Chapter 2: Chemical changes caused by microorganisms Flashcards
PROTEINS
enzymes act on proteins to yield _____, simpler peptides to amino acids before proteins can serve as nitrogenous food for most microorganisms
polypeptides
PROTEINS
the breakdown of protein to _____ by proteinases may give a bitter taste
peptides
PROTEINS
the breakdown of protein to peptides by proteinases may give a _____ taste
bitter
PROTEINS
the breakdown of _____ by peptidases to simpler peptides to amino acids result in the development of desirable and undesirable flavors in foods
polypeptides
PROTEINS
the breakdown of polypeptides by peptidases to simpler peptides to amino acids result in the development of _____
desirable and undesirable flavors in foods
PROTEINS
the anaerobic decomposition of proteins as well as their breakdown products may result in the production of foul-smelling, sulfur-containing products (hydrogen, methyl, mercaptans plus ammonia and arnines [histamine, putrescine, and cadaverine])
putrefaction
PROTEINS
deamination and decarboxylation of amino acids may result in the production of glycoxylic acid, acetic acid, ammonia, methylamine, and methane that may give food its _____
objectionable flavors and odors
usually preferred by microorganisms as substrate for energy production
these are hydrolyzed to simple sugars before utilization
cho
CHO
simple sugars are oxidized to _____ (3)
co2, h2o, energy (ATP)
CHO:
fermentation by yeasts, yielding ethanol and co2
alcoholic fermentation
CHO:
fermentation by homofermentative lactic acid bacteria yielding lactic acid
simple lactic acid fermentation
CHO:
fermentation by heterofermmentative lactic bacteria yielding lactic and acetic acids, ethanol, glycerol, and co2
mixed lactic acid fermentation
CHO:
fermentation by coliform bacteria with lactic, acetic and formic acids, ethanol, co2
coliform type of fermentation
CHO:
fermentation by propionic bacteria, producing propionic, acetic and succinic acids, and co2
propionic fermentation
CHO:
fermentation by anaerobic bacteria yielding butyric and acetic acids, co2, hydrogen, and acetone, butylene glycol, butanol, and 2-propanol
butyric-butyl-isopropyl fermentations
oxidation of organic acids to cho by microorganisms makes food more alkaline
organic acids
organic acids
may be completely oxidized to co2 and water
aerobic
organic acids
saturated fatty acids may be degraded to acetic acid via the _____
b-oxidation pathway
lipids, pectic substances, and other compounds
are hydrolyzed by microbial enzymes to fatty acids and glycerol
fats
lipids, pectic substances, and other compounds
fats may also be oxidized by the _____ forming peroxidase that give the characteristic flavor and odor of rancid fats
lipoxygenases
lipids, pectic substances, and other compounds
the water-insoluble pectic substance is acted upon by pectinases to yield pectin, a water-soluble polymer of galacturonic acid
protopectin
lipids, pectic substances, and other compounds
are oxidized to their corresponding organic acids like acetic acids
alcohols
