Chapter 16 (Micro Iii)

Front 1

intrinsic factors that affect microbial growth in food

Back 1

availability of water
specific nutrients present in the food
the pH of food
whether the food has natural compounds

Front 2

extrinsic factors that affect microbial growth in food

Back 2

temperature
humidity
presence of gasses (like O2)

Front 3

what is water activity

Back 3

measurement of the amount of water in a sample that is available to a microorganism to enable growth. Water can be present in a food item but may be inaccessible to a cell because water interacts with molecules within the food.

Front 4

how is water activity related to food spoilage

Back 4

foods with low water activity (dry foods/high concentrations of salt or sugar) do not support microbial growth and can remain unspoiled for extended periods of time

Front 5

how do microbial growth phases get manipulated to reduce food spoilages

Back 5

delay microbial entry to LOG PHASE by increasing time in lag phase.

reducing growth rate
reducing initial microbial load in the food.

pH and temp can be manipulated to reduce the growth rate -->delay log phase.

Front 6

how is water availability reduced in food products

Back 6

drying or adding high amounts of salt, sugar, or other solutes.

Front 7

why does adding high amounts of sugar, solutes, and salts prevent spoilage?

Back 7

reduces the availability of water thus preventing bacterial growth

Front 8

how do various temperatures used to control microbial growth

Back 8

cold temp: halt/greatly slow growth of pathogenic and spoilage bacteria.
Heat: kill or damage microbes to prevent them from spoiling food.
- pasteurization

Front 9

how do the following chemicals function as food preservatives
aceic acid
sodium benzoate
sodium nitirte

Back 9

acetic acid and sodium benzoate are both weak acids that produce protonated molecules that can cross the membrane to lower the internal pH --> inhibits growth of many pathogens and spoilage organisms.
- sodium nitrite inhibits growth because dissociated nitrite interferes with iron sulfur proteins that are needed for bacterial respiration.

Front 10

how can biocontrol methods like bacteriocins be used in food preservation

Back 10

bacteriocins are molecules produced by one type of bacteria to kill other, usually related.

- they can be added to food to selectively kill certain potentially harmful bacteria.

Front 11

how are different radiation methods used to control/destroy microbes in food products?

Back 11

ionizing radiation involves exposing food to high energy x-rays or gamma-rays which destroy microbes by producing extensive oxidative damage to protein and DNA.
- able to penetrate deep into food.
ultraviolet radiation - when surface or air sterilization is required - causes dimers in bacterial DNA that inhibit transcription and DNA replication

Front 12

what is MAP

Back 12

modified atmosphere packaging

keeps food in a sealed environment with a right combination of gas to prevent spoilage.
-- no O2 high Co2 to limit growth of aerobic microbes.
- raw meats are given high O2 to discourage anaerobe growth

Front 13

what's hurdle technology

Back 13

hurdle technology refers to refrigeration, low pH and low water availability simultaneously.

at levels where the individual factor would be ineffective at inhibiting growth.

Front 14

how is lactic acid bacteria used in food production

Back 14

ferment certain types of food including dairy products.
- produce lactic acid during their metabolism which contributes to the flavor of yogurt and other fermented dairy products -- also serves to preserve the product by limiting the growth of spoilage bacteria