Acids in Digestion

Spring 2024

When my father z”l went to pharmacy school at George Washington University, his course of study had a heavy concentration of chemistry. His background in chemistry proved extremely useful in his forty-year career as an examiner in the U.S. Patent Office. On his workbench, he had shoe boxes with all his pharmacological paraphernalia: Bunsen burners, beakers, and little vials of litmus paper. As a child, I remember my fascination with watching the red litmus paper turn blue when dipped into a base and the blue litmus paper turn red when dipped into an acid. These were literal litmus tests, a term which over time has crept into everyday language to denote a means of determining an outcome.

Although the world of industrial kashrus may not require the deep analysis found in chemistry textbooks, it behooves kashrus administrators and mashgichim to have a working knowledge of chemical compositions and formulations. Solid knowledge of food chemistry and technical know-how is essential to arriving at the correct halachic conclusions.

To start our journey, we need to define some fundamental terms: acids, bases, and pH. Scientifically, an acid is a substance that can donate a hydrogen ion to another substance; a base is a substance that can accept a hydrogen ion. As taste descriptors, an acid is “tart or sour” while a base is “bitter and soapy.”

How does a litmus paper determine the acidity or baseness of a product? Incredibly, it is the acid or base itself which reacts with the dye in the paper. The natural blue dye turning red in the presence of an acid and the natural red dye turning blue in the presence of a base are caused by hydrogen exchange – hence, the name pH: potential of hydrogen. A pH of 1 through 6 indicates acidity, a pH of 7 is neutral, while a pH of 8 to 14 indicates a product is basic.

Potassium hydroxide is a good example of a base. As mentioned above, a base is soapy and bitter. Putting enough potassium hydroxide into water to raise the pH over 11 is a food grade davar hapogem according to STAR-K Rabbinic Administrator Rabbi Moshe Heinemann shlit”a. The benefit to food manufacturers is that it fulfills the requirements of pegima (off-taste) while not compromising the food grade properties of the water you are trying to make pogem (to bitter).

Acids play a fundamental role in the foods we eat. To flavor, to enhance, to preserve – acids can do it all. Let’s look at some of the fundamental food-grade acids.

Citric Acid

Citric acid is naturally found in citrus fruits such as oranges and lemons. It is an acidulant, meaning it either imparts a tart, acidic flavor or enhances the sweetness of foods. It is used in beverages, jams, jellies, canned tomatoes, confections and a plethora of other food applications. An acidulent aids digestion and the absorption of nutrients. Citric acid is used in the pre-washed vegetable industry to control the pH of the wash water and to control the growth of harmful bacteria.

Natural citric acid derived from lemon juice does not present any kashrus or Kosher for Passover (KFP) concerns. However, to produce citric acid in large quantities, commercial citric acid is produced using microbial fermentation using a fungus called Aspergillus niger, grown on a sugar culture. Most commercially produced citric acid is derived from corn, the predominant ingredient used in China, which is then dried into a crystallin powder. This does not present a kashrus concern for year-round use but is an issue for Pesach for those who do not use kitniyos shenishtanu.

Citric acid produced from sugar can be produced KFP without concern. On rare occasions, European citric acid is produced from a wheat media, which would render it unfit for Pesach.

Ascorbic Acid

Ascorbic acid, also known as vitamin C, is likewise found naturally in citrus fruits. It is not as acidic as citric acid and is used commercially to protect color changes in fruits such as sliced apples. Synthetic ascorbic acid is produced from glucose, which is generally derived from corn starch that has been broken down with the aid of enzymes, acetone and hydrochloric acid. Other starches can also be used as the source material. Ascorbic acid from tapioca starch is acceptable for Pesach, while wheat starch (obviously) is not.

Lactic Acid

The STAR-K Hotline often fields the query, “Is lactic acid milchig?” The word lactic throws a lot of people off. The truth is that commercially produced lactic acid is pareve even though it can be produced from lactose milk sugar. It is produced through the fermentation of glucose or sucrose, typically derived from corn. Again, if cane sugar were the starter material, lactic acid could be produced KFP; if produced from lactose, the lactic acid is considered dairy.

Fatty Acid

Fat is a word that strikes fear in the hearts of most diet-conscious consumers. Healthy fats, however, are necessary to maintain a healthy diet; the body breaks down dietary fats into fatty acids that provide the body with energy. Fatty acids are found in meats and vegetables. They have a myriad of applications in the cosmetic, pharmaceutical and food worlds.

One of the most well-known fatty acids is stearic acid. A synonym for meat stearic acid is tallow. One of the most popular uses of this ubiquitous fatty acid is in the world of candy and pill making as a release agent. As the name clearly suggests, a release agent ensures that the candy or caplet does not stick to the equipment.

One of my greatest challenges was to kasher the century-old Mallinckrodt calcium stearate plant in St. Louis, Missouri. The calcium was being produced from ground limestone. White powder and animal-based stearic acid dust covered every possible surface in the plant, which took me a full three weeks to convert from treif to kosher.

Tartaric Acid

During wine making, wine barrels accumulate a buildup of a crystal-like sediment known as veinshtein, which is a combination of tartaric and potassium bitartrate, or tartaric acid. When the sediment has dried for twelve months, it is ground into a white powder commercially known as cream of tartar. This is a unique halachic kashrus transformation, in which twelve-month-old non-kosher wine sediment is transformed into kosher cream of tartar – which can then be used in baking powder, jellies, carbonated beverages and leavening.

Acetic Acid

Acetic acid is a natural by-product of vinegar fermentation. It is the component that gives the vinegar its taste and aroma. Of course, the kashrus of vinegar depends on its starter material. The white vinegar purchased in your neighborhood market is produced from corn. Red wine vinegar and balsamic vinegar can be either very kosher or very non-kosher, depending on the source used to convert the wine to vinegar.

Glacial Acetic Acid

Glacial acetic acid is produced synthetically and is typically the KFP vinegar found in the Passover section of your supermarket. Vinegar is an extremely versatile staple in every balabusta’s kitchen (and laundry room).

It is truly fascinating to see Hashem’s handywork at play as tart acids and bitter bases pass through the litmus tests of halacha. I’m sure my father would agree.