Yogurt is a fermented milk product. While the pH of milk can range between 6 and 8, the fermentation process yogurt undergoes reduces the pH of yogurt to 4.3 or 4.4. Additional ingredients like citrus fruits and the duration of fermentation can make yogurt even more acidic.
Acidity and alkalinity are determined using pH. Since yogurt has a pH between 4.3 and 4.4, it is considered to be an acidic food.
What Is pH?
The term pH is used to define the acidity or alkalinity of a solution. The pH scale ranges from zero to 14. The strongest acid would have a pH of zero, while the most basic (also known as alkaline) items would have a pH of 14. Most foods have a pH between about 3 and 8.
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Anything with a pH of 7 is considered neutral. Water is an example of a neutral food, but since it can come from a variety of sources (from local springs to your kitchen tap), it's possible to have alkaline water or acidic water. Most water typically has a pH around 7, unless it's been treated to be more alkaline.
The majority of foods people consume have a pH that's less than 7. Foods with a pH between 6.9 and 4.6 are considered low acid foods, while those with a pH less than 4.6 are considered high-acid foods. Since yogurt has a pH between 4.3 and 4.4, it is considered a high-acid food.
The pH of Yogurt
Yogurt generally has a pH between 4.3 and 4.4, but this pH can change depending on the specifics of how the yogurt is made. Basically, yogurt is made by heating and cooling pasteurized milk, then culturing the milk with live bacteria. These bacteria have to include Lactobacillus bulgaricus and Streptococcus thermophilus, but may also include other healthy probiotic bacteria like:
- Bifidobacterium bifidum
- Bifidobacterium lactis
- Bifidobacterium longum
- Enterococcus faecium
- Lactobacillus acidophilus
- Lactobacillus bulgaricus
- Lactobacillus casei
- Lactobacillus gasseri
- Lactobacillus plantarum
- Saccharomyces boulardii
Adding bacteria to yogurt is typically the last major step in creating this food product. The fermentation step lasts between four and seven hours but may last longer. It is the duration of this step that determines the flavor of yogurt and its exact pH.
Fermentation of Yogurt
Yogurt that is allowed to ferment for shorter periods tends to have a naturally sweeter, milder flavor and a higher pH. This is why the pH of curd is higher than that of yogurt — it is fermented for a much shorter period of time. Most milk products fermented for shorter periods of time are considered to be low-acid foods or even "almost neutral" foods. In contrast, when yogurt is allowed to ferment for longer periods of time, it becomes increasingly sour in flavor and more acidic.
In order to stop the fermentation process from continuing, the temperature of yogurt must be changed. The bacteria in yogurt become dormant when cooled below 98 F (36.7 C). This prevents the yogurt from continuing to ferment but keeps the bacteria viable. Live, active, probiotic bacteria are good for your gastrointestinal tract.
Not all fermentation processes are stopped in the same way, though. Some yogurts are heat-treated afterward, which kills the bacteria instead. The National Yogurt Association has a Live and Active Cultures Seal that allows you to identify yogurt products that have retained healthy probiotic bacteria. Products with these seals have 100 million live cultures per gram unless they are frozen, in which case they have a minimum of 10 million live cultures per gram.
Alkaline Diets and Yogurt
The alkaline diet was originally designed to improve renal health, specifically preventing kidney stones and urine infections. It's also meant to promote a healthy blood pH, around 7.35 and 7.45, since blood is highly regulated by the kidneys. Alkaline diets may be beneficial as they can:
- Increase the pH of your urine
- Increase intracellular magnesium levels
- Increase vitamin D levels
- Improve the function of chemotherapeutic agents
- Improve potassium-sodium balