In fruit and vegetables, establishing the optimal harvest time is a crucial issue, since fruit shelf-life potential and quality are closely related to the ripening stage at the harvest. In cold store it is very importants to establish maturity changes as well.

The DA-Meter - developed by Prof. Costa's team from the University of Bologna - is an instrument that, by means of its absorbency properties, allows to measure the chlorophyll's content in a fruit.

The content in chlorophyll in a fruit is a precise index of a fruit's ripening state. Thus, the DA-Meter allows to know the ripeness state, and the way it works does not depend on the season's weather conditions, a factor which influences other kinds of measurement such as the brix index.

The DA index, measured with the DA-Meter, is useful at many stages in the production and consumption's cycle of fruit.

As a matter of fact, it can be used:


1) by the farmer, in order to optimize the trees pruning, to obtain a very homogeneous product and, as a result, to reduce the number of picking stages;
2) by the farmer, during the harvest-time, in order to identify the best moment for the picking;
3) in the cold rooms, in order to know the maturation state of the stored fruit;
4) in the packing-house, the DA-Meter has been used to select the correct fruit for different marketing destinations (less ripe fruit for distant markets, riper
fruit for local market).
5) at the retailer, in order to buy products at the intended maturation level and in order to select the most ripened product for selling.

The DA-Meter is a very promising tool both for practical and scientific applications, since it allows to monitor on-tree fruit ripening (as well on the same fruit):

as a matter of fact, decreasing index ranges correspond to increasingly advanced stages of the ripening process, as showed by the differences in ethylene emissions, and by the quality traits of fruit with different DA values.

 

The DA index refers to the content of chlorophyll-a in the mesocarp without being influenced by the peel colour, the values of the DA index decrease during the maturation of fruits.

 

The DA-METER

The DA-meter is a portable instrument for the measurement in laboratory and on field. This device combines simplicity of utilization with good quality of stored measures, and enables either to make immediate use of the obtained data or to store them for future applications. For this purpose, it is provided with an SD Card (having a maximum capacity of 2 GB, which is sufficient to store a quantity of measures absolutely bigger than the real needs), and with a USB interface which enables the immediate connection to a computer immediately.

The DA index


The DA is an index of the chlorophyll quantity in fruit and, as a consequence, of its ripeness state. This index decreases in value during the ripening process of the fruit, until it reaches very low values when the ripening is complete. Each kind of fruit has specific DA values. So far the DA-Meter has been tested on apples, pears, peaches, nectarines, apricots, plums and on Honeydew melons, for example:


- in apple, the DA index relates to the ethylene emission levels, the starch content, and the flesh firmness: as a matter of fact, decreasing values of the index correspond to an increased hormone production, starch index and to a lower firmness. On the basis of these relationships, the DA index allows to identify the pre-climacteric, the onset of climacteric and the full climacteric stages of fruit ripening.


- in pear, the DA index has been used to subdivide fruits at the harvest into different homogeneous classes at different growth levels. These classes are characterized by a different post-harvest ripening, as indicated by a significant variation in the emission of ethylene, and in the quality parameters (firmness, soluble solids, chlorophyll), as well as by a different response to those regulators that inhibit ethylene production. In fruits with a lower DA index (riper), those regulators influence the ripening process, while, in fruits with a higher DA index (less ripe), the treatment causes a separation between pulp softening and chlorophyll degradation.

 

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