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22 Adar 5762 - March 6, 2002 | Mordecai Plaut, director Published Weekly








Mushrooms and Kashrus

by Rav Moshe Vaye

Mushrooms have been in the kashrus news recently, as canned mushrooms produced in China, which are very common in Israel, were found to have bugs that were not previously detected. In the wake of this discovery, Rav Moshe Vaye investigated the issue and wrote this report of his findings.

A Survey of the History of Mushrooms

From various halochos explained in Shas it seems that in the times of Chazal mushrooms were already a popular delicacy:

In the gemora (Brochos 40a) we learn that the brochoh on mushrooms is shehakol because they grow from the air, not from the ground.

In Brochos (47a) Rashi explains that the amora Shmuel liked to eat mushrooms at the end of the meal.

Also in maseches Kesuvos (61a) it mentions "tavshila de'ardi" (see Rashi there), and in Nedorim (25b), "He who vows to abstain from fruit of the earth may not eat any fruit (vegetables), but may eat mushrooms."

The Yerushalmi in Ma'asros (1:1) explains that mushrooms are exempt from terumos and ma'asros because they are not planted from seeds.

As far as the laws of shmittah, the Meiri (Avoda Zora 14) says that mushrooms do not have kedushas Shevi'is since they do not grow from roots.

Infestation in Mushrooms

Although as far as the laws of brochos are concerned mushrooms are not considered to nourish from the ground, when it comes to the prohibition of insects, the Ramo (Yore Dei'ah 84:6) explains that they are considered attached to the ground: "Insects that grow in mushrooms have the same status as those in other vegetables and we do not say that they are not considered attached to the ground since we do not make a "borei pri ho'adomoh" on them."

The Taz explains that they are called attached to the ground and the insects are considered to have swarmed on the ground. (This is in contrast to the opinion of the Issur Veheter brought in Darchei Moshe who considers mushrooms as separate from the ground as far as insects as well.) See also in Biur HaGra (loc. cit. 19).

We find another reference to infestation in mushrooms in the Maharshal (Yam Shel Shlomo, Chapter Eilu Treifos) who writes that he avoided eating dried mushrooms because they are muchzak betolo'im. The Pri Chodosh (84:19) quotes him and adds that they should also not be eaten because of the danger since many wild mushrooms are poisonous. He says that they used to feed them to cats before eating them, and some of the cats died or became insane.

The Darchei Teshuva brings down from the Shulchan Govohoh that they ate mushrooms, but that the dried ones were very infested and they used to eat them only after careful inspection, by breaking them into pieces and checking for small holes inside them, which is a sign of infestation.

The Pri Megodim (84, Sifsei Daas siman koton 33) discusses using mushrooms by filtering, "As far as dried mushrooms, which are definitely infested, we have to look into whether it is permitted to wrap them in a linen cloth and place them in a pot of food to sweeten the food. And this is not considered being mevatel issur lechatchiloh, since his intention is only to use the juice of the mushrooms. It would seem that it is forbidden to do so, but one should not reprimand someone who does so using a very thick cloth through whose holes the insects cannot pass."

In another place (Orach Chaim 453 in Eshel Avrohom siman koton 3) he writes that with dried mushrooms using this method it is permissible to eat the juice even if the mushrooms are wormy, but he should still first remove whatever insects he can.

In Chochmas Odom (38:18) he writes that mushrooms are muchzak betolo'im, and this is also brought in Metzudas Zion on Kitzur Shulchan Oruch (46:39) and in the sefer Shimusho Shel Torah.

Mushroom Growing

In nature, there are about 2,000 species of wild mushrooms that are fit for human consumption, in addition to many species of poisonous mushrooms, most of which are lethal.

In olden times mushrooms were eaten, but there was no way to grow them commercially since they do not have seeds.

Three hundred fifty years ago, the French succeeded in growing mushrooms in caves around Paris (where they still grow mushrooms today), but it was only about 100 years ago that a commercially viable method of growing mushrooms was devised by sprouting mushroom spores. About 10 years later, in the U.S., a building in which mushrooms could be grown was developed, turning mushroom-growing into a commercial agricultural endeavor.

