Artificial procedures for removing Persimmon astringency

Dom · December 14, 2022, 3:51pm

Artificial procedures for removing Persimmon astringency.

Author: Francois Drouet

As a documentary or even for inspiration, I combined in this article the information I was able to gather about artificial methods for removing Persimmon tartness when it is naturally present in it (in fact, there are many varieties of non-astringent Persimmon).

I have classified them into traditional (historical) and modern (industrial) methods, which I propose sequentially, summarizing the principle and purpose of such procedures.

I conclude the article with an overview of products sold in France through commercial channels that are subject to artificial Persimmon tartness removal.

PRINCIPLE AND PURPOSE OF ARTIFICIAL PROCESSING

The astringent taste of some Persimmon varieties (Diospyros kaki) is due to the absorption by tongue proteins of a substance called kaki tannin (purified in 1978 by Matsuo and ITO), which is stored in a soluble state in specialized fruit cells.

Artificial processing methods suppress the astringent taste of persimmons by polymerizing Kaki tannin, which turns it into an insoluble and non-astringent compound.

The purpose of such procedures is to remove tartness, while maintaining the hardness of the fruit, which allows it to be consumed like an Apple.

In order for the fruit to be firm, it had to be harvested when it was not ripe (in fact, before it reached the ripening stage, which begins to soften it).

In general, fruits are harvested as soon as they lose all their green color. They are pale yellow and very hard.

The processing to which they are almost immediately subjected is an artificial inhibition of astringency, which does not allow them to ripen. At the end of this processing, they are not overripe. They retained the hardness and color they had during harvesting.

But processing did not cause them to lose their ability to ripen like on a tree.

If they are not eaten immediately, they continue their natural maturation, changing color and texture, as if their astringency has not been artificially removed. They will gradually mature as if they remained astringent.

Procedures for artificially suppressing tartness should not be confused with procedures designed to facilitate or speed up the maturation of persimmons. They end up with a fruit that is so soft that persimmons are considered astringent or non-astringent.

For example, mixing Persimmon astringent with apples so that the ethylene released by them accelerates its maturation is not an artificial treatment to suppress the astringency of persimmons. This does not eliminate the astringency of the fruit, which must be consumed solid. This contributes to its development to physiological maturity, which will make it ready to eat only soft.

We can also speed up the maturation of naturally non-viscous persimmons with hard fruits or more or less soft fruits, according to everyone’s wishes. In this case, we see that the Apple placed on the fruit is responsible for accelerating maturation, while the fruit does not need to suppress tartness, because it is not naturally tart.

For industrial methods, the Protocols of “forced maturation” and “astringency suppression” are very different and do not coincide.

But for historical methods, if in theory we can distinguish between “suppressing tartness” and “accelerating maturation,” there may be some confusion in practice. The nature of the fruits obtained (hard or soft) is not always indicated in the literature.

HISTORICAL METHODS

Artificial treatment of Persimmon astringent to remove its astringency dates back several centuries, and therefore there are methods that can be described as “historical”.

In Japan, there are several traditional processes that have existed or still exist:

Astringent persimmons are placed in empty barrels that are used to store sake (fermented rice drink), which are hermetically sealed. After six to seven days, the fruit loses its astringency and becomes very juicy.
astringent fruits are placed in a new barrel and placed on top of hot water seasoned with leaves of a local Polygonum species called “Tade”, which removes their astringency.

Other processes are used in China:

Astringent persimmons are artificially aged by placing them in jars, alternating with Docynia delavayi (Franch) Schneider fruits. Then cover with rice straw. After 10 hours, the fruit ripens and can be eaten.

The fruit is placed in large clay vases and sprayed with a 10% lime solution and left, depending on the variety, for 3 to 7 days before the astringency disappears.

Fruits are treated with smoke, which acts very quickly (two days) to eliminate the astringency. But the disadvantage of this method is that the fruits are poorly stored, and they are not suitable for transportation.

In Indonesia, to suppress tartness while maintaining a pleasant crunchy texture, persimmons are picked semi-ripe and soaked in lime for 24 hours. Fruits processed in this way are devoid of astringency and elastic, but on the skin they have a powdery white coating of lime.

In Taiwan, tart persimmons are harvested in waterproof jars with liquid lime. After 5-7 days of soaking at room temperature of 25-28 °C, the fruits lose their astringency, remaining firm, and even acquire some crunchiness.

Soaking in water is reported in the literature, but it is not known in which countries it is used or used:

The fruit is immersed in boiling water and allowed to cool in the water overnight.

