Acids, Water and Bases – Flashcards
Unlock all answers in this set
Unlock answers| Boiling 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 |
