FSNC01 10
FSNC01 10
FSNC01 10
The difference between refrigeration and cool storage on the one hand and freezing
and frozen storage on the other should be noted. Cool storage generally refers to storage at
temperatures above freezing, from about 16o-C down to –20C. Commercial and household
refrigerators are usually operated at 4.5-70C. Commercial refrigerators sometimes are
operated at a slightly lower temperature when a particular food is being favored. Whereas
pure water will freeze at 00C, most foods will not begin to freeze until about –2oC or lower.
Frozen storage refers to storage at temperatures that maintain food in frozen condition. Good
frozen storage generally required temperature of –180C or below. Refrigerated or cool
storage generally will preserve perishable foods for days or weeks, depending on the food.
Frozen storage will preserved foods form months or even year if properly packaged.
Refrigeration and cool storage in general is the gentlest method of food preservation.
It has relatively few adverse effects on the taste, texture, nutritive value, and other attributes
of foods, provided simple rules are followed and storage periods are not excessive. One
cannot say this of heat, dehydration, irradiation, and other methods of preservation, which
often immediately result in changes in food, however small.
Although refrigeration and cool storage reduces the rate of food deterioration, with
most foods it will not prevent deterioration to anywhere the same degree as does heat,
dehydration, irradiation, fermentation, or true freezing. Indicates the generally useful storage
life of plant and animal tissues at various temperatures. At 00C, which is lower than most
commercial or household refrigerators, the life of such perishables as animal flesh, fish,
poultry, and many fruits and vegetables is generally less than 2 weeks. At the more common
refrigerator temperature of 5.5oC, storage life is often less than 1 week. On the other hand,
these products held at 220C or above may spoil in 1 day or less.
Quick cooling does not simply mean immediate placement of bulk foods into a
refrigerated railroad car or warehouse in all cases. Cooling is the taking of heat out of a
body. If the body is large, the time to remove sufficient heat can be so long as to permit
considerable food spoilage before effective preservation temperatures are reached. The
hydrocooler of accomplishes rapid cooling aided by subdivision of the produce as it is fed
through the machine. Similarly, subdivision of bulk produce favors cold air circulation in
refrigerated storage rooms. Leafy vegetables may be quickly cooled by spraying them with
water and creating a vacuum to promote evaporative cooling. Current use of cold nitrogen
gas from evaporating liquid nitrogen in refrigerated trucks, railcars, and ship holds also aids
in providing intimate cold contact and quick cooling of produce. This has the further
advantage of displacing air from the refrigerated area, which can be beneficial for certain
products. Bulk liquids are best cooled rapidly by passing them through an efficient heat
exchanger before putting them into refrigerated storage. Animal carcasses at time of
slaughter are at a temperature of about 38oC which must be lowered to about 20C in less than
24 h if quality is to be maintained.
The principal requirements for effective refrigerated storage are controller low
temperature, air circulation, humidity control, and modification of gas atmospheres.
Proper air circulation helps move heat away from the vicinity of food surfaces toward
refrigerator cooling coils and plates. But the air that is circulated within a cold storage room
must not be too moist or too dry. Air of high humidity can condense moisture on the surface
of cold foods. If this is excessive, molds will grow on these surfaces at common refrigeration
temperatures. If the air is too dry, it will cause drying out of foods. All foods are different
with respect to supporting mold growth and tendency to dry out, and so for each, an optimum
balance must be reached. The optimum relative humidity (RH) to be maintained in cool
storage rooms for most foods is known. Summarizes the best storage temperatures and
relative humidities for many food items and their approximate storage life.
Large cuts of meat are often packaged in sealed plastic bags or they may be sprayed
with various moisture-resistant coating. Cheeses that are ripened for many months in cold
warehouses are also packaged in plastic films. An older method is to coat the cheese with
wax. This not only minimizes moisture loss but affords protection against contamination and
growth of surface molds. Eggs in the shell tend to lose moisture as well as carbon dioxide.
This can be retarded by coating the eggs with a thin edible oil, such as mineral oil, to seal the
minute pores of the egg shell.
Since animal as well as plant tissues consume and give off gases, it would be expected
that gas equilibria would effect many food properties. This certainly is so with respect to the
pigment changes of red meat the growth and metabolic patterns of surface ripening as well as
spoilage microorganisms, and the staling rate of cold storage eggs. In the latter case, besides
oil coating to minimize water and carbon dioxide losses, eggs have been stored in warehouses
enriched with carbon dioxide to minimize loss of this gas which is associated with egg pH
and freshness.
