Does Flour Need to be Sifted?

The question of whether flour which might contain insects needs to be sifted is subject to dispute – in practice, the poskim instructed flour should be sifted * If flour that was not checked for worms was baked, after-the-fact, the food may be eaten * Even according to the strict method, if one does not find insects in the flour once every ten times, there is no obligation to check * White flour produced and marketed by a responsible and well-organized company – is presumed to be uninfested * In places where flour is purchased wholesale, or the storage conditions are inappropriate, it should be checked * In whole wheat flour the concern of insects is greater, but in some companies it is also presumed to uninfested


Q: For many years, whenever sifting flour with a sieve, I have never found insects. When I spoke about this with a Haredi friend, she told me she finds insects in her flour. How can this be? Because she finds insects, does that mean I have to continue checking, although I’ve never found any?

A: The issue of worms and insects, which in the Torah is called “shratzim“, comprises numerous matters. I will attempt to breakdown the halachic issues, describe reality, and summarize the halakha.

Prohibited and Permitted Insects in Fruits

The Torah forbade shratzim that breed on land, as it is written: “Every small animal that breeds on land shall be avoided by you and shall not be eaten” (Leviticus 11: 41). However, regarding shratzim that grow in detached fruits, as long as they crawl inside the fruit and have not left it – there is no prohibition (Chulin 67b; S. A., Y. D. 84:2). And if the shratzim grew in the fruit while they were attached to the tree, in the opinion of most poskim they are forbidden from the Torah (S. A., ibid 6).

Permitted and Forbidden Worms in Flour

Just as there is no prohibition of insects that grew in detached fruit that did not leave it, so too, there is no prohibition of worms that grew in flour and did not leave. Therefore, some poskim say that even if one sees there are worms in flour, as long as we did not see they left it and returned, there is no prohibition to eat the flour (Rokeach 461; Sha’arei Dura 54: Agudah). In the opinion of most poskim, when there is concern that the shratzim left and returned, they are forbidden (Rosh, Maharach, Or Zaruah, Shulchan Aruch 84: 5, Shach, Taz, Plati, and Aruch HaShulchan).

However, in the opinion of some poskim (Pri Toar and Chochmat Adam) even if the worms crawled in the flour – it is forbidden, for each particle of flour is considered a “fruit” in its own right, and when crawling from particle to particle, they leave the place where they grew. Nevertheless, their opinion was rejected by all Rishonim and the vast majority of Achronim. Consequently, as long as the worms did not leave the flour, they are still not prohibited (Aruch HaShulchan 84: 45-46).

The Controversy of Whether to Check Flour

The poskim disagree whether it is necessary to sift flour that doubtfully contains worms. In the opinion of many, there is no need to because of safek sfeka (compounded doubt): one safek (doubt) – there may be no worms in it, and a second safek – there may be worms in it, but they did not leave, and consequently they are not prohibited (Taz 84:12; Knesset Hagedolah; Shulchan Gevoha 2; Simchat Cohen, Yoreh Deah, 149).

There are some poskim who say that the flour should be checked, because in some laws we find that when there is concern and it is possible to check, we do not posek leniently not to check on the basis of the argument of safek sfeka (Pelati 47: 7; Minchat Yaacov 80:4 footnote 14).

In practice, in recent generations the rabbis instructed to sift flour, since worms were often found in it. Nevertheless, all agree that if one baked or cooked unchecked flour, the pastry or dish is kosher.

When is One Obligated to Check Food for Worms?

This law is divided into three situations: 1) foods that usually have no shratzim – may be eaten without being checked. 2) A dish that in most cases has no shratzim, but in its miut ha’matzuy (substantial minority) there are shratzim – from the Torah, it does not need to be checked, since the rule is we follow the rov (majority). However, from Divrei Chachamim (rabbinical ordinance) l’chatchila (ideally), one must check it, but be’di’avad (after-the-fact), when there is no possibility of doing so, it is permissible to follow the rov, and eat it. 3) Foods that commonly have shratzim – must be checked, and as long as they have not been checked or cleaned of the shratzim, they are forbidden to be eaten.

How is Miut Ha’Matzuy Measured?

There some poskim who say that the measurement of “miut ha’matzuy” which requires being checked from Divrei Chachamim, is more than 25 percent (Rivash), while others say it is more than 10 percent (Mishkanot Yaacov). The question is: what is the size of the unit by which the percentages are determined. In practice, there are four options, and each one is correct from a different perspective.

1) A meal: From the perspective of the person preparing the meal, it does not matter much if he sifts flour for two people who will eat, or ten, for each time he sifts the flour, he focuses on the sifted flour as a single unit. 2) A serving: From the perspective of the person eating, the dish is the only thing he focuses on. 3) The fruit: If we consider the food, then the unit is measured as the fruit or vegetable appears before us, whether large or small. And as far as packaged foods go, such as flour or beans, – they are viewed as they appear before us in their package, whether it be a kilo, a pound, etc. 4) One bite: If we focus our thoughts on the halakhic perspective, we will have to relate to each bite as a unit in itself, because this is the manner of eating, and consequently, the units must be determined accordingly.

