Milk Goes Modern: Developments in Milk Processing and Kashrus for Pesach

Rabbi Gavriel Price

Passover marks the birth of a nation. In that context, it’s appropriate that we discuss the most nourishing of foods: milk. A number of modern developments in milk processing affect the kashrus of milk for Pesach. They include vitamin enrichment, the processing of oatmilk on production lines that process dairy milk, and lactose-free milk.

Vitamin Enrichment

In the 1930’s a group of medical professionals teamed up with food manufacturers to address a range of problems of nutrition deficiency in the United States. Rickets, a condition of soft or weak bones, had been a widespread problem among American children since the 19th century. Advances in understanding the physiological role of vitamins indicated that rickets was caused by a deficiency in vitamin D. In 1933, vitamin D was first isolated and purified in an industrial process and by the end of the decade the first dairy processors began to add the vitamin to address the problem (other foods that were fortified to address public health issues include enriched flour and iodized salt 1 ).

In the 1940’s, when milk processors introduced low-fat and fat-free milk, researchers noted that its natural vitamin A content, which resides in the fat component of milk, was reduced. Processors therefore began to add vitamin A to low-fat and fat-free versions of milk. 2

Vitamins A and D are still routinely added to milk. Is there any concern of chametz?

The OU is familiar with the manufacturing process of both of these vitamins because we certify the production sites. They are made using materials that are neither chametz nor kitniyot. Processing aids peripheral to the actual constituents of these vitamins may be kitniyot. When special productions are made for Passover, those ingredients are removed from the process.

The analysis of the impact of vitamins A and D on milk does not, however, end there. Dairy processors – the sites that actually bottle the milk – cannot add pure vitamin A or pure vitamin D to milk. These vitamins will not, on their own, dissolve properly into milk, the amounts needed are truly minuscule and difficult to manage, and regulations governing proper dosage is exacting. A middleman, therefore, provides the indispensable service of blending the vitamins into a liquid medium that will allow the dairy processors to add the vitamins in such a way that the vitamins will be soluble (dissolve) uniformly into the milk at precisely the right volume.

This liquid blend contains water, a vegetable oil, a carrier (or solvent) and an emulsifier (a specialty ingredient that allows for water and oil to blend).

The dairy processor adds the vitamin blend to milk at a ratio of one milliliter to every 100 quarts (or one part in 100,000) of low-fat or fat-free milk and only one milliliter to every 500 quarts of standard milk. 3

While this blend does not contain any obvious chametz, even if the blend was to contain a chametz ingredient, the general rule is that chametz added to a mixture prior to Passover is nullified in the mixture, provided it is less than one in sixty parts 4 (that which chametz is never nullified – issur mashehu – applies only when the chametz is mixed in on Passover 5 ).

OU Passover certified milk production requires that the vitamin blend be certified for Passover, in which case both the vitamins and the other components of the liquid vitamin blend are certified for Pesach (although there is discussion in halachic literature about the status of milk for Pesach if a cow primarily ate chametz, practically speaking the issue is irrelevant in the United States; chametz is not a standard component of their diet).

Given the complexities involved in the addition of vitamins to milk, the OU recommends purchasing Passover certified milk or buying milk prior to Passover.

Equipment Used to Process Both Dairy Milk and OatMilk

Although oats are not soluble in water, oat sugar, a component of the oat, is soluble in water. A recently developed food-engineering technique separates the oat sugar from the rest of the oat in a water medium, enabling the oat sugar to dissolve in water. The beverage is called oatmilk, and it has become exceedingly popular in both Europe and in the United States in the last few years.

Oatmilk is chametz. It undergoes a heat step known as pasteurization. Dairy milk is also pasteurized. Is oatmilk pasteurized on the same production lines that process standard dairy milk? If so, would equipment that processed oatmilk compromise the Pesach status of dairy milk that was processed on those lines?

Before answering these questions, it is important to appreciate a technical, but easily graspable, distinction in pasteurization.

Dairy Milk Pasteurization

Broadly speaking there are two types of bacteria natural to dairy milk. Some are pathogens, or disease-causing bacteria. A second class of bacteria are non-pathogenic and, from a health perspective, are benign.

