Another long-winded reply!

I use a large plastic bucket that lets the bottles sit below the water surface. This way I can see any bubbles rising from poorly capped bottles (rarely happens!)

However, all is good… You will have generated more than enough pasteurisation units (PUs) with your process.

Very roughly 25 PUs will have been generated in your bottles while heating from 135F (57C), plus150 PUs while sitting at 155F (68C) and another 25 PUs while cooling down from 155F to 149F (60C).

In reality, it is now generally accepted that anything over 30 PUs is enough for cider, with 50 PUs as the conservative target.

In your case, the 10 minutes at 155F wasn’t really needed but it is a good “belt, braces, and safety pins” overkill, which you can back off from as you get more confidence in the process. I generally pull the bottles out once the target temperature is reached.

**This next bit will make your head spin and eyes glaze over**… but persevere. The general formula for calculating PUs is = t x10 raised to the power of ((T-Tref)/Z). Where t is the time of heat exposure in minutes, T is the temperature (degrees C) reached, Tref is the temperature at which pasteurisation starts (60C for beer and cider), and Z is the coefficient of thermal resistance of the organism being targeted.

That all sounds a bit messy, but fortunately del Veccio (a brewing scientist in the 1950’s) developed a simplified version using numbers that are specific to beer (and cider). The formula named after him is...

PU = t x 1.393^(T-60)… a bit of a mission with a calculator but quite straightforward with excel or something similar. i.e. use the formula t x POWER(1.393,T-60).

The reason for going through this gobbledegoock is that I use a spreadsheet where I record the time and temperature in the bottles during the pasteurisation process. The spreadsheet calculates the amount of PUs generated and displays a graph of accumulating PUs. Two slightly different versions of the spreadsheets for recent batches (September 2023 and April 2023) are attached below. In my case they also show the theoretical pressure in the bottles at each temperature.

Unfortunately, we can’t attach excel files to HBT posts so the attachments are pdf. I can PM the various formulae if anyone needs them, but they are quite easy to work out if you are familiar with excel.

There are two ways of capturing the data. The first method that I used was to start my phone stop-watch running and record the average temperature at each minute in a "monitoring" bottle of water in the pasteuriser. My current method is to record the elapsed time at each degree change in temperature (see a post by Bembel 11 May 2016).

Both methods produce similar results, but the second method was prompted by a countdown temperature probe that I found which beeps at every degree of temperature change, so I don’t have to keep an eye on the stopwatch. It simply makes life easier.

I hope you managed to read this far, and it helps.

Cheers!