INTRODUCTION
Pig is one of the most efficient feed converting animals
among the domesticated livestock. It is the only litter
bearing animal among meat producing livestock having the
shortest generation interval and high feed conversion
efficiency. Piggery farming has been recognized as one of
the profitable venture among the rural masses. This
venture has proved to be one of the most important
livelihood options. Generally the pigs are reared for pork,
considering the increasing trend of pork consumers;
Piggery farming will certainly take a industrial form of
livelihood in future.
Pigs are kept for the production of pork and bacon.
Most breeds, if properly managed and fed are capable of
producing either pork or bacon. Pig meat (pork) is a very
important source of animal protein in human diets. In the
areas where pigs are reared on tree range, they are most
valued as a kind of “savings” to the farmer trom where he
can tap in times of cash shortage and emergency needs.
Commercial production under semi-intensive conditions
is becoming more popular because of its favorable rate of
return on investments.
Commercial pig farming in India for meat production
is one of the best and profitable business ideas for the
Indian people. There are several highly meat producing pig
breeds available around the globe. Some of those are very
suitable for commercial meat production according to the
weather and climate of India. A few years back, pig farming
had a bad image in the society (only socially back warded
down-trodden class Indian people used to raise pigs since
the time immemorial and they were not respectable people).
But at present the scenario has changed tremendously and
commercial pig farming in India is no more restricted to
lower class people.
Physical Characteristics of Pigs
Pigs are medium-sized mammals whose thick bodies
weigh anywhere from 77 to 770 pounds (35 to 350
kilograms). Some domesticated, tamed, breeds weigh up
to 990 pounds (450 kilograms). Pigs measure 34 to 83
inches (86 to 211 centimeters) in length and stand 21 to
43 inches (53 to 109 centimeters) high. The exception is
the pygmy hog, which is the smallest species and never
grows longer than 28 inches (71 centimeters).
The neck is short and the head is long and pointed.
The snout is able to move separately from the head. The
eyes are small, the ears are long, and each foot has four
toes. The two middle toes are flattened and have hooves.
The upper canines, cone-shaped teeth on each side of the
front of the mouth, are big and curve upward, protruding
from the mouth. Skin color varies, depending on the
species, from brown to near black. Some species have
manes or tufts of hair. Others have warts on the face.
Pig Breeds
(1) Large White Yorkshire
It is a large sized and most extensively used exotic pig
breed in India. Their body is solid white colored with erect
ears, dished face and snout of medium lengths. An adult
boar (male pig) weights around 300 to 400 kg and an adult
sow weights around 230 to 320 kg. Large White Yorkshire
is an excellent pig breed for the purpose of cross breeding.
Jangali Bandel/Wild Boar
Jangali Bandel / Wild Boar Found in the wild
throughout the country, for the commercial production to
receive seed Rs 10,000 per piglet to be paid to the National
Park and Wild Life Conservation Department of Nepal.
Height ; 90 – 95 cm, Weight; 200 - 250 kg
Banmpudke
Banmpudke is the domesticated form of Jangali
Bandel. Known as smallest domesticated breed of pig.
Color varies red – brownish to black. Reached adultery at
187 days. Gestation period is 114 days with farrowing
interval of 138 days. Average litter size is 4.7 and weaning
size is 3.4 with birth weight 650 gm. Matured males average
20 and female 19 kg live weight. Resistance to several
diseases and parasites.
BEHAVIOUR OF PIGS
Pigs are highly intelligent, curious animals who engage
in complex tasks and form elaborate, cooperative social
groups.
Their uncanny physiological and behavioral similarities
to humans have given pigs a mysterious and often mythical
quality that lends itself to folklore and fables.
Pigs were once considered wicked and dirty, but science
has helped to shed light on the depths of their remarkable
cognitive abilities and to extend a greater appreciation for
these often maligned and misunderstood animals.
