Acids, Water and Bases – Flashcards

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Boiling point of water
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100 degrees C
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Freezing point of water
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0 degrees C
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Free water in food
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non-chemically bound, loosely entrapped, can be easily pressed out of/dried from foods; dispersing agent
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Absorbed water in food
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structural water, held by weak hydrogen bonds
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Bound water in food
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water of hydration, tightly held by chemical bonds (water-ion, water-water dipole interactions) as in crystals
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Moisture Sorption Isotherm
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relationship (plot) between moisture content and water activity for a food at constant temperature; influences food quality and microbial stability
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Water activity, Aw
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RH/100, important in food systems; measure of ability of water molecules to be reactive
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Aw .95
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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

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Aw .90 *
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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

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Aw .87
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Microbes: Many yeasts, Candida, Torulopsis, Hansenula, micrococcus

Food ex: Fermented sausage, sponge cakes, dry cheese, margarine, foods with 65% sucrose or 15%NaCl

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Aw .80 *
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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

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Aw .75
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Microbes: Most halophilic bacteria, Mycotoxigenic aspergilli


Food Ex: Jam, marmalade, glace fruits, marzipan, marshmallows

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Aw .65
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Microbes: Xerophilic molds, Saccharomyces bisporus

Food ex: Rolled oats with 10% moisture, jelly, molasses, nuts

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Aw .60 *
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Microbes: Osmophilic yeasts, few molds

Food ex: Dried fruits with 15-20% moisture, caramel, toffee, honey

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Aw .50-.03
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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

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Halophiles
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Organisms that thrive in very high salt concentrations ex. the Great Salt Lake in Utah
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Xerophiles
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Organisms that survive in low moisture conditions ex. molds and yeast such as mold growth on bread
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Osmophiles
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Organisms that grow best in relatively high sugar or salt environments ex. organisms that ferment jams and jellies
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Thermophiles
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Organisms that grow best in relatively high temperature (~80c). Not relevant in food systems/production but useful in biotechnology.
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Aw under .5%
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Dried Foods
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Aw <0.9
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unfavorable to bacterial growth
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Aw < 0.8
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unfavorable for mold, yeast growth
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Aw < 0.85
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inactivation of most enzymes
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Aw <0.7
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inactivation of most fungi
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Aw <0.60
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inactivation of microorganisms
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Emulsions formation
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(either dispersed or continuous phase) in development of foods ex. sausage, salad dressings
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Heat Transfer promotion
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(thermal energy conduction) promotes cooking
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Ingredient
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serves to influence flavor, texture, quality of food
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Plastisizer effect
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lowers glass transition temperature, affecting mouthfeel/texture of food
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Solvent
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disperses heat, other ingredients, promotes reactions (hydrolysis)
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Dehydration
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relatively low vaporization temperature, pressure (for preservation variation, portability, blendability, etc...)
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Food Acids-wide range of physical and chemical properties
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depending on type: includes amino acids (aspartic, glutamic acid), organic acids (citric, malic, tartaric acids), fatty acids (stearic, butyric), inorganic acids (phosphoric)
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Proton donors
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weak proton donorss, weak acids- small amount of ionic dissociation
strong proton donors, strong acids-strong ion dissociation
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pH
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hydrogen ion concentration; more highly dissociated the acid, the more H+ ions present, to lower the pH(more acidic, stronger acid)
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pH Meter
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measures pH value (0/HCl-14/NaOH; 7=Neutral)
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Titratable Acidity
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Measure of the total acidity (both dissociated and undissociated hydrogen ions); used to monitor acid forming reactions (pH shifts) like fermentation
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Texturizer
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dough softening (fumaric acid), prevent clumping (low hygroscopicity)
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Flavorants
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sour, sweet impact; sweet flavor enhancement
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Buffering capacity
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maintain pH despite addition of acids or alkalis
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Leavening
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promote gas/CO2 formation with bicarbonates
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Antimicrobial
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lower pH (4.0 or less); higher with Hurdle approach
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Acid Foods
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pH 4.6 or below, naturally occuring ex. Oranges (pH 3-4), lemons (pH 2.2.-2.4), tomato juice (pH 4.1)
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Acidified Foods
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Low acid foods; acids added to low pH (4.6 or less) ex. Pickles, Colas (pH 2-4)
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Low-acid Foods
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pH 4.6 or greater (to neutral pH) ex. Coffee, black(pH 5.0), beef extract (pH 5-6)
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Fermented Foods
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Low acidic food due to microbial fermentation ex. Cheese (pH 5-6)
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Alkalis
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compounds with pH greater than 7.0 (base) and water solubility
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Most typical use of pH in food production
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adjust pH to desired (less acidic) levels; most foods are acidic
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pH Adjustments often needed for...
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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)
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Most common alkali used:
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NaOH "sodium hydroxide" (Food Grade, 50%) also called liquid caustic soad
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