Before fermentation, total nitrogen (present in the form of ammonia and amino acids) is commonly measured in must to ensure an adequate concentration of yeast available nitrogen (YAN) for efficient fermentation. Any ammonia not consumed by the yeast during fermentation remains in the finished wine. Ammonia in wine can impact flavor and microbial stability in the final product. Typical concentrations for ammonia in finished wine range between 3-50 mg/L.
Ammonia in wine is commonly measured with an ion-selective electrode (ISE). First, an ionic strength adjuster (ISA) is added to the wine. The ISA fixes the sample so that ion concentration, not just activity, can be measured. Additionally, the ammonia ISA contains a pH adjuster to buffer the sample above pH 10. Below pH 10, ammonia is present as the ammonium ion. Above pH 10, all ammonium in the wine is converted to ammonia gas (NH3). Ammonia ISEs use a gas permeable membrane, which selectively permits the passage of ammonia gas across. As ammonia diffuses across the membrane, it changes the pH of an internal electrolyte. A pH electrode housed inside the body of the ammonia ISE detects the pH change. The change in pH is directly proportional to the ammonia concentration.
A selection of portable and benchtop ISE meters are available to measure ammonia in wine using a ammonia ion selective electrode.
Below are the most common conductivity products for measuring ammonia during the wine making process.
For the Winemaker we offer the HI5000 series benchtop meters These meters are our most advanced meters incorporating the latest microprocessor to bring exceptional features and performance for the most demanding user. These meters are completely customizable to user specific requirements. The meters have an Ion Selective Electrode (ISE) input and are pre-programmed with the molecular weight and ion charge for ammonia so that measurements can be displayed in various forms of concentration units.
A portable ISE meter is available to measure ammonia. The portable meter is convenient in that it does not take up much benchtop space and can be stored in the carrying case when not used. The portable meter, like the benchtop meters, requires a stirrer for mixing the sample when performing the measurement.
Ion Selective Electrodes
Ammonia ISEs in this category include both combination and half cell versions. A reference half-cell electrode for use with the ammonia half-cell can also be found in this category.
In this category are the calibration standards and ISA solutions used to calibrate the meters and perform ammonia concentration measurements.
Accessories in this category include magnetic stirrers for adequate mixing along with replace parts for the ammonia ISE.