Social Behaviour
Social behaviour is highly developed in pigs. Within
hours, newborn piglets begin to form social dominance
relationships with littermates and eventually a stable
hierarchy is formed. Fighting is therefore rare except when
closely matched mature males encounter each other during
the breeding season. Aggression may occur during the
autumn when food becomes concentrated in patches but
it is usually regulated by the ‘submissive’ behaviour of
lower ranking individuals.
The early associations between piglets often persist into
adulthood, particularly among females. It is believed that
pigs can remember up to 30 other individuals, consistent
with the finding that pigs are rarely observed
to congregate in groups of over 20. The basic social unit
consists of one to several females and their offspring with
other loosely associated individuals. This organisation
remains more or less stable until the beginning of the
rutting season in October when the boars join the females.
Mature males are relatively solitary but bachelor groups
may form in the late summer. Sows usually give birth in
spring though it is known that they can give birth
practically all year round. In good feeding conditions, sows
can give birth twice a year. In social groups, the breeding
is often synchronised.
Rooting Behaviour
Rooting behaviour appears to be an important part of
the behavioural repertoire, a rewarding experience and
perhaps a behavioural need. The pigs’ natural inclination
to root can also provide a useful cultivation and weeding
tool. However, rooting can also lead to environmental
damage. There are apparently no real differences between
rotational and set-stocked systems with regard to levels
of rooting, foraging and feeding behaviour.
Keeping pigs on the right soil type and the use of
rotational grazing is key to the exploitation of the former
and minimising the impact of the latter. A system of
integrating pigs into a crop rotation is described by Lund
and Weary whereby a once a year farrowing herd is moved
periodically within a crop rotation programme.
Maternal Behaviour
Maternal behaviour Young piglets are very active and
are able to stand within a few minutes after birth. They
sample the sow’s 14 teats before attaching to one with
which they will remain for the rest of the nursing period.
Newborn piglets also go up to the sow’s nose and sniff. This
may be important for future mutual recognition. It is
common for piglets to be born within a range of sizes and
for the smaller ones to be born last. The larger, earlier born
piglets attach themselves to the more productive anterior
teats, which they then vigorously defend. This means that
the strongest piglets get the most food, significantly
increasing their survival chances at the expense of the
weakest.
PIG BREEDING
Managing the Sows
Sows that are to be kept for breeding should be selected
and separated from the litter at about 3 months of age.
They should not be allowed to get too fat because this will
create fertility problems. They should get a little exercise
to remain in good condition.
Young sows are mature enough to conceive at about
six months of age. They should not be served (mated) too
early however as it is better to wait until they are fully
grown. If they are well fed and healthy this will usually be
at about eight or nine months. Mating too early will result
in small litters, problems at birth, a loss of condition and
poor growth of the sow.
Mating can only be successful during the sowís period
ëon heatí (ëoestrusí). Sexually mature, non-pregnant and
non-lactating sows come on heat for two or three days
about every three weeks. However if the boar is kept
separate from the sows and gilts (young sows, not yet
mated), as he should be, it may sometimes be difficult (but
nevertheless essential) to recognise the heat.
Recognising the Heat
Twice a day (in the morning and in the evening), a check
should be made of the sowís oestrus condition. This should
be done some time after feeding, preferably in the morning.
Doubtful cases can be looked at again in the afternoon.
Differences in breed and climatic variations in the tropics
sometimes make it difficult to recognise oestrus. The first
sign is a redness and swelling of the vulva, which is more
obvious in gilts than in sows. Another sign is that other
sows in the pen start to mount the sow on heat.
The clearest indication is the reaction of the sow to the
boar. If a boar is brought alongside the sowís pen, a sow
on heat will advance towards the boar. They exhibit a
typical ear display (especially noticeable in breeds with
erect ears). If the sow does not react convincingly, then the
boar should be let into the pen. The boar will nose the vulva
and prod the sow in the belly and flank. If the sow accepts
he will mount her. A good oestrus sow will stand rigid when
mounted, with her back legs slightly apart (the so-called
standing reflex).