The term hypobaric storage has been used to describe another type of CA storage. In
this case the refrigerated storage area is maintained under reduced pressure and high
humidity. This decreases the amount of air, and with it the amount of oxygen in the area,
while the high humidity prevents product dehydration. Hypobaric storage has been used in
warehouses as well as enclosed truck bodies.
The deterioration of foods during cool storage are influenced by the growing
conditions and varieties of plants, feeding practices of animals, conditions of harvest and
slaughter, sanitation and damage to tissues, temperature of cool storage, mixture of foods in
storage, and other variables.
Still other common changes during refrigerated storage involve loss of firmness and
crispness in fruits and vegetables, changes in the colors of red meats, oxidation of fats,
softening of the tissues and drip page from fish, staling of bread and cake, lumping and
caking of granular foods, losses of flavor, and a host of microbial deterioration’s often unique
to a specific food and caused by the dominance of a particular spoilage organism. Some
foods should not be refrigerated. Bread is an example. The rate of staling of bread is greater
at refrigeration temperatures than it is at room temperature.
In the food industry, cooling generally is used for its preservation value. There are
many situations, however, where cooling provides other advantages and improves the
processing properties of foods. Cooling is employed to control the rates of certain chemical
and enzymatic reactions as well as the rates of growth and metabolism of desirable food
microorganisms. This is the case in the cool ripening of cheeses, cool ageing of beef, and
cool ageing of wines. Cooling also improves the ease of peeling and pitting peaches for
canning. Cooling citrus fruits reduces changes in flavor during extraction and straining of
juice. Cooling improves the ease and efficiency of meat cutting and bread slicing. Cooling
precipitates waxes from edible oils. Water for soft drinks is cooled before carbonating to
increase the solubility of carbon dioxide. More will be said about these applications of
cooling in later chapters.
Economic Considerations:
As a compromise, the refrigerated area often is held somewhere within the range 2-
o
7 C with no special provisions made to control humidity. Even under these conditions,
refrigeration significantly improves the safety, appearance, flavor, and nutritional value of
our food supply. If further reduces losses from insects, parasites, and rodents.
As a preservation methods, freezing takes over where refrigeration and cool storage
leave off. Freezing has been a major factor in bringing convenience foods to the home, more
time for food constituents to be in contact with concentrated eutectic mixtures and damaging
concentration effects are intensified.
A Btu is the quantity of heat that will raise or lower the temperature of 1 lb of water
10F through the range 32-2120F at normal atmospheric pressure. A calorie is the amount of
heat that will raise or lower the temperature of 1 g of water 10C (from 14.5 to 15.50C) at
normal atmosphere pressure. (1 Btu = 252 calories = 1055 joules or 1.055 kJ.)
Different substances can absorb different amounts of heat and are said to have
different heat capacities. The heat capacity of water is 1 Btu/(lb oF) or 1 cal/(goC).
There are two types of heat: sensible heat and latent heat. Sensible heat is readily perceived
by the sense of touch and produces a temperature rise or fall as heat is added or removed
from a substance. Latent heat is the quantity of heat required to change the state or condition
under which a substance exists, without changing its temperature. Thus, a definite quantity
of heat must be removed from water at 0oC to change it to water at 00F. This would be equal
to 28+144+15 or 187 Btu.
CHAPTER 18
Freezing ← Packing
Methods of freezing
2. Quick freezing
In this process the food attains the temperature of maximum ice crystal
formation (0 to –40C) in 30 minutes or less. Such a speed results in formation of
very small ice crystals and hence minimum disturbance of cell structure. Most
foods are quick frozen by one of the following three methods.
Since liquids are good heat conductors, food can be frozen rapidly by direct
immersion in a liquid such as brine or sugar solution at low temperature. Berries in sugar
solution, packed fruit juices and concentrates are frozen in this manner. The refrigeration
medium must be edible and capable of remaining unfrozen at –18oC and slightly below.
Direct immersion equipment’s such as Ottesen Brine Freezer, Zarotschenseff “Fog” Freezer,
T.V.A. Freezer, Bartlett Freezer, etc., of commercial importance earlier, are not used today.
Advantages:
i. There is perfect contact between the refrigerating medium and the product.
Hence the rate of heat transfer is very high.
ii. Fruits are frozen with a coating of syrup which preserves the colour and
flavour during storage.
iii. The frozen product is not a solid block because each piece is separate.
Disadvantage:
It is difficult to make a syrup that will not become viscous at low temperature.
