Author Topic: Mould size & pressure  (Read 3682 times)

beeman

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Mould size & pressure
« on: January 23, 2009, 08:40:14 AM »
I would like to revisit a post on this forum, which states that a larger mould requires more pressure. The premise being, that as the mould size increases in surface area then the pressure has to increase to compensate. This information is totally wrong.  A pressure of 50lbs on a 4 inch mould is still the same as 50 lbs on an 8 inch mould. The only thing affecting the results of that pressure would be an increase in height of the cheese in the mould.

Increasing the height from 3" to 6" of the curds in the mould would require a slight increase in pressure, but it is so slight that for all practical purposes it is not adjusted.
« Last Edit: January 24, 2009, 02:42:41 AM by Webmaster »


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Offline Wayne Harris

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Re: Mould size & pressure
« Reply #1 on: January 23, 2009, 10:45:43 AM »
50lbs is not pressure.  Its a measurement of force.  (Force = Mass X Acceleration)
Pressure, however, is defined as force per unit area applied.

While you are correct in saying that the force (50lbs) would remain the same, the pressure would in fact decrease as the area applied increased. (used bigger moulds)

That is why if you need a specific PSI for a wheel of cheese, you need know the area of the wheel, and adjust your applied force.

According to several authors, most books here are written assuming a 4" mould.  Within these books,  the two terms are sometimes used interchangibly.  That can be confusing.


Hope that helps....  :)




« Last Edit: January 26, 2009, 07:14:45 AM by Wayne Harris »
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Offline chilipepper

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Re: Mould size & pressure
« Reply #2 on: January 23, 2009, 10:53:03 AM »
Another thing to make sure we are clear on is the fact that pressure we are discussing is the pressure over the most common 4 inch diameter mold and how that translates to an 8 inch diameter mold, etc. 

Quote
The only thing affecting the results of that pressure would be an increase in height of the cheese in the mould.

beeman, I just want to make sure that we are on the same page in this discussion regarding pressure as it seems you are referring to increasing the height of the mold to 8 inches. Increasing the height would indeed have the same surface area as the mold diameter is not increased so pressure applied would be the same.  In this regard, both of the discussion are correct we just maybe need some illustrations! :)

Offline Wayne Harris

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Re: Mould size & pressure
« Reply #3 on: January 23, 2009, 11:00:49 AM »
Regarding pressure (as expressed in PSI) and hieght of the curd in a mould,  I have been harboring a thought/question.

If my curds in an "X" inch mould were say 2 inches deep,  or  12 inches deep,  would you use the same pressure?

Would you get a good "knit" of the curd down deep in the middle on the deeper cheese?


Would a deeper cheese (of the same diameter) warrent an increase in pressure?

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Offline Likesspace

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Re: Mould size & pressure
« Reply #4 on: January 23, 2009, 01:21:02 PM »
Let me preface the following statement by saying that I am not an expert (by any stretch of the imagination) on this subject. The only thing that I do have is my own individual results.
When I moved from using a 4" diameter mold to a 6" diameter mold, I did so with no increase of weight and my wheels turned out fine.
Yet when I moved from a 6" diameter mold to a 7.5" diameter mold (and especially the 8" diameter mold),  I began to have a LOT of trouble.
Whereas before, my wheels would always knit together and come out very good, my first attempts at larger cheeses came out looking cracked and very rough from inferior knitting of the curd.
I honestly had no idea what was going on and only after asking for help on this board did I find out that higher pressures are required for larger diameter wheels.
At first I was skeptical (see my posts in the referenced discussion) but eventually came to accept that this information is correct.
I did eventually accept this information because:
 
1. I gave pressing at a higher weight a try and it worked (and has continued to work) perfectly.
2. I received information from Jim at New England Cheesemaking Supply, stating that this information is correct.

As far as being able to give scientific evidence of the validity of these claims, I am not able to do so.
I can, however say that it has worked for me, in my own cheesemaking.
Good luck to everyone no matter what method you choose to use.

Dave


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Offline Likesspace

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Re: Mould size & pressure
« Reply #5 on: January 23, 2009, 01:59:06 PM »
Btw..
I do feel that Beeman's ideas on the importance of milk are valid points.
After three years of making cheese, I'm just now discovering that small changes made in the starting product can yield drastic results in the final product.

Dave

Offline Cartierusm

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Re: Mould size & pressure
« Reply #6 on: January 23, 2009, 02:33:46 PM »
What videos are you watching? Because the only videos I’ve found on the web are for entertainment on how cheese is made not an actual instructional video. If you have a link or an instructional video that teaches cheese making I’d be more than happy to view it.

