Melons – a (not only) Summer Delight

Report from a day in the lab

Leonie Moser

 

Melons are a popular, refreshing treat for young and old, especially in the summertime. From watermelons to the many types of sugar melons, there is something to tickle everyone’s taste buds. Our analyses of 135 samples from 2016 to 2020 show that we can enjoy our melons without worrying about contamination from pesticide residues.

 

All About the Melon

In the hot days of summer melons are a popular form of refreshment. Fully 87 % of melons are consumed from June to September [1]. In Germany, a good six kg per household are eaten annually, and about 60 % of all households buy at least one melon once a year [1].

Melons are often thought to be a fruit, but they are fruit vegetables, and belong to the gourd family (cucurbitacuae), like pumpkins and cucumbers. A distinction is made between watermelons (citrullus lanatus) and sugar melons (curcumis melo) [2].

 

Watermelons (Citrullus lanatus)

Illustration1: Picture of Watermelons with yellow and red fruit flesh.

Illustration 1: Watermelons with yellow and red fruit flesh

 

Watermelons like a sunny and moist but not wet growing environment. The plant is not frost-hardy and, due to its long ripening time, its cultivation in temperate climates is difficult [3]. Nevertheless, some farmers in Germany have recently started experimenting with its cultivation [4].

Among all types of melons, watermelons account for the greatest amount grown world-wide, at 104 million tons (2018). Germany imports 410,000 tons annually, the largest amount coming from Spain (280,000 tons), followed by Italy (81,000 tons). Smaller amounts come from Turkey and South America (Brazil and Costa Rica) [1, 5].

Watermelons should not be stored at temperatures under 10 °C. Moreover, they are sensitive to ethylene, which is released by some fruits such as ripe apples or bananas. They should be stored away from such fruits, to prevent the flesh of the melon from becoming soft and mealy [6].

Watermelons contain 90 % water and 8 % carbohydrates, as well as small amounts of fat and proteins. Given their high water content and low calories of just 37 kcal per 100 gr., watermelons are a healthy, refreshing thirst quencher in the summer [6, 7].

 

Sugar melons (Curcumis melo)

Illustration 2: Cantaloupe (C.melo cantalupensis).

Illustration 2: Cantaloupe (C.melo cantalupensis)

 

There are several types of sugar melons, including the well-known cantaloupes, musk and honeydew melons, as well as the lesser-known types, such as the charentais and futoro melons.

 

Abbildung 3: Illustration 3: Charantais melon: the small European form of the cantaloupe melon.

Illustration 3: Charantais melon: the small European form of the cantaloupe melon.

 

Illustration 4: Musk melon.

Illustration 4: Musk melon

 

In 2018, 27 million tons of sugar melons were produced worldwide, 130,000 tons of which were imported to Germany. As with watermelons, most came from Spain (73,000 tons), but Brazil followed with 20,000 tons and Italy took third place [1, 5].

Sugar melons shouldn’t be stored at a temperature of under 7 °C; otherwise, cold-damage such as loss of firmness could occur. In addition, sugar melons release ethylene, so they should be stored separately so as not to disturb the ripening process of other fruits and vegetables [2].

Sugar melons also contain a high percentage of water, at 85 %; the amount of carbohydrates lies at 12 %, somewhat higher than watermelons. The calorific value is, therefore, also higher, at 56 kcal per 100 grams [7].

 

What is Analyzed?

Regulation (EC) No. 396/2005 mandates the maximum levels of pesticide residues (MRLs) in foods; for melons, listed in Annex I of the regulation, these include the entire fruit with peel. For the analysis, the whole melon is quartered, the sections opposite each other are taken, and then chopped, and homogenized.

 

Analytical Results

From 2016 to 2020 a total of 135 conventionally produced melon samples were analyzed for residues of over 750 different pesticides. The residue situation presents a positive picture: the proportion of samples with exceedances of the MRL was just three percent over the entire five-year time period (see Table 1).

 

Table 1: Residues in Melons from Conventional Cultivation (CVUAS 2016 - 2020)
Year
No. of Samples
Samples with Residues
Samples with Multiple Residues
Samples
> MRL
Substances > MRL
2016
37
37 (100 %)
37 (100 %)
2
Chlorfenapyr, Flonicamid (sum)
2017
20
20 (100 %)
18 (90 %)
1
Pyrimethanil
2018
50
48 (96 %)
44 (88 %)
1
Propiconazole, Thiabendazole
2019
26
25 (96 %)
24 (92 %)
-
-
2020
2
2
1
-
-
Total
135
132 (98 %)
124 (92 %)
4 (3 %)
 

 

Multiple Residues

Illustration 5 shows the distribution of multiple residues found in the analyzed samples. In all, 92 % of the samples contained multiple residues (see Table 1), and one sample exhibited residues of up to 17 different substances. This was an exception, however; more than 50 % of the samples had residues from five or fewer substances. The melon with the smallest percentage of multiple residue cases was the watermelon, at 80 %. The honeydew melons and cantaloupes were affected at a rate of 95 % and the musk melons at 100 % (see Table 2).

