Cross-posted from another blog, Eating Science, which just began at the initiative of Kate Prengaman (a UW Journalism colleague) and myself.
If there’s one thing a science education teaches you it’s that pH is crucial. The concentration of hydrogen ions has everything to do with, well, everything. So I wasn’t too surprised to find that pH is the star of the show in old world dry sausage techniques.
During an interview with Jeff Sindelar, assistant professor and meat extension specialist at University of Wisconsin – Madison, I was looking for a more explicit explanation of the science involved in artisinal meat curing. Turns out, it comes down to diffusing a very charged relationship between meat and moisture. To smoothly convince water to walk away, it’s important to understand two things: the chemical nature of water and the effect of pH.
The chemical nature of water
Fresh meat, Jeff said, is 70-80% water and in a dry sausage you need to reduce that to about ~50%. The best way to do that, he explained, is to work with the divalent nature of water. A water molecule (H20) is made of two hydrogen atoms, which each have a positive charge, and one oxygen atom, which has a negative charge. The characteristic of having both negative and positive charges is called divalency.
Since water is divalent, it’s really good at staying in meat that a sausage maker wants to dry. If there’s any negative charge in the meat, water’s hydrogen atoms bond. But then again if there’s any positive charge, water’s oxygen atom bonds. Thus, if you want to efficiently dry a sausage, you need to create a charge-free meat environment that water will quietly slip out of in search of electric partnership. That’s where our old friend pH steps in.
The power of pH
Manipulating the concentration of hydrogen ions, or the pH, of meat can change the number of positive and negative charges. And if you get the pH just right the meat will have an equal number of both, leaving it with a neutral charge. The pH at which the meat has exactly the same number of positive and negative charges is called the isoelectric point Jeff told me.
The traditional drying process uses fermentation to manipulate the pH of a sausage. Usually, the pH in the meat and spice mixture is a little higher than the isoelectric point. To bring it down, bacteria that is good at producing lactic acid is mixed in along with the garlic, salt, pepper, and spices. After the mixture is stuffed into casing and divided into links, it’s held at the ideal temperature for the bacteria. Then, sausage makers monitor the pH. When the bacteria produce enough lactic acid to drop the pH to the meat’s isoelectric point, the links are moved into a drying box.
“So if you do not ferment a dry sausage it might take you three months or longer to dry the product and lose 30% moisture,” Jeff said. “f you reduce the pH so that it’s the same as the isoeletric point of the meat you can dry that product in 12-14 days.”
Firmness is the main indicator of a finished product. And sausage makers check that with…their hands. They double check with a scale to calculate exact water loss percentage.
Photos by Emily, taken at the Underground Food Collective in Madison, WI