Indirect freezing may be defined as freezing by contact of the product with a metal
surface which is itself cooled by freezing brine or other refrigerating media. This is an old
method of freezing in which the food or package is kept in contact with the passage through
which the refrigerant at –18 to –46oC flows. Knowles Automatic package Freeszer, Patterson
Continuous Plate Freezer, FMC Continuous Can Freezer and Birdseye Freezers are based on
this principle.
C) By air blast:
In this method, refrigerated air at –18 to – 340C is blown across the material to be
frozen.
The advantages claimed for quick freezing over slow freezing (sharp freezing) are: (I)
smaller ice crystals are formed. Hence there is less mechanical destruction of intact cells of
the food. (ii) period for ice formation is shorter, therefore, there is less time for diffusion of
soluble material and for separation of ice, (iii) more rapid prevention of microbial growth,
(iv) more rapid slowing down of enzyme action.
Although most foods retain their quality when quick frozen by the above methods, a
few (mushrooms, sliced tomatoes, whole strawberries and raspberries) require ultrafast
freezing. Such materials are subjected to cryogenic freezing which is defined as freezing at
very low temperature (below –600C). The refrigerants used at present in cryogenic freezing
are liquid nitrogen and liquid carbon dioxide. In the former case, freezing may be achieved
by (I) immersion in the liquid, (ii) spraying of liquid, or (iii) circulation of its vapour over the
product to be frozen.
(4) Dehydro-freezing
(5) Freeze-drying:
In this process food is first frozen at –180C on trays in the lower chamber of a freezer
drier and the frozen material dried (initially at 300C for 24 hours and then at 200C) under high
vacuum (0.1 mm Hg) in the upper chamber. Direct sublimation of the ice takes place without
passing through the intermediate liquid stage. The product is highly hydroscopic, excellent in
taste and flavour and can be reconstituted readily. Mango pulp, orange juice concentrate,
passion fruit juice and guava pulp are dehydrated by this method.
Quick-freezing rapidly slows down chemical and enzymatic reactions in foods and
stops microbial growth. A similar effect is produced by sharp freezing, but less rapidly. The
physical effects of freezing are of great importance. There is an expansion in volume of the
frozen food and ice crystals form and grow in size. These crystals are larger in slow freezing
than in quick freezing and more ice accumulates between tissue cells and may crush the cells.
Water is drawn from the cells to form ice. It is claimed that ice crystals rupture fruit and
vegetable tissue cells and even microorganisms. The increased concentration of solutes in the
cells hastens their salting out, dehydration and denaturation of proteins and causes
irreversible changes in colloidal systems, such as the syneresis of hydrophilic coloids.
Further, freezing is considered to be responsible for killing microorganisms. The vegetative
cells of yeasts and moulds and many Gram-negative bacteria are susceptible. While Gram-
positive bacteria including staphylococci and enterococci are moderately resistant, while
spores of bacilli and clostridia are insensitive to freezing.
During storage of food in the frozen condition, chemical and enzymatic reactions
proceed slowly. Unfrozen concentrated solution of sugars, salts, etc., may ooz out from fruits
or concentrates during storage as a viscous material called ‘metacryotic liquid’. Fluctuation
in storage temperature results in an increase in the size of ice crystals resulting in physical
damage to the food. Desiccation of the food at its surface is likely to take place during
storage. When ice crystals evaporate from the surface of fruit, ‘freezer burn’ is produced
which usually appears as dry, grainy and brownish spots where the chemical changes
mentioned above take place and the tissues become dry and tough. There is slow but
continuous decrease in the number of viable microorganisms on storage.
Storage at – 180C
CHAPTER 19
FOOD QUALITY
The terms food quality and food safety are often used interchangeable, it is important
for the food industry professional to distinguish between them. Food quality is the extend to
which all the established requirements relating to the characteristics of a food are met. Food
safety in the extent to which those requirements relating specifically to characteristics or
properties that have the potential to be harmful to health or to cause illness or injury or met.
Appearance
Flavour
Aroma
Texture
Viscosity
Product durability
Wholesomeness
Packaging
Labelling
Food safety is the assurance that food will not cause harm to the consumer when it is
prepared and eaten according to its intended use. The assurance that a food will not cause
harm, injury or illness, is determined by
i. Whether all harmful substance present in the food have been eliminated, reduced
to an established acceptable level and
ii. The food has been prepared, handled and stored under controlled and sanitary
conditions in conformance with practices prescribed by government regulations.
Quality control within food processing industry demands constant vigilance at the
stages in processing so that the necessary adjustments can be made at appropriate time. The
specific responsibility of quality control is the ensure that system used produces a standard
acceptable product with respect to nutrition, purity, wholesomeness and palatability.