 

Illustration 5: Multiple Residues in Melons from Conventional Cultivation.

Illustration 5: Multiple Residues in Melons from Conventional Cultivation

 

Table 2: Residues in Melons from Conventional Cultivation

 

No. of Samples
Samples with Residues
Samples with Multiple Residues
Samples > MRL
Substances > MRL
Watermelon
35
32 (91 %)
28 (80 %)
-
-
Honeydew melon
58
58 (100 %)
55 (95 %)
1
Propiconazole, Thiabendazole
Cantaloupe
20
20 (100 %)
19 (95 %)
1
Chlorfenapyr
Musk melon
22
22 (100 %)
22 (100 %)
2
Flonicamid (sum) Pyrimethanil

 

Watermelons contained the lowest average level of residues (0.031 mg/kg) and the lowest number of different substances detected per sample (3.9). There were also no exceedances of the MRL over the time frame of 2016 to 2020. Musk melons contained the largest number of substances per sample, at 7.4, and honeydew melons contained the highest average amount of residue, at 0.37 mg/kg (see Table 3).

 

Table 3: Residues in Melons from Conventional Cultivation
 
No. of Samples
No. of Substances per Sample (with all residues)
Ave. Amount, excluding Fosetyl* (mg/kg)
Watermelon
35
3.9
0.031
Honeydew melon
58
6.5
0.37
Cantaloupe
20
6.4
0.2
Musk melon
22
7.4
0.11

*Due to the comparably high levels of the fungicide fosetyl found in plant-based foods, the average amount per sample is presented without fosetyl, in order not to distort the overall picture.

 

All in all, the melons from South America contained somewhat higher numbers of residues per sample. However, the MRL exceedances occurred with melons grown in the EU.

 

Which Residues were Found?

Residues from a total of 104 different substances were detected in the 135 samples analyzed between 2016 and 2020. Thirty of these were found in ten or more samples. The most frequently detected substance was the insecticide imidacloprid (in 61 samples), and the fungicides azoxystrobin and fosetyl (in 41 samples each). Exceedances of the MRL occurred for substances that were detected in only a few samples. Propiconazole and Chlorfenapyr were found in only one sample, for example, but the amounts were above the maximum level.

 

Melons from organic cultivation

Only four melons from organic cultivation were analyzed in the timeframe of 2016 to 2020. Pesticide residues were detected in two of these samples, but the levels were under the orientation value of 0.01 mg/kg. None of the samples had multiple residues. In these cases, the adage held true: if the label says it’s organic, then it is so.

 

Our Conclusion

Melons are a popular, healthy and refreshing summer treat. The results of our analyses from 2016 to 2020 show that, given the very low levels of residues, consumers can continue to enjoy eating melons without concern.

 

Photo credits

CVUA Stuttgart, Pesticide laboratory

 

References

[1] Dr. Hans-Christoph Behr, AMI Markt Bilanz Obst 2019, Agrarmarkt Informations-Gesellschaft mbH Bonn, ISSN 1869-8891

[2] BLE Produktinformation Melone
https://www.ble.de/SharedDocs/Downloads/DE/Ernaehrung-Lebensmittel/Vermarktungsnormen/VermarktungsnormenObstGemuese/Flyer/Melonen.pdf?__blob=publicationFile&v=1

[3] Plants for a future: Citrullus lanatus

[4] https://www.faz.net/aktuell/stil/essen-trinken/bayern-im-sueden-deutschlands-gibt-es-melonen-16366396.html

[5] Food and Agriculture Organization of the United Nation

[6] BLE Produktinformation Wassermelone
https://www.ble.de/SharedDocs/Downloads/DE/Ernaehrung-Lebensmittel/Vermarktungsnormen/VermarktungsnormenObstGemuese/Flyer/Wassermelonen.pdf?__blob=publicationFile&v=1

[7] Souci/Fachmann/Kraut, Die Zusammensetzung der Lebensmittel, Nährwert-Tabellen, 8. Auflage, Wissenschaftliche Verlagsgesellschaft mbH 2016, ISBN 978-3-8047-5072-2

 

Translated by: Catherine Leiblein

 

Print article      Share: Facebook. Twitter. LinkedIn. Share it via Email.

 

Report published on 02.11.2020 10:10:49