• store room with apple




  • Spinach Fluorescence photo

     



  • HarvestWatch system with labels


  • FIRM Sample chamber kennel

  • Sample system layout


  • HarvestWatch FIRM sensors in a commercial DCA store room


  •  
    DCA controls superficial scald




  • Dynamic Controlled Atmosphere (DCA) storage of fruit with HarvestWatch technology provides the marketplace with high quality fruit without the use of chemicals
  • Chlorophyll, a pigment found in all higher plants, is a fluorophore. This image of spinach chlorophyll dissolved in solution shows how chlorophyll fluoresces red
  • The HarvestWatch™ system is a specialised fluorometer developed by Dr. Robert Prange and colleagues (AAFC and Satlantic Inc., Nova Scotia, Canada) and distributed by Isolcell Italia S.p.A. It uses fluorescence (Fα) to let storage operators know when their fruit are stressed
  • FIRM sample chamber (kennel)
  • A typical HarvestWatch system with multiple hubs and sensors
  • Six chlorophyll fluorescence (HarvestWatch) FIRM kennels in a commercial apple DCA store room
  • DCA using the HarvestWatch system controls superficial scald in apples and pears

How does DCA, using HarvestWatch, compare with DCA using ethanol sensing?

Answer:

Expenditures - HarvestWatch has a one-time capital expenditure for chlorophyll fluorescence sensors and software. Since DCA costs are one-time capital expenditures, there are no recurring annual charges compared with other chemical-based alternatives, e.g. ethanol, and the HarvestWatch technology adds to the asset value of the storage facility.

The technical features of DCA that are appealing to users are:

•           Non-destructive measurements on large surface areas can be taken of any chlorophyll-containing fruit or vegetable.

•           The measurement is rapid, ca. 1 minute, and the frequency can be easily altered.  The default setting is every hour.

•           The method is non-chemical.  It does not rely on adding any chemicals or analysing any chemicals.

•           Real-time monitoring of produce allows for on-site or remote monitoring and archiving of data for future reference.

•           There is no calibration needed, either before or while in operation.  The sensors are very stable.  Some of them are over 10 years old.

•           It detects changes in the product due to senescence, decay or incorrect storage conditions, i.e. temperature, unwanted toxic gases such as ammonia refrigerant.

Its non-chemical feature makes it appealing to industrial users who wish to reduce post-harvest chemical use or store ‘organic’ product. Others have adopted it because it is a one-time capital expense that can have a pay-back period of 2-3 years, compared with repeated annual expense with competing chemical-based methods.

What fruit should be chosen as sample fruit in the kennel?

Answer:

The sample fruit in the kennel should reflect the average of the fruit in terms of maturity, size and colour.  The fruit should be placed so that the side facing the sensor is at the transition between the sun and shade side. In some fruit, e.g. apples, the 'sun' side, compared with the 'shade' side, has not only more chlorophyll but may also differ slightly in maturity and LOL.

Once the Fα 'spike' is observed, indicating the lower oxygen limit (LOL), the O2 should be increased at least 0.2% (or 0.3% in 'Delicious' apple) to account for the small LOL variation that may occur in the fruit.

What is the recommended value range for chlorophyll fluorescence?

Answer:

In the raw Fα setting, the values should be at least 1,500 to 2,000 initially.  One can have initial values that are lower, but this is not recommended since it will result in the normalised Fα setting having more signal noise due to calculation of the normalised value.

The recommended procedure to achieve raw Fα values of 1,500 or more is to fill the kennel with sample fruit so that each fruit is 'seen' by the small fluorescence detector located in the middle of the FIRM sensor.  DO NOT stack fruit because only the top fruit in the stack will be measured.

Take some raw Fα measurements and if the values are too low, replace fruit with ones that are larger or greener so long as they are still representative of the fruit.

If the signal remains lower than 1500 even after this is done that is not a problem so long as one recognises that the normalised Fα values may have more noise.  An alternative is to use the raw Fα measurements.

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References

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System Overview

This new technology was developed and patented in Canada in 2001 by a research team led by Dr. Robert Prange and Dr. John DeLong.  Further research evaluation was conducted internationally, especially by Dr. Angelo Zanella of the Agricultural Research Institute Laimburg Italy which led to commercialisation in the U.S.A and Italy in 2003-2004.

The technology detects stress, e.g., low oxygen, by continuously monitoring changes in the chlorophyll fluorescence of the stored product. The major application of HarvestWatch technology is in dynamic controlled atmosphere-chlorophyll fluorescence (DCA-CF) storage of fruits and vegetables.

By the end of 2015, close to 1/2 million tonnes of apples and pears were being stored in >1680 DCA-CF rooms in >15 countries worldwide.