LESSON 6 Flashcards
Blanching
- Inactivate enzymes in plant tissues, preventing enzymatic degradation.
- Wilt vegetable products to enable packing of the products into containers.
. off inter- and intracellular oxygen and other gases from plant tissues so that containers are not deformed by excessively high internal pressures due to expanding gases within the container and to permit formation of a vacuum in the container after thermal processing
Pasteurization - temp and time
at least 72°C for 15 seconds (high temperature short time or HTST process)
Pasteurization - principles
Inactivate pathogenic (disease causing) bacteria and viruses in low acid food products such as milk.
Commercial sterilization (CS) - temp and time
Minimum treatment of 121°C moist heat for 15 minutes.
Commercial sterilization - principles
“The condition obtained in a food that has been processed by the application of heat, alone or in combination with other treatments, to render the food free from viable forms of microorganisms, including spores, capable of growing in the food at temperatures at which the food is designed normally to be held during distribution and storage”. Therefore, commercially sterilization involves the destruction of spoilage-causing and disease-causing microorganisms*
* Commercially sterile foods may contain small numbers of extremely thermophilic bacteria spores; however, the spores cannot germinate and produce actively growing cells at room temperature, nor would they cause disease.
Ultra-high temperature processing (UHT) and Aseptic packaging - temp and time
Heated to 140-150°C very rapidly by direct injection of steam, held at that temperature for short period of time (e.g. 4-6 seconds) and then cooled, in a vacuum chamber to flash off the water added in the form of condensed steam
Ultra-high temperature processing (UHT) and Aseptic packaging - principles
Application of “ultra high temperature” (heat) to food before packaging, then filling the food into pre-sterilized containers in a sterile atmosphere.
Decimal reduction time or D-value
The time required to kill 90% of the microbial population exposed to a specific temperature
What effects do different conditions have on the D-value?
If the temperature is increased, the D-value would decrease because the rate of microbial death would increase.
The magnitude of the D-value depends on how the constituents of the food affect the sensitivity of the microorganism to the killing effects of heat. The protective effect of food constituents are discussed in more detail later in this lesson.
z-value
the number of degrees required for a specific thermal death time curve to pass through one log cycle
F-value
A measure of “lethality” or the capacity of the heat treatment to sterilize
Margin of safety
the probability that a container of food could still contain a viable spore of Clostridium botulinum after the completion of the thermal processing
MOS - low acid foods
Typically, for low acid foods (pH greater than 4.6) a margin of safety of 12D is applied
MOS - acid foods
Temperatures at or below 100°C for a few minutes should be an adequate heat treatment. Typically, a 5D thermal process is usually used for acid foods.
Retort
an environment of pressurized steam within a vessel
Retort temperature and pressure
A processing temperature of 250°F (121°C) is achieved by establishing a steam pressure of 15 pounds per square inch within the retort.
Steel body cans “tin can” (observations)
Steel body cans with a thin layer of tin (‘tin cans”) are the most widely used containers.
Can withstand high temperatures and pressure differentials
Not readily breakable
The can lids provide a good indication of the presence of a vacuum and thus a hermetic seal (a seal that is impervious to the transmission of gases, water and microorganisms)
The steel, and very often the tin plating, must be protected with lacquers to minimize reaction of the metals with food constituents
Glass jars (observations)
More resistant to corrosion and reaction with food constituents
Allows the consumer to see the contents in the container.
Glass is heavy and bulky and must be packaged with extra protection to prevent physical breakage of the glass during transportation
Glass filled containers must also be processed in the retort with extra care to prevent breakage due to thermal shock.
Sterile cartons (Tetra Pak) (Observations)
Carton laminates are first sterilized by treatment with hydrogen peroxide followed by forming and filling of the cartons under sterile conditions. A chemical sterilizing agent must be used for this type of packaging material since exposure of the laminated material to high temperatures required for heat sterilization would destroy the packaging material
Retortable pouch (observations)
The retortable pouch is a relatively new form of packaging. The pouch is made of a laminate of plastic films and aluminum.
heat penetrates these pouches faster due to their thinner profile, allowing the 12D thermal process at the cold point to take place in a much shorter period of time than the conventional metal can or glass bottle.
Nutrient retention is superior in foods thermally processed in the retortable pouch.
The pouch itself must be packaged in an outer protective carton to minimize physical damage to the food due to handling by the consumer and to avoid inadvertent puncture of the container
Plastic cans/bottles (observations)
New types of plastic packaging materials that can be produced in the shape of a can or bottle
Can be hermetically sealed and thermally processed in a steam retort to achieve the 12D process for low acid foods.
Newer plastic bottles can be used with UHT-Aseptic packaging technologies
Some of these containers are used for foods that are ready to eat. These containers, unlike metal cans and glass bottles can be placed in the microwave oven.
Blanching - purpose
mainly inactivates undesirable enzymes in food. It is usually used in combination with other preservation (processing) methods.
Thermal Processing (TP)
designed to kill microorganisms and extend the food’s shelf life.