At that time mushrooms were grown only in cool climates, such as Western Europe and several American states. Fifty years ago, they began to be grown in the Far East during the cold season, and for the past 30 years they have been grown in climate-controlled buildings in which they can grow all year round.

Only 10 different varieties of cultivated mushrooms are grown throughout the world, and the worldwide production totals over a million tons a year.

In Israel, a limited amount of fresh mushrooms are grown but the bulk of the mushrooms consumed here are imported, canned mushrooms. Until 20 years ago, the bulk of the imports were from Holland. However, with the development of the mushroom industry in China, the center for imports switched to China, since mushroom- processing requires cheap manual labor, which is in abundant supply in China.

Consumption in Israel has grown considerably over the past years, and today 50 million cans a year(!) are imported, mainly from China, with some coming from Holland, France, and Poland. This is an amount that is about the same as that imported to Germany, which has more than 13 times the population of Israel.

Mushroom Infestation

Mushrooms are prone to many forms of infestation, especially fly maggots and mites. (Maggots are tiny worms that develop into flies). The main pests are:

1. Maggots of the sciarid fly. These are white with a black head, and range in length from 4 to 8 mm. The fly lays her eggs inside the compost used to nourish the mushrooms, from which the maggots hatch and enter the mushrooms. They burrow tunnels inside the mushroom stem and cap.

2. Maggots of the phorid fly (MEGASELIA). These flies are attracted to the odor of the growing medium from a distance of many kilometers! Each female lays about 50 eggs in the compost, from which white maggots hatch. The maggots penetrate the mushrooms, making holes in the mushroom.

3. Larvae of the cecid fly (MYCOPHILA). These are very tiny flies, 2 mm. long. The maggot is 2- 3 mm. long. They are very prolific, and in an untended bed there may be 4 1/2 million larvae in a square meter.

4. Mites. The mushrooms may harbor mites, which look like white or brown grains of sand crawling around on the mushroom. They produce stains and holes in the mushroom.

Mushrooms that grow wild are liable to be extremely infested, and so Jews were always scrupulous to eat them only after meticulous inspection (see Section B above).

For example, in Mexico there is a type of mushroom that is considered a delicacy, which is picked in forests but it is very infested.

In developed countries, cultivated mushrooms are grown under special conditions to prevent insect infestation. On the other hand, mushrooms that are not tended may be very heavily infested.

Preventing Infestation

To prevent infestation, mushroom-growers grow them under special conditions.

Modern mushroom-growing takes place in dark growing halls which are completely sealed, with all the air filtered through fine filters. The halls are climate- controlled, and are equipped with heating, cooling, steam, ventilation, and circulation equipment. Inside the building, long iron shelves called "beds" are arrayed. The growing medium is spread on the shelves. It consists of compost containing wheat chaff, rice chaff, and organic fertilizer, to which vegetable matter is added. A layer of earth is spread over this. The compost is pasteurized to kill any living organisms such as bacteria, mites, and the eggs of various flies and larvae which attack mushrooms. In addition, the buildings have exterminations periodically. Entry to the building is permitted only to those wearing special clothing, to prevent insects from reaching the mushrooms. The mushrooms grow evenly and are harvested by automatic robot machines.

Cultivated mushrooms, grown in good, modern conditions such as described above, are usually free of insects. In case of neglect or mishap, the mushrooms may become infested. For this reason, in my sefer, Bedikas Hamozon Cahalocho Part I, I recommended checking the mushrooms. With good- quality mushrooms, it is enough to check a sample.

Fresh mushrooms grown in Israel have been found to be clean of infestation, and may be eaten after checking a sampling.

Mushroom-Growing in China

Although the Chinese have been growing mushrooms only for the past 20 years, the methods used are primitive, and against all accepted modern procedures that we described above. Each farmer builds his own improvised growing hut in his yard.

The huts are built either from stone or bamboo, over which black plastic sheets and tree branches are spread. The huts are more open than closed, and flies and other pests that attack mushrooms can enter without any difficulty. Even the stone buildings that are used have many openings with plastic curtains that do not seal the openings, as well as an open entry way.