Pasteurization is a heat-step designed to destroy bacteria. Pathogens are destroyed at a lower temperature than the bacteria that are benign but cause spoilage.

Standard pasteurization for dairy milk is only a safety measure, and is therefore set at the lowest temperature needed for the destruction of pathogens (that temperature is 160 F for 15 seconds). It is not set at the higher temperatures that would be required to destroy the greater range of bacteria that cause spoilage.

In practical terms, this means that the milk found in the refrigerated section of the market, and that typically appears in a plastic container, has been processed to standard pasteurization temperatures.

In contrast, shelf-stable milk has been heated to ultra-high temperatures that succeed in destroying even those bacteria that can cause spoilage. These milk products are packaged in cardboard boxes that usually are not refrigerated, although occasionally are also located in the refrigerated section of a store.

Oatmilk Ultra-High Temperature Processing

Oatmilk, and other specialty milks, are only produced as a shelf-stable product. They are therefore only produced on equipment that is used for other shelf-stable products 6 .

Therefore, the introduction of oatmilk on the market does not intersect with the processing and packaging of shelf-stable (non-shelf-stable) milk.

However, the equipment used to process oatmilk might be used for shelf-stable standard dairy milk.

Does this mean that standard dairy milk should not be purchased for Pesach, considering that there is a possibility that the equipment used to perform the ultra-high-pasteurization on the oatmilk is also used on the shelf-stable dairy milk?

Certain considerations in the nature of ultra-high-temperature processing rule out the likelihood that dairy milk would, even post-facto, become unsuitable for Pesach. Still, unless there are extenuating circumstances, it is best to avoid shelf-stable dairy milk 7 .

Similarly, other milk alternatives such as almond milk, soy milk and coconut milk are shelf-stable products that are processed at ultra-high temperatures in the same facility that, nowadays, is likely to process oatmilk. In our Dietary Supplement List, we have listed a number of products that should only be used for those in need.

Lactose Free Milk

Milk naturally contains lactose, which is sugar. Many people have difficulty digesting lactose in milk.

Lactose sugar is technically a disaccharide, which is helpful for us to know insofar as this word denotes a molecule with two parts (“di-“). An enzyme called lactase (the -ase suffix means that it is an enzyme) has been developed to split those two parts.

When lactase is added to milk, it essentially pre-digests lactose, by breaking it down to constituent parts. The result is that someone who otherwise would not be able to drink milk (or in any event have difficulty tolerating it) can now enjoy it without repercussions.

Lactase may be made using chametz, although not necessarily. It is added to milk at exceptionally small amounts. As mentioned earlier, chametz that is mixed into a mixture prior to Passover is nullified provided it is present at less than one in sixty parts; lactase is present at significantly less than that amount 8 .

For those that use lactose-free milk and cannot forego the product during Pesach, the OU permits its use, but it should be purchased before Pesach.


1. The History of Food Fortification in the United States: Its Relevance for Current Fortification Efforts in Developing Countries Author(s): David Bishai and Ritu Nalubola Source: Economic Development and Cultural Change, Vol. 51, No. 1 (October 2002), pp. 37-53

2. The Dairy Practices Council, “Guidelines for Vitamin A and D Fortification of Fluid Milk” 2001.

3. Ibid page 7

4. Shulchan Aruch OC 447, 2.

5. OC 447, 1

6. A dairy processing executive explained that specialty milks like oatmilk must be made in sufficient volume to meet supermarkets’ minimal requirements. Standard dairy milk processors do not have the economic incentive to use their equipment for oatmilk; they are generally more than occupied processing standard dairy milk. Specialized processing facilities that make shelf-stable products do have an interest in making oatmilk products.

7. Although rare, some manufacturing sites use steam to heat one product. It is then recovered and injected directly into another product. If the first product heated by the steam is chametz, it would be best to avoid using the second product for Pesach.

8. Mishna Berurah, 447, 14 notes that a chametz ingredient that is added deliberately to a food to perfect a physical property of the food (for example, to give it firmness or body) would not necessarily be nullified. Because lactase does not contribute to a physical enhancement, it does not fall under this category.

Rabbi Gavriel Price

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