Pasteurization Research

[Jay Kenney]

This came across my screen sometime during the pandemic and now that the days are shorter and the nights longer I had time to read it again, dig deeper and now invite the group's comments given that most of us here have long relied on 50 PUs, however achieved, as the requisite minimum. 

 

"Abstract--A Preliminary Evaluation to Establish Bath Pasteurization Guidelines for Hard Cider
Though in-package water bath heat pasteurization for hard cider production is commonly employed to improve product safety and stability, there is a considerable lack of research-based guidelines to inform industry practices. In this study, fermented cider was bottled and inoculated with high populations of Saccharomyces cerevisiae and Zygosaccharomyces rouxii yeast. The bottles were then subjected to water bath pasteurization 60 °C at varying lengths of time. For both yeast species, populations were reduced to undetectable levels after just 1 min of processing time. Though validation of each individual process is recommended, cider producers may be able to sufficiently reduce the risks of spoilage organisms with minimal water bath pasteurization, especially when combined with other methods to reduce the presence of spoilage organisms."
Beverages 2020, 6(2), 24; A Preliminary Evaluation to Establish Bath Pasteurization Guidelines for Hard Cider  Received: 14 February 2020 / Revised: 11 March 2020 / Accepted: 30 March 2020 / Published: 13 April 2020

A slightly older article on beer reached a similar conclusion.  "The results from the present study indicated that a >8.7 log reduction in the cell numbers of the selected organisms was achieved at just 1.59 PU. It has to be borne in mind that this study only focused on the vegetative forms of bacteria. The most heat resistant morphological forms of bacteria and yeast are spores, which were not investigated in this study. Further studies should focus on the heat inactivation of heat resistant yeast ascospores which are potential beer spoilers." 

[Nicholas Bradstock]

I think there’s a clue in the last para in the beer study.  There is potentially a greater risk of spoilage from spore-forming yeasts, and perhaps bacteria, in apple juice & cider (wild yeasts and ambient temp making) than in boiled wort and cultured yeasts.

EG:  Saccharomycodes Ludwigii used to be the greatest actual threat in cider processing in the 70s....

Just a thought

Nick

iPhone

On 4 Dec 2020, at 03:45, Jay Kenney <kenne...@gmail.com> wrote:

This came across my screen sometime during the pandemic and now that the days are shorter and the nights longer I had time to read it again, dig deeper and now invite the group's comments given that most of us here have long relied on 50 PUs, however achieved, as the requisite minimum. 

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[Andrew Lea]

Yes Nick is surely right. A mixture of “real life” cider organisms are the only test, not just a couple of selected yeasts from a culture collection.

Some years ago i visited a craft cider maker in Western Canada.  He wanted to use the minimum effective pasteurisation and had done some trials with various PU regimes on his own cider and had worked in conjunction with the food microbiology dept of his local University looking at actual “total viable counts” after pasteurisation. In this way he had established that the minimum needed for his cider was 20 PU. I have to say that sounds a lot more realistic in real life than the very low values reported in the papers cited below.

Andrew

Wittenham Hill Cider Portal
www.cider.org.uk

On 4 Dec 2020, at 09:21, 'Nicholas Bradstock' via Cider Workshop <cider-w...@googlegroups.com> wrote:

I think there’s a clue in the last para in the beer study.  There is potentially a greater risk of spoilage from spore-forming yeasts, and perhaps bacteria, in apple juice & cider (wild yeasts and ambient temp making) than in boiled wort and cultured yeasts.

To view this discussion on the web, visit https://groups.google.com/d/msgid/cider-workshop/ADC0F0F1-4D12-4DB3-BD41-8ED867899DDF%40btinternet.com.

