Temperature of Boil

[indica86]

Wondering if temperature of the boil makes a difference. Mine is around 97.5°c.

I have been brewing all grain for a while and not had any issues, just wondering.

 

[SBOB]

if its 'boiling' at 97.5 then you're either 700m above sea level or need a new thermometer

 

[pcmfisher]

Do you think it is too high or too low?
How were you thinking of changing it?

 

[indica86]

700m above sea level

yes.

Well for a boil it is low.
Was wondering if there is a disadvantage with anything not being boiled off/ changed as it should be.

 

[Lyrebird_Cycles]

At 700m the rate of isomerisation of alpha acids will be about 7% lower. It's included as a factor in my bitterness calculator if you are interested.

Other things like DMS boiloff follow similar kinetics. If you extend the boil slightly you should be right.

There is some evidence that a longer time at a lower temperature gives a different bitterness character, this is a possible explanation for the effect of first wort hopping which many people like, myself included.

 

[indica86]

Thanks.
Not ever been an issue but was wondering is all.
The IBU thing is interesting as I quite often use a fair bit of hops and never find beer overly bitter. DMS I have not ever noticed.

 

[rude]

Looks like a good boil to me ( no expert though )

I boil for 90 mins, hard for the first 30mins

Then monitor volume with my measuring stick ( basic set up )

I no chill & aim for 25L to fill cube with 23 L

Sometimes end up with more & sometimes less

Start with 32 L to 34 L

Whats you're starting finishing volumes ?

 

[mstrelan]

Are you sure your thermometer is accurate?

 

[indica86]

I am 700m above sea level, the temp of boiling water is lower with lower air pressure.

 

[Feldon]

There's an article on the effects of altitude on brewing in an old issue of How-to-Brew magazine:

High Elevation Brewing
Author: Glenn BurnSilver Issue: December 2004

At high altitudes, water boils at a lower temperature. How does that affect mile-high homebrewers? Read this article and find out. Plus: a high-altitude recipe from a New Mexican brewery at 7,000 ft.

Indigenous cultures living high in the Andes and Himalayas have been concocting fermented alcoholic beverages for thousands of years. The Incas brewed above 12,000 feet while brewing activities in Tibet occur well above that. A group of adventurous California brewers produced homebrew on the summit of the highest point in the continental US, Mt. Whitney (at 14,497 feet), using only a camp stove for heat. So why is it that high elevation brewing poses problems for some homebrewers with the advantage of more sophisticated equipment than clay urns and wood fires?

Perhaps the answer lies in a desire to achieve a perfect product, rather than simply enjoying a good beer. For years I have brewed at high elevations, topping out at 9,200 feet in my mountain home, without making a single adjustment to my brewing process. And, while brewing at high elevations can cause some minor problems — the obvious factors being lower boiling temperatures, under utilization of hops and a lack of oxygen — the need to "correct" a batch is a matter of debate.

Hop utilization: It's all in the boil

Hop under-utilization is the main concern surrounding high elevation brewing. Lower boiling temperatures at elevation can decrease hop alpha acid utilization and beer bitterness can be thrown off. Mark Garetz, author of "Using Hops, the Complete Guide to Hops for the Craft Brewer," has developed a correction factor equation for hops based on elevation, yet he doesn't put a lot of stake in needing adjustments. "My real world advice would be not to worry about it too much. This is still a pretty small difference," Garetz says. "Usually (the brewer) won't be able to tell the bitterness difference."

(continues at: http://byo.com/hops/item/752-high-elevation-brewing )

 

[Lyrebird_Cycles]

Garetz's equation is incorrect, he didn't take into account the fact that iso alpha degradation rate diminishes more quickly with temperature than does alpha acid isomerisation.

The difference is pretty small: his equation gives about 8.5% reduction in utilisation over a 90 minute boil where the value when degradation rate is factored in is about 7%.

He's also used an approximation of the Antoine equation but that's even more trivial.