270 ◾ Fundamental Food Microbiology
Flat Sour Spoilage
The cans do not swell, but the products become acidic because of germination and growth of
facultative anaerobic Bac. stearothermophilus. Germination occurs at high temperatures (43°C and
above), but growth can take place at lower temperatures (30°C and above). The organism ferments
carbohydrates to produce acids without gas but with some off-flavor and cloudiness.
Thermophilic Anaerobe (TA) Spoilage
This spoilage is caused by the growth of anaerobic Clo. thermosaccharolyticum with the production
of large quantities of H 2 and CO 2 gas and swelling of cans with a sour and cheesy odor. Following
germination in the thermophilic range (43°C and above), the cells can grow at lower temperatures
(30°C and above).
Sulfide Stinker Spoilage
This spoilage is caused by the Gram-negative anaerobic spore former Desulfotomaculum nigrificans. The spoilage is characterized by a flat container but with darkened products with the odor
of rotten eggs resulting from H 2 S produced by the bacterium. H 2 S, produced from the sulfurcontaining amino acids, dissolves in the liquid and reacts with iron to form the black color of iron
sulfide. Both germination and growth occur in the thermophilic range (43°C and above).
Spoilage Resulting from Insufficient Heating
Insufficient heat treatment results in the survival of mainly spores of Clostridium and some Bacillus
spp. Following processing, they can germinate and grow to cause spoilage. The most important
concern is the growth of Clo. botulinum and production of toxins.
Spoilage can be from either the breakdown of carbohydrates or proteins. Several Clostridium
spp., such as Clo. butyricum and Clo. pasteurianum, ferment carbohydrates to produce volatile
acids and H 2 and CO 2 gas, causing swelling of cans. Proteolytic species, Clo. sporogenes and Clo.
putrefacience (also proteolytic Clo. botulinum), metabolize proteins and produce foul-smelling
H 2 S, mercaptans, indole, skatole, and ammonia as well as CO 2 and H 2 (causing swelling of cans).
Spores of aerobic Bacillus spp., surviving inadequate heating, do not grow in cans. However,
spores of some facultative anaerobic Bacillus spp., such as Bac. subtilis and Bac. coagulans, grow
with the production of acid and gas (CO 2 ).
Spoilage Resulting from Container Leakage
Damaged and leaky containers allow different types of microorganisms to get inside from the environment after heating. They can grow in the food and cause different types of spoilage, depending
on the microbial types. Contamination with pathogens makes the product unsafe.
Conclusion
This chapter discusses why different food types or food groups differ in microbial spoilage characteristics. The predominant nutrients being metabolized and the predominant microorganisms
Flat Sour Spoilage
The cans do not swell, but the products become acidic because of germination and growth of
facultative anaerobic Bac. stearothermophilus. Germination occurs at high temperatures (43°C and
above), but growth can take place at lower temperatures (30°C and above). The organism ferments
carbohydrates to produce acids without gas but with some off-flavor and cloudiness.
Thermophilic Anaerobe (TA) Spoilage
This spoilage is caused by the growth of anaerobic Clo. thermosaccharolyticum with the production
of large quantities of H 2 and CO 2 gas and swelling of cans with a sour and cheesy odor. Following
germination in the thermophilic range (43°C and above), the cells can grow at lower temperatures
(30°C and above).
Sulfide Stinker Spoilage
This spoilage is caused by the Gram-negative anaerobic spore former Desulfotomaculum nigrificans. The spoilage is characterized by a flat container but with darkened products with the odor
of rotten eggs resulting from H 2 S produced by the bacterium. H 2 S, produced from the sulfurcontaining amino acids, dissolves in the liquid and reacts with iron to form the black color of iron
sulfide. Both germination and growth occur in the thermophilic range (43°C and above).
Spoilage Resulting from Insufficient Heating
Insufficient heat treatment results in the survival of mainly spores of Clostridium and some Bacillus
spp. Following processing, they can germinate and grow to cause spoilage. The most important
concern is the growth of Clo. botulinum and production of toxins.
Spoilage can be from either the breakdown of carbohydrates or proteins. Several Clostridium
spp., such as Clo. butyricum and Clo. pasteurianum, ferment carbohydrates to produce volatile
acids and H 2 and CO 2 gas, causing swelling of cans. Proteolytic species, Clo. sporogenes and Clo.
putrefacience (also proteolytic Clo. botulinum), metabolize proteins and produce foul-smelling
H 2 S, mercaptans, indole, skatole, and ammonia as well as CO 2 and H 2 (causing swelling of cans).
Spores of aerobic Bacillus spp., surviving inadequate heating, do not grow in cans. However,
spores of some facultative anaerobic Bacillus spp., such as Bac. subtilis and Bac. coagulans, grow
with the production of acid and gas (CO 2 ).
Spoilage Resulting from Container Leakage
Damaged and leaky containers allow different types of microorganisms to get inside from the environment after heating. They can grow in the food and cause different types of spoilage, depending
on the microbial types. Contamination with pathogens makes the product unsafe.
Conclusion
This chapter discusses why different food types or food groups differ in microbial spoilage characteristics. The predominant nutrients being metabolized and the predominant microorganisms