The Function of Hekhsher Okhel
Foodstuffs can only receive imparted tuma (ritual impurity) if they first undergo a process known as hekhsher (being made fit) by contact with one of seven mainstream liquids. According to Chullin 34b, the requirement of hekhsher is based on two Torah verses. The assertion of two different sources may imply two very different models toward understanding the function of hekhsher okhel.
The first verse (Vayikra 11:34) describes the food object and mandates that it first come in contact with liquid: all food which is eaten which first comes in contact with water can receive tuma. This verse portrays contact with water as necessary to confer upon the item a status of food and render it suitable for tuma transfer. In order to be susceptible to tuma, an object must be categorized as okhel (food). Just as the foodstuff must be edible and of a minimum quantity, similarly it must be cleansed by contact with a liquid. Until the requisite cleaning, the material is not defined as “okhel asher yeiachel,” food which is typically eaten, and therefore cannot receive tuma. In this model, hekhsher okhel is necessary to confer a full status of “shem okhel” upon the item.
Our model for determining the status of food is borne out in several locations. Rashi, in his commentary on Vayikra 11:37, asserts that the legal status of okhel is only acquired through this aforementioned hekhsher, which reinforces the role of hekhsher as a deciding factor in food categorization. A gemara in Chullin (18) equates the function of hekhsher okhel to the completion of an oven construction. Just as an unfinished oven isn’t yet considered a halakhic kli (vessel) and doesn’t absorb tuma, similarly unwashed food is not considered fully prepared and therefore cannot receive tuma. By way of these two gemarot, a structural parallel is created between completing the construction of an oven and cleaning foodstuffs through contact with liquid. In each instance the object in question becomes completed and can now receive tuma. Similarly, the Chinukh (mitzva 160) equates hekhsher okhel to the ripening stages of fruits for teruma (priestly portion) and ma'aser (tithing). Just like teruma cannot be taken prior to the natural maturation of fruits, tuma cannot be transmitted until hekhsher okhel. The parallel seen here establishes hekhsher as a final stage in the creation of halakhic okhel.
By contrast, a second verse (Vayikra 11:38) describes the actual tuma transfer, but does not discuss the status of the food that receives the tuma. If water falls on seed and a dead carcass touches the seed, tuma is transferred. Such a description suggests that hekhsher okhel does not alter the status of the food but rather becomes the vehicle for tuma to be transferred. In other words, the first verse suggests that contact with liquid is necessary to legally define the object as food which is, by virtue of its status, capable of receiving tuma. The second verse implies that contact with liquid facilitates the actual ma'aseh tuma (transfer of tuma). Ramban’s comments on Vayikra 11:37 indicate a preference for this model. He claims that many tuma-conferring items are covered in dust and cannot adhere properly to foodstuffs unless that food is moist. Consequently, the Ramban claims that the need for moisture is to enable adherence to an item and thus tuma transfer. According to the Ramban, hekhsher okhel enables the mechanics of tuma transfer rather than fully developing or completing the object.
This question about the nature of hekhsher okhel may help solve an interesting qualification of hekhsher: the liquid must contact the foodstuff after it is harvested. Water that contacts the item before it has been harvested does not create the hekhsher, as we will see shortly. Rashi (Chullin 118b s.v U-keshem) and the Rambam (Hilkhot Makhshirin 1:1) each wrestle with the issue of attached and detached produce. Both Rashi and the Rambam issue an apparently technical solution. They explain that if any contact with liquid were to create hekhsher, all food would inevitably undergo hekhsher as a result of contact with rainwater. Inasmuch as the Torah assumes that only some produce experiences hekhsher, undoubtedly the contact must occur after detachment. Neither Rashi nor Rambam provides a logical structure as to why pre-detachment hekhsher is insufficient; they merely prove that it cannot yield hekhsher.
A subsequent question about the function of hekhsher okhel may significantly influence the application of hekhsher okhel. To that end, it is unclear how much of the surface area of the food must come in contact with the liquid in order to qualify as hekhsher. The gemara itself does not directly address this issue, but the Vilna Gaon (Shulchan Arukh OC 158:9) infers that even limited contact with liquid would suffice to render hekhsher. By contrast, the Arukh La-ner on Keritut 15b infers from the Rambam (Makhshirin 1:1) that the entire item must be cleansed by the liquid; the Rambam employs the term "immersed," which suggests that the entire food is enveloped in the liquid. Rashi and Tosafot address a gemara in Pesachim (20a) which rules that animals which passed through a river undergo hekhsher through contact with the river water. Rashi assumes that a droplet will ultimately touch the flesh after shechita (ritual slaughter). Tosafot claim that the entire skin became moistened, presumably demanding that the entire surface area become moistened.
Perhaps this question is influenced by the nature of hekhsher: if hekhsher merely enables the passage of tuma, perhaps even limited contact with liquid facilitates the process. Moistened food can absorb tuma from a conveyor, whereas completely dry food cannot. However, if hekhsher is meant to represent the final preparation of the produce, a comprehensive cleansing would be necessary.
An additional question arises regarding the requirement of deliberate liquid contact. This issue may also depend on the nature of hekhsher. The gemara in Bava Metzia 22a asserts that the contact must be deliberate rather than accidental, but does not elaborate whose knowledge is necessary for hekhsher to occur. The Rambam (Tumat Ochlin 12:11) posits that only the awareness of the owner is sufficient for valid hekhsher. By contrast, Tosafot in Bava Kama (98a s.v. hah) claim that any human awareness is sufficient for hekhsher. Once again, the dispute about how to achieve nichuta (consciousness) may be a product of what hekhsher is trying to accomplish. If hekhsher aims to define the produce as fully developed food, perhaps the recognition of the owner is all that is necessary to change the status by virtue of his ownership. However, if hekhsher enables proper tuma transfer, any hekhsher recognized by a human is deemed meaningful enough to register as part of the tuma process.
Hekhsher is not necessary in two significant cases, and they deserve further attention. By examining these scenarios further, the function of classic hekhsher can be more positively identified. Why are these cases exceptional, such that they do not require hekhsher?
One such exception is that of food belonging to hekdesh (sanctified for Temple use). As the gemara in Chullin 36b asserts, these foodstuffs do not require actual hekhsher since chibat ha-kodesh machshartan, the affection people feel for hekdesh suffices in place of actual hekhsher. The gemara in Chullin 36b therefore supports hekhsher as a model by which okhel status is conferred upon food. As we have learned, typical foodstuff is not considered okhel until it is cleansed and prepped for consumption. However, the high regard people have for hekdesh renders any hekdesh food material as okhel even is not fully prepared. If hekhsher were an instrumental stage in transferring tuma, it should be required in situations of hekdesh as well. In truth, Rashi (Chullin 36, Zevachim 46, and Menachot 21) repeatedly suggests that hekdesh is not an exception and that this rule is only a Rabbinic chumra (stringency). Assuming, as Tosafot do, that the rule is indeed de'oraita (Torah law), it would imply an object-based function to hekhsher.
An additional exception surrounds Rabbi Shimon's position regarding shechted (ritually slaughtered) animals. Rabbi Shimon contends that animals do not require actual liquid contact since the act of shechita prepares the animal for consumption and functions as hekhsher. Such an exception would suggest that hekhsher represents the final stage of produce preparation. Since shechita is pivotal in halakhically preparing meats, it may serve a similar function to actual hekhsher and replace it. If hekhsher entailed part of the tuma transfer process, it is not immediately clear how Rabbi Shimon could have imagined that shechita would supplant or obviate it.