The growing medium is not properly sterilized, and in most places no professional extermination is done. The huts are located in swampy areas, and the puddles of water provide an excellent breeding ground for flies.

The farmer harvests the mushrooms by hand at dawn when the weather is cool, loads them onto his wagon or motorcycle, and quickly takes them to the plant (the texture of the mushroom is delicate and changes quickly), where they are immediately processed by boiling. The plant receives mushrooms from hundreds of growers, and it is impossible to control the quality of the sources.

Therefore in almost every can from China there are some infested mushrooms. For example, out of a six-can sample that was checked, infestation was found in five of the cans. In another case, 8 cans out of 9 were found to harbor infestation. Only some of the mushrooms in the can are wormy, generally 3-5 mushrooms out of the 15-25 mushrooms in the can. Insects were found in both whole and cut mushrooms.

The maggots are hard to identify, because they are found underneath the thin skin that connects the stem to the cap, or inside the flesh of the mushroom. The maggots are tiny -- 1-3 mm. long -- and identical in color to the mushroom itself. Identifying them requires expertise and sharp eyes.

Unlike the infestation in wild mushrooms, these maggots do not make holes in the mushroom and the mushroom seems superficially to be of superior quality. Because of the maggots' tiny size and their being hidden under the peel, this infestation was not discovered in the past, although apparently it has existed for many years. (We found infestation in cans that were several years old.)

The conclusion is that, without radical changes in the methods of growing mushrooms in China, there is no possibility of producing clean mushrooms there. It will be possible to try to do so only if the openings of the solid buildings are sealed with fine mesh, the growing medium is effectively sterilized and the buildings are also disinfected (insects and mites live inside the bamboo frames), and the beds are professionally exterminated.

The entire growing and production process must be supervised by experienced mashgichim who make sure that the buildings are sealed, check samples of mushrooms from the buildings, ensure that the packing plants use produce only from certified stone buildings, and check large samples of the finished product during the entire production season, as well as laboratory tests of the finished product which confirm that it is completely insect-free.

Mushrooms in Other Countries

In conjunction with the investigation of mushrooms from China, mushrooms imported from other countries were also checked. Surprisingly, in mushrooms originating from countries using modern methods, a high rate of infestation was also found!

For example, infestation was found in whole mushrooms from Holland; a very high rate of infestation was found in frozen and canned mushrooms from France. Mushrooms from Spain and other countries were also found to harbor infestation.

Mashgichim who went to Holland then discovered that in Holland, only cut mushrooms are generally produced. Whole mushrooms, which require intensive manual labor, are imported from China (!), canned in Holland and reexported.


The can or container should be marked as having been produced under special supervision, and that the mushrooms are insect- free.

These conditions also apply to frozen and dehydrated mushrooms. Dehydrated mushrooms should be stored in airtight containers or in a vacuum, to prevent new infestation from developing during prolonged storage.

Halachic Questions

1. Q. Can we consider the surfaces on which the medium is laid as a vessel with the halachic status of a "flowerpot without a hole" (otzitz she'eino nokuv)? If so, could the worms in the mushrooms be considered a worm that was born in something detached from the ground and never went out, which is not ossur? (See Yoreh Dei'ah 84:4).

A. In my sefer Bedikas Hamozon Cahalocho (Note 6 in Chapter 3), I write about a similar question that was brought before Rav Shlomo Z. Auerbach zt"l concerning vegetables grown in a flowerpot without a hole. He was asked about the status of a worm that hatched inside the flesh of a leaf growing in the flowerpot and never went out, and he answered that it requires further clarification and we would have to find a precedent (ra'aya) to permit it.

In Darchei Teshuva (84:82) he quotes both the Minchas Yitzchok, who is undecided as to whether insects in mushrooms that grow inside vessels are considered as "crawling on the ground," and the Orach Mishor, who says that the mushrooms are definitely considered attached to the ground, making the worms prohibited.

