Chapter 2: Chemical changes caused by microorganisms

Question 1

PROTEINS

enzymes act on proteins to yield _____, simpler peptides to amino acids before proteins can serve as nitrogenous food for most microorganisms

Answer 1

polypeptides

Question 2

PROTEINS

the breakdown of protein to _____ by proteinases may give a bitter taste

Answer 2

peptides

Question 3

PROTEINS

the breakdown of protein to peptides by proteinases may give a _____ taste

Answer 3

bitter

Question 4

PROTEINS

the breakdown of _____ by peptidases to simpler peptides to amino acids result in the development of desirable and undesirable flavors in foods

Answer 4

polypeptides

Question 5

PROTEINS

the breakdown of polypeptides by peptidases to simpler peptides to amino acids result in the development of _____

Answer 5

desirable and undesirable flavors in foods

Question 6

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])

Answer 6

putrefaction

Question 7

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 _____

Answer 7

objectionable flavors and odors

Question 8

usually preferred by microorganisms as substrate for energy production

these are hydrolyzed to simple sugars before utilization

Answer 8

cho

Question 9

CHO

simple sugars are oxidized to _____ (3)

Answer 9

co2, h2o, energy (ATP)

Question 10

CHO:

fermentation by yeasts, yielding ethanol and co2

Answer 10

alcoholic fermentation

Question 11

CHO:

fermentation by homofermentative lactic acid bacteria yielding lactic acid

Answer 11

simple lactic acid fermentation

Question 12

CHO:

fermentation by heterofermmentative lactic bacteria yielding lactic and acetic acids, ethanol, glycerol, and co2

Answer 12

mixed lactic acid fermentation

Question 13

CHO:

fermentation by coliform bacteria with lactic, acetic and formic acids, ethanol, co2

Answer 13

coliform type of fermentation

Question 14

CHO:

fermentation by propionic bacteria, producing propionic, acetic and succinic acids, and co2

Answer 14

propionic fermentation

Question 15

CHO:

fermentation by anaerobic bacteria yielding butyric and acetic acids, co2, hydrogen, and acetone, butylene glycol, butanol, and 2-propanol

Answer 15

butyric-butyl-isopropyl fermentations

Question 16

oxidation of organic acids to cho by microorganisms makes food more alkaline

Answer 16

organic acids

Question 17

organic acids

may be completely oxidized to co2 and water

Answer 17

aerobic

Question 18

organic acids

saturated fatty acids may be degraded to acetic acid via the _____

Answer 18

b-oxidation pathway

Question 19

lipids, pectic substances, and other compounds

are hydrolyzed by microbial enzymes to fatty acids and glycerol

Answer 19

fats

Question 20

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

Answer 20

lipoxygenases

Question 21

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

Answer 21

protopectin

Question 22

lipids, pectic substances, and other compounds

are oxidized to their corresponding organic acids like acetic acids

Answer 22

alcohols