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 HI84533U-01 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 HI84533U-01 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.
| Specification Name | Detail |
|---|---|
| sku | HI84533U-01 |
| Range | “(as N) Low Range: 2.14 to 28.57 meq/L; 0.21 to 2.85 meq%; 30.0 to 400.0 mg/L; High Range: 21.7 to 71.4meq/L; 2.14 to 7.14 meq%; 300 to 1000 mg/L” |
| Resolution | Low Range: 0.01 meq/L; 0.01 meq%; 0.1 mg/L High Range: 0.1 meq/L; 0.01 meq%; 1 mg/L; |
| Accuracy (@25ºC/77ºF) | ±0.1 mg/L or 3% of reading, whichever is greater |
| Sample Volume | Low Range: 10 mL High Range: 5 mL |
| Methods | acid base titration |
| Principle | endpoint titration, adjustable (pH 8.0 – 8.5 in 0.1 increments) |
| Pump Speed | 10 mL/min |
| Stirring Speed | 600 rpm |
| pH Range | -2.0 to 16.0 pH; -2.00 to 16.00 pH |
| pH Resolution | 0.1 pH / 0.01 pH |
| pH Accuracy (@25ºC/77ºF) | ±0.01 pH |
| pH Calibration | one, two, or three-point calibration, four available buffers (4.01, 7.01, 8.20, 10.01) |
| Temperature Compensation | manual or automatic |
| mV Range | -2000.0 to 2000.0 mV |
| mV Resolution | 0.1 mV |
| mV Accuracy (@25ºC/77ºF) | ±1.0 mV |
| Temperature Range | -20.0 to 120.0°C; -4.0 to 248.0°F; 253.2 to 393.2 K |
| Temperature Resolution | 0.1°C; 0.1°F; 0.1K |
| Temperature Accuracy (@25ºC/77ºF) | ±0.4°C; ±0.8°F; ±0.4 K |
| Logging Data | up to 400 ( 200 titrations, 200 pH/mV readings) |
| Electrode | HI1131B glass body, refillable, with BNC connector and 1 m (3.3’) cable (included) |
| Temperature Probe | HI7662-T stainless steel temperature probe with 1 m (3.3’) cable (included) |
| Environment | 0 to 50°C (32 to 122°F); RH max 95% non-condensing |
| Power Supply | 12 VDC adapter (included) |
| Dimensions | 235 x 200 x 150 mm (9.2 x 7.9 x 5.9”) |
| Weight | 1.9 kg (67.0 oz.) |
| Ordering Information | HI84533 is supplied with HI1131B pH electrode, HI7662-M temperature probe, HI7082 electrode fill solution (30 mL), HI84533-50 titrant solution (230 mL), HI84533-55 pump calibration solution (120 mL), HI84533-61 formol base reagent (230 mL), HI84533-62 pH adjustment reagent (30 mL), HI84533-60 hydrogen peroxide reagent (30 mL), 100 mL beakers (2), tube set (aspiration tube with titrant bottle cap and dispensing tube with tip), dosing pump valve, 5 mL syringe, 1 mL plastic pipette, cleaning solution sachets for wine deposits and wine stains (2), 12 VDC adapter, instruction manual and quality certificate. |
| Warranty | 2 years |