Fruits of the ‘Hachiya’ variety are stored in hot water (40 °C) for 24 hours, become non-astringent two days after processing, remaining hard.

Various methods of alcohol treatment that were used by the Japanese (barrels containing sake) exist all over the world, for example:

In the United States, fruit is tightly sealed in barrels containing alcohol or cognac.
In Spain, fruit is still picked and placed in a solid container, such as a pot, in which alcohol is first placed, such as “L’aguardiente” or cognac, making sure that the fruit is not in contact with alcohol. A day later, the container is opened, and we see that the astringency of the fruit has disappeared.

The ingenuity of the methods is sometimes surprising: the bite of the Mediterranean fruit fly (Ceratitis capitata) has been observed to cause persimmons to ripen. Inspired by this observation, it was possible to ripen the fruit by pricking it with a needle soaked in alcohol and holding it in an airtight container.

This method was given in 1924 by L. Trabut in his article “Diospyros Edibles” (Journal of Applied Botanical and colonial agriculture, Volume 4, No. 40, p. 829-834), was reopened in the 1980s in California.

Indeed, Julia F. Morton, in the Persimmon section of his monumental work fruits of a warm climate, pp. 411-416, 1987, Miami, Florida, reports this as a process that was discovered several years ago in California. She states that the fruits, after they have been pricked, are covered with straw in a tightly closed box for 10 days.

INDUSTRIAL METHODS

At the end of the twentieth century, the goal of marketing and exporting hard viscous persimmons without tartness led to the development of methods for mass processing of fruits that can be described as “industrial”.

We will consistently review the various processes that have been tested, the main processing used on the production line.

VARIOUS RESEARCH PROCESSES

The most common method is carbon dioxide (CO2) treatment in enclosed, temperature-controlled rooms.

Ethylene is used in a similar way, but this may have the disadvantage of softening the fruit below the hardness level recommended for transportation.

Thus, in the United States, for the Hachiya Variety (the main variety grown commercially in California), it was found that treatment with ethylene (10 ppm) at 20 °C allows hard fruits to get rid of astringency. But after the use of ethylene, excessive softening of the fruit occurs, which prevents their commercialization.

The air enriched with 80% CO2 for 24 hours, at 20 °C in a closed chamber, allows you to suppress astringency, while maintaining hardness.

The use of ethanol (ethyl alcohol) is also practical.

In Japan, about twenty years ago, 35-40% ethanol was sprayed on persimmons and stored in airtight containers for 10 days at 20 °C. The Hard, non-astringent fruit obtained was of good quality and suitable for marketing.

Ethanol has also been used in Japan on commercial plantations by individually packaging the fruit on the tree, wrapping each fruit in a plastic bag containing a little ethanol until they are ripe. The astringency disappears after three days. The fruit can then be harvested.

A Chinese-Japanese research team published in 2002 the results of a comparative study of ethanol and carbon dioxide treatment involving 25 binder varieties. Depending on the Variety, the results were very variable. However, ethanol exposure was lower or equal to carbon dioxide exposure, never better.

Many other processes have been successfully tested: acetylene formed by burning calcium carbonate in closed chambers at temperatures from 20 to 28 °C and a relative humidity of 80%, firing sawdust under the same conditions, carbon dioxide in the solid state (dry ice), introducing dinitrogen in processing mixtures, etc.

BASIC AVAILABLE PROCESSING

The hard and astringent Persimmon on the market in France comes from foreign production networks using carbon dioxide to suppress astringency.

The processing parameters (carbon dioxide concentration, duration, temperature) depend on the grade, but they remain in the same order (the concentration should be high, between 80 and 95%, the temperature should be between 20 and 25 °C, the processing time is about 24 hours, not less than 20 hours).

USE OF CARBON MONOXIDE TREATMENT

Four production lines use astringency suppression with carbon dioxide to market persimmons:

