#### Lyrebird_Cycles

##### Well-Known Member

- Joined
- 10/7/16

- Messages
- 1,439

- Reaction score
- 775

In a recent thread on mash enzymes I posted some information on the rate of thermal degradation of the enzymes which was possibly a little maths heavy for many readers.

Thinking about ways of making this info more accessible, I came up with the idea of the enzyme Degradation Unit (DU), analogous to the Pasteurisation Unit (PU) used for estimating thermal death rates of spoilage organisms. The two phenomena are governed by the same sets of equations as could be expected given that thermal death is the result of the denaturation (coagulation) of essential proteins. In keeping with the premise of this thread I'll go into the background maths in a later post.

I propose that 10 DU is the net thermal dose that reduces enzyme activity to 1/10 its former level (eg 90% of activity is lost) so 1 DU is equivalent to roughly 20% activity loss and 3 DU is equivalent to 50% activity loss. Again the maths behind this will follow.

Just like pasteurisation, you add the DUs but multiply the effect: if 5 minutes at a particular temperature gives 10 DU and 3 minutes at another temperature also gives 10 DU, the total is 20 DU and the enzyme activity will be reduced to 1/100th ( = 1/10 x 1/10) its initial level.

There are two ways of presenting the required information: the number of minutes at each temperature to reach 1 DU and the number of DUs per minute at each temperature. Of course these are simply the inverses of one another.

Minutes for 1 DU at various temperatures:

temp C...55.....60.....65.....70.....75.....80.....85.....90.....95.....100

alpha......28.....20.....14.....10.....7.1....5.0....3.5....2.5....1.8.....1.2

beta........16.....9.2....5.3...3.1....1.8....1.0....0.59...0.34...0.20...0.11

DU/minute at various temperatures:

temp C....55.......60.......65.......70.......75......80.......85.......90.......95......100

alpha.....0.035..0.050...0.071..0.10....0.14....0.20....0.28....0.40....0.57....0.80

beta.......0.063..0.11.....0.19.....0.33....0.57...0.98.....1.7......2.9......5.1......8.8.

As an illustration of how this information might be used, let us take the common supposition that a 10 minute mash out at 75 oC will kill off the mash enzymes.

From the table we can see that at 75 oC 10 minutes will provide 1.4 DU for alpha and 5.7 DU for beta. This will result in a loss of about 30% of enzyme activity for alpha and 70% for beta: a moderate reduction in the first case and a significant reduction (but not complete elimination) in the second.

Thinking about ways of making this info more accessible, I came up with the idea of the enzyme Degradation Unit (DU), analogous to the Pasteurisation Unit (PU) used for estimating thermal death rates of spoilage organisms. The two phenomena are governed by the same sets of equations as could be expected given that thermal death is the result of the denaturation (coagulation) of essential proteins. In keeping with the premise of this thread I'll go into the background maths in a later post.

I propose that 10 DU is the net thermal dose that reduces enzyme activity to 1/10 its former level (eg 90% of activity is lost) so 1 DU is equivalent to roughly 20% activity loss and 3 DU is equivalent to 50% activity loss. Again the maths behind this will follow.

Just like pasteurisation, you add the DUs but multiply the effect: if 5 minutes at a particular temperature gives 10 DU and 3 minutes at another temperature also gives 10 DU, the total is 20 DU and the enzyme activity will be reduced to 1/100th ( = 1/10 x 1/10) its initial level.

There are two ways of presenting the required information: the number of minutes at each temperature to reach 1 DU and the number of DUs per minute at each temperature. Of course these are simply the inverses of one another.

Minutes for 1 DU at various temperatures:

temp C...55.....60.....65.....70.....75.....80.....85.....90.....95.....100

alpha......28.....20.....14.....10.....7.1....5.0....3.5....2.5....1.8.....1.2

beta........16.....9.2....5.3...3.1....1.8....1.0....0.59...0.34...0.20...0.11

DU/minute at various temperatures:

temp C....55.......60.......65.......70.......75......80.......85.......90.......95......100

alpha.....0.035..0.050...0.071..0.10....0.14....0.20....0.28....0.40....0.57....0.80

beta.......0.063..0.11.....0.19.....0.33....0.57...0.98.....1.7......2.9......5.1......8.8.

As an illustration of how this information might be used, let us take the common supposition that a 10 minute mash out at 75 oC will kill off the mash enzymes.

From the table we can see that at 75 oC 10 minutes will provide 1.4 DU for alpha and 5.7 DU for beta. This will result in a loss of about 30% of enzyme activity for alpha and 70% for beta: a moderate reduction in the first case and a significant reduction (but not complete elimination) in the second.

Last edited: