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UNIT 10 MEAT PRESERVATION
Structure
10.0 Objectives
10.1 Introduction
10.2 Principles of Meat Preservation
10.3 Methods of Meat Preservation
10.3.1 Drying
10.3.2 Low Temperature Preservation
10.3.3 High Temperature Preservation or Thermal Processing
and Smoking
10.3.4 Curing
10.3.5 Antibiotics and Bacteriocins
10.3.6 Fernlentation
10.3.7 Packaging
10.3.8 Irradiation
10.3.9 Hurdle Technology
10.4 Let Us Sum Up
10.5 Key Words
10.6 Some Useful Books
10.7 Answers to Check Your Progress
10.0 OBJECTIVES
After reading this unit, you will be able to:
explain the need to preserve the food and food products, especially the
meats; and
describe different techniques of meat preservation, their advantages and
limitations, and the type of meats to which these can be applied.
10. INTRODUCTION
Generally, preservation of food is done in times of plenty to make its use in
times of scarcity. The main aim of the meat preservation is to check meat spoilage,
which causes some changes in texture, flavour and odour of meat and finally
loss of its wholesomeness. Consumers prefer 'fresh' meat for its texture, taste,
aroma and flavour. At the same time, consumers want 'safe' meat for consumption
as soiled or spoiled mear is likely to carry disease-causing (pathogenic)
microorganisms that may cause food poisoning. Muscle of healthy animals is
known to be free from microorganisms, due to various defence mechanisms
operating in the live animal body, which keep the microbes under check. However,
breakdown of these mechanisms under diseased conditions or by slaughter of
the animal and subsequent handling of the meat, especially under unhygienic
conditions, leads to microbial contamination and spoilage of meat. The type and
by several factors such as
level of microbial contamination of meat is influenced
feeding habit of animals, mode of animal transportation, environment of abattoir,
abattoir practices and carcass handling and processing procedures. The microbial
contamination of meat leading to spoilage or food poisoning is most pronounced
Microbiology When meat has been obtained from a diseased animal,
When meat has been processed under filthy (unhygienic) conditions,
When meat has been stored under conditions that favour microbial growth.
In view of above, it becomes clear that microorganisms affect the safety and
keeping quality of meat and meat products. To overcome these problems, such
conditioiis are created which are not favourable for growth and survival of the
microorganisms, e.g., severe cold or hot, lower water activity, gases (oxygen,
nitrogen, sulphur dioxide, carbon dioxide etc.), chemicals and increased acidity
of medium. Methods that are commonly used to store or preserve meats
significantly reduce or retard the microbial growth and therefore, play a vital
role in ensuring safety of meat, controlling the spoilage and extending the shelf
life. In other words, meat preservation aims at enforcing measures that prevent
the occurrence of deteriorative changes in meat brought about by microbial,
chemical and physical processes. However, the total elimination of meat
contamination is difficult to achieve. Hence, it is important that microbial
contamination of meat is minimized to retard meat spoilage as well as to prevent
the health hazard that may arise from the co~lsumption of contaminated meat.
The modern meat preservation methods, which mainly include 'cold-chain' with
or uithout packaging in suitable material and environment, has greatly facilitated
the distribution of meat to distant places in the country as well as to other nations.
In order to make most efficient use of these preservation methods, let us
understand their principles, applications, advantages and limitations.
10.2 PRINCIPLES OF MEAT PRESERVATION
The science and technology of meat preservation methods including heat, cold,
chemicals, packaging and irradiation, aims at the following three major principles:
i) Prevention or delay of microbial spoilage: This can be achieved by four
following approaches:
Keeping out the microbes: By asepsis, avoiding contact with meat, taking
hygienic measures during processing.
Removal of microbes: By removal of affected part or filtration or
centrifugation or sedimentation etc.
Hindering the growth activity of microorganisms: By preserving meat
at low temperature, drying, creating
ahaerobic condition or addition of
chemicals.
Destruction of microorganisms: By heating, irradiation, high-pressure
application etc.
/ decomposition of the food: This
ii) Prevention or delay of self-autolysis
can be done by :
Destruction or inactivation of meat enzymes: By mild heat treatment
(blanching) of meat.
Prevention of chemical reaction: By antioxidants to prevent oxidation
of fat.
iii) Prevention of mechanical damage to the meat caused by insects or
handling: This can be achieved by :
The use of insect repellents/insecticides in the meat processing premises.
Proper dressing, processing and handling of meat and meat products.
--3
Check Your Progress 1 Meat Preservation
1) Enlist the principles of food preservation.
.....................................................................................................................
2) The microorganisms can be destroyed by ..............., .............. and ..........
10.3 METHODS OF MEAT PRESERVATION
The preservation of fresh meat has been practiced since time immemorial.
Ilowever, Nicolas Appert of hance was the first person to attempt it scientifically
in 18 10 as he developed canning method, which was patented later. There are a
number
of methods that are used for keeping meat safe by controlling the growth
of bacteria and molds.
