I've been wandering around looking for a chart or some information of PSI per cheese styles.
Now that I have a huge press that can get me 11+ psi, I am curious about what the proper PSI is for traditional cheddar, gouda, jack, havarti, etc. All the darn instructions you find on the net are just arbitrary weight: 50 lbs. What does 50lbs. mean? Ricki Carroll uses a 7.5" mold with 50 lbs., but that's around 1.3 psi. Not much!
So, here is a thread to have everyone jot down the PSI for different styles, unless someone made a good chart of PSIs for styles.
---------------
Saior Con Queso and others have been saying trad. cheddar is up to or over 25 psi. But, what is a reasonable psi for cheddar, and how does the higher psi effect the final taste and texture? Anyone have experience in super pressing home cheddar?
I pressed a 6 gallon (8in mould) of cheddar under 19(ish) PSI
I will say that I brok my follower, and the cheese doing that. I pushed the center in and bent it. There was a fracture in the cheese.
i would not use more than 10psi going forward for that amount of cheese.
My next 25 gallon batch, will get about 10psi.
http://www.foodsci.uoguelph.ca/cheese/welcom.htm (http://www.foodsci.uoguelph.ca/cheese/welcom.htm)
This link has pressure in kilopascals which is newtons/square meter. One Kp = .145 psi The only recipes listed where real pressure is needed are the colby and cheddar ones; both 75 kp or 10 psi (but then he says 10-20 psi).
He makes this statment:
"Pressing varies from little or none for soft cheese up to 172 kPa for firm Cheddar cheese. The warmer the curd, the less pressure required. Mechanical openings may be reduced by vacuum treatment before, during or after pressing."
Look at the inidvidual recipes to see the variations. 172 kp is 25 psi. They also vacuum them while pressing it seems which must make a difference in knitting as Wayne has commented on. I am satisfied with 15 psi on my cheddars for now. I did a colby this week and just used the same pressure. Everything else seems to need much less. The max I used on gouda was 5 or 6 I think and I will let you know how it turns out in a month. (Or sooner if I get antsy)
I may very well be ignorant of some other hard cheeses though. This is a good question.
Hm, they also have shorter press times on that site, which means there is a palpable equation somewhere for time in the pressing equation. Pity we don't know it.
My goudas were all under 1.1-3 psi for 12 hours, and I love them. With a bit of smoke and color in there, they will be even better.
okay this may sound strange but what if ....
You put your curds in the mould ... slipped it in a vacumm sealer bag, vacuumed it then put the pressure on? It'd have to be a fairly small mould but it might answer some questions.
I use rubber heating mats for starting seeds, I have thought about wrapping my hoops with one of these during pressing. This would probably keep the curds at 80F and facilitate easier melding. However, this would also accelerate bacterial growth. Don't know if this would be a good thing or not.
Sailor do you mean during aging or just while packing the mold?
As Farmer pointed out, the U of Guelph site says "The warmer the curd, the less pressure required." So I have been thinking for a while about wrapping my hoop with the warm seed starter mat, WHILE the hoop is in the press. I think this might be especially helpful on larger batches.
FYI, I use the seed starter mat all the time to make yogurt and cream cheese. I sit a bowl of Mozzarella curds on the heating mat until the Moz reaches a pH of 5.2 and then it's ready to stretch. Even with inferior milk, you can just wait for the pH drop. Works like a charm every time.
Hi Everyone,
I am looking to jump into this PSI discussion. The reason is that I made a farmhouse cheddar from Ricki Carroll's book and pressed it in a large diameter cheese mold which resulted in a thin (2lb) cheese. Is Ricki talking PSI when she says 25 lbs or is she talking gross weight?
If she is talking PSI and I am using a 5" cheese mold, are the following calculations correct?
Mold Area = Pi * (2.5)^2 = 19.6"^2
Desired pressure = 25 PSI
Required Weight = 19.6 * 25 = 490 lbs
First of all, is this the correct way to calculate the weight required for a given PSI and mold diameter?
Beyond that, is 25 PSI a crazy pressure to go for? I hope so!
Most recipes for home cheesemakers refer to weight, not PSI. 25 pounds means 25 pounds, not 25 PSI. A 25 POUND pressing on a 5" hoop is considered "moderate". I would consider this between 1.5 and 2 PSI. The problem is that you can't use the same 25 POUNDS on an 8" hoop and get the same results. That would require 75-100 POUNDS to get the same PSI.