Nevertheless, even if we are machmir (stringent) and determine that the miut ha’matzuy is already measured from 10 percent, and that the unit of measurement is the quantity prepared at one time, then if a worm is not found at least once in ten times flour is sifted, then the flour does not contain worms in the amount of miut ha’matzuy, and it is b’chezkat naki (presumed to be uninfested), and does not require checking.

The Status of Flour in the Past and Today

In the past, flour was worm-infested for two reasons. One reason is that the grinding process was not complete, and therefore, eggs from which worms were hatched remained in the flour. The second reason is that flying and crawling insects came in contact with the flour and laid eggs in it, from which worms hatched. Today, however, as a result of the technological improvements and the demand of the public for high-quality goods free of bugs, the state of flour marketed for domestic consumption in developed countries has improved greatly. For this purpose, reliable companies ensure that flour is well grounded so that most of the eggs are destroyed in the grinding process, and in order to destroy the remaining eggs, nitrogen gas is used, or the flour is heated. Immediately afterwards, the flour is packed in closed bags to protect it. Nevertheless, when the packs of flour are left in dirty places or on the ground, or for a long time on a shelf or in a storage room, there is a good chance that insects will puncture the packages, and hatch eggs in the flour.

The Practical Halakha

Consequently, white flour marketed in sealed packages by reliable companies and by way of responsible chains and stores, and stored in one’s house in a clean place for no more than a few weeks, is b’chezkat naki (presumed not infested), and does not need to be sifted, since the rare cases where worms are found do not amount to the measurement of miut ha’matzuy. Nevertheless, while pouring the flour, it is desirable to examine it with a normal look-over, in order to see that it is indeed clean as usual.

However, white flour purchased wholesale or in the marketplace needs to be sifted. One must also sift flour from reliable companies bought in stores where the merchandise is left on a shelf or in a storeroom for a long period of time, or stored in a dirty place, because in such places there are insects that penetrate the bags and lay eggs. Apparently, because in some stores in Haredi populated areas outdated merchandise is occasionally sold at lower prices, members of Haredi society find more worms in flour and legumes.

In any case, one who buys flour from a doubtful source should check it, and if it turns out not a single insect is found for every ten times sifted, it is b’chezkat naki, and does not need to be checked. And as long as the flour continues looking as good as it did before, one does not have to check it.

A company or store whose flour was considered uninfested, but a few times insects were found in it, to the point where it seems that its miut ha’matzuy contains shratzim – its presumption of being uninfested ceases, and from that point on, one should be careful to sift the flour bought from that company or store. But if this happened because, as an exception, they had stored the flour in a place prone to trouble, or for too long a period, it has not lost its presumption of being uninfested.

Additional Cases that Require Checking

Restaurants and businesses must also sift flour, since they often buy it wholesale and low-priced, and usually do not have proper conditions to store it.

Even flour that is known to be uninfested or already sifted, if placed in the open air or in an open container for 24 hours – and on a hot day, even for a few hours – it is liable to become infested, and therefore it should be sifted. Someone who wants to ensure that flour does not get infested after opening the package or after sifting, should store it in the refrigerator.

Whole Wheat Flour

In whole wheat flour, since it is coarsely ground, sometimes eggs remain, and therefore it should be sifted. Some companies that market whole wheat flour, destroy the eggs by using nitrogen, and pack it in vacuum-sealed packages, and their flour is b’chezkat naki and does not need to be checked. In addition, there are companies that market flour that from the time of grinding is kept refrigerated, and as long as they are careful that it does not go for 24 hours without refrigeration, it does not require checking, because the eggs do not hatch in cold conditions. If a buyer does not know the quality of the whole wheat flour from the company he bought, he should check it, and if he does not find one bug in every ten checking, it is b’chezkat naki, and does not need to be checked.

The Stricter Opinions

All this is according to halakha. However, there are machmirim (poskim who are stringent), who claim the reason shratzim are not found after sifting is because their color and size are the same as a grain of flour, and without special conditions, cannot be distinguished. We are talking about a tiny insect of the mite family, called kardit ha’kemach (Acarus siro), or the flour mite, whose color and size resemble a grain of flour, and measures between 0.3 and 0.6 millimeters, such that a normal person cannot see it. According to the machmirim they are forbidden, and in order to remove them, the flour must be sifted in a sieve whose netting is 70 Mesh (70 holes per inch), or be’di’avd (after-the-fact), 60 Mesh. After the sifting, the sieve must be cleaned thoroughly, because perhaps some of the flour-dust in it may be tiny vermin that are liable to multiply. The reason why a 70 Mesh sieve is useful for sifting them, despite their being the same size of a grain of flour, is probably because their tiny legs slightly enlarge their volume.

However, the chumra (a voluntarily assumed restriction more stringent than what is required by Jewish law) of the machmirim is contrary to tradition and halakha. It is contrary to tradition, because until about fifty years ago, God-fearing people did not have sieves in their houses. And it is contrary halachically, because one does not have to concern himself with such miniscule shratzim, for the Torah was not given to ministering angels but to human beings, and therefore it is sufficient to sift flour that is not b’chezkat naki in a sieve of 30 Mesh. Perhaps I will discuss this issue in my next column.

This article appears in the ‘Besheva’ newspaper and was translated from Hebrew.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.