Selecting the Boar
Selecting a boar is even more important than choosing
your breeding sows. In choosing a breeding boar, the same
factors should be taken into account as for the sows; this
includes the presence of 12 nipples. Avoid choosing a boar
too highly in-bred from your existing stock, as in-breeding
will lead to reduced fertility, poor growth, and lower levels
of disease resistance.
Feeding and Housing the Boar
Boars should be kept neither too lean nor too fat. They
need plenty of exercise. In very hot conditions or when
suffering from fever, they can remain infertile for a long
time. A boar that is ill should be rested for 1 to 2 months
and be replaced by another for this period.
Boars should be housed in individual pens, for if they
are kept with non-pregnant sows it becomes impossible
to tell whether and when he has served the sows, and
whether or not they are in-pig. It is therefore important to
separate the boar from them.
The Birth and Care of the New-Born Piglets
On average delivery will take place 115 days after
conception (3 months, 3 weeks and 3 days). The sow will
usually farrow during the night or evening. In the last 14
days of pregnancy the udder will increase in size. It feels
firmer, and the nipples stand out more towards the end of
the pregnancy. In gilts the udder begins to develop after
two months of pregnancy.
Care of the New Born Piglets
A few minutes after the birth the umbilical cord may
be pulled gently away or cut if necessary (to about 5 cm
length). After birth, the navel of each piglet should be
soaked in a cup of iodine solution to prevent inflammation
and tetanus. Each piglet should be rubbed carefully, dry
with a cloth.
Make sure the piglets are able to suck from the udder
as soon as possible after birth. Their sucking will encourage
the sow to let down her milk.
Problems Related to the Birth
Although there are normally very few complications at
birth it is advisable to be at hand. If the whole process of
delivery takes longer than 8 to 12 hours then there is
something wrong. In particular the last piglets may be born
in the membrane and will suffocate if they are not taken
out. It is also true that sows do not pay much attention to
their offspring until all the litter has been delivered. Piglets
that waste no time in searching for milk may easily be
crushed if the sow lies down again in the course of the
farrowing. By being on hand to intervene in time this can
be prevented.
HOUSING MANAGEMENT
This may still be an appropriate method for some farms,
but today most farmers will need to fence in or
otherwise confine their pigs in some way to prevent them
from trespassing on others property. Pigs are crafty
creatures, especially if they perceive food Within reach, and
they will go under, through, and over many barricades in
search of a morsel. Careful site planning and materials
selection will keep you and your pigs happy.
Selection of Housing Location
Avoid locating hog pens in any area where water pools
or the ground becomes excessively muddy during rainy
seasons. As light slope will help drain away rain water and
urine and keep your pigs more comfortable. In case of a
large scale pig farm, the site selected needs also to be: well
connected to roads throughout the year, Suitable for
manure disposal, connected to reliable water and electricity
sources.
Fencing
If you raise your pigs outdoors, fencing is a primary
concern. Hog fences should be at least 32 inches high for
smaller pigs and upto 60 inches high for larger pigs.
Fencing can be constructed of many materials, including
wood, hog or cattle panels, pipe, field fence, electric wire,
and barbed wire. Each has advantages and disadvantages.
Housing and Equipment
Pig houses must be well constructed for maximum
performance of the animals. For backyard operations
houses can be constructed using locally available material
such as bamboo, planks etc. Movable houses are
constructed for pigs on range. For permanent pig houses
the flooring must be concrete (neither too rough nor too
smooth) to allow for easy cleaning and minimize occurrence
of parasites and diseases. Pig houses should be provided
with concrete feeders and water troughs though other
materials such as automobile or truck tires cut in halves
may be improvised as drinkers.