25 PSI is definitely a crazy amount for most cheeses. However it can be appropriate for a cheddar type, but beyond the ability of most small presses. Your calculations are exactly right.
If you use the same hoop all the time, weight is fine. If you change hoops then PSI is really important to consistent results.
Ok, thanks for the reply. I get it now.
I did notice that my first farmhouse cheddar (pressed in a ~10" diameter mold) had a lot of air spaces present. I think the PSI was just too low.
So I am setting up my air cylinder press and have a question regarding PSI.
How do you measure this, I have a regulator and co2 supply for carbonating my kegged beer but the gauge would not read as low as some of the pressures required for cheese making, ie. a 6" mold cheese recipe requiring 50lb would only need 1.77psi and even less for 25lb. The gauge on my reg goes up to 80psi so it's not possible to measure as low as .5 psi.
Can anyone tell me what the max pressure their regulator gauge is?
Cheers
Andrew
So many of my questions regarding psi/weight were answered on another thread, but I just thought of something... If I am making a 3 gallon (were previously 2 gallon) but the hoop size is the same, does the weight remain the same?
It seems to me that if I am making a 3 gallon colby, but the recipe weights are for a 1 gal recipe, I would need to compensate for the increased density?
If the hoops size (diameter) remains the same, and you wish to maintain the same PSI between the 2 and 3 gallon batches. then yes, by all means use the same weight.
Quote from: Sailor Con Queso on February 06, 2010, 12:23:24 AM
Most recipes for home cheesemakers refer to weight, not PSI. 25 pounds means 25 pounds, not 25 PSI. A 25 POUND pressing on a 5" hoop is considered "moderate". I would consider this between 1.5 and 2 PSI. The problem is that you can't use the same 25 POUNDS on an 8" hoop and get the same results. That would require 75-100 POUNDS to get the same PSI.
25 PSI is definitely a crazy amount for most cheeses. However it can be appropriate for a cheddar type, but beyond the ability of most small presses. Your calculations are exactly right.
Wow, that does seem like an awful lot of weight! Sorry if I missed this being discussed in more detail elsewhere, but what are the home cheesemakers here realistically getting to in terms of PSI or weight per mold size for their Cheddars? I am starting from the Ricki Carrol 'Traditional Cheddar' recipe that just suggests '50 lbs' as the final pressing weight for 24 hours.
I did see this from the U. of Guelph link in their traditional Cheddar recipe: "Press overnight at 75 kPa (10 - 20 lbs/in2). Start with low pressure and gradually increase to 75 kPa." So . . .that's 10-20 PSI, right? I am using a 4.5" diameter mold, so using same calcs :
Mold Area = Pi * (2.25)^2 = 15.9 sq in.
Desired pressure = 10-20 PSI
Required Weight = 15.9*10 to 15.9* 20 = 159 - 318 lbs (!)
You calculations are correct. Lots of other variables involved in getting the curds to knit (curd temp, length of pressing time, etc.) but obviously pressure is an important one. That weight may seem unmanageable but with a press with a levered arm and pulleys that weight may be reduced by a factor of 10 or more. Right now I am getting 15-20 psi on a 10 inch hoop (more for my 8" and less for my 12"). My press has a mechanical advantage of 4. I put between 300 and 400 lbs on it. Over 300 is downright scary to be honest especially when it starts creaking. :)
You're calculations are a little off. I have attached a PSI Calculation spreadsheet that should help.
That being said, bear in mind that the U of Guelph's procedures and recipes are geared for large scale commercial production. From a practical level spring type presses for the home cheesemaker can really only handle 50 pounds. After that the spring bottoms out and you start bending metal pieces. That is why many recipes like Ricki Carrol's don't tell you to press at more than 50. Even on my big lever presses, I almost never go over 10 psi.
Pressing longer may work, but that also allows your cheese to build up too much acid. On a 4" hoop, I would shoot for 100# if you can, see how it works and go from there. If you don't get a perfect knit, it's not the end of the world.
QuoteYou're calculations are a little off. I have attached a PSI Calculation spreadsheet that should help.
Not sure what you see Sailor. It appears to line up with the chart you posted to me.
QuoteIf you don't get a perfect knit, it's not the end of the world.
Agreed.
It's really close to my chart. Just being a little anal.