It is practices to lest the stage of maturity in order to determined the stage of maturity,
exact time at which average quality of the lot harvested will be at optimum for processing.
Raw material inspection includes test for genuineness, composition, freedom from
contaminants and conformity with official standards. Standards like AGMARK, BIS, PFA
and FPO wherever applicable may be adopted or a standard with acceptable criteria –
enumerating the various tests with their limits framed may be documented.
5. Process control
Finished product examination of carried out to determine the extent to which the
desired quality specifications have been achieved. The ability to with stand storage can be
conferred Eg. In canned fruits chemical analysis, physical properties of finished products are
carried out to determine. General composition, to check that composition confirmed to meet
legal requirements.
Microbial examination is carried out to check processing conditions. The ultimate
criterion for desirability of the product is checked by sensory evaluation. It is done by both
expert sensory judgment as well as market testing.
The control must be exercised to protect the product from post – process
contamination to keep it in good condition and to preserve the flavour until it reaches the
consumer. It is essential, therefore, to choose appropriate, packaging material. The labeling
must be clear and informative. Overall, a good and attracting product helps in its successful
marketing.
CHAPTER 20
FOOD SAFETY
The safety of the food is principally assured by the control of hygienic conditions
at the source of production and processing. The process of safety becomes complex
because of the handling of large quantity and variety of foods that reaches the consumer.
As the unhygienic hazards are borne by the food material, product and all subsequent
operations must ensure their control after production, processing, distribution and
storage.
2. Microbial contamination
The use of chemicals in the production of food products not only masks the
quality, disguises the deterioration and constitutes deliberate adulteration which is
potentially very harmful to heath. Chemical contamination may be classified as
a. Food preservatives: It is advised that the food preservatives like colouring matter, food
additives, artificial sweeteners antioxidants, emulsifiers / stabilizers, flavour / flavour
enhancer etc. if used, should be of approved quality and processed
b. Metallic contamination: The metallic contamination of the food products may take
place during processing in unhygienic metal containers, use of non-standard raw
materials or ingredients, chemicals etc. The major metallic contaminants occurring in
food products are lead, copper, tin, arsenic, chromium, iron, nickel, mercury and
cadmium.
c. Pesticides / insecticides: The agriculture products used in the food processing like food
grains, cereals, oil seeds, fruits and vegetables are generally contaminated with high
levels of residual pesticides / insecticides which are sprayed during cultivation.
4. Toxic contamination
Argemome oil
It is suggested that food industry must adopt the latest emerging technologies
which helps in quality improvement and upgradation of the processing foods and to use
the raw materials and ingredients of approved standard quality.
Also the food products must be made available in suitable food grade packaging
which helps enhanced shelf life, maintenance of hygienic conditions, protects from
microbiological contamination, insect infestation and retention of its wholesomeness. It is
therefore a great responsibility of the food processing industry to protect the interests of
the consumers and to process and supply safe food.
CHAPTER 21
Food should be produced under hygienic conditions to insure good quality as well
as freedom from any risk of food poisoning. Since each commodity under goes many
processing stages, the product will be exposed to contamination by processing equipment
and processors. Consequently, there is a risk of quality deterioration and contamination
by food poisoning bacteria.
2. Cleaning procedure
3. Personal hygiene
a. Location: Food plants shall be ideally located with respected to raw material supply
and market to minimize unnecessary delay and transportation.
b. Plant layout: The process flow shall be laid out in such a manner as to minimize or
prevent cross contamination.
d. Floor: Floors shall be slopped towards the drain and cleaned with hot water or
chlorinated water (100 ppm) or high pressure spray at least once each working day. A
depression in floor in front of the entrance containing appropriate sanitizing solution
should be provided to sanitize boots and shoes of handlers before entering the processing
plant.
e. Walls: Walls shall be, no double walls which could harbour rodents and constructed to
exclude pests and rodents. Walls within the processing area shall be water proof and lined
with glazed tiles to a height of not less than 150 cm from the floor for easy cleaning
corners between walls shall be rounded off.
f. Drains: Drains shall be adequate to remove all the waste effectively and shall not be
connected directly to a sewer. Where drains do connect to a sewer they shall be equipped
with traps. Drains shall be fitted with removable gratings and round bottom and be fitted
with screens at strategic points to remove solid wastes.
h. Tables: All tables, benches etc, shall preferably be of metal construction, but if wood is
used, it shall be rendered non-porous. They shall be kept clean by frequent washing with
a suitable detergent and disinfectant.