So you’re saying when they press 15 50 lbs. wheels of cheddar in a row, which I’ve seen in person, the pressure remains the same? Because 50lbs of force wouldn’t even move the entire line of cheese let alone press it.
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beeman

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Re: Mould size & pressure
« Reply #7 on: January 23, 2009, 03:24:39 PM »
If you apply 50lbs of weight to a disc of 4" then scale that disc to 10" there will still be 50lbs of weight required to achieve the same result. The weight at the edges would be the same, your position implies that the weight would diminish towards the edge of the mould, as the mould gets bigger.
The only time that internal pressure will change is if you increase the height of the cheese in the mould.

Likesspace. There are so many variables in making cheese, so it would be difficult to tie down what made the necessary change to improve your wheels. You have been talking milk improvements which will improve your melding when moulding.
« Last Edit: January 24, 2009, 02:44:08 AM by Webmaster »

Offline Cartierusm

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Re: Mould size & pressure
« Reply #8 on: January 23, 2009, 03:36:10 PM »
I never made a position of diminished pressure toward the edge. I simple stated that the surface area of bigger molds increase and so should the pressure, it's all about pounds per square inch. Try this experiment take a 10 lbs. spring place 50lbs of weight on it. It collapses, then put 10 springs under the same 50 lbs., they won't even compress a little, well maybe a little, but certainly not very much, much less collapse.
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Re: Mould size & pressure
« Reply #9 on: January 23, 2009, 03:56:55 PM »
Hey guys, keep it civil!

Just to add my 2 cents to this topic, it is not just about dimensional data and weight, it would only be that way with a low viscosity homogeneous material like water. I think there are also the variables of:
  • A varying viscosity of the curd being pressed in the vertical, horizontal, and time axes.
  • The configuration on escape routes for the whey, ie holes on bottom, sides, and top of base, hoop and follower and whether a cloth is used.
  • The permeability of the curds near the escape route for the whey impeding the interior's whey to escape.
  • Temperature and time etc.

The consequence is that cheese making is an art as in artisan which is why we all have so much fun making it ;D.

Anyway rightly or wrongly that's just my opinion.


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Offline Wayne Harris

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Re: Mould size & pressure
« Reply #10 on: January 23, 2009, 04:50:57 PM »
Civil it is then.  ;)

I would agree Beeman that from a cheese making perspective, there are certainly bigger fish to fry than cheese mould force/pressure. And I know all too well that I am not an authority on much here.  (which explains why am here and not doing this professionally)

But the relationship between force expressed as weight, that is applied to a specific sized area does have a mathematical relationship that is well defined. 
Pressure = Force/Area Change the weight, or the area, the pressure changes.

The more salient question might be is pressure even important; what are the right pressures; when should they be applied relative to whey expuslion; and how important are the pressure numbers...
Those i do not have down.  I am still taking my own empirical data, and borrowing heavily from the more seasoned veterans here.


 

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Offline Cartierusm

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Re: Mould size & pressure
« Reply #11 on: January 23, 2009, 06:05:14 PM »
Wayne I thought you were the seasoned verteran, or maybe just seasoned.. ;D

I mean I've been trying to figure out if height of the wheel is something I should take into consideration as well.

There is just so little imperical data out there and tons of disinformation, that's why were here to discuss these things.
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Offline Wayne Harris

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Re: Mould size & pressure
« Reply #12 on: January 23, 2009, 07:01:36 PM »
As I delve into my library to research on pressing,  I find that the Aussies discovered back in 1962 that if you press cheddar curds in a vacuum, you get that classic closed cheddar curd without the need for "cheddaring"

So,  we can add vacuums to the discussion of pressure topics.

(my head is gonna start spinning soon)

 :P

« Last Edit: January 26, 2009, 07:15:56 AM by Wayne Harris »
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Offline Wayne Harris

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Re: Mould size & pressure
« Reply #13 on: January 27, 2009, 12:31:09 PM »
(Full disclosure:  This was a post of mine in the other forum that i thought might be reasonable to post here)
I was further thinking that for mould of a given diameter, there *may* be reasons to increase the force.

So,  for example, given the same type of cheese:

A mould that has a curd depth of 3” will require a pressing protocol.

That same mould that has a curd depth of 20” might require a modification of the pressing protocol.

I know 20” depth is an extreme,  But I wanted illustrate my point.  Curds do have a certain sponginess, and drag at the sides of the moulds that both provide resistance to pressing. This resistance would increase with depth, and may require more psi for the same diameter mould.

I might be overthinking it, and i certainly won’t be making any 20” tall wheels of cheese,  but I might make a wheel 10"X6”
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Offline Cartierusm

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Re: Mould size & pressure
« Reply #14 on: January 27, 2009, 02:40:01 PM »
Wayne I agree with you totally. I've got on my list of things to do to figure out the pounds per cubic inch and see where that gets me. I will be working from known figures I have of cheese after pressing. So I'll be figuring cubic inches from a compressed cheese.
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