Dr. Geeta Chauhan
Division of Livestock Products Technology
Indian Veterinary Research Institute
Izatnagar, Bareilly (UP), India
Food preservation has been known and used since
ancient times. The art was used to preserve various
food commodities like meat, fish, fruits and
vegetables, by applying methods such as drying,
salting and smoking etc. These traditional methods are
of great importance in present times as well. With the
advancements, the food preservation has become
more a science based on the latest developments in
science and technology.
The primary cause of food spoilage is the action of
micro organisms like bacteria, molds or yeasts added
by enzymes. These microbes require favorable
environment fortheirsurvival and underunfavorable
conditions, they fail to grow and die. The prevention
of food spoilage is the primary purpose of food
preservation. Thus, the underlying principle of food
preservation methods is to create the unfavorable
conditions for the spoilage micro organisms.
Factors affecting microbial
Intrinsic Factors Extrinsic Factors
Physical structure of
Carbon dioxide or
Types and numberof
micro organisms in the
Principles of Meat
1.Cold Treatment- it furtherincludes
•By efficient refrigeration, meat can be preserved in a
condition approaching its natural state for periods
adequate forcommercial requirements.
•The appearance, weight and flavor of meat are little
•In refrigeration, meat temperature decreases to 4-7ºC
oreven to 1-2ºC in meat intended forlongerstorage.
• Techniques used for carcass refrigeration may be
Dry (air) refrigeration- this technique used in meat
industry is of three types-
•It is mainly used in small abattoirs
•Involves 3 steps
Step 1- carcass ‘draining’ or‘drying’
Step 2- Pre refrigeration- at 10ºC; 75% RH
Dry (air) refrigeration
Used forred meat and
Step 3- Refrigeration- at 4-7ºC; 85- 90% RH
• In this method, dry carcass surface is beneficial in
terms of surface micro flora suppression and causes
weight loss of 3%.
2. Rapid airrefrigeration-
• carcasses are exposed to air at -1 to +1ºC, 90% RH
and 1-3m/sec circulation for18-36 hrs.
• It causes weight loss of 1.5-2%
3. Ultra rapid refrigeration- involves two phases
Phase I- carcass exposed to intensive circulation (2-
4m/sec) at temp. -4 to -6ºC; 90% RHfor1-3 hours.
Phase II- carcass is refrigerated at -1 to 2ºC for14-22
hours with circulation 0.3 m/sec.
• Weight loss is around 1%.
Wet (water) refrigeration- this method can be applied
1.Spraying poultry carcasses with cold water- it is a
hygienic practice as reduces chances of cross
this method requires considerable amount of water
( 10-12 lit/carcass).
1.Submerging the carcasses in basins with running cold
water, for1 hour- this method requires lesseramount
of water(up to 4 lit/carcass).
• In Industrial abattoirs, freezing of meat is done in
‘freezing tunnels’ under air circulation of 2-4m/sec
with airat -20 to -40ºC and 95- 100% RH.
• The cryoscopy points of meat is between -1.5 and
-1.8ºC (muscle tissue) and -2.2ºC (fatty tissue).
• Approximately 75% of water in meat is freezes at
-5ºC, 90% at -30ºC and 100% at -60ºC.
• During frozen storage, microbial storage is
• Frozen meat products can be stored for longer
duration up to 12 months.
• Disadvantage- Freezing may cause some adverse
effects on meat quality that may affect its sensory
2. Salting and Curing-
• Salting- treatment of meat with salt
Curing- treatment of meat with brine i.e., mixture of
salt, nitrites/nitrates and othercompounds.
• It can be done by application of either of the 3
a.Dry method- meat surface is treated with dry salt or
brine and held at temperature 0-7ºC for 2-4 weeks.
During this period, salt or brine ingredients goes into
the meat and thus, releases amount of bound water.
b.Wet method- meat is submerged in salt/ brine
solution. This allows ingredients to diffuse from solution
c.Combined method- meat is firstly dry salted or cured
and then, heated with salt/brine solution.
•Various ingredients used for salting and curing are-
• Two main objectives of applying smoking technique
to achieve popularcolorand flavor
to inhibit spoilage and pathogenic micro organisms.
• Smoke is produced endothermically from damp wood
meats are hung in room
having wood containers for
conditions are difficult to
smoke is produced by
conditions are well
temperature of 200ºC.
• It involves migration of moisture from innerlayers
towards surfaces and evaporation from the surface.
• Initially, drying is done at low temperature of about
10-15ºC and as wateractivity decreases, temperature
is increased that enhances drying rate.
• Drying should be done in a gradual mannerto avoid
the formation of hard, dry layeron surface.
• Lyophilization- method of meat drying
Here, meat is frozen and then exposed to very low
pressure in vacuum at 20-40ºC. This results in the
removal of 90% of waterand meat product of same
volume but 70% of initial weight.
5. Heat treatment-
killing of pathogenic microbes
inactivation of meat enzymes
• The heat treatment may be done in following ways-
a.Pasteurization- in waterat temperature < 100ºC
This destroys all vegetative cells of psychrophilic and
mesophilic microbes but vegetative cells of thermophilic
bacteria and spores survive.
b.Boiling- in waterat 100ºC so as to reach product’s
centertemperature at 80-90ºC
This kills all vegetative cells but not the spores
c.Sterilization- at temperature > 100ºC in autoclave
This kills all vegetative forms and spores
• Fermentation is a phase of intensive growth and
metabolism of lactic acid bacteria.
• The activity of this bacteria produces lactic acid that
reduces the pHand thus, acting as a preservative.
• The process occurs normally over2-5 days until pH
lowers to 4.6-5.
• To enhance the speed of fermentation, selected lactic
acid bacteria called ‘artificial culture’ can be added.
Hurdle Concept and Technology
• Hurdle technology is a method of controlling or
eliminating pathogens in food products by combination
• These approaches can be thought of as ‘hurdles’ the
pathogen has to overcome to remain active.
• The right combination of hurdles ensure elimination of
all pathogens or reducing them to harmless in the final
• In developing countries, the application of hurdle
technology is very important for foods that remain
stable, safe and tasty without refrigeration storage.
• Some of the principle hurdle used in food preservation
Parameter Symbol Application
High Temperature F Heating
Low Temperature T Chilling, Freezing
Reduced water activity aw Drying, curing,
Increased acidity pH Acid addition or formation
Reduced Redox potential Eh Removal of oxygen or
addition of ascorbate
Biopreservatives Competitive flora such as
Other preservatives Sorbate, sulfites, nitrites.
• Some hurdles may influence the safety and quality of
foods because of anti microbial properties and at the
same time, improve the flavor e.g.. as in Maillard
• The same hurdle could have positive or negative
effects on foods depending upon-
Basis of hurdle technology
• The physiological responses of microbes i.e., their
homeostasis, metabolic exhaustion and stress reaction
forms the basis of application of Hurdle technology.
• The disturbance of the homeostasis is the key
phenomenon of food preservation.
• The goal forfood preservation is the multi target
preservation of foods in which logically applied
hurdles will have a synergistic effect.
• Thus, hurdle technology is an important tool to
enhance shelf life of livestock products.
• It can also be used forthe development of various
novel food products.