Oxidisation - dare I ask?

[rotten]

G'day guys.
Some of you may think "not this old chestnut again". But searches simply aren't providing the answers I'm after. I splash unintentionaly when transferring hot wort from place to place. I recently brewed a bigger batch than normal so there was even more splashing than normal.

I work on the theory that the boil takes care of any isues, as with ridding the wort of any unwanted bugs. I have more splashing again when I rack, the temp then is usually cold. I haven't noticed any undesireable effects as yet, but there is always a first time.

So what symptoms should I watch for if it is in fact a problem?

If it is a problem, is it pre-boil as well as post boil?

Hot or cold? or both?

[Bum]

G'day guys.
So what symptoms should I watch for if it is in fact a problem?

If it is a problem, is it pre-boil as well as post boil?

Interesting question and one I've not seen discussed before. The boil should drive off all O2 but is the "damage" already done? I have read that O2 can bond to "bits" of the grain in the mash even but no idea if the boil would sort the issue out.

If you're not noticing any issues (wet cardboardy flavours, short shelf life/staling, possible gushers (so I'm led to believe)) then just continue to minimise the splashing as best you can and hope for the best while you piece together a method of transferring that removes the splashing entirely (if it bothers you).

[speedie]

General it is hot side that is an issue but as you stated I do or have similar things happen when brewing

Most big breweries pump there finished mash into another vessel for spagring so I would assume that there is a chance of oxygen pickup some where along the line
I pump in a similar fashion and haven’t had any issues to date

Then on the cold side when transferring to the fermenter it is the normal practice to splash or aerate the wort for active yeast growth others use a aquarium pump or diffuser stone to introduce oxygen

Post fermentation is the area to be careful with in regard to introducing oxygen
The taste is described as metallic
Cheers squirty
You double batcher you
speedie

[squirt in the turns]

I have read that O2 can bond to "bits" of the grain in the mash even but no idea if the boil would sort the issue out.

Very interesting... I wonder if this can be a problem once the clear wort is run off, as there shouldn't be too many bits of grain left at that point. So, does this mean we should we be careful to avoid aerating the mash? I made my first pilsner at the weekend and ended up stirring quite vigorously just to bring the temp down a degree or two. I'm guessing that if there are any flaws in my process, this is the beer that will reveal them.

I collect my runnings in a fermenter, which I then return to the urn, balancing the fermenter on the rim of the urn and my knee while draining via the tap (I don't bother with a hose) until it's light enough to just tip out it one go. Plenty of splashing happens then, I can tell you. This has been my process for all 4 AG batches I've done and I'm yet to notice any off flavours. However, with the first batch being only a couple of months old, I can't speak of the effect on shelf-life.

I think the general consensus is that post-boil hot-side aeration can lead to the wet cardboard problem. As you say Rotten, the boil should kill any nasties and also drive off O2. On the 2nd page of this thread: http://homebrewandbeer.com/forum/viewto ... =2&t=10101, Grog refers to a podcast that addresses this with an experiment. I haven't listened to it yet, but given my careless pre-boil practices, it would probably be a good idea. At all other times (aside from splash pouring into the fermenter), I'm at pains to avoid aeration, but I'm only dealing with 23L batches, so the lifting and moving around is not difficult.

[drsmurto]

You are talking about two very different effects.

Hot wort is theoretically susceptible to HSA - hot side aeration. Splashing of hot wort could introduce oxygen which could react with molecules in the wort.

@Bum - the oxygen doesn't react with grain particles, it reacts with molecules in the wort such as melanoidins converting them to molecules with undesirable flavours.

The reason i believe this isn't as big an issue as some people make out is the solubility of a gas in a liquid at any given temperature. As you increase the temperature the solubility of a gas decreases. At the temperature of the mash/mash out the solubility of oxygen will be less than wort at room temperature.

I sparge into buckets which is then tip the wort (~78C) into my kettle from a height of ~60 cm which causes splashing. I haven't noticed any products of oxidation in any of the beers i have stored for long periods. There are photos around showing commercial brewers doing similar with splashing prior to the boil. The action of boiling a liquid drives off any gases dissolved in the solution such that at the end of the boil you will have no dissolved gas in your wort. If you were to aerate it at this point prior to chilling it you are likely to run into problems.

Splashing when racking fermented beer is a huge no no. This is the point where you can almost instantaneously oxidise your beer and introduce the classic wet cardboard flavours. The trick is to get a hose long enough to coil up in your second vessel. I also put a kink in the hose part of the way down and open to the fermenter to allow the beer to fill the tube to that point. This creates a siphon and removes any air in the tube to that point and also removes air bubbles in the tap. Let the kink go and the beer should flow smoothly into the bottom container which minimal splashing. I also tilt the lower vessel to ensure the tube is immediately under the surface of the beer to further reduce splashing.

Hope something in this essay like response is useful.

Cheers
DrSmurto

[jayse]

as far as staling the oxygen can bind to wort compounds when hot this itself may not affect the beer if it does not last long, ie you drink it up fairly quickly however over time in the beer these compounds can breakdown making the oxygen availible once again once this happens the oxygen then reacts with the alc which creates the stale wet carboard flavours.
Hot side aeration has been quoted as happening as cool as 30c, now there must be a thousand no chillers out there saying bullshit to this, it may be a case of what can happen does not always show itself in anyway that us mere mortals can pick.

There is the fact that gases don't disolve well in hot liquids and any oxygen that may at these temps be quickly be knocked out, however oxidation is greatly increased with temp so at such a temp it may happen extremely quickly, whereas when cold it may take months.
So I think this may be one of the more important points, ie when people say hey its hot it won;t disolve and if it does it will get boiled out pretty quick, its not as simple as that when you note the oxygen may in fact react very quickly in hot wort before it is knocked out.

In the end anyway the oxidation would show itself in the beer overtime as it is when the compounds are broken back down again freeing the oxygen, the oxygen would then react with the alcohol, so its not actual flavours developed when its hot rather then its the reactions that take place later down the track when these compounds break back down again.
With that it may be said that you possibly will not have any noticable affect from hsa in very fresh beer.

There are other affects of oxygen in the kettle and mash etc but i think its this staling that is more to the point of this thread.

Cheers
Jayse

[rotten]

Thanks guys, feel free to take the thread further, it's all good. I'm always looking to improve my knowledge while perfecting the basics.

[bullfrog]

I love that Jayse has been registered since April 05 and only posted 16 times. He does raise some very good points, though. I have never experienced adverse qualities in my beer from my splashing about of hot wort (I splash a bit pre-boil, never post) but all of my beer gets kegged and drunk pretty quickly (never have any one keg longer than two months) so the effects of HSA could perhaps be something that only one who planned to keep their beer for a great number of months should worry about.

[jayse]

I love that Jayse has been registered since April 05 and only posted 16 times.

Yeah I have been lurking around for a few years, a couple of those posts were possibly abuse towards that annoying individual from wagga back in the day when he was causing havoc with every brew forum.