Easy to Eat, Complex to Certify: Yogurt is a Favorite Food for the Cultured Among Us

Yogurt was first produced thousands of years ago. Dairy history and legend indicate that yogurt originated in Iran or Turkey. One story has it that an ancient Turk was carrying milk in his goatskin for some time, whereupon he noticed that the substance had developed into a thick, creamy mass (precipitated by the bacteria in the goatskin and the warm temperature).This new product was referred to as ‘yogurut’.

In 1900, a Russian biologist named Dr. Ilya Metchnikoff, of the Pasteur Institute in Paris, was able to isolate bacillus cultures for yogurt production, marking the beginning of modern yogurt manufacture. Dr. Metchnikoff demonstrated that yogurt’s bacteria fought dangerous germs in the colons of mammals, and he theorized the positive effects of yogurt bacteria cultures on humans. Shortly thereafter, yogurt became a staple in the American diet. Today, yogurt continues to be popular, and a large variety of kosher certified yogurts are available.

Why is yogurt so popular such that it has become one of the fastest-growing dairy products throughout the world? There are two answers to this question: a) variety in taste, and b) health benefits.

Yogurt is an ultra-pliable food which can be manipulated, filled, thickened and flavored in countless ways. Unlike most dairy products, yogurt has virtually no bounds. When one considers the multitude of flavors, fruit and confectionery fillings, thickeners and sweeteners used in the many varieties of yogurt available to us, it is clear that there are thousands of possibilities. (Ever heard of cheese with fruit filling, banana-flavored butter, sour cream with chocolate chips…? Yogurt is the only dairy food which is so flexible so as to accommodate all of these flavorings, additives and who knows what else.)

The health benefits of yogurt are quite unique. Its bacteria cultures (to be noted later in this article) assist in the digestive and gastrointestinal tracts, and they enhance overall immunity by attacking disease-promoting organisms throughout the body’s food trail. It is even suspected that some infections and pre-tumorous conditions may be killed by yogurt’s live bacteria.

In addition to the standard forms of yogurt common to Northern and Western Europe and North America, Mediterranean yogurt — most often from Grecian or Middle Eastern recipes — has become incredibly popular throughout the world at large.

Let’s take a closer look at these unique types of yogurt:

Greek Yogurt is manufactured in a manner akin to all “standard” yogurts, but with one major exception: After the yogurt mix is heated and inoculated (see below for details), it is strained. This straining allows for excess whey liquid to exit, leaving behind an ultra-thick yogurt product that has the consistency of sour cream.

Greek Tzatziki is often manufactured by plants that produce Greek yogurt. Tzatziki is a flavorful dip that is made from Greek yogurt, with added cucumbers and spices, always including garlic.

Since Greek yogurt contains more yogurt curd and less whey, its fat content is higher than than of other yogurts. This hightened fat content is responsible for Greek yogurt’s unmatched thickness and creaminess.

Labneh is a Middle Eastern yogurt-type product which is quite simialr to Greek yogurt, but is often somewhat thicker and is marketed as a soft cheese delicacy. (Labneh means “white”, referring to the product’s color.) Like Greek yogurt, labneh is strained in order to remove whey and obtain a thick texture; however, due to variances in bacterial cultures used and/or the duration of straining, labneh achieves a thickness even greater than that of Greek yogurt, to the extent that some chefs refer to labneh as “Lebanese cream cheese”. In fact, labneh has been traditionally strained to such an extreme in order that it could be made into balls and thereby preserved long-term for use when traveling.

Kefir is a yogurt-type beverage made by fermenting milk with kefir grains. These grains consist of yeast and bacteria, in an environment of sugars, proteins and lipids. Kefir production is said to have originated in the Caucusus region, and kefir has become most popular throughout Russia and nearby lands, from Eastern and North-Central Europe to Siberia. Although kefir is technically not yogurt, many yogurt producers manufacture kefir due to processing similarities.

Yogurt cheese and kefir cheese are created by extreme straining and pressing of yogurt and kefir, such that they can be molded into a cheese-type food.

Of all dairy products, yogurt is among the most complex in terms of its kosher requirements and proper supervision.

Basic Production

All yogurt begins with milk. The milk’s fat ratio may be adjusted by adding cream or non-fat dry milk. Afterwards, sugar or artificial sweetener may be added. Stabilizers — which create the desired consistency — are then batched into the yogurt mix. Then, the mix is usually pasteurized, subsequent to which it is dosed with acid-based dairy cultures (most commonly lactobacillus bulgaricus and streptococcus thermophilus), after which the cultured mass is left to incubate for a specific of time in closed yogurt vats.

Following incubation, fruit filling, flavors and even colorants may be added. The product is then filled into cups or tubs and is ready to go. (It is important to note that the only hot phase is pasteurization. The rest of the process is cold, ambient or warm.)

This all seems pretty straightforward. Why, then, did we make certification of yogurt out to be so complex?

