When it comes to different flavors and smells. Some of these compounds are water-soluble, some of these compounds are fat soluble.
In respect to sharks meat, there's an interesting process that sharks use to excrete. Oh, you're in, and they do it through their flesh and their skin. This entails then the meat having high levels of ammonium, uric acid and urea. Although i have herd of shark meat there's a delicacy in iceland mainly prepared as cured meat.
The use of milk to neutralize these volatile chemicals possible. An article from the website sciencedirect.com, has scientific paper written on similar chemical reactions.
"The Influence of Ammonia on the Development ofRancidity in MilkC . H . C a s t e l l"
-----In summary-----
Describe the mechanism by which milk absorbs ammonium.(often encountered as ammonia gas, NH₃, which dissolves in water to form ammonium hydroxide, containing ammonium ions, NH₄⁺).
Milk's ability to absorb ammonia stems from several of its properties, primarily its high water content and the chemical nature of its components:
- High Water Content & Ammonia's Solubility:
- Milk is typically about 87% water.
- Ammonia (NH₃) is extremely soluble in water. This is the most significant factor. Ammonia gas readily dissolves into the water phase of milk.
- This solubility is due to ammonia's ability to form hydrogen bonds with water molecules. The nitrogen atom in ammonia has a lone pair of electrons, and the hydrogen atoms are slightly positive, allowing strong interactions with the polar water molecules (H₂O).
- Chemical Reaction (Acid-Base Interaction):
- Ammonia is a weak base. When it dissolves in water, it establishes an equilibrium:
NH_3 (aq) + H_2O (l) \rightleftharpoons NH_4^+ (aq) + OH^- (aq)
(Ammonia + Water ⇌ Ammonium ion + Hydroxide ion)
- Milk is naturally slightly acidic, typically with a pH between 6.5 and 6.7. This slight acidity comes from components like dissolved carbon dioxide (forming carbonic acid), citrate, phosphate buffer systems, and crucially, acidic groups on proteins.
- The basic ammonia (or the hydroxide ions it produces in water) can react with the acidic components in milk. This neutralization reaction effectively "pulls" more ammonia gas out of the air and into the milk solution to maintain the equilibrium. For example, free protons (H⁺) from milk's acidity can react directly:
NH_3 (aq) + H^+ (from milk) \rightarrow NH_4^+ (aq)
- Interaction with Proteins:
- Milk is rich in proteins, primarily caseins (about 80%) and whey proteins (about 20%).
- Proteins are large molecules made of amino acids. These amino acids have various side chains, some of which are acidic (like aspartic acid and glutamic acid, containing carboxyl groups -COOH) and some basic (like lysine and arginine, containing amino groups -NH₂).
- At the slightly acidic pH of milk, many of the acidic side chains exist in their negatively charged carboxylate form (-COO⁻), while basic groups can be protonated (-NH₃⁺).
- The dissolved ammonia (NH₃) or ammonium ions (NH₄⁺) can interact with these charged or polar groups on the protein molecules.
- Basic NH₃ can react with the acidic protons of -COOH groups.
- Positively charged NH₄⁺ ions can be electrostatically attracted to negatively charged -COO⁻ groups on the proteins.
- Hydrogen bonding can occur between ammonia/ammonium and various polar groups on the protein surface.
- This binding to proteins essentially sequesters the ammonia, further enhancing the milk's capacity to absorb it from the surroundings.
- Interaction with Other Components (Minor):
- Milk also contains fats (in an emulsion), lactose (a sugar), minerals (like phosphates), and vitamins. While the primary absorption mechanisms are water solubility and interaction with acidic components/proteins, these other components contribute to the overall complex environment where these interactions occur. Phosphate buffer systems, for instance, play a role in maintaining milk's pH and can react with the added base (ammonia).
In Summary:
Milk acts like a sponge for ammonia primarily because:
- Ammonia dissolves very readily in milk's abundant water content.
- Ammonia, being basic, reacts chemically with the natural slight acidity of milk and specifically with acidic functional groups present on milk proteins.
- Proteins provide numerous sites for binding ammonia/ammonium ions through electrostatic interactions and hydrogen bonding.
This ability is why milk is sometimes anecdotally suggested to remove odors (like ammonia from cleaning products, though water works well too) from refrigerators, as it effectively traps the volatile gas molecules. However, absorbing significant amounts of ammonia would also negatively impact the milk's taste, smell, and quality.
