dehydration |
relatively low vaporization temperature, pressure (for preservation variation, portability, blendability, etc...) |
Food Acids-wide range of physical and chemical properties |
depending on type: includes amino acids (aspartic, glutamic acid), organic acids (citric, malic, tartaric acids), fatty acids (stearic, butyric), inorganic acids (phosphoric) |
Proton donors |
weak proton donorss, weak acids- small amount of ionic dissociation strong proton donors, strong acids-strong ion dissociation |
pH |
hydrogen ion concentration; more highly dissociated the acid, the more H+ ions present, to lower the pH(more acidic, stronger acid) |
pH Meter |
measures pH value (0/HCl-14/NaOH; 7=Neutral) |
Titratable Acidity |
Measure of the total acidity (both dissociated and undissociated hydrogen ions); used to monitor acid forming reactions (pH shifts) like fermentation |
Texturizer |
dough softening (fumaric acid), prevent clumping (low hygroscopicity) |
Flavorants |
sour, sweet impact; sweet flavor enhancement |
Buffering capacity |
maintain pH despite addition of acids or alkalis |
Leavening |
promote gas/CO2 formation with bicarbonates |
Antimicrobial |
lower pH (4.0 or less); higher with Hurdle approach |
Acid Foods |
pH 4.6 or below, naturally occuring ex. Oranges (pH 3-4), lemons (pH 2.2.-2.4), tomato juice (pH 4.1) |
Acidified Foods |
Low acid foods; acids added to low pH (4.6 or less) ex. Pickles, Colas (pH 2-4) |
Low-acid Foods |
pH 4.6 or greater (to neutral pH) ex. Coffee, black(pH 5.0), beef extract (pH 5-6) |
Fermented Foods |
Low acidic food due to microbial fermentation ex. Cheese (pH 5-6) |
Alkalis |
compounds with pH greater than 7.0 (base) and water solubility |
Most typical use of pH in food production |
adjust pH to desired (less acidic) levels; most foods are acidic |
pH Adjustments often needed for... |
Promotion of enzymatic activity (typical pH 6.5-8); Promotion of Maillard reactions/Flavor development (pH~8 ideal); Taste Enhancement, less sourness or "acidic bite"; Promote texture effects (precipitate, extrude proteins) |
Most common alkali used: |
NaOH "sodium hydroxide" (Food Grade, 50%) also called liquid caustic soad |