Testing new sensor technologies to improve fruit quality and consistency of fresh cherries in export markets

Agriculture Victoria are currently testing a new Atago PAL Hikari-16 refractometer (Figure 1A) that non-destructively measures soluble solids concentration (SSC, °Brix) by infrared technology in fresh cherries and will compare results with an Atago PAL-1 refractometer (Figure 1B) which requires the destruction of fresh cherries to obtain a small amount of juice prior to measuring the SSC.

Atago pocket refractometer Infrared

Figure 1A: Atago pocket refractometers used to measure soluble solids concentration in fresh cherries - non-destructively by infrared

Figure 1B: Atago pocket refractometers used to measure soluble solids concentration in fresh cherries - destructively on juice

Method

Two cherry batches were sourced, one from a retail outlet and another directly from a grower in central Victoria. Three SSC measurements were recorded on opposite cheeks for 20 – 25 cherries and the measurements averaged for both instruments.

Results and discussion

Both instruments were successful at measuring soluble solids concentration (SSC; °Brix) in fresh cherries (Table 1). SSC ranged between 13 to 20 °Brix. The relationship between the two instruments shows that the Hikari-16 consistently under-estimated SSC compared to the PAL-1 refractometer for both cultivars (Table 1 and Figure 1). There was less variability in the relationship for the cultivar sourced from the supermarket (r2 = 0.82) compared to 'Samba' cherries (r2 = 0.61).

In summary, preliminary results show that the Hikari-16 refractometer consistently measured between 0.8 and 1.8 °Brix less than the PAL-1 refractometer depending on the cherry cultivar (Table 1). Also, the variability in measurements (standard deviation, SD) was lower for the Hikari-16 when compared directly to the PAL-1 refractometer for each source. Further testing is planned on other cultivars during the season to see if the correlation improves.

Table 1. Measurement of SSC in fresh cherries using the nondestructive infrared Atago refractometer (Hikari-16) and the destructive Atago refractometer (PAL-1).

Table: Measurement of SSC in fresh cherries
Graph: Comparison of the soluble solids concentration - Cherries

Figure 1. Comparison of the soluble solids concentration measured in fresh cherries for both Atago refractometers.

For more information, please contact: Glenn Hale glenn.hale@agriculture.vic.gov.au

Acknowledgment

Agriculture Victoria has a cool chain monitoring and traceability project that is funded by Agriculture Policy’s - Export Development Investment Strategy (EDIS) group and is working with Cherry Growers Australia (CGA) to test new sensor technologies that will help improve fruit quality and consistency of fresh cherries in export markets.

This project is funded by Agriculture Policy’s Export Development and Investment Strategy through the Growing Food and Fibre Markets program.