Food Chem: Acids
Ka
acid ionization constant for weak acids, large Ka=stronger acid
acidified food
added acid to get </= 4.6 and Aw>0.85
milk protein coagulation
adding acid (H+) for pH of 4.6, neutralizes casein proteins, making it insoluble (no longer repels each other) and it precipitates into a curd
acetic acid, acetates, diacetates, dehydroacetic acid
antimicrobials used in baked goods, condiments, confections, dairy products, fats/oils, meats and sauces for yeast and bacteria
propionic acid, propionates
antimicrobials used in bakery products and dairy products for mold
benzoic acid, benzoates
antimicrobials used in beverages, fruit products, margarine for yeasts and molds
lactic acids, lactates
antimicrobials used in meats and fermented foods for bacteria
sorbic acid, sorbates
antimicrobials used in most foods, beverages, and wine for yeasts, mold, bacteria
raising agent and shelf life enhancer in the baking industry-It adds firmness, and is a source of calcium for food products
calcium lactate
dissociated acid molecules
cannot penetrate the cell membrane, cause damage to the membrane protein. This alters membrane permeability for minerals, such as sodium and potassium, changes the osmotic cell pressure and ultimately leads to cell death.
yeast fermentation
carbohydrates are converted to carbon dioxide gas and ethanol
citric acid
citrus juice, jams
additivity
combination of 2 or more chemicals is the sum of he expected individual responses
Calcium lactate
compound produced by exposing calcium carbonate to lactic acid (C3H6O3)
organic salts
compounds formed from organic acids in which the hydrogen atom of the COOH is replaced by a metal ion such as sodium, calcium, or potassium
double acting baking powder
contain 2 types of acid, first creates gas when mixed with liquid, the second creates gases in oven heat
organic acids
contain COOH, has antimicrobial effect caused by undissociated and dissociated acid molecules
butyric acid
fatty acid in rotten meats, rancid butter, etc.
acid food
foods naturally below or equal to 4.6
potassium sorbate
inhibit molds and yeasts in cheese, wine, yogurt, dried meats, dried fruit products, apple cider, soft drinks, fruit drinks, baked goods, herbal dietary supplements; used in 0.025%-0.1%
phosphoric acid
inorganic, cola, cereal bars
pKa
inverse of Ka, lower pKa, stronger the acid
fermentation in dairy
lactose hydrolysis->glucose fermentation->lactic acid
chemical leavening
leavening acids generate H ions that facilitate the release of CO2 from baking soda to cause dough expansion
undissociated acid molecules
lipophilic and can penetrate cell membranes of pathogenic bacteria. weakens microorganism and inhibits enzyme activity stopping propagation
fermented foods
low-acid food subjected to the acid producing action of certain microbes to reduce the pH of the food to ≤ 4.6
quick breads
made with chemical leavening, CO2 release faster through acid-base reaction
titratable acidity
measure of total acidity, dissociated and non-dissociated hydrogen ions
baking powder
mix of baking soda and acid
pH
pH=-log[H+], food is usually in 2-8 range
low-acid food
pH>4.6, Aw>0.85
leavening
production of gas by yeast fermentation, by the reaction of an acid with baking soda or by the heating of salts
amino acids
protein, sports supplements
acid
sour, corrosive, neutralized by alkalis, change litmus from blue to red
dough softening
sulfhydryl group apart of cysteine group on gluten becomes oxidized during flour mixing, baking and storage, losing the hydrogen. Form s-s disulfide bonds, tightening the dough structure. Add fumaric acid to reduce back to SH to soften
sodium benzoate
used in acidic foods like salad dressings, carbonated drinks, jams and fruit juices, pickles and condiments; FDA limits to 0.1% by weight, reacts with ascorbic acid to form benzene (carcinogen)
acetic acid
vinegar, fermented vegetables
ascorbic acid
vitamin C in citrus fruits, cranberry drink
buffer system
weak acid and its salt, has the ability to maintain pH stability in foods up to 1/2 pH unit on either side of pKa, ie acetic acid (vinegar)/sodium acetate & lactic acid (milk acid)/calcium lactate
Sodium acetate
white, hygroscopic, crystalline solid having an odor of acetic acid (vinegar), used to season potato chips, and as a antimicrobial/preservative in RTE meat or cheese products
malic acid
wine, apples
lactic acid
yogurt, cheese