10.3.1 Drying
Drying has the distinction of being the first and simplest method that has been
adopted for the preservation of meat since antiquity. Drying refers to the removal
a*) from the food. It is known that microorganisms and
of moisture (reduction in
enzymes require adequate water in food for their sustenance. When moisture is
removed from the food (during drying process), the activity of microorganisms
and enzymes is inhibited and the shelf-life of the product enhanced at ambient
temperature.
1-Iowever, at present, this method appears to be of little importance
and commercial value, in the preservation of meat. I-Iowever, in case of processed
meat strips, which are air dried for preserving long lasting proteins, eg., Biltong
is yet in practice. This method has some public health problems as there is
likelihood of getting meat contamination with Salmonella organisms during the
process of handling, preparation, storage and the viability of the pathogen in the
contaminated product has been reported for more than six months. Salt and heat
treatment help in destroying parasitic cysts especially cysticercoids present in
the meat and only sun drying is not that much eiyective.
10.3.2 Low Temperature Preservation
Low temperature preserves the food material by rctarding the microbial growth,
enzymatic and the chemical reactions that deteriorate the meat and cause spoilage.
The most widely used methods based on this principle of preservation by low
temperatures are refrigeration (chilling or icing) and freezing.
a) Chilling: Refrigeration(chil1ing refers to preservation by lowering the
temperature of the meat to a point above the freezing temperature. Chilling
is also widely used for short-term preservation of meat as it has no adverse
affect on appearance. flavour or nutritional value. Meat carcasses are
normally chilled / refrigerated immediately after the slaughter at about -
1°C, usually in the dark to avoid the oxidation of fat. In the presence of 10
per cent carbon dioxide, the storage life of the meat is further increased
because the growth of molds is inhibited. The rate of chilling the carcasses
depends on the size and heat capacity (specific heat) of the carcasses, amount
of fat covering, temperature and air circulation in the chill room. Rapid
cooling is necessary to prevent spoilage, especially around the lymph
Microbiology nodes. But it should not be in such a way that it induce cold shortening.
The chill room temperature remains between -5 and -2OC (before the
carcasses are loaded) and the temperature of the chilling room should remain
below 3OC at all times.
b) Freezing: At chill temperature the meat is cooled to 2 O°C. Meat starts
freezing at -1 .S°C.This method of preservation has its own importance
because properly processed meat retain most of fresh properties for extended
length of time. Freezing aims at preventing the multiplication of harmful
bacteria, molds and yeast as water is converted to ice and therefore, remains
no longer available for microbes. Freezing occurs at different rates in
different parts
ofthe material being frozen. The rate is faster at some points,
for instance on the surface, while in the deeper parts of the material there is
a point at which cooling is slowest. This point is known as the 'thermal
center'. About half of the water is frozen to ice at
-2.5OC. Three quarters of
it are frozen at -7OC and some water still remains intact at -18 OC. Then, the
(- 18 to -20 or -30°C) until
meat is further cooled to its storage temperature
its thermal center reaches the storage temperature.
Freezing of meat is achieved by two ways namely, quick and slow freezing. Fast
-20°C within 30 minutes
freezing is quick where temperature of meat is lowered to
by directly or indirectly passing refrigerated air onto the meat, whereas in slow
freezing, the required temperature is attained within 3-72 hours. Both of these
processes have merits and demerits as the formation of large and small ice crystals
ultimately cause damage to
the meat resulting in "drip" on thawing. The maximum
formation of ice crystals occurs in the temperature range of -1°C to -PC, which
is called as 'zone of maximum ice formation'. Quick or blast freezing may
produced an undesirable conditions called 'freezer bum' in which surface appears
bleached due to patchy evaporation of moisture from the surface of meat. To
prevent this, either freezing is done under moist condition or the meat is first
chilled and then transfered to a freezing units. Frozen meat can be preserved
upto 6- 12 months. In order to keep meat fiozen during transportation, the freezing
of meat is done at temperature as below as -25°C.
Freezing methods: Freezing methods as per FA0 can be classified into four
categories based on the freezing rate. They are
as below.
Table 10.1: Freezing methods and Freezing rate
Freezing method Freezing rate
Slow freezing 0.2 cm / Hour
Quick Freezing 0.5 - 3.0 cm / Hour
Rapid freezing 8 5.0 - 10 cm/Hour
- 100 cm / Hour
Ultra rapid freezing 10
Depending on the principle of their operations, the freezing methods can also be
classified into four broad categories namely (i) Contact with cold solids (ii)
Contact with cooled liquids (iii) Contact with cooled air and (iv) Two phase
freezing systems.
Freezing and frozen storage of meat and meat products: Frozen storage results
in a gradual decrease in the odour and flavour acceptability. The manner of
freezing, the kind of packaging and temperature of storage have significant effects
on the duration of satisfactory qualities of frozen meat.
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