Let’s go through some of the above steps again more carefully, this time from the perspective of a kosher certifier.


Milk is milk. No kosher problems here.

Cultures, however, are another story. Most dairy cultures are grown in labs that handle kosher and non-kosher materials beyond the imagination. Some cultures are grown on surfaces which are non-kosher, and some are nourished with non-kosher nutrients. Cultures are kosher only when their environments and nourishments are fully kosher. Thus, we are working with pretty sensitive issues.

Cream and non-fat dry milk, used to adjust yogurt fat ratios, are also kosher-sensitive. Some cream (called “whey cream”) can derive from whey, which is often non-kosher, and even regular cream (called “sweet cream”) frequently shares equipment used for non-kosher whey cream manufacture. Non-fat dry milk can be dried (changed from fluid milk to powder) in spray towers also used for processing non-kosher meats, cheeses, etc. Thus, proper kosher supervision for cream and non-fat dry milk is most certainly necessary!

When we get to stabilizers, we approach the most hazardous area of yogurt certification. The recent trend in the yogurt industry has been to increase the thickness of product, creating a “Swiss-style” consistency. The most common stabilizer to achieve this result is gelatin, most of which comes from the bones and hides of non-kosher animals. It is for this reason that many varieties of yogurt bear no kosher symbol or just feature a generic “K”, which is commonly used by some kosher agencies that permit the consumption of gelatin derived from non-kosher sources in kosher products. Most widely-accepted kosher agencies, however, will not certify such yogurts, due to the presence of non-kosher gelatin. Other non-kosher stabilizers contain a mix of gelatin and non-animal based substances. Stabilizers present in kosher-certified yogurt are exclusively starch-or-gum based. These stabilizers need proper kosher certification, as they can be processed on non-kosher equipment and can even contain trace amounts of gelatin, if not properly supervised.

Fruit fillings, flavors and colorants are often non-kosher. These items can contain carmine, which is red dye extracted from insects. Fillings utilize stabilizers, whose kosher-sensitivity is discussed above. Non-kosher grape derivatives are often present. Fillings and flavors can be produced on non-kosher equipment. Kosher status must obviously be verified.

Kosher Production

The first step in certifying the kosher status of yogurt is to ascertain that all ingredients are kosher. The next task is to determine if the plant also makes non-kosher product and — if so — to evaluate whether or not the plant can handle a kosher program in light of its non-kosher production. There are five categories of non-kosher issues: (1) batching, (2) pasteurization, (3) post-pasteurization, (4) formulas and (5) kosherization.

Batching: Dry stabilizers and dry or liquid sweeteners are batched into the milk mix which will form into yogurt. Ingredients must be assessed for kosher status upon batching. Often, ingredients which will later be present in the final product in miniscule quantities are batched at quite large ratios into a batch pre-mix, which will initially be added to a small amount of milk and then will be later fed into the entire yogurt mix. If any non-kosher ingredients are present in a batch pre-mix, they can render the entire batch non-kosher and even compromise the kosher status of equipment down the line.

Pasteurization: Every material that is pasteurized is — of course — exposed to hot equipment. Non-kosher ingredients that pass though a pasteurizer can render it non-kosher. Non-kosher ingredients used in uncertified yogurt can therefore make the yogurt plant’s pasteurizer and related equipment non-kosher, requiring kosherization after each non-kosher campaign.

Post-Pasteurization: Once we have assured that the pasteurization system is kosher for potential kosher-certified production, we need to see if there are any ramifications of non-kosher yogurt later on in the manufacturing process. Gelatin-based yogurt — as well as yogurt with non-kosher fruit fillings, colors or flavors — often shares the same incubation or storage tanks and fillers as kosher yogurt. This equipment must be reliably cleansed before it is used for kosher product, and tanks cannot hold kosher and non-kosher product for 24 hours or more, even though the use of all of this equipment is never at hot temperatures.

Formulas: When a plant processes non-kosher yogurt (or any other non-kosher product, in general), the kosher agency must carefully review formulas to verify that kosher yogurt utilizes only kosher ingredients. The more non-kosher production at a given plant, the more time and work will be required for the rabbinic field representative (RFR) to go through the books or computer records for formula review.

Kosherization: As noted above, non-kosher yogurt run through a pasteurization system can necessitate kosherization after it is processed. In this case, the kosher agency may work out a system by which the plant’s automated cleaning routine meets kosherization specifications. The RFR reviews charts generated by the CIP (cleaning in place) system to assure that necessary temperatures are reached and that required steps are always performed, and he verifies production and cleaning sequencing upon each visit as well. If the system is not automated and verified so as to accomplish a kosherization when cleaned, then an RFR must be present for each kosherization session.

We now have a better understanding of the various kosher issues that pertain to yogurt. Additives, stabilizers, cultures, flavors and equipment make yogurt into a complex product.

Complex…but delicious.

OU Kosher Staff