Disrupting Protein Structures (Acid, Base, Alcohol Addition)

from a comment by Chuckwagon, dated August 21, 2015 sausage making

On August 16, 2015 at 21:04 El Duk (where’s my shotgun?) wrote:

Let’s get Chuckwagon to comment on wine & vinegar vs. cultures vs. Fermento, regarding how it affects product flavor and consistency. He’s done some great writing about the various cultures available. (Unfortunately, finding it among the heaps of other drivel, uh, information on the website may be a bit of a challenge. Seems like his various write-ups on summer sausage were useful in that regard, though.)

Drivel? What? Drivel… drivel! Why you… you… Okay, you flying menace! You…. you… feathered foul ball! It only took me 5 days to answer this one. Whew! You asked for it El Duckster!

Protein Structures

Because proteins have both acidic parts and basic parts, the acidity of the solution they are in changes their behavior. Acids release protons (hydrogen nuclei) and bases accept protons. In an acidic solution, the basic parts of the protein accept protons from the acidic solution and become positively charged. The positive charges repel one another, and the protein molecules are less likely to combine with one another.

In a basic solution, the acidic parts of the protein lose a proton, and become negatively charged. This also results in repulsion between the protein molecules, and combination is reduced. Charged areas of the protein interact with water molecules, because water is a polar molecule, with one end negative and one end positive. These charged ends are attracted to opposite charges on the protein.

Vinegar is one of the products of the grape. Acetic acid is the main component of vinegar. It also contains anthocyanins , flavonols , vitamins, mineral salts, amino acids and non-volatile organic acids such as tartaric, citric, malic, and lactic acids. Studies have demonstrated that grape juice enhances the resistance to oxidative modification of low density lipoprotein (fat).

The tertiary structure of a protein is what we get when the protein folds into a three dimensional shape. There is an entire class of proteins called globulins because of their shape and often soluble proteins are globular or almost spherical in shape. Insoluble proteins like collagen in connective tissue, elastin in tendons and arteries, and keratins in hair, hooves, and nails, are forms of fibrous protein. Some proteins are combined with other molecules to form conjugated proteins. In the nuclei of cells, nucleic acids combine with proteins to form nucleoproteins. Combined with just a little carbohydrate a protein is called a glycoprotein (from the word for sugar). Combined with more than about 4% carbohydrate, proteins are called mucoproteins. And combined with fat, they are lipoproteins.

These properties form what is called the quaternary structure of a protein. As you might guess from the name, there are four kinds of structure in proteins. In their natural state, proteins like egg albumin and milk casein are soluble in water. Most of their hydrogen bond forming parts are tucked inside the folded structure of the protein, making them unavailable for forming bonds with other molecules. They are all the same shape, so that they all have the same properties, and can form crystals.

Destruction of (Denaturing) Protein Structures

There are several mechanisms that destroy these properties. Heat, acids, strong alkalis, alcohol, urea, salicylate, and ultraviolet light are among the more common ways that proteins become denatured. As denatured proteins unfold, many of the hydrogen bonds that preserve the three dimensional structure of the proteins are broken. Instead of a uniform solution of molecules that are all the same shape, in a denatured protein, the molecules can take on a limitless number of different shapes and they become water soluble.

In cooking, we control the denaturing of proteins in several ways. We can control the temperature, we can control the acidity, we can use copper bowls to beat the egg white and catalyze the formation of disulfide bonds in the proteins, and we can control the fat or air content when we beat the proteins.

Again, as stated above, because proteins have both acidic parts and basic parts, the acidity of the solution they are in changes their behavior. Acids release protons (hydrogen nuclei) and bases accept protons. In an acidic solution, the basic parts of the protein accept protons from the acidic solution and become positively charged. The positive charges repel one another, and the protein molecules are less likely to combine with one another.

In a basic solution, the acidic parts of the protein lose a proton, and become negatively charged. This also results in repulsion between the protein molecules, and combination is reduced. Charged areas of the protein interact with water molecules, because water is a polar molecule, with one end negative and one end positive. These charged ends are attracted to opposite charges on the protein.

The Effects Of Alcohol On Sausage:

Denaturation occurs when proteins are exposed to disruptive physical forces such as heat in cooking, or “kneading” a sausage mixture, or by the introduction of chemicals such as alcohol. A common example of a denatured protein is the albumin in an egg as it becomes hard-boiled with the introduction of heat. The gelatinous egg albumin becomes solid.

Proteins are large molecules composed of amino acids, which are arranged in a variety of complex structures. The “primary protein structure” is the simple linear sequence of amino acids within the protein. The “secondary protein structure” is divided into subgroups identified by three shapes. The “alpha helix” looks like a spiral staircase and is a structural protein. The “beta-pleated sheet” looks just like its name implies. The “random coil” does not have a specifically defined shape and this is the one found in collagen although it may link together alpha helices and beta sheets so that proteins may contain all three secondary structures.

Proteins also adopt a tertiary (third in order or formation) structure that is achieved by looping and folding the chain over itself. This folded structure occurs because certain portions of the molecules have an affinity for water. From here, the explanation gets overly scientific for us sausagemakin’ wranglers. Suffice it to say, when a protein is denatured, the molecule’s tertiary structure is corrupted, and this disruption affects the molecule’s secondary (helical) structure without altering its primary structure. In other words, denaturation does not break any of the primary chemical bonds that link one amino acid to another but it changes the way the protein folds in upon itself. Denaturation occurs when proteins are exposed to strong acids or bases, high concentrations of inorganic salts, or organic solvents such as alcohol. In addition, heat or even irradiation can cause denaturation.

Now, here’s the kicker! Whenever the three-dimensional structure of the protein is disrupted, the molecule’s biological activity is affected and sometimes the effects may even be detrimental with side effects. Some denatured proteins can result in illness or even death. However, not all denaturing processes are harmful. Certain denaturing processes are beneficial. Remember the “boiled egg”? And what about the sticky meat mass so vital to good texture in sausage? Without the development of actomyocin by the proteins actin and myocin, our sausage would literally fall apart.

So, the question remains. Does alcohol denature the proteins in meat? The answer is unquestionably yes. To see for yourself, try making a burger from meat that has had alcohol added to it. It just won’t bind together. On the other hand, does it leave flavor behind? Again, yes it does. My favorite breakfast sausage is Italian Red Wine Sausage. What a flavor! Yes, somewhere there is a proper balance. Somewhere there is a suitable tradeoff. There must be prudence and good judgment with the addition of alcohol to our sausage. When I add wine, I use a spray mister and spray the mixture as it emulsifies or is mixed. The lesson here? Add it slowly and add it sparingly. sausage making

Best Wishes,
Chuckwagon

PS. For a further discussion of this topic, see several writers’ questions and Chuckwagon’s writings at this link: http://wedlinydomowe.pl/en/viewtopic.php?t=5319&highlight=soy+protein+concentrate

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