I see a trend among the group where several people seem to want to see just how much pressure they can apply to their cheeses. Overkill IMHO. For me the point of PSI is consistency, not mashing cheese into pancakes, just because you can. If you get a good knit and remove the excess whey, that's good enough. If you aren't getting a good knit on Cheddars, etc, increase the PSI and/or look at some other solutions. JD - in your case, you know you need that kind of pressure with your bigger wheels but not everyone need to use 300 pounds. ;)
I feel that pressing time is sometimes more important than actual weight or pressure. When you press an unsalted cheese for too long, residual whey remains, the bacteria can continue converting lactose, and you can end up with an acidic and/or dry cheese. It's all about balance. If it ain't broke, don't fix it. In my case I have to look at techniques where I can produce the same quality cheeses consistently.
Good point about consistency. That really is the goal. I know it may seem like folks are overly "psi happy" but there is a lot of difference between a 6" and 8" cheese (almost double the pressure required) and I think sometimes folks don't realize how much more weight it takes to stay consistent. It is a big jump for home cheesemakers from 6" to 8". Everybody wants a big wheel but it requires a different setup not just a bigger hoop and more milk. BTW, did you get my stuff?
Absolutely. There is a HUGE difference between a 6" and an 8" hoop. On my setup with 8" Tomme molds I press with 125 pounds (~2.5 psi) for "light", 250 pounds (~5 psi) for "medium" and 375 pounds (~7.5 psi) for "firm". Unless something goes screwy during a make, I rarely press any heavier than that. My only regular exception is Cantal which I still only press at 10 psi. To me 20 psi is just not necessary.
There are other ways to encourage a good knit. For example with Cheddar the curds can really cool down quickly during the milling process. One option is to throw the curd back into the pot and warm them back up before hooping. Or put the curds in the hoop and put the entire hoop back in the pot. If milling takes a long time, the pH can drop significantly (an additional .2) before salting. I mill by hand and it takes me about 45 minutes to process a 35 gallon batch. That's 45 minutes of additional acid production. I find that a pH that is too low seems to resist a good knit. For that reason, I drain and cheddar a little earlier so that it is not over acidified at salting. Normal drain for Cheddar is around 6.1. I drain at 6.2-6.3 to compensate for the long milling time.
Well, I am appreciating all of the well-informed participants here, and while my first reaction to the PSI discussion was, ugh, math, I am feeling much better about it now. It's clearly the right way to look at pressing needs accurately independent of cheese size.
I managed to get up to about 140 lbs in my wacky stacked pressing scenario, so for a 4.5" diameter mold I figure that's about 8.75 PSI, which I held for 24 hrs after some time building up to it. That will have to do, and based on looking at the exteriors, everything seems very well knit together and quite smooth. There are some very faint translucent white lines just barely visible here and there that look like they might have once described curd boundaries, but they are near-nonexistent.
Looking forward to seeing how these turn out . . .
(http://www.picvalley.net/u/2910/1580341437754390721288134410e5F51HXSVD73pJTM0ALu.JPG)
Here's a pic of the cheeses just before bandaging. I can see on the right one that I used too much folded-over cheesecloth when pressing, and on the left you can see the light tracery of white lines (I wonder if I might have not mixed the cheese salt in well enough before pressing and that might account for them?)
They look great. If the wrinkles bother you, you can take the cheesecloth off after pressing and lightly press for 30min to remove the wrinkles. I just let it go. After aging it isn't noticeable.
Quote from: Sailor Con Queso on October 26, 2010, 01:30:14 AM
Absolutely. There is a HUGE difference between a 6" and an 8" hoop. On my setup with 8" Tomme molds I press with 125 pounds (~2.5 psi) for "light", 250 pounds (~5 psi) for "medium" and 375 pounds (~7.5 psi) for "firm". Unless something goes screwy during a make, I rarely press any heavier than that. My only regular exception is Cantal which I still only press at 10 psi.
Yes, I am very bored here in my hotel, and felt like making graphs.
I'm sorry you are bored. But grateful for the graphs! I've save them for future reference. Thanks for your efforts. They were not in vain.
Susan
QuoteYes, I am very bored here in my hotel, and felt like making graphs.
LOL. Boredom is the mother of great graphs.
Yeah, who knew back in high school that math would make cheese making so neat. Thanks for being bored, Wayne.
-Boofer-
Thought occured to me to just include the Excel file that I used to make these.
You can put whatever PSI in you like and make your own chart.
pm me if you have questions.
very nice work with the chart Wayne. Which version of Excel did you use?
created in Excel 2010.
However,
I saved in that backwards compatible format....
(Excel 97-2007)
I choose not to use the OpenDoc (most compatible) format, as i did not know if the chart formatting would survive....
Nice charts Wayne!