The content of amino acids and other nitrogen compounds in fruit juices and wines is expressed as total assimilable nitrogen and is determined by the formol method using an acid-base titration. The formol number (also known as formol index) is a parameter used for evaluation of the quality of fruit juices and wines.

In wines, the concentration of alpha amino acid in grapes change as a function of maturity and crop load (yield to vine size ratio). The concentration increases with fruit maturation and decreases with crop load. In the fermentation of wine, there is a minimum amount of amino acid and other nitrogen compounds (e.g., 150 to 200 mg/L of yeast assimilable nitrogen) that has to be present in the must/juice. Too low of an amount will result in a stuck fermentation in which there is not enough nitrogen for the yeast to thrive. Because of the importance of nitrogen in fermentation, it is desirable to determine the nitrogen concentration before fermentation.

In fruit juices, the formol nitrogen number is one of the basic parameters measured to determine quality. Depending on the type of fruit, the number can increase or decrease with maturity. In orange and grapefruit juice, lower values are observed when the fruit is not suitably mature or there has been frost damage. In pineapple juice, a low number could be indicative of over-dilution with water or a disproportionate amount of the core was used. To determine the adulteration of fruit juices, the formol number, along with the chromatography characterization of amino acids, can be used.

Double Junction pH Electrode

The HI84533 is supplied with the HI1131B glass body pH electrode. This electrode is refillable and features a double junction, minimizing the contamination of the electrode. This versatile electrode has a spherical sensing glass bulb that provides a wide surface of contact with a wine or fruit juice sample. The sensing portion is composed of high temperature glass, making it ideal for direct measurements or titrations in the beverage industry.

Piston Driven Dosing Pump

The heart of the HI84533 is the piston driven burette pump. This type of dosing system uses a motor in which each dose is very precisely controlled and the volume dispensed is accurately determined. The piston driven burette is controlled dynamically so that the volume of titrant being dosed is automatically adjusted based on a voltage response of the previous dose. This type of dosing speeds up the titration process by allowing for more titrant to be dosed at the start of the titration and then very small doses as the endpoint is reached.

Automatic Stirrer

The built-in stirrer is automatically maintained at a speed of 600 rpm, regardless of the viscosity of the solution being titrated.

On-Screen Features

Easy-to-Use Interface The HI84533 has an intuitive user design with clearly defined keys and a large screen that is easy to navigate. The meter has a built-in tutorial mode that, when enabled, will walk the user step by step through the titration process. A dedicated HELP key is always available to allow access to content-specific information during both calibration and titration.

Procedure Warnings Users are warned if there is an error in procedures such as the titration exceeded the maximum volume of titrant.

Graphic Mode This mini titrator displays in-depth data during titration, including a real-time graph of the titration curve.

Log-on-Demand The HI84533 allows for data logging of up to 400 samples: 200 titration results and 200 pH/mV readings. Data can be stored and exported to a USB drive or a PC using the USB connection.

pH/mV Meter In addition to being an automatic titrator, the HI84533 also can be used as a pH/mV meter. As a pH meter, it has many features of a professional grade benchtop including automatic calibration up to three points with four available buffers, a 0.01 pH resolution, accuracy of ±0.01 pH, automatic temperature compensation and comprehensive GLP data.

CAL Check™ Accuracy is always ensured with Hanna’s unique CAL Check feature, which analyzes the response of the electrode during the calibration process. Based on electrode response in the buffer, indicators are displayed on screen to alert the user of potential problems during calibration. These indicators include Buffer Contaminated, Electrode Dirty/Broken, and overall probe condition. The CAL Check function not only ensures an accurate pH reading when the HI84533 is used as a pH meter, but also an accurate titration since the endpoint of a total acidity titration is determined by a set pH value.