In Spain, in the Valencia region, to produce a hard and non-astringent Persimmon sold under the name “Persimon”: the fruits of the ‘Rojo Brillante’ variety, astringent during harvesting, are placed in a chamber containing 95% carbon dioxide for 24 hours at a temperature of 20 °C (this procedure applies before all fruits are placed in a cold room)
*In Israel, to get a hard and non-astringent Persimmon, which is sold under the name “Sharon”: the fruits of the “Triumph” variety, which are astringent during harvesting, are treated with carbon dioxide in a closed atmosphere for 24 hours while they are still solid.
In Spain, the provinces of Huelva and Seville, to get a hard and non-tart Persimmon, which is sold under the name “Sharoni”: fruits of the same variety as in Israel ( ‘Triumph’), astringent during harvesting, are treated with carbon dioxide in a similar way.
In South Africa, the same commercial product as in Israel and southern Spain is obtained from the same grade (binder) ‘Triumph’ with a similar carbon dioxide treatment to suppress astringency. It has the trade name “Sharon fruit” (agreement with the Israeli chain on the use of the name).
A number of other exporting countries, including Italy, are beginning to position themselves (or are preparing to do so) in the market of Persimmon astringents, which are sold without astringency when treated with carbon dioxide.
In France, the Marsillarg experimental gardening center in Ayrault created an experimental garden with a collection of Diospyros kaki varieties in 2011.
It is designed to experiment in local conditions of various parameters of biological culture and determine the technical and economic profitability that allows marketing in a tense market, currently dominated in volume (and price) Spanish.
Its purpose is to serve as a pilot Center for producers who want to engage in commercial Persimmon culture.
FOUR PRODUCTS COMMERCIALIZED IN FRANCE
Below are four products exported to France (and most of the world …) after carbon dioxide suppression of the binder:" Persimon “(Spain),” Sharon “(Israel),” Sharoni “(Spain) and” Sharon fruit " (South Africa).
Recall that the first one is obtained from the astringent fruit of the ‘Rojo Brillante’ variety and that the next three have the astringent fruit of the 'Triumph’variety.
We can see in the photos that these varieties have very different fruits, which makes it easy to recognize them.
This is true even if fruit sizes vary greatly for each variety, depending on the category. In the highest caliber, the ‘Rojo Brillante’ variety produces very large fruits for the Diospyros kaki Persimmon species.
It may happen that you will notice that the pulp of the fruit has become brown shades (a brown color that can turn black) unattractive. This is a defect that indicates that the fetus has been exposed to carbon dioxide for too long. But at least it doesn’t change.
Persimmon
Note that " Persimon “is written with only one” m", contrary to the English word" persimmon " means Kaki (Diospyros kaki), as well as another Persimmon.
This registered variety name ‘Rojo Brillante’ treated with carbon dioxide cannot be used by new producers (for example, Italy). Even in Spain, Persimon cannot be used by all manufacturers that produce and export this type of product. The Persimon trademark is a monopoly of producers whose fruits win the I’AOP “Kaki Ribera del Xuquer” (Valencia region). To strengthen this monopoly, some manufacturers write: “Persimon ® “.
Distributors are associated with the” Persimon " product name, distribution brand name (also attributed to other types of fruit from the same distributor): Bouquet, El Temple … So you can find “Persimon Bouquet” or “Persimon El Temple” on the shelves.
Product availability: mid-October and January.
Spanish manufacturers are trying to expand the marketing season by improving the methods of preserving their product.
But they face a serious obstacle: unlike other varieties, ‘Rojo Brillante’ is poorly stored at low temperatures (damage to cells provided that the storage temperature is below 11 °C, which as a result leads to a loss of hardness when moving to ambient temperature).
Thus, after astringency suppression treatment, it is usually stored at 15 °C for 20 days.
The use in storage chambers of 1-methylcyclopropene (1-MCP), an ethylene inhibitor, allows you to maintain hardness for 30 days at 15 °C and for 40 days at 1 °C.
The 1-MCP industrial process is a monopoly of AgroFresh, which sells SmartFresh products to manufacturers. This process is still a minority in Spanish cooperatives.
ORIGINAL ISRAELI SHARON
Israeli exporters of “Sharon” can not compare with Spanish prices for the same type of product.
In order not to encounter Spanish products on the market, they have developed cold storage technologies (controlled atmosphere, temperature 0-1 °C), which allows them to differ from three to four months of the marketing season.
Thus, the Israeli “Sharon” is available mainly from January to March.
Sharon
Spaniards usually refer to” Sharon “as a product whose trade name is"Sharoni”.
However, the use of the Spanish production network named “Sharon” is not allowed. It is not used in advertising, packaging, or labels.
ORIGINAL SOUTH AFRICAN SHARON
In South Africa, the product "Sharon “is commonly referred to as"Sharon fruit”.
The Sharon brand is the same as in Israel, because there are close economic ties between the South African production network and one of Israel’s largest manufacturers / distributors (Mor International).
In recent years, South Africa has exported Sharon fruit to France, although Israel’s much older industry is more important.
Available “Sharon fruit” from South Africa in the off-season in Europe (April to August).
For the production network, there is an complementarity of this offer with the offer of “Sharon” made in Israel.
For the European Consumer, this allows you to find “Sharon” in kiosks from January to August.