The Sow and Sow Pen
In an intensive pig production system, provision is
made for five single sow pens per boar, because the sow
has to stay there for five weeks and a sow/boar ratio of
1:20 has to be maintained. To manage enough contact
between boar and sows, partitions are placed over the
slatted area between the adjoining boar and sow pens,
because pigs tend to defecate while communicating with
pigs in adjoining pens. Alternatively, the sow may be placed
in a pen directly next to the boar right after she weaned
her litter. For individual feeding.
Farrowing Pens
The most important considerations regarding housing
during farrowing and the first seven to ten days there after,
are to supply optimum temperatures to the sow and her
litter and to limit deaths among the piglets through
trampling or overlying. Sows should be placed in
disinfected farrowing pens one week before farrowing to
allow time for adjustment to the new surroundings. The
sow or gilt is washed and treated for scabby skin, not less
than two days before she farrows.
Weaners and Weaner Housing
For many years it was customary in South Africa to
wean pigs at the age of 35 days, although there is the
tendency to wean pigs at an earlier stage. This section
focuses on housing for pigs weaned at 35 days, with two
litters grouped together, all-in-all-out pens, housing for
early weaned pigs and flat deck housing.
DISEASES
A disease outbreak in a piggery can have disastrous
consequences: The management practices already
described, if carefully followed, will minimize the
occurrence of diseases. That prevention is better than cure
is very relevant in the pig industry.
A clean, sanitary environment provides the best
prevention for internal and external parasite which can be
serious problems. Confinement prevents pigs from
contaminated fields and dirty lots. Anthelmintics and other
drugs, when properly used, aid in elimination of parasites.
Antibiotics also protect pigs against disease proliferations
and reduce disease outbreaks. They can also promote
growth in pigs when given at recommended levels. For
diseases that can be prevented through vaccination, a
Veterinarian should be contacted to provide such services
routinely.
A basic knowledge of the main diseases which may
affect a pig herd is necessary so that a producer can
diagnose the condition and implement control measures
as quickly, as possible. Some of the common parasites and
diseases that affect pigs are highlighted.
INTERNAL PARASITES
The internal parasites are more common to pigs on
free-range. An example is the round worm (Ascaris
Lumbricoides) which causes lots of damage to pig herds.
The round worm can grow up to 300mm long and 6mm
thick in the small intestine. Heavy infestation leads to
inherit in piglets, weakness and loss of weight.
Worms are one of the most serious threats to pig
keeping. There are more than 30 types affecting the
intestines of pigs. The most important two are the intestinal
roundworm and the tape worm.
Tapeworm
Tapeworms are flat and long ribbon like creatures
which are common in all parts of the world. Tapeworms
do not have a digestive system so they receive their food
through their skin as they absorb our nutrients. They
especially absorb folic acid and vitamin B-12. These
parasites may cause what is referred to as “verminous
intoxication” as they put out and leave dangerous waste
products in our bodies. These tapeworms can roll
themselves into a ball and can be felt on the right side of
the abdomen under the liver.
Lice
These are blood suckers that also cause irritation of
the skin. The hog louse is the largest louse species (6,4mm)
commonly associated with domestic animals. It is found
most frequently in the folds of skin behind the ears and
between the legs. The blood-sucking activity of hog lice
results in much irritation and discomfort to swine.
Symptoms
• Itching
• Skin may show red spots or bite wounds.
• Thick skin and rough hair coat.
• Anaemia in severe cases especially in piglets.
Prevention
• General cleanliness.
• Treat piglets before putting them in fattening house.
Fatteners don’t need to be treated.
• Treat gilts before first service.
• Treat boars twice a year.
• Treat new stock on arrival and seven days later. Piglets
below three weeks should not be treated.
PORK PROCESSING
Stunning
The animal should be killed as quickly and humanely
as possible. In most slaughter plants, hogs are
immobilized either by electrical stunning or carbon dioxide
gas suffocation. On the farm a hog can be stunned by
striking it one sharp blow with a mechanical stunner or
by shooting it in the forehead midway between and slightly
above the eyes. The first attempt should be successful.
