Food Processing Technology Degree and Diploma

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Y.Bavaneethan.
Lecturer
Department of Food Technology

2. Introduction
• Chilling is the unit operation
• temperature of food is between -1ºC and 8ºC.
• used to reduce the rate of biochemical and microbiological
changes,
• extend the shelf life of fresh and processed foods
• Not all foods can be chilled
• tropical, subtropical and some temperate fruits can chilled
• Problem - suffer from chilling injury at 3–10ºC above their
freezing point
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3. Chilled foods are grouped into three categories
according to their storage temperature range as follows
1. -1ºC to +1ºC (fresh fish, meats, sausages and ground
meats, smoked meats and breaded fish).
2. 0ºC to +5ºC (pasteurised canned meat, milk, cream,
yoghurt, prepared salads, sandwiches, baked goods,
fresh pasta, fresh soups and sauces, pizzas, pastries and
unbaked dough).
3. 0ºC to +8ºC (fully cooked meats and fish pies, cooked
or uncooked cured meats, butter, margarine, hard
cheese, cooked rice, fruit juices and soft fruits).
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4. Important
• The successful supply of chilled foods to the consumer is
heavily dependent on;
• chill stores, refrigerated transport and retail chill display
cabinets, domestic refrigerators.
• Precise temperature control is essential,
• at all stages to avoid the risk of food spoilage
• In particular, low-acid chilled foods,
• susceptible to contamination by pathogenic bacteria
• fresh and pre-cooked meats, pizzas
• must be packaged and stored under strict conditions of
hygiene and temperature control.
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5. The ”standard” Cold Chain
• The cold chain for perishable foods as “the uninterrupted
handling of the product within a low temperature environment
during;
• the postharvest steps of the value chain including harvest,
collection, packing, processing, storage, transport and
marketing until it reaches the final consumer”.
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7. • Refrigeration is useful in preserving the,
• freshness of food in storage,
• by reducing the rate of chemical reactions and
• reducing the rate of growth of microorganisms.
• Most fresh foods must be stored in the refrigerator to delay
their deterioration and decomposition.
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8. Cooling contributes towards extending the shelf life of
perishable foods and improving food quality by:
• Reducing respiration --> lessens perishability.
• Reducing transpiration --> lessens water loss and shriveling.
• Reducing ethylene production --> Delays ripening and natural
senescence (aging).
• Decreasing activity of micro-organisms --> decreases the rate of
decay.
• Reducing browning and loss of texture, flavour and nutrients.
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9. Fresh Food (Unprocessed)
• The factors that control the shelf life of fresh food in chill
storage include:
1. The type of food
2. The part of the crop selected
• fastest growing parts have the highest metabolic rates
and the shortest storage lives. eg: Fruits
3. The condition of the food at harvest
• the presence of mechanical damage or microbial
contamination, and the degree of maturity
4. The temperature of harvest, storage, distribution and retail
display
5. The relative humidity of the storage atmosphere,
• which influences dehydration losses.2/13/2020 Y.Bavaneethan 9

