Heat/thermal processing

sterilization

- complete destruction of microorganisms, bacterial spores (250°F for 15 mins)

commercial sterilization

- degree of sterilization in which all pathogenic and toxin-forming organisms have been destroyed as well as other types of organisms which if present could grow in the product and produce spoilage under normal handling and storage conditions

- clostridium botulinum -> anaerobic

pasteurization

- heat treatment employing temperature below 100°C for the preservation of food

- destroy all pathogenic microorganisms that may be associated with the food and could have public health significance

- extend product shelf-life from a microbial and enzymatic point of view

blanching

- mild heat treatment commonly applied to fruits and vegetables prior to freezing, drying, and conning

- inactivation of enzymes -> peroxidase

- enhance drying/rehydrations

- removing tissue gasses -> tissue wilting & improve vacuum

- enhance color of green vegetables

- reduce microbial load

conduction

- mode of heat transfer

- occurs in solid foods wherein an energy is transferred from one molecule to another

cold point = slowest heating point

convection

- mode of heat transfer

- heat is transferred as a result of temperature gradient

- natural and forced

natural convection

- thermal gradient as a result of temperature gradient

forced convection

- facilitated by mechanical agitation

radiation

- mode of heat transfer

- occurs as a transfer of heat energy by electromagnetic radiation

microwave heating

- between 300 megahertz to 300 gigahertz

- hertz = 1 cycle per second

- 900 megahertz is a common microwave frequency

- 2450 megahertz is the most common microwave frequency

heating food prior to packaging

- milk pasteurization

- batch pasteurization

- aseptic technique

batch pasteurization

- low temperature and long time (145°F for 30 mins)

- high temperature and short time (161°F for 15 secs)

aseptic technique

- commercially sterilized outside the container, 275°F for 2-3 secs and packed aseptically

- shelf-stable