Improperly placed bullets could cause the animal much
pain and injure helpers or other livestock. Animals that
become excited during stunning will not bleed as well as
those less excited. As always the case whenever using
firearms, exercise all appropriate safety precautions.
The animal can be scalded by several methods. The
easiest method is to have two barrels, one for heating the
water and one for use as a scalding vat. Fifty-five gallon
barrels will be large enough for most hogs. The scalding
barrel can be buried in the ground at a slight angle; thus
movement of the hog in and out of the barrel is easier. Be
sure the angle of the barrel is not too flat or the barrel will
not hold enough water to cover the carcass. Another
method for scalding is to have a scalding vat or a barrel
under which a fire can be built. This method requires more
construction, and the temperature of the water is difficult
to control. Slow scald is usually best. Scalding water
temperatures between 140° and 140°F are optimal. At
these optimal temperatures, 3 to 6 minutes of scalding are
required to loosen the hair and scurf (layer of accumulated
oil, dirt, and the outer layer of cells on the skin). In the fall
when the winter hair is beginning to grow, the hair of most
hogs is difficult to remove. Higher water temperatures (146°
to 150° F) or longer submersion times are usually required
for scalding during this “hard-hair” season. About l/4 cup
of rosin, lime or some other alkaline material added to the
scald water to aid in scurf removal results in a whiter skin.
On the farm, regulation of water temperature is difficult.
Add boiling water to the scalding barrel, then add cool
water to adjust to the proper temperature. Begin with the
scalding water at 155" to 160" F because it cools rapidly.
At these high temperatures, the carcass must be kept in
motion and pulled from the barrel several times.
Skinning Method
The skinning procedure used for pork carcass is similar
to that used for beef carcasses. Skinning requires less
equipment and can be done faster than scalding and
scraping. We have commonly believed that the skin was
needed on hams and bacon to assure proper curing;
however, this belief is not necessarily correct. A poor
skinning job can lower the quality of the belly for bacon.
After stunning and bleeding the animal, move the
carcass to the location of the hoisting equipment. Place the
carcass on a sheet of plywood, a concrete slab, or straw.
Wash the blood and dirt from the carcass. Turn the carcass
on its back and hold it in place with blocks placed on each
side.
Evisceration
Lossen the anus by cutting around it, deep into the pelvic canal.
Pull outward and cut any remaining
attachments; be careful not to cut into the large intestine.
When the anus is loosened, tie it with a piece of string to
avoid contaminating the carcass.
Splitting and Head Removal
Wash the inside of the carcass before splitting. With
the saw, begin splitting from the inside between the hams.
Keep the split as near the center of the backbone as
possible, and saw through the tail region to a point midway
through the loin. Move around to the back and continue
sawing through the shoulder and neck to the base of the
head. If the split gets off center. continue sawing through
to the next vertebra and then realine the saw.
Remove the head at the atlas joint (the joint closest to
the head). 1 his joint should be exposed if the carcass is
properly split. After cutting through the joint cut downward
along the jaw bone, leaving the jowls attached to the
carcass. If desired, remove the tongue, wash it thoroughly,
and place it with the liver and heart.
SAUSAGES
Cooked Sausages is an ideal meat product. It can be
made by many different formulations and in any
forms. All edible parts of the carcars can be used in an
efficient way, thus making it possible to utilize its entire
nutritional capacity. It is ready-to-eat food that can be
eaten cold or heated, as a part of a meal or on its own.
Sausage Types
Sausage can be simply defined as a product
manufactured from ground or chopped meat; combined
with salt, spices and other ingredients; and shaped in some
manner, usually by means of various sizes and types
casings. The origin of sausage-type products precedes
recorded history. Over the centuries, sausage making has
been refined and developed into an art strongly tied to
various ethnic groups. Today scientific principles are
employed to improve production procedures, product
quality and product safety.
