Acids and Bases are very general terms describing the chemical`s ability to release or pick up protons (H+ ions - really hydronium ions, but let`s keep it simple) in an aqueous solution. HCl will dissociate into H+ and Cl- ions in water very efficiently, so is a strong acid. Acetic acid releases acetate ions and H+, but not all that efficiently by comparison, so is a much weaker acid. Bases are the same - strong, medium, weak, etc.Â
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Just because a chemical is described as acidic or basic (alkaline) down`t necessarily mean it will either give up or pick up H+ ions in aqueous solution. Capsaicin does`t act as a base or an acid, in these simple terms, in aqueous solution below pH 9.Â
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That means the acetic acid concentration won`t affect it`s ability to behave as it does on the nerves that have capsaicin receptors. Capsaicin acts on those receptors to produce it`s characteristic heat all the way from pH 9 down to pH 2. In fact, it binds to it`s receptor far more tightly at low pH. Capsaicin is also barely soluble in aqueous solution, as it is a fat-loving molecule, so that alters the way capsaicin can be thought of in terms of the pH. pH only applies to water-based solutions. For example, if you used heavy water made from deuterium instead of hydrogen, you will not measure the pH of the solutions, you will measure the pD of solutions. Similarly, pH does not exist as a concept in organic solvents.Â
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So, in answer to your question, the vinegar will not elicit any change in capsaicin function at all. Neither will temperature.Â