10. Certain products require additional
temperature consideration:
• Shell eggs and shellfish can be stored up to 7.2° C.
• this temperature is too warm for other “perishable” products
• these two products are generally stored at 5° C.
• Other “perishable” foods need to be closer to 0° C
• to keep their quality and decrease bacterial growth
• Fresh raw chicken best stored at temperatures between 0-1.5° C.
• Care must be taken to avoid the chicken temperature falling
below -2.7° C,
• this will prohibit it being sold as fresh chicken.
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11. • Raw fish (tuna, mahi mahi, and bluefish,) if temperature abused,
can form Scrombrotoxin and result in Scrombroid (Histamine)
poisoning.
• The formation of toxins can be caused by the presence of certain
bacteria (Coagulase Positive Staphylococcus, Clostridium
Perfringens, Bacillus Cereus) in raw foods.
• This toxin formation is serious because these toxins cannot be
removed by cooking, frying, baking or heating the products.
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12. • The toxins also cannot be detected by taste, odor or
appearance, so there are no warning signs for the
consumer.
• For these reasons, it is essential that “perishable”
products be stored cold and protected against
temperature abuse at all times, in all areas of the
distribution center (receiving, storage and shipping).
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13. The shelf life of chilled processed
foods is determined by:
• The type of food
• The degree of microbial destruction or enzyme
inactivation achieved by the process
• Control of hygiene during processing and packaging
• The barrier properties of the package
• Temperatures during processing, distribution and
storage.
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14. • Once a product has been chilled,
• the temperature must be maintained by refrigerated
storage.
• Chill stores are normally cooled by,
• circulation of cold air produced by mechanical
refrigerator.
• Foods stored on pallets, racks, or in the case of carcass
meats, hung from hooks
• Foods, such as cheese, which flavour development takes
place during storage
• Adequate air circulation is also important when high storage
humidity is used for fresh fruits and vegetables.
• Otherwise increase the risk of spoilage mould growth.
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15. Dairy Products
• Dairy products stored in the refrigerator at temperatures of
2°C to 4°C (36° to 39°F).
Follow these guidelines:
1. Fat in dairy products has a tendency to absorb strong odours
from the storage surroundings.
• store dairy products in their own area in protective
coverings.
2. Do not store dairy products in a vegetable cooler.
3. Keep the refrigerator clean at all times.
4. Rotate dairy products when fresh product arrives.
5. Dairy products should be delivered on a daily basis.
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16. Fresh Meats, Poultry, and Seafood
• These items are the most difficult to store and the most
expensive food items.
• All carcass meats should be unwrapped and hung so that
air can circulate around them.
• They should be stored at 1°C to 3°C (34°C to 37°F) in a
walk-in refrigerator.
• Place absorbent paper under the meats for quick cleanup
of any unwanted drips.
• Fresh meat must not be kept too long.
• Boned meat should be kept no longer than three days.
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18. • Even at optimal storage conditions, fresh fish has a
maximum storage life of 10 to 15 days
• For unprocessed meat, refrigerated storage is limited to
about one week
• This process is highly temperature dependent,
• with certain bacteria doubling their count in 1h at 25°C,
compared to 36h at -2°C .
• Optimum short-term storage temperatures for fresh meat
range from approximately -2°C to 4°C, while fish is best
kept at 0-2°C .
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19. Fruit and Vegetables
• Maximum storage life ranges from under,
• two weeks for high perishability produce (e.g. ripe
tomatoes, leaf lettuce) to
• up to several months for long-lasting fruit and vegetables
(e.g. apples).
• Perishability is largely influenced by,
• a crop’s water content, vulnerability or softness of tissue,
and respiratory activity.
• mostly tropical/subtropical fruit and vegetables, require
storage temperatures in the range of approx. 5 to 15°C
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20. • If temperatures are allowed to fall below safe temperatures,
• this may result in chilling damage, reduced shelf-life
and quality loss.
• Exposure to alternating cold and warm temperatures can
result in sweating (moisture accumulation on the
commodities surface),
• which in turn enhances decaying processes
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21. What is chilling injury?
• Chilling injury affects many fruits and vegetables.
• Most crops of tropical and subtropical are sensitive to chilling injury.
• Some crops of Temperate Zone origin are also susceptible.
• These crops are injured by low, but nonfreezing, temperatures.
• At these temperatures, the tissues weaken because they are unable to
carry on normal metabolic processes.
These alterations lead to the development of a variety of chilling injury
symptoms, such as
• surface pitting,
• discoloration,
• internal breakdown,
• failure to ripen,
• growth inhibition,
• wilting,
• loss of flavor, and decay.2/13/2020 Y.Bavaneethan 21

22.  The length of time produce can be stored varies widely.
• For example, hardy vegetables such as carrots and cabbage will
last for weeks,
• while delicate vegetables such as lettuce should be bought as
fresh as possible as they do not keep for long.
 Moisture on vegetables tends to soften them, causing rot.
 vegetables, they can be unattractive to the eye.
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