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