Thermal Processing
No description yet. This curated deck is ready for daily study.
Card preview (24)
What are the 3 basic mechanisms by which food is transferred?
conduction, convection, and radiation
What is conduction?
Heat and energy is transferred from one molecule to an adjacent molecule (through containers without a gross change in relative positions of the molecules. This is done with solid foods.
What is convection?
The transfer of heat by groups of molecule that move as a result of differences in density or as a result of agitation. This is done with fluid foods.
What is radiation?
Heat transfer by electromagnetic waves emitted by hot objects. This is done through infrared, microwave, and dielectric heating.
What are 4 types of thermal processes?
• Cooking • Blanching • Pasteurization • Sterilization
What is the objective of cooking foods?
To increase palatability (mainly), destruct some spoilage and pathogenic microorganisms, and inactivate deteriorative enzymes. It also inactivates some anti-nutritional factors and improves digestibility.
What are some undesirable changes to cooking?
Loss of nutrients and decline of sensory quality
How are nutrients lost during cooking?
• Lysine bioavaibilty goes down • Heat sensitive vitamins are killed (A & D) • Water soluble vitamins goes down (B vitamins)
What is the objective of blanching?
Inactivate deteriorative enzymes and kill spoilage bacteria.
What are two types of blanching?
• Atmospheric steam/boiling water 2. Pressurized steam/ hot gas
Why is blanching done before freezing or canning?
To prevent damage
Describe a typical industrial blanching machine.
A mesh convayer carries food through steam atm in a closed tunnel
When is blanching done?
Before freezing and canning and before drying.
Why do you blanch before freezing and canning?
To remove gases and clean tissues.
Why do you blanch before drying?
To extend shelf life and destroy enzymes.
What is Lipoxygenase?
development of off-flavour in soybeans and grozen veggies, colour change in flour, loss of vitamin a and fatty acids
What is polyphenol oxidase?
Responsible for enzymatic browing
What is pectinase
Responsible for softening of plant tissue by breaking down pectin
What is the “hot break process”
The loss of viscosity in tomato juice if not treated immediatly
What is used as an indicator of the severity of nutrient loss during blanching?
The loss of absorbic acid because it is thermally labile and subject to enzymatic breakdown.
What type of blanching effects nutrient loss the most and the least?
Most: water blanching with cold water Least: Steam blanching with cold air
What is pasteurization?
A heat treatment that kills part of the microbial population that is present within food whilst only minimally changing sensory or nutritive value
What is the primary object of pasteurized milk?
To kill pathogenic microorganisms and extend shelf life.
What pathogens are targeted in milk through pasteurization? (2)
Mycobacterium tuberculosis and coxiella burnetti