i. Containers: All containers, trays etc shall be constructed of suitable metal or plastic,
and shall be kept clean by frequent washing.
j. Water supply: There shall be provided at all times within the factory, a sufficient
supply of potable water, clean and free from any harmful chemical or bacterial
contamination.
k. Equipment: All equipments shall be thoroughly washed at the end of each working
shift. Working space, passage ways and areas to which persons have access should be
unobstructed and sufficient to permit movement without contamination of food contact
surfaces by clothing or personal contact.
l. Paints: Paints on wall and ceilings shall be non-flaking and non-peeling and shall not be
of lead-based material.
m. Lighting: All lighting shall be reasonably free from glare and distributed so as to avoid
shadows, Glass light-bulbs or glass fluorescent tubes shall not be placed directly over
products and bulbs or tubes shall be protected within shatter proof glass globes or sleeves
respectively.
n. Refuse: Refuse shall be removed from the establishment at least once daily and
disposed of in a satisfactory manner, in an event it shall be kept well away from the food
being processed.
o. Toilet facilities: Sufficient toilet facilities shall be provided for persons employed in
the premises. It shall be situated away from the processing area and allow a one way
passage into and out of the privy accommodation and at the exit end, there shall be fitted
an adequate number of wash basins and a supply of hot H2O, soap and disposable towels
for the worker to sanitize herself / himself before entering the processing area.
p. Locker rooms: Locker rooms and eating facilities shall be provided and must be well
maintained for the comfort and safety of workers.
q. First aid: Sufficient quantities of first aid appliances and requisites, including water
proof wound dressings, shall be provided and maintained an a clear and readily available
conditions.
2. Cleaning
Cleaning means removal of diet from soiled surfaces. However thorough the
cleaning is, it cannot remove all bacteria with the diet. A clean surface is not necessarily
sterile and a sterile surface does not necessarily look clean.
a. Sterilizing agents: Sterilizing agents will render microorganisms harmless and may
have a residual effect which delays further growth of bacteria. However sterilizing agents
do not work effectively in the presence of large amounts of dirt. It is therefore necessary
to clean a dirty surface first and then to sterilize it to destroy any remaining
microorganisms. Examples of sterilizing agents are chlorine (hypochlorite powder,
tablets and domestic bleaches), quaternary (ammonium compounds) and detergent
sterilizer combinations.
b. Cleaning agents: Cleaning agents are chemical compounds which increase the
effectiveness of water in removing dirt and foreign materials from a surface. Many types
are available, each with the ability to remove specific contaminants or soils from certain
areas. Clean agents can be classified according to their acidity or alkalinity. This is
measured by the pH of a solution of the cleaning agent and water at the specific
concentrations.
4. Strong alkaline cleaners > 11.5 Stubborn soils, fats and grease
Note: Personal using cleaning products must carefully read and observe instructions on
the package. Acidic and strongly alkaline cleaners can cause severe skin burns. Eye
protectors and rubber gloves shall be worn by persons applying these cleaning agents. It
pressure spray is used for it application, a complete suit of protective clothing is
recommended.
3. Personal hygiene
a. Protective clothing
Hair covers must be worn by everyone entering the processing area to avoid loose
hair falling on food products.
Face masks shall be worn to cover nose and mouth when processing ready-to-serve
food. Because healthy carriers of coagulase positive staphyloccus aurecus harbour
the organisms in their nose and throat, and will thus contaminate the food through
talking and breathing.
Protective gloves when used for handling food shall be disinfected at each break in
the working shift.
Clean washable rubber boots shall be provided to workers working in wet floors.
No smoking shall be permitted in the working areas. This applies to all workers,
managers and visitors, spitting must not be tolerated in any area other than the
toilet.
A person about the sneeze or cough, shall turn his head away from materials or
products, and bring a tissue to his nose and mouth.
Finger nails shall be well trimmed. They look neater, are easier to keep and
eliminate potential growing places for bacteria. Fingernail polish shall not be worn.
Food handlers shall not wear jewellery or any other discorations while working in
the processing area.
Employees shall wash their hands frequently using germicide soap, always after
visits to the washroom and before handling food products. Knowledge of proper
use and maintenance of toilets shall be instilled in the workers.
A medical check shall be kept on employees. Skin breaks such as cuts and
abrasions must always be covered immediately with a sanitary dressing (A dirty
bandage is just as dangerous as an open wound, both to other people and to the
person).
Spoilage due to the action of microorganisms on the product which affects its
shelf-life and quality.
Contamination with foreign material such as dirt’s hair, dust and residues from
processing equipment and cleaning agents.