Exotic Fruit – Not That Exotic and Better Than Imagined

Report from a day in the lab

Ellen Scherbaum, Hanna Marks

It was only a few decades ago that they were really exotic, the fruits that came from the tropics and subtropics. The typical menu those days was oriented toward what grew locally and what was in season. Pome fruits such as apples and pears, berries like strawberries and currants, stone fruits such as cherries and mirabelles and - something very special – citrus fruit in the winter, from the mediterranean; those were the types of fruit commonly eaten.

In the meantime, the world has gotten smaller, and our plates are filled with fruits grown the world over. Strawberries are available throughout the year and exotic fruits have become commonplace. That they originally came from afar and were something very special has practically been forgotten.

In the European Union only specific pesticide substances are authorized, and these only for specific applications. If the goods come from so-called third countries, however, different substances may also be found in our fruits. Good reason for us to take a closer look at the most common exotic fruits.

Ship or airplane – a good question for fruit as well

Exotic fruits still come from long distances. To keep the prices as low as possible, the fruits are harvested while still unripe, and then transported in cooled ship containers, in a so-called controlled atmosphere (CA storage). This helps prevent the goods from rotting during the often long trips. When the goods arrive they are ripened in special ripening rooms; green bananas are turned yellow, and dark green mangoes are made red-yellow and soft. An appropriate atmosphere is created, which speeds up the ripening process (see Info Box). Storage in a controlled atmosphere is also used for apples, pears and kiwis, to mention just a few, as this is the only way to make possible the availability of such fruits during the whole year. Exotic fruit that ripens on the vine can only be sent by air, and a hefty price is to be paid: a mango flown in by plane costs 5 Euros or more.

Pesticide Residues

Between 2015 and July 2019 a total of 736 samples of exotic fruit from conventional production were analyzed. Residues of one or more pesticide substances were detected in 636 of the samples (86 %). Exceedance of the legally permitted maximum levels for one or more substances occurred among 54 samples (7.3 %). An additional 20 samples contained chlorate in amounts above the maximum authorized level. Chlorate was used earlier as an herbicide, but is used today more for the disinfection of water (see Info Box).

Table 1 presents the residue situation for exotic fruits from conventional production.

Table 1 presents the residue situation for exotic fruits from 2015 until July 2019. There are two different average amounts of pesticides per sample given. The first column shows the amount of all analyzed pesticides found, and the second column excludes the fungicide fosetyl, as residues of this substances are often very high (MRLs up to 300 mg/kg fruit), which distorts the larger picture.

Exotic fruits do well in comparison with fruits in general. In 2018 the rate for all fruits containing residues was 95 %, with an average of 5.8 substances and 2.4 mg/kg per sample. Only the rate of MRL exceedances was lower during this time frame for all fruits, at 4.6 %, than for exotic fruits, at 7.3 % (see our report “Residues and Contaminants in Fresh Fruit from Conventional Cultivation, 2018“).

Usually the peeling is analyzed together with fruits and vegetables, even when it isn’t consumed. The background for this practice is that maximum residue levels are so established that foods grown in accordance with good agricultural practices are able to stay under these limits. Exotic fruits often have a thick outer covering that isn’t eaten; these include pineapples, bananas, pomegranates, kiwis, mangoes, maracujas and papayas. For the consumer, this means that the edible part of these fruits are often less contaminated with residues than the overall results presented here would suggest.   

In the next section individual exotic fruits with a high market share are described in more detail.

Pineapple

Table 2 gives an overview of the residue situation for pineapples. A total of 79 samples were analyzed, mostly from Costa Rica, followed by Ghana. All of the analyzed samples contained residues. Frequently appearing substances included: fosetyl (sum), ethephon, prochloraz (sum), fludioxonil, diazinon, triadimenol, lambda-cyhalothrin, piperonyl butoxide, triadimefon, and methoxyfenozide. These are mainly insecticides and fungicides. The fungicide fosetyl (sum of fosetyl and phosphonic acid) was detectable in 78 of the 79 samples, the growth regulator ethephon in 54 samples. Prochloraz, triadimenol and triadimefon are often used after the harvest to prevent, for example, fungi from entering into the pulp of the fruit via a cut in the fruit. Ghana was notable for having a violation rate of 33 %, although the nine analyzed samples are not to be seen as representative.

*No percentage calculated for sample sizes < 5

Banana

Table 3 gives an overview of the residue situation for bananas. Our samples came mainly from South and Central America. All 46 analyzed samples contained residues. Frequently occurring substances included the following insecticides and fungicides: azoxystrobin, thiabendazol, fenpropimorph, chlorpyrifos, bifenthrin, imazalil, buprofezin, and myclobutanil. The fungicides thiabendazol, fenpropimorph and imazalil are mostly used after the harvest for protection during storage. All in all the situation for bananas looks good; only one sample contained chlorate in an amount above the maximum level.

*No percentage calculated for sample sizes < 5

Fig

Table 4 gives an overview of the residue situation for figs. The 41 analyzed samples came mostly from Turkey and Italy. The residue situation is overwhelmingly positive; more than 50 % of the samples contained no residues at all. The number of different substances per sample was very low, at 0.6.