However, in fact the above questions are irrelevant, since the growing surfaces in which the mushrooms are grown everywhere are like nets. In Europe the nets are made of metal, and in China they are just strips of bamboo holding up the medium. The floors of the huts in China are earth, not concrete, so that the medium cannot be considered a flowerpot without a hole. In addition, the flies lay their eggs in the medium itself, where the maggots develop, move around, and then go into the mushrooms, so that they cannot be said to have hatched inside the mushroom.

2. Q. Since infestation was found in the majority of the cans, both whole and cut, and canned mushrooms should not be used, what is the halochoh bedi'eved, for example a food that was cooked with mushrooms that were not checked? Can the mushrooms be removed and the food eaten?

A. In my sefer Bedikas Hamozon Cahalocho, page 182 question 4, I asked HaRav Shlomo Z. Auerbach zt"l a similar question and he answered that we do not hold that the insects are transferred (ein machzikim mimokom lemokom), and the food is permitted. And the gedolei haposkim today also paskened the same way regarding mushrooms.

If it is not possible to remove the mushrooms, there is a possibility of leniency bedi'eved and one may eat the food.

Infestation was also found in dehydrated mushrooms which are used in manufacturing soup mix. If the soup has whole or sliced mushrooms, the mushrooms should be removed. Soup with finely ground mushrooms may be eaten. With soup with small pieces of mushroom, it is desirable to grind the soup well. This is the opinion of the gedolei haposkim as well.

3. Q. May a manufacturer store dehydrated mushrooms for 12 months, after which the insects are like dust? (See my sefer Bedikas Hamozon Cahalocho chapter 9 of the halocho section). Usually during prolonged storage, new insects develop in the food (ibid. chapter 5 paragraph 8). Therefore, one of the kashrus organizations suggested storing the mushrooms in an air-conditioned warehouse to prevent new infestation. Is air-conditioning like freezing, which preserves the worms in their current state (see HaRav S. Z. . Auerbach's teshuva there, question 7), or is air-conditioning like winter conditions? Nowhere do we find that in winter conditions or in a cold country the din of 12 months does not apply.

A. The gedolei haposkim answered that it depends on what actually happens, and we should follow up what happens during storage: whether the worms dry up and turn into dust, and whether the mushrooms remain free of new infestation.

4. Q. If someone has a large supply of infested mushrooms, may he give them or sell them to a non-Jew, or must he be concerned that the non-Jew will sell them to a Jew? (See Bedikas Hamozon Cahalocho Chapter 10 paragraph 3 in the halocho section).

A. The gedolei haposkim answered that here in Israel, where it was widely publicized that the mushrooms are infested, one need not worry that they will be sold to a Jew, and one may sell them to a non- Jew.

5. Q. Whereas a mashgiach can check at most 30 - 40 cans a day, and a day's production comprises tens of thousands of cans, can we rely on this as a representative sample, since it is only a very small percentage of the total? On the other hand, when the mushrooms were infested we found infestation in 4 out of 5 cans, and even in cleaner specimens, infestation was found in 2 out of 10 cans, so that a sample of 30 - 40 cans can give a reliable picture of the situation.

A. The gedolei haposkim answered that in a case like this, we can rely on a sample of this size.

Procedure for Checking FRESH Mushrooms

1. Try to use only fresh, firm, nice-looking mushrooms.

2. Wash the mushrooms well to remove the remnants of the growing medium (dark crumbs). Remove any dark spot or mushy area.

3. Separate the cap from the stem and examine the resulting hollow area in the cap, as well as the upper surface of the stem, checking for small "pinprick" holes. In addition, one should look for small white worms on the upper part of the stem.

4. Examine the brown gills (made up of thin brown lines) on the underside of the cap, to see whether the area is mushy, or if there are small white or red mites.

5. Break the cap into several pieces (3-4) or slice it. Do the same to the stem. Check for small holes or mites.

If holes are found, do not use that mushroom and check the rest of the mushrooms well. If mites are found, do not use any of the mushrooms from that package.

With high-quality mushrooms, one can rely on checking a sampling of the mushrooms. If infestation is found in the sampling, the entire batch must be checked.


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