Unit 9 - Thermal and Non-thermal Processes

What does milk pasteurization use?

HTST, LTLT and ULT

What is HTST

High temp short time (72 degrees for 15 seconds)

What is LTLT

Low temp long time (63 degrees 30 mins)

ULT

(140-150 degrees for 2 second)

What are some Thermal technologies?

Pasteurization and commercial sterilization

What are some non-thermal technologies?

Irradiation, microfiltration, high pressure, pulsed eletric fields

What are the elements of thermal destruction curve?

D (thermal death value for a temperature at a time) , Z ( temperature to achieve a 1 log reduction in D), F (The food safety objective, this is desired end reduction), Fo (the references temperature for sterilization)

What is the formula for D value

Dt value = Time/(logNo - logNi) (Ni is final population) this is measured in time

What is the formula for Z?

This in the temp for a 1 log reduction in D and is measured in temperature, Z = (T2-T1)/(logD1 - logD2)

What is the formula for F value?

F = D(log No -Ni)

What are the primary and secondary objectives of Thermal processing?

Primary is to destroy the most heat resistant pathogenic spore-forming organism (botulism) and secondary is to destroy vegetative and spore-forming spoilage organisms (they are usually more heat resistant than pathogenic ones)

What is the difference between sterilization and commercial sterilization?

Sterilization is the inactivation of all microbes and commercial sterilization is being free of most microbes but those that remain are unlikely to grow and cause spoilage during storage

What is an example of high temprature processing?

Pasteurization

What does pasteurization do? What time of products do we use this for?

Kills target pathogens and extends shelf-life however it does not inactivate all present microbes, It is used for milk, fruit juice, meat surfaces, liquid egg and honey

What is a sign that sterilized foods have spoiled? What causes this?

Packaging (cans) may be blown up, or it could be flat sour spoilage (no blowing up), which can be caused by underprocessing or container damage

Are all thermally processed foods canned?

No they can be in aseptic containers as well like milk, sauces, soups

What is true of thermal processing with high acid foods?

They require less thermal processing, the goal is to kill most heat resistant (botulism) and these are acid sensitive so less processing will be required to prevent them from growing

What is Irradiation Pasteurization?

Just a combination of the techniques

What is Food irradiation? What does it require?

It is the processes of using ion radiation to treat food, it requires labelling and is cold pasteurization, this requires a second facility and is expensive, a super beam x ray is used to do this in food

What is a superbeam X-ray?

They shoot high energy particles that disrupt protein enzyme structures and indirectly form free radicles from oxygen and water

What are the benifits of irradiation?

can be used on dry grains to kill paricites, leaves fewer chemical residues, different amounts of radiation is required for different food types

What is the target reduction of pathogenic microorganisms by irradiation?

3-4 log reduction in in spoilage and pathogen bacteria

What kind of microbes are most resistant to irradiation?

Spore formers>gram positives>gram negatives

What are the advantages and disadvantages of irradiation?

Advantages: Increases shelf-life, keeps appearance, effective at killing and reducing spoilage organisms

Disadvantages: People don’t like it, must have a label, requires a second facility, expensive, open to abuse

What are some filtration techniques?

Microfiltration, nanofiltration, reverse osmosis

What reduction can we expect from microfiltration?

3-4 log reduction

What are the advantages and disadvantages of microfiltration?

Advantages: effective at reducing numbers, maintains nutritional value, permits lower temperatures for thermal pasteurization, extends shelf-life

Disadvantages: Membranes don’t last, expensive, still needs to be pasteurized

What is High pressure processing?

Use high pressure to disassembleribosomes to inactivate microbes (400 KPa), can be added to their processes to enhance them, it acts uniformly through the product

What are examples of HPP foods?

Vaccum packed and MAP packed foods

Why is HPP used?

It is a way to inactivate pathogens without using thermal techniques, extends shelf-life, retains nutrients, makes texture better

What are the advantages and disadvantages of HPP?

Advantages: Effective, minimal effect on quality, preserves nutrients

Disadvantages: Not good for high capacity lines, expensive, can discolour foods

What is UV light used for? How does it work?

Can denature DNA and cause photodegradation of enzymes and oxidants, and can have a hard time penetrating foods and liquids uniformly

What is Gas Plasma?

Causes oxidative damage, UV damage, and DNA leakage, it is effective, non-thermal, chemical free and can be used in package however it is small scale, high voltage, expensive and takes a long time