Unit 9A

Question 1

sterility is achieved when ?

Answer 1

all parts of the product have been heated to 121 ( reached by using steam) and held at that temperature for 15 mins

Question 2

is sterility used for foods, why or why not?

Answer 2

no, this would cause to become inedible or lose all nutritional value

Question 3

what is used for canning

Answer 3

commercial sterility

Question 4

definition of commercial sterility

Answer 4

all pathogenic and toxic forming organisms are killed and spores are inactivated
gives shelf life of over 2 years- safe while still providing foods quality

Question 5

for low acidic foods what temperature is needed to achieve commercial sterility?

Answer 5

above boiling point of water

these are achieved by steam under pressure

Question 6

pasteurization vs commercial sterility?

Answer 6

pasteurization is usually below the boiling point of water

because of this it results in a shorter shelf life bc the spores normally survive

Question 7

blanching is used for ?

Answer 7

denature deleterious enzymes such as polyphenol oxidase and lipoxygenase
usually used prior to freezing or other preservation techniques

Question 8

what is D-value

Answer 8

a decimal reduction time: the heating time at a specific temperature to reduce the microbial population by 1 log unit or 90%

Question 9

if you assume a can has 10^6 spores than a thermal process resulting in _____ while result in 10^-6 spore and represent commercial sterility

Answer 9

12 D ( 12 decimal reductions ) from 10^6 to 10^-6 is 12 decimals

Question 10

how is d value found

Answer 10

experimentally by a plate count on samples that have been heated to different temps

Question 11

higher temps would result in

Answer 11

lower D value and a stepper slope

Question 12

z value

Answer 12

thermal resistance

Question 13

how do you find z value

Answer 13

plotting log D vs temperature

temperature increase corresponding to the reduction of D by 1 log

Question 14

what does D100= 2 mins mean

Answer 14

it means that it takes 2 mins at a temperature of 100 degrees to reduce the microbial population by 1 log (or 90%)

2D’s would be 4 mins
12D’s would be 12x2= 24 mins ( achieve commercial sterility!)

Question 15

explain a z-value of 18 degrees

Answer 15

z value is the temperature increase it takes to reduce the D value by 1 log (factor of 10)

so if D100=20 mins and the z value is 18 degrees
then D118= (20/10)= 2 mins

so D12 at D100= 20 x 12= 240 mins
D12 at D118= 2x 12= 24 mins

Question 16

what is best for quality attributes?

Answer 16

short time and high temperature (HTST)

Question 17

what are the 2 types of thermal processing?

Answer 17

1) conventional processing - traditional canning where you package first and then heat
2) Aseptic ( free from contamination ) processing- process and then package such as tetra brick

Question 18

explain batch retort

Answer 18

a large pressure cooking that is called a batch retort in which cans are loaded and sealed and than heated with steam under pressure

Question 19

what are thermocouples

Answer 19

thermocouples are placed inside a can and placed in the slowest to heat up place “cold point” ( centre for conduction and centre 1 third up in convection ) and are used to determine how food heats up in a retort