Are all kaki (persimmons) the same, or are there differences?

Report from a day in the lab

Nadine Korte

 

Suspicion of pesticides: furry, numb feeling on the tongue and a bitter after-taste. Yet analyses for pesticides and contaminants in kaki yield no findings over the legal limit. Then what is behind these symptoms and how can they be avoided?

 

All about the kaki

All types of the Diospyros Kaki are labelled simply as „kaki“. They are one of the oldest cultivated plants from East Asia, and enjoy more and more popularity here in Germany. In the meantime these sweet, yellow to orange-red, tomato-sized fruits can be found in supermarkets almost year-round.  In the winter months from October to April most of the kaki come from Spain, while in the summer, from June to September, they come mainly from South Africa. In addition to vitamins A, C, and the B’s, these fruit also contain the minerals potassium and phosphorus. In Germany the most commonly sold varieties are „Rojo Brillante“, „Kaki Tipo“ und „Triumph“ [1].

 

Astringent effects have natural causes

Consumer complaints reach CVUA Stuttgart again and again, with reports of furry, numb feelings on the tongue, or a bitter after-taste when eating a kaki: read pesticide alert! However, analyses of the samples brought in by consumers show no residues of pesticides or contaminants over the legal limit.  So what’s going on?

The cause of these symptoms is the astringent effects of kakis. Kakis naturally contain tannins. These substances cause the tongue to contract, leaving behind a furry feeling. Especially unripe fruit contain higher amounts of tannins, which break down as the fruit ripens. It is recommended, therefore, to eat kaki when it is ripe, when the fruit flesh is soft and transparent. The pulp can be spooned out of the peel, similar to a kiwi. Those who prefer to eat the fruit in a firmer consistency can buy the „Sharon“ kaki. This seedless variety from Israel contains few tannins and can be consumed before it is fully ripe, without astringent effects.

More and more frequently, procedures are being used on some varieties after the harvest to minimize the astringents and thus enable consumption of the fruit when it is still firm, and not completely ripe.   

 

Illustration 1: Rojo Brilliante (left); Illustration 2: Sharon (right).

Illustration 1: Rojo Brilliante (left); Illustration 2: Sharon (right).

 

Analytical results

As part of the official food control program, a total of 39 samples of kaki fruit were analyzed at CVUA Stuttgart for the presence of residues from more than 700 pesticides and contaminants (see table 1) over the last three years. Residues were detected in 33 of the samples; 22 of these contained residues from two or more substances, so-called multiple residues. Two kaki fruit samples exceeded the legally established maximum level. Both samples were in violation due to an excess of chlorate. Chlorate residues in plant-based foods are not necessarily the result of an application of herbicide, however. They can also end up in food as a result of environmental pollution ((see more information on chlorate in the report (in German) „Rückstände und Kontaminanten in Frischobst aus konventionellem Anbau 2017“) [2].

 

Table 1: Residues in kaki fruit from conventional cultivation (CVUAS 2016–Oct. 2018)
 
Total Samples
Samples w/ Residues
Samples w/ Multiple Residues
Samples >
Max. Limit
Substances >
Max. Limit
No. of Samples
39
33
22
2
Chlorate (2x)

 

Multiple Residues

Illustrations 3 and 4 show the total distribution of multiple residues in analyzed samples of kaki fruit and other exotic fruit.  A comparison of the residue situation for the two fruit categories shows that kaki contain a much smaller number of pesticides per sample than other exotic fruits, in which residues of up to 12 different substances have been detected.

 

Illustration 3: Multiple residues in kaki fruit from conventional cultivation.

Illustration 3: Multiple residues in kaki fruit from conventional cultivation

 

Illustration 4: Multiple residues in exotic fruit from conventional cultivation.

Illustration 4: Multiple residues in exotic fruit from conventional cultivation

 

Summary

As a rule, residues from pesticides and contaminants are not responsible for the furry feeling on the tongue or the bitter after-taste when eating kaki fruit. On the contrary, in comparison to other exotic fruits, kakis contain few such residues. The cause of such astringent effects are the naturally occurring tannins, which are higher in unripe fruit. It is recommended, therefore, to eat kakis that are completely ripe, or to consume varieties that contain fewer tannins, such as the Sharon fruit.

 

Photo Credits

CVUA Stuttgart, Pesticide laboratory

 

References

[1] Bundesanstalt für Landwirtschaft und Ernährung (BLE): Produktinformation Kakis

[2] Bundesinsitut für Risikobewertung (BfR): Der Eintrag von Chlorat in die Nahrungskette sollte reduziert werden

 

Translated by: Catherine Leiblein

 

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Report published on 21.12.2018 11:07:06