*No percentage calculated for sample sizes < 5

Pomegranate

Table 5 gives an overview of the residue situation for 113 analyzed pomegranate samples. The majority of samples came from Turkey. In the last few years these samples have been very conspicuous for their high rate of MRL exceedances, at 40 %. The situation was much better for other countries. The following substances were frequently found in the pomegranate samples: fosetyl (sum), fludioxonil, difenoconazol, acetamiprid, boscalid, chloranthraniliprol, imidacloprid, chlorpyrifos, carbendazim (sum), pyraclostrobin, lambda-cyhalothrin, pyriproxyfen, propiconazole, spirotetramat (sum), cyprodinil, and deltamethrin. These, too, are mostly fungicides and insecticides. At 4.4 substances per sample, the pomegranate is one of the more seriously contaminated exotic fruits. The rule is valid here, too: the peeling is analyzed together with the fruit, and the pomegranate juice has fewer residues.

*Some samples contained more than one substance above the MRL

**No percentage calculated for sample sizes < 5

Kaki, Sharon

Table 6 gives an overview of the residue situation for kakis and sharons. Most of the 66 analzyed samples came from Spain. Kaki and sharon scored well, with 1.7 substances per
sample. Chlorate was the main culprit of MRL exceedance, which can occur as a result of water disinfection. Substances that were more frequently detected included the fungicide fosetyl (sum of fosetyl and phosphonic acid) and the insecticide lambda-cyhalothrin, as well as the growth regulator ethephon.

*No percentage calculated for sample sizes < 5

Kiwi

Table 7 gives an overview of the residue situation for kiwis. A total of 89 samples were analyzed, mainly from Italy and New Zealand. With a rate of 2.5 substances per sample and only 2 % in violation, the residue situation gets good marks. Frequently detected substances were fosetyl (sum), fludioxonil, forchlorfenuron, iprodion and fenhexamid. These are substances used for mildew; only fenchlorfenuron is a growth regular, which enlarges the size of kiwis, table grapes and peaches. In 2011 this substance made it into the news after an improper application in melons in China caused them to explode [4].

*No percentage calculated for sample sizes < 5

Mango

Most of the analyzed samples came from Brazil and Peru, but the overall range of countries from which they came was especially diverse. Fully ripe fruits transported to us by airplane are considered very aromatic, and are offered as „air freighted mangos”. Table 8 gives an overview of the residue situation for mangos.

*No percentage calculated for sample sizes < 5

Similar to citrus fruits, mangos are often treated with fungicides after the harvest. Notification of this treatment isn’t required, however, because the outer skin of mangoes is not generally eaten. The most frequently detected substances were prochloraz and thiabendazol, though these were mainly found on the peeling, followed by the fungicides fosetyl, azoxystrobin and carbendazim. Insecticides and growth regulators were also detected with frequency. Mangoes contained an average of 3.1 substances per sample and had a rate of 9 % exceedances of the MRL in this analytical timeframe.

Maracuja, Passion Fruit

Table 9 gives an overview of the residue situation for maracujas. Our samples came mainly from Colombia and South Africa. Excluding the problem with chlorate, most of the MRL exceedances were from the Colombian maracujas. The most commonly found fungicides were also here: azoxystrobin, tebuconazole, fosetyl (sum), trifloxystrobin and difenoconazole. Passion fruits contained an average of 3.8 substances per sample; 33 % exceeded the MRL in this analytical timeframe. More than half of the exceedances were due to chlorate, but with the exclusion of chlorate, the rate is still 15 %.

*Some samples contained more than one substance above the MRL

**No percentage calculated for sample sizes < 5

Papaya

Table 10 gives an overview of the residue situation for papayas. Our samples came mostly from Ghana and Brazil. Especially noteworthy: the fruits from Ghana were practically free of residues, while the Brazilian papayas contained an average of 6.4 substances per sample and 5 out of 11 samples were registered as exceeding the maximum residue level.

*Some samples contained more than one substance above the MRL

**No percentage calculated for sample sizes < 5

Our conclusion

Even when they come from afar, exotic fruits from conventional production often have fewer residues of plant protection substances than local fruits. Although the rate of samples containing residues is relatively high, at 86 %, similar to other conventional fruits, the number of different substances in each sample was comparably low. There were some exceedances of the legal maximum levels, but these differ greatly according to the country of origin. The fruits with good results included bananas, figs, kakis, kiwis in general, and papayas from Ghana. Not so good in this analytical timeframe were pomegranates from Turkey, papayas from Brazil and maracujas from Colombia.

Photo Credits

Pesticide laboratory, CVUA Stuttgart.

References

[1] Robert K. Prange et al, Innovation in controlled atmosphere technology, 2005 Stewart Postharvest Solutions (Uk) Ltd, Online ISSN 1945-9656

[2] Rolf Blancke, Farbatlas Exotische Früchte, Ulmer Verlag 2000, ISBN 3-8001-3520-5

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

[4] Spiegel Online: Explodierende Melonen entsetzen Landwirte, downloaded on 26.08.2019

Translated by Catherine Leiblein.

Report published on 18.11.2019 10:51:06