2. INTRODUCTION
Canning is a method of preservation of food
in which food contents is processed and
sealed in airtight container such as
metal,glass, thermostable plastic or
multilayered flexible pouch
Heating is the principle factor to destroy
most of the microorganisms and the
permanent sealing is to prevent
recontamination
Canning provides a shelf life typically
ranging from one to five years, although
under specific circumstances it may be
more or less
3. FOODS THAT ARE CANNED
ON THE BASIS OF PH
1) Low acid foods : The foods that fall under th
pH 5.0 to 6.8 such as meat,fish,poultry,dairy is
referred to as low acid foods
2)Acids food : The foods with pH values between
4.5 and 3.7 are referred to as acids food.Eg:Fruits
such as pear,oranges, apricots and tomatoes
3)High acids food : The foods with pH ranges
between 3.7 down to 2.3 such as pickled
products,fermented products,jams,jellies etc are
referred to as high acids food
4. Spoilage of canned food occurs by three
ways:
1) Survival of spores of thermophilic
bacteria due to inadequate heating of
canned food
2) Allowing germination and growth of
thermophilic bacteria due to
inadequate cooling after heating or
improper temperature storage
3) Recontamination of microorganisms
from outside through leak in the
container
Canned food spoilage
5. 2
» Spoilage by mesophilic
spore forming bacteria
1.Spoilage by mesophilic
Clostridium species
2.Spoilage by mesophilic
Bacillus Species
4
» Spoilage by Yeast and
Mold
1
» Spoilage by thermophilic
spore-forming bacteria
1.Flat sour
2. Thermophilic anaerobic
spoilage
3. Thermophilic Anerobic
Sulfide Spoilage
3
» Spoilage by non-spore
forming bacteria
Types of biological spoilage of
canned food
6. SPOILAGE BY THERMOPHILIC
SPORE-FORMING BACTERIA
1.Flat sour
*Occurs only in low acid foods (such as peas and corn) and acid foods (such as tomatoes or tomato juice)
*Caused by the species of Bacillus such as Bacillus coagulans and Bacillus stearothermophilus
*Souring due to acid formation
*No gas formation(no swelling of can)
*Source is usually plant equipment (e.g blanchers),sugar and starch
*can be detected only by culture methods
B. coagulans-
* germinate at 43 °C and above
* Grows well between at 30-50 °C
* Homofermantative under anaerobic cond.
* Heterofermentative under aerobic conditions
B. stearothermophilus
* Optimum growth temp. is 55 °C
8. 2.Thermophilic Anerobic Spoilage
* Anaerobic Clostridium thermosaccharolyticum
is responsible
* H2 and CO2 gases produced at high temp.
* Swells the can and causes bursting
* Seen at medium acid can food products
* Sour fermentation and butyric or cheesy odor
THERMOPHILIC SPORE-FORMING
BACTERIA
9. Thermophilic spore-forming
bacteria
3.Thermophilic Anaerobic Sulfide Spoilage
* No swelling, H2S production and rotten egg odor
* HS produced by organism dissolves in the liquid and reacts with tin
*Iron sulfide precipitation gives black color in food and the inner wall of can
Obligate anaerobes are responsible Disulfotomacullum nigrificans
*They germinate and grow at thermophilic range
*Low acid canned foods (pears, corn, etc.)
*It indicates under processing, slow cooling or hot storage
11. Spoilage by mesophilic spore-
forming bacteria
1. Spoilage by mesophilic Clostridium species :
°C. butyricum and C. pasteurianum are mostly responsible
* Ferment sugar to produce volatile acids (butyric acid) ¢&
Produce H2 and CO2 gases with swelling
* Also C. sporogenes, C. putraficiens, C. botulinum are proteolytic
and putrefactive organism(metabolizes protein)
&Foul smelling compounds H2S , mercaptans, indoles and
ammonia
*Best grow in low acid canned food such as
meat,fish,corn,pea
12. Mesophilic spore-forming
bacteria
2.Spoilage by mesophilic Bacillus species
*Mesophilic Bacillus spore are not heat resistant as well as the
thermophiles
*They survive in inadequate heated canned foods (in low acid home
canned foods) at 100° C
*Mostly spoiled foods are Seafoods, meats and evaporated milk. °B.
polymyxa and B macerans cause spoilage in canned peas, asparagus,
spinach, peaches and tomatoes
*Usually spoiled food by contamination through leakage container
13. Spoilage by Non-sporeforming
Bacteria
* Non-spore forming bacteria survive in cans because of
mild heat treatment or leakage of the can
* Thermoduric nonspore forming bacteria can survive at
mild heat treatment
* Enterococcus, Microbacterium, Streptococcus
thermophilus, some species of Micrococcus and
Lactobacillus
14. * Acid forming Lactobacillus and Leucocnostoc spp. Can survive in
underprocessed tomato products, pears and other fruits
* Heterofermentative — release CO2-swell the can by the production
of gas.
* Due to leakage of the can- Psedudomonas, Alcaligenes,
Flavonabacterium, proteus and other microorganisms can also
causes spoilage
17. Their presences in canned foods
indicates under processing,
leakage,recontamination and
poor evacuation
Fermentative yeast can spoil
canned fruits, jams, jellies, fruit
juices, syrups and sweetened
condensed milk
Swelling the cans by CO2
production
yeast may grow on the surface of
pickled meat, pickles, olives and
similar products
Spoilage by
Yeast and
Mold
18. Molds are the most common food
spoilage microoganisms in home
canned foods due to high sugar
content (70%)
Mold species such assclerotia and
bysschlamys are heat resitance and
surie the mild heat treatment
Others may enter through leakage in
the can
Defects:moldy taste,odor,color fading
and presence of mold mycelia
