Measurements of fruit and vegetable concentrates

Producers of concentrates rely on sugar concentration (°Brix) monitoring to optimise the evaporation process in terms of time and energy consumption. The concentration (°Brix) values measured at the inlet and outlet of the evaporation column provide best data for automated process control.

Anton Paar’s inline refractometer L-Rix 5100 has proven to be well suited for the continuous monitoring of sugar concentration for food and beverage production processes and can be directly installed into the production line or tank to measure concentration in °Brix in real-time.

1. Concentrates production

Concentrates are made of fresh produce with the aim to make fruits and vegetables available throughout the year independent of the season and to reduce costs for storage and transportation.

Evaporators are used to decrease the water content of the juices or pastes. Depending on the product, this can be up to 35 °Brix for tomato concentrates and up to 65 °Brix for juice concentrates. The most common finished products are purees, cloudy or pulpy juices and clear juices single strength or concentrate.

The most important measure in the evaporation process is the sugar concentration of the juice, paste or concentrate, which is expressed in °Brix. The inline monitoring of the sugar concentration of both, the product at the inlet of the evaporation column and the concentrate at the outlet, is critical for the optimisation of the process and the quality of the final product.

Refractometers have been widely used for many years in the food industry, for measuring products such as sugar in refineries, jams, soft drinks and fruit juices. As these products can be turbid and pulpy, an in-line refractometer is perfectly suited to measure the refractive index and determine the sugar content of intermediate and final products.

2. Concentration monitoring

The Anton Paar inline refractometer L-Rix 5100 is installed at the inlet and/or the outlet of the evaporation process, as seen in Figure 1, and measures the sugar concentration and line temperature continuously.

To avoid layer build-up or deposits on the sensor head caused by turbid and pulpy samples, there are different installation options available. The installation of the sensor at a 90° bend of a pipe guarantees direct inflow of the sensor and continuously fresh product in front of the sensor optics. Precondition is, that the flow rate is high enough.

Figure 2 shows two possibilities for installations with built-in components on the opposite side of the pipe.

A deflector is used in non-stop productions and increases the flow rate. The prism is cleaned by increased shear rate of the sample. A cleaning nozzle is used in empty lines in batch productions to remove deposits by rinsing the prism with hot or cold water.

The °Brix measurement with RI (Figure 3) not only includes the concentration of dissolved sugars but all soluble solids in the concentrate. Dissolved substances other than sugars will influence the result of the concentration in °Brix measurements and may be corrected with a product specific adjustment if required.

3. Measurement Setup

The Anton Paar solution for controlling the evaporation process consists of the L-Rix 5100 Inline Refractometer, which is installed directly in the line and measures the refractive index and temperature continuously.

Specifications of L-Rix 5100:

L-Rix 5100 is installed directly into the process line using a VARIVENT® or TriClamp® flange.

The application specific calculations are carried out in the mPDS 5 or with the Pico 3000 (optional also with HMI) evaluation units. Up to 4 Sensors can be connected to one mPDS 5 and the results can be displayed and transferred to a PLC or to the Davis 5 data acquisition and visualisation software. 

Alternatively, the L-Rix can be connected to a Pico 3000 RC housing for remote control (for a single production line).

4. Benefits 

The reliable and accurate L-Rix 5100 enables 

• precise monitoring of the °Brix concentration in real-time
• improved end-product consistency
• optimisation and control of the evaporation process
• avoidance of human and sampling errors
• significant energy and time savings

5. Other Anton Paar Applications in Juice Production

Oxy 5100

• Inline measurement of dissolved oxygen (DO) in fruit juices for extended product shelf life

L-Col 6100

• Inline colour measurement of fruit juices and nectars

L-Rix 5100

• Inline quality control of sugary drinks and desserts (juices, nectars, preserves, compotes)
• Inline measurement of jams, jelly and honey
• Inline concentration measurement at dissolving granulated sugar for the production of sugar syrups

Learn more about the L-Rix 5100 Inline Refractometer
Contact us to discuss your application

Anton Paar Australia I Email: info.au@anton-paar.com, Tel: +61 2 8315 4400 

Anton Paar New Zealand I Email: info.nz@anton-paar.com, Tel: +64 9 414 319

Top image credit: iStock.com/margouillatphotos