Concentrated all grain boil

[jab]

Just curious if anyone has done a concentrated boil of all grain wort and then diluted it to achieve the required sg? Is there a reason why a full wort boil is so important with all grain?

Cheers. Jim

[drsmurto]

I've done a 30L boil then diluted back to 40L as i cant get a 40L batch out of my kettle.

You still have to boil all the wort, not just some of it.

So if you have the ability to boil it all at the desired gravity then thats the preferred option. The megabreweries brew high gravity but thats more of a $$$ thing i believe.

[jab]

I was thinking something along the lines of starting with 18l of wort and boiling for an hour, then diluting to achieve the desired volume/sg. I believe this will effect hop utilisation. Are there any other flavour impacts? The reason I ask is that Ive been doing partials that are about 1kg of grain shy of being ag. My next brew is going to be a mild and I was considering doing away with the extract and having a go at an improvised all grain. I am slowly getting my all grain setup together but still lack the facility to do a 30l boil. Is this worth trying or should I just wait?

[drsmurto]

If it gets you into AG quicker then go for it.

Yes, it does have an impact on utilisation - it lowers it so you need to up your 60 min hops to account for this.

If you haven't already, download beersmith (free 30 day trial but worth every cent IMO). Makes the calculation much easier.

I haven't noticed an impact on flavour or aroma. The only reason i dont do concentrated boils anymore is it reduces the volume i sparge with and IMO reduces the malt flavour (and reduces my efficiency). I took a recipe i know very well (golden ale) and used this technique. The malt was very subdued compared to the normal method so i have stopped doing this altho i did confirm my suspicions with 2 other beers i have made before - my Landlord and a stout - same result.

Since going back to full volume boils i find i have better balance in my beers.

As i said, if this gets you into AG earlier do so. Once you have the cash to buy a bigger mash tun and kettle then you can do full volume boils and compare the 2 for yourself.

[jab]

Thanks Drsmurto. Thats pretty much where my heads at. Just needed someone to back me up.

Cheers, Jim

[Trough Lolly]

Just curious if anyone has done a concentrated boil of all grain wort and then diluted it to achieve the required sg? Is there a reason why a full wort boil is so important with all grain?

Cheers. Jim

G'day Jim
Further to Doc's sensible advice, there are a lot of processes occurring during a boil. The following PDF document is well worth downloading if you've ever wondered what the hell goes on during a boil...For those of us who don't want to pull down a PDF document, here's the intro that provides a broad outline of why we boil;

The purpose of wort boiling is to stabilise
the wort by:
• Killing spoilage micro-organisms.
• Reducing the amount of coagulable nitrogen thus promoting colloidal stability.
• Extracting the desirable principles of hops to give beer its characteristic aroma and flavour.
• Reducing undesirable volatile compounds through evaporation.

Clarified wort is usually collected directly in the wort kettle or run to a wort receiving vessel (often called a pre-run or underback) before being transferred to the wort kettle.
The wort kettle is fitted with heating, either using direct fuel combustion or indirectly, using steam. The wort in the kettle is first heated from wort separation run off temperature, which is between 65°C and 78°C, to boiling (usually just above 100°C, at atmospheric pressure because of the dissolved solids). The kettle contents are then boiled for between 30 and 120 minutes.
Wort boiling has a high energy demand and accounts for as much as 40% of the energy consumption of a brewery. Most of the energy required to heat worts to boiling point is recovered during wort cooling through the use of heat exchangers, heating up the incoming brewing water (liquor) in preparation for the next brew. This gives a heat recovery efficiency of up to 99%. The additional energy required to evaporate the water vapour during the boil is generally lost up the chimney. It is by reducing this energy loss that real savings can be achieved.
A variety of schemes are available to recover part of the energy from evaporation. The most effective ways to reduce energy consumption are by reducing % evaporation rates. The average % evaporation rates have fallen over the last 30 years from around 12 – 20% to between 4 – 8%. In order to appreciate the consequence of reducing evaporation rates it is necessary to understand the principle changes which occurring in the wort during boiling.

http://www.ibd.org.uk/cms/file/307

Notwithstanding the necessary hop level adjustments, there's no reason why you can't do a concentrated boil and then dilute - but I would not get too extreme, eg, boil 10L and expect to have a balanced 23L batch afterwards. I would avoid diluting by more than 30% of post boil volume...and remember that the boiled wort is vulnerable to infection after the boil, especially if you use water that isn't "clean" / pre-boiled.

Cheers,
TL