Polyphenolic Meter PM-03

This portable instrument, which permits the measurement of the PMI (polyphenolic meter index) , the index of the polyphenolic potential of red grapes, to be taken directly from grapes in the vineyard will be available in it’s first commercial version in just a few days.

The instrument, called PM.03 is produced by the society Caeleno di Verona. It consists of simple pincers that have a calibrated light source and a photodiode positioned on the opposing sides. The grape is taken directly from the plant in the vineyard and pressed to eliminate the pulp. The skin is placed in the pincers and the measuring, which takes 15 seconds, is done.

The instrument is very easy to use and supplies, right in the vineyard, information on the polyphenolic and antocian potential contained in red grape skin.

The values are measured in PMI (poliphenolic meter index) and shift between 80.0 P.M.I. for grapes with little phenolic substance to about 600.0 P.M.I. for deeply coloured grapes (the scale starts at 0.0 P.M.I. and goes to 700.0 P.M.I.) 

The Method

When you arrive in the vineyard, turn on and calibrate the instrument according to the instructions.

Once calibrated, the instrument will remain operative until it is turned off. Therefore it is convenient to leave it turned on until all measures are done. If it should be turned off, when turned back on it will automatically request recalibration.

Pay attention to the fact that if you do not calibrate the instrument it will not function.

If, by mistake, the pincers open during measuring, the value ERR will appear. The data will automatically be eliminated from the analysis results. 

The Measure

• Select the grape and squeeze it between your fingers to eliminate the pulp.
• With the same hand position the double skin in it’s holding space on the pincers.
• Close the pincers and press the red button on it.
• The red flashing light indicates a measure being taken. When the measuring is done the light will turn off and you can measure another grape.

The instrument measures one grape at a time, and therefore it is important to make yourself a plan for sampling based on the function of the surfaces you need to measure.

To determine an average of “n” you are recommended to analyze about 30-40 grapes per sample (ZONE on the keyboard). At the end of a series of measures you change “ZONE” and you go on to the next sampling. When the collection of data for a “ZONE” is completed you can visualize the medium, minimum, and maximum right there in the field.

Measuring time is about 15 seconds, and it is recommended that during the measure (red light flashing) you select the next grape to be measured and continue to proceed in this manner until  you’ve finished a series of measures. In this way you optimize time and you can correctly measure a sample of a vineyard or a row. For example, you can measure moving along one row and return measuring another.

To reduce variations caused by different grapes in the bunch it is recommended that you select each grape from the same position in the bunch (for example from the point or the wing). This rule is valid for the maturation curve as well as for direct confrontation (between vineyards, rows, plants, cultivation techniques, ecc.).

Upon return to the office the data can be printed in excel by means of a USB cable installed with the program supplied with the PM-03.

This way memory is reset to zero, to eliminate the possibility of losing collected information because of an accidental touching of the wrong button during the collection of data in the field. The keys on the keyboard are set to be pressed with decision as to avoid unwanted consequences. 

Possible Things to Determine

• Maturation curve
• Polyphenolic potential
• Direct Comparison between different plots of land
• Comparison of rows
• Comparison of exposure position
• Effects of irrigation, Greens pruning, different treatments, other agricultural and cultivation techniques.