Study of the effect of CONCERVOL coating on the postharvest life of cherries

INTRODUCTION

The cherry is a highly perishable non-climacteric fruit. Its post-harvest life is very short due to its lack of reserve compounds and high respiratory intensity. Its deterioration begins with browning and drying of the peduncles, darkening of the color of the fruit, dehydration of the fruit and development of rottenness. During post-harvest, the main diseases are produced by the development of fungal rot, the main fungi responsible being Monilinia fructigena (brown rot), Botrytis cinerea (gray mold), Penicillium expansum (blue mold), Alternaria spp. and Rhizopus stolonifer. Currently, the sector of the national cherry has chemical fungicides approved by the European registry for application during the postharvest of cherries.

The main pre-harvest diseases of cherries are produced by the development of molds of fungal origin. The mold appears as the development of a dark spot that is attacking the entire fruit and is spread in a dusty form on the surface of the fruit. To control mold, fungicides with captan and tebuconazole are applied (J. Alonso and R. Alique, 2006).

The infection by Monilia spp manifests especially in rainy years, during the time of flowering and development of the fruit, quickly infecting the fruits in the presence of humidity and warm temperatures, between 20 and 26ºC.

The infection by Botrytis cinerea is prone in senescent fruits and fruits with prolonged conservation. Under conditions of low relative humidity, abundant gray spores are produced, while in humid conditions an abundant cottony mycelium develops. Its development, although slowly, can occur at 0ºC.


Infection with Penicillium expansum occurs on damaged or senescent fruit. The infected fruit will develop a host of tiny blue-green spores, with great dispersion capacity. Early varieties of cherries such as Burlat are more sensitive than late varieties. It is recommended not to store cracked fruit and careful handling. Low storage temperatures slow down the development of the disease.

Rhizopus stolonifer infections occur during the post-harvest of the fruits. It develops in fruits with epidermal lesions produced by cracking and handling. It has a high capacity for propagation and infection through the spread of spores. For the development of the fungus temperatures above 4ºC are required, recommending the conservation of fruits at 0º C to avoid their development.

The infections by Geotricum candidum have gone from being an occasional disease to a problem of great importance, causing already important damages in early varieties and Lapins. G. candidum causes a soft rot of the fruits which exude a strong smell of fermentation and rancidity. The fruit develops the disease in the postharvest, observing the symptoms mostly in markets of destination.

Image 1: Rots caused during the postharvest of cherries by Monilia spp (A), Botrytis cinerea (B), Penicillium expansum (C), Rhizopus stolonifer (D), G Candidum (E).

PRODUCT IN STUDY

CONCERVOL NATURE-2 is a product for the coating of fruits, based on sucrose esters (food additive E-473). Its application on the surface of the fruit creates a semipermeable barrier to gases that reduces respiration rates, helping to maintain the color, smell and appearance of the fruit. Likewise, it also decreases perspiration, preventing weight loss caused by dehydration.

MATERIAL AND METHODS  

Location of the test and plant material
The tests will be carried out in the different calibrators of the ACVJ facilities.

The chosen variety will be California 4.

Design
The treatment will be carried out in the different hoppers of gauge 3.

The theses will be:

• Thesis A: Control (water)

• Thesis B: Concervol

Treatment
The treatment will be carried out in gauge 3, by immersion in the treatment pond, the immersion time will be 15 seconds and the dose indicated by the manufacturer.

After calibration they are packed in jars of approximately 500 grams and are transferred to the chamber.

The conservation will be carried out in chamber at a temperature of 0-5 ºC and Hr of 95%.

Valuations
Four evaluations will be made at 0,7,14 and 21 days after treatment. It will be applied on the variety Lapins.

The evaluated parameters will be:

1. Reduction of microbiological risk : Molds and stains. There will be a visual count of molds and spots present in each sample. The percentage will be calculated based on the weight.

2. Dehydration : weight loss of the samples.

3. Firmness : They will be analyzed by durofel scale with a digital durometer.

4. Content in soluble solids : The content in soluble solids is a good indicator of the sugars of the fruit and its degree of sweetness. They will be determined by means of a digital refractometer, they are expressed in Brix.

RESULTS

Next, the average data of the parameters studied in both theses are summarized according to the method described above:

On the one hand, we will analyze the results of dehydration, hardness and brix:

Dehydration in cherries treated as a control is very similar during the test period. It is convenient to point out that at the end of the trial, the cherries treated had a lower weight loss, as shown in the graph, reaching a difference of 5 grams after 21 days compared to the control.

Regarding the hardness of the pulp, it is observed how the control thesis gradually decreases firmness, from 74 to 69, while in the treated thesis a maintenance of the hardness is seen until the end of the test.

Regarding the brix or concentration of sugars, the values ​​are identical in both theses and throughout the trial, therefore, an effect on this parameter can not be deduced.

On the other hand, we will analyze the results of quality and shelf life, using the amount of good cherries, with spots and appearance of molds:

In the witness thesis, we started with a lower percentage of good cherries (35%) and a high percentage of cherries with spots (28%). Neither witness nor treated have molds.

The amount of good cherries decreases very sharply in the control while in the treated ones it is more sustained, going from 35% to 10% in the control and from 40 to 14% in Concervol. The appearance of a stain in both theses is high, although in terms of values ​​it is lower in the postharvest treatment.

In both theses molds appear from the 14 days of study, in both the percentage of rots found is very low, being higher in the witness thesis.

CONCLUSIONS

• Weight loss : the postharvest product cushioned the weight loss in the cherries treated.

• Hardness : the treated cherries maintained firmness throughout the trial.

• Brix degrees were not affected by the treatment.

• The quality and shelf life were decisive in that the treatment with Concervol decreased the appearance of spots and molds.

• The application of the product generated foam in the treatment tanks so it was necessary to add an antifoam.

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