[Jay Kenney]

I agree with Nick that cider is not beer and that a lab is not the real world and that 1 PU is certainly insufficient with most of the apples that I source and under the conditions I operate. Andrew's anecdote about the cider operation in CA reminds me of another thread (about the amount of SO2 required to permit a semi-wild fermentation to take off) where he threw up his metaphorical hands and told all of us here in the states to quit relying on 50 year old data from LARS and create our own. A similar plea could be made here, though each analysis would be specific to that cidery's operations and the fruit/juice it sourced in any given year. But working with a local university would be the way to approach it and create the necessary data. 

[Brian Drake]

Is there any downside (other than additional pasteurization time/energy) to higher PU's?  Organoleptically speaking? 

Brian

OOLLC

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[Andrew Lea]

More PUs means more Maillard chemistry takes place, hence potentially developing more “cooked” flavours. This is true for all food processing. The use of SO2 can minimise this, by binding up the early Maillard compounds.

Whether this becomes an organoleptic problem is a matter of perception. Generally, a properly pasteurised cider in the presence of SO2 shows little or no cooked flavour on a straight tasting. It may do on an A/B comparative tasting, though.  

The upside of pasteurisation is that it is cheap and easy for the small producer and pretty much controllable with a robust bottled product at the end of it. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

On 4 Dec 2020, at 21:06, Brian Drake <dra...@gmail.com> wrote:



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[gareth chapman]

That's interesting about the cooked flavours, this year we put a batch of juice on to pasteurise and got totally distracted so it ended up with well over an  an hour at 75 degrees, the shed smelt strongly of cooked apples, however there isn't the slightest hint of cooked flavour in the finished juice.

Back to the subject in hand, the original article does mention that low PU pasteurising may be suitable when combined with other methods to prevent spoilage.
Anecdotally, I have a few ciders, several years old,  knocking about that are absolutely fine that are unpasteurised and with the only intervention being an initial addition of sulphite at the point of pressing.

[Andrew Lea]

Just to clarify, ciders only need to be pasteurised if they contain fermentable sugar (usually added) and enough nitrogen to complete further fermentation. 

If they finished naturally sweet eg from keeving or multiple rackings, and they have low nitrogen status, pasteurisation is not required. 

Andrew

——————————

Wittenham Hill Cider Page

www.cider.org.uk

On 5 Dec 2020, at 11:01, gareth chapman <chappe...@gmail.com> wrote:

That's interesting about the cooked flavours, this year we put a batch of juice on to pasteurise and got totally distracted so it ended up with well over an  an hour at 75 degrees, the shed smelt strongly of cooked apples, however there isn't the slightest hint of cooked flavour in the finished juice.

To view this discussion on the web, visit https://groups.google.com/d/msgid/cider-workshop/413b4620-67ec-4e48-9c87-51e2c509d32en%40googlegroups.com.

[Alan stone]

Very surprised - cooked apple flavour is very common in home pasteurised ciders - even smaller commercial ones. It is not an unpleasant taste - but not what you want

Sent from my iPhone

On 5 Dec 2020, at 11:09, Andrew Lea <ci...@cider.org.uk> wrote:

Just to clarify, ciders only need to be pasteurised if they contain fermentable sugar (usually added) and enough nitrogen to complete further fermentation. 

To view this discussion on the web, visit https://groups.google.com/d/msgid/cider-workshop/FB844AD9-5BAD-4961-8EDB-E11924C44F48%40cider.org.uk.

[Andrew Lea]

Then I would suggest they have been over-pasteurised or have not used SO2 to mitigate the Maillard. 

Or you are supremely sensitive to such flavours ;-)

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

On 5 Dec 2020, at 11:57, 'Alan stone' via Cider Workshop <cider-w...@googlegroups.com> wrote:

Very surprised - cooked apple flavour is very common in home pasteurised ciders - even smaller commercial ones. It is not an unpleasant taste - but not what you want

To view this discussion on the web, visit https://groups.google.com/d/msgid/cider-workshop/0A16B8B6-44A0-41D7-8086-1D860702D0BE%40btinternet.com.