Malic Acid
Fumaric Acid
Maleic Anhydride
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Self-Teaching Guide

Flavour Profile
Am I Using the Ideal Acidulant(s) to Achieve the Flavour Profile I Want?

Acidulants are not the same in terms of sourness and flavour impact. Some show persistent sourness, while others show sourness that dissipates quickly. The choice of ideal acidulant(s) for your application depends on this and other factors such as the sweetener(s) used, the flavour in question, and the sequence of sensations desired when the product is tasted.

Am I Using the Most Economical Acidulant(s) Possible for This Application?

Acidulant blends are more economical than single acidulants due to additive and synergistic effects between acidulants. On average, sourness increases as a function of (acidulant concentration)0.80. Since 20.80 = 1.74 and 10.80 + 10.80 = 2, a 15% increase in sourness can be achieved by using a 50/50 blend of acidulants (2/1.74 = 1.15). Additive and synergistic effects differ depending on acidulant combinations.

Can I Have Both?
Can I Improve Flavour Profile and Lower Ingredient Cost at the Same Time?

The use of acidulants that improve and enhance a particular flavour profile can also result in an ingredient cost savings. This is particularly true in the case of acidulant blends.

What is pH?

pH is just another way of stating the hydrogen ion concentration. It is the negative log of the hydrogen ion concentration. Since the hydrogen ion concentration is normally a very small number - for example, 0.000025 M - it is easier to say "pH of 4.6" than "0.000025 molar concentration of hydrogen ion". To convert pH back to hydrogen ion concentration, use 10-pH.

What is a pKa?

The pKa of an acid is the negative log of its dissociation constant. For example, if the dissociation constant of an acid is 0.00056, then the pKa is the negative log of 0.00056, or 3.25. To convert back to Ka, the dissociation constant, use 10-pKa. The lower the pKa, the stronger the acid.

What is a Dissociation Constant?

The dissociation constant, Ka, is a measure of how strong an acid is. The higher the dissociation constant, the stronger the acid. For example, Acetic Acid has a Ka of 0.00001754 and a pKa of 4.76 (4.76 is the negative log of 0.00001754) and is a weakly dissociated acid. As shown in the following formula, the dissociation constant is actually an equilibrium constant. The use of square brackets indicates molar concentration. For example, [Acetic Acid] is the molar concentration of Acetic Acid.

As shown in the formula, when Acetic Acid is added to water, very little of it converts to hydrogen ion and acetate ion. Most of it stays in the form of undissociated Acetic Acid. A strong acid like Nitric Acid, on the other hand, is mostly converted to hydrogen ions and nitrate ions, as indicated by its large dissociation constant.

What is a Buffer?

A buffer is a partially neutralised acid that resists changes in pH. Buffer salts such as Sodium Citrate or Sodium Lactate, which are fully neutralised acid salts, are normally used to partially neutralise the acid. In the process of doing so, they become partially neutralised and contribute to the buffer capacity of the system. Different combinations of acids and salts can be used as buffers, for example, Malic Acid with Sodium Lactate at a pH of 3.5. In this case, both the partially neutralised Malic Acid and the Lactate ion contribute to the capacity of the buffer system.

How Much Buffer Salt Should be Added to Maintain a Specific pH?

In the Bartek Technical Bulletin "Buffer Salt/Malic Acid Combinations", there is a table that lists Buffer Salt/Malic Acid weight ratios to achieve a given pH.

When Would a Buffer be Used?

A buffer would be used to maintain the pH of a product within a narrow range. Buffers reduce the variation in the pH of a product, as shown on the graph below. pH variation is detrimental to consistent quality.

What is Buffer Capacity?

The buffer capacity is the resistance of the system to a change in pH. It is measured, or calculated, in equivalents of acid or base that change pH by 1.0 unit in 1 liter of solution. As shown in the graph below, Fumaric Acid has greater buffer capacity than other acids near a pH of 3.0. This is due to its low molecular weight and to its low dissociation constant.