By altering raw materials (including spices and
composition), processing procedures, spice and other nonmeat
ingredient usage and level, casing size and type,
smoking and cooking procedures, a wide variety of
sausages can be produced. Classification of all sausages
into specific categories is very difficult, since any given
sausage may be produced in a number of different ways.
Extreme caution must be used when adding nitrite to
the sausage batter since overdoses of this ingredient can
be toxic to humans. As little as 3-7 grams of nitrite can be
very toxic and lethal to humans. Because of the safety
concern in using nitrite, it is not readily available in pure
(100%) form. In addition, since straight sodium nitrite is
added at a very low level (1/4 ounce per 100 pounds of
meat) it would be difficult to accurately weigh out the
desired amount on commonly available scales. Therefore,
for safety and accuracy, salt blends already containing
nitrite at the proper level are best used by home sausage
makers when the recipe calls for nitrite or nitrate addition.
Mortons “Tender Quick Salt” (contains 0.5% nitrate. 0.5%
nitrite and 99.0% salt) is an example of such a blend,
containing a very small amount of nitrite and nitrate. It is
available in many grocery stores. When this blend is used
as the salt source for products which call for nitrite or
nitrate, these curing ingredients will automatically be
added to the batter at a safe and proper level.
Casings
Home sausage makers often inquire about where they
can buy sausage casings. Usually a small supply of natural
and synthetic casings can be purchased from local meat
processors, who use these casings in the manufacture of
their own line of sausages. Most casings used in sausage
making are natural, collagen or synthetic. Natural casings
are from the G.I. tract of animals. Most fresh bratwurst
are in pork casings. Natural casing wieners and some
breakfast sausages are in lamb casings. Ring bolognas are
typically in beef casings. Natural casings always have a
natural “curve” to them and a very desirable “snap”.
BACON
Originally developed as a method of preserving pork
before the widespread use of refrigeration, bacon
remains a popular product in its own right. Its production
varies from country to country but typically involves the
treatment of boneless pork cuts with curing salt, usually
added as a brine. As practiced in North America, bacon is
produced from boneless pork belly that is not smoked,
sliced thinly, and vacuum packed, while in Ireland and the
United Kingdom, the most popular bacon is made from
cured pork loins. In continental Europe, bacon lardons
(cubes) are used mainly as a cooking ingredient.
Salt (sodium chloride) and nitrite are essential for
curing, although nitrates (sodium or potassium) are still
used in some brines. Both major ingredients, salt and
nitrite, are multifunctional. Salt acts as a preservative by
lowering water activity, gives bacon its characteristic salty
flavor, and increases the water-holding capacity of meat
by solubilizing myofibrillar protein and increasing the
myofibrillar lattice spacing. Although nitrite chemistry is
relatively complex, the basic functions of nitrite are well
known. It (1) acts as a preservative, (2) promotes the
formation of the cured meat color, (3) contributes to cured
meat flavor, and (4) acts as an antioxidant.
Injection of Pork Sides
Whole sides, usually bone-in and rind-on, were injected
with a brine containing salt, nitrate, and nitrite. Injection
was carried out manually, using a single needle. The brine
was introduced at multiple points (25-30) along the carcass
in order to obtain a reasonably uniform distribution.
Pig Production and Slaughter
Most bacon is made from pigs, of various genetics,
reared in intensive indoor systems and fed a commercial
concentrated diet. The pigs have a fast growth rate and are
slaughtered at 90-110 kg when they are 5 to 6 months old.
Such pigs are relatively lean, the average backfat thickness
of UK pigs being about 11mm. Bacon from organically
produced pigs—reared less intensively and using organic
feed—inevitably commands a premium price.
COOKED HAM
The processing of cooked ham involves the use of brine
that is either injected or infused through soaking,
followed by the application of thermal treatment. The final
quality depends on both the raw materials and the
processing. The most outstanding factors are the type of
meat cut, the type and amounts of ingredients, the injected
volume of brine, the rate and extent of tumbling, and the
cooking time and temperature. The goal is to obtain a
product with high sensory quality that is microbiologically
safe, usually based on minimum temperature-time
treatments. The best-quality products are generally
produced with a low-brine injection level and no addition
of polyphosphates. In general, the more water is injected
into the ham, the poorer is the quality, since water
retention is facilitated by some compounds like
polyphosphates and starches.
The consumption of cooked ham is relatively high, since
it is a very popular meat product. For instance, it may
account for as much as 26% of the delicatessen products
sold in Europe, with France, Spain, and Italy being major
consumers. There are different manufacturing technologies
for the production of cooked ham, depending on the raw
materials and the processing conditions.
Types of Products
There is a broad range of types of cooked ham, which
generally are classified depending on different
characteristics. In general, cooked hams can be classified
according to the raw material used for the processing, the
composition of brine ingredients (like the use of
polyphosphates, starches, and carrageenan), the
technological yield (from 85% to higher than 110%), and
finally, the ham presentation (boneless, bone-in, pieces,
whole legs, and so on).
The manufacture of cooked ham has been evolving in
order to solve different problems such as the increased
proportion of exudative meats or the reduction of the salt
content and processing time. The intensive selection for
leaner pigs in response to consumer demands resulted in
an increased proportion of exudative pork meat. The
protein of this meat exhibited poor texture, lower waterholding
capacity, and poor cooked cured color. In order to
improve the functionality of these meats, several binders
have been used, including starch, carrageenan, and soy
proteins.
MEAT PACKAGING
Meat has long been considered a highly desirable and
nutritious food. Unfortunately it is also highly
perishable because it provides the nutrients needed to
support the growth of many types of micro-organisms.
Fresh meat requires presence of oxygen for maintaining
color for consumer appeal. Packaging fresh meat is carried
out to avoid contamination, delay spoilage, permit some
enzymatic activity to improve tenderness, reduce weight
loss, and where applicable, to ensure an oxymyoglobin or
cherry-red colour in red meats at retail or customer level.
It has a shorter shelf life. Cured meats degrade in presence
of oxygen. Two decisions are important while selecting
packaging material i.e. shape or form and material.
Selection of packaging material would depend on product
factors such as color, stability, storage conditions,
microbial condition, preservatives and degree of
processing. Processed products require more sophisticated
and extensive packaging because they will be stored at
higher temperatures for longer periods than refrigerated
products.
Single-Layer Films
One common use of single-layer films is the wrapping
of meat pieces, processed meat products, bone-in or
boneless meat cuts or even entire carcasses. These films
are usually self-adhesive, i.e. they cling together -”cling
film”- in the overlapping areas. Hence they provide good
protection from external contamination and to some extend
from evaporation, but no protection from oxygen, as they
are not hermetically closed or sealed packages. Foils with
good self-adhesive properties are PE, PA, PVC and PP.
Another important utilization for single-layer films is
in freezer storage. For meat blocks, meat cuts or smaller
portions of meat or meat products, single-layer films are
stretched tightly around the meat surface before freezing.
The tight film prevents evaporation losses, which occur
during freezer storage of unpacked products. The film is
in tight contact with the products surface, in order to avoid
evaporation, ice formation and freezer burn at non contact
spots. Suitable cold resistant films for freezer storage are
PA or PE.
Multi-Layer Films
Practically all the other films used for meat packaging
are designed as strong oxygen and water-vapour barriers.
In order to fully achieve these requirements, films with good
barrier properties for oxygen and water vapour respectively
are combined.
Layer A: Outside layer (mechanically strong, gas barrier
to oxygen).
Layer B: Middle layer (barrier to oxygen).
Layer C: Inside layer = sealant layer (capable of being
melted and welded under pressure to the sealant layer of
the opposite sheet of the bag/pouch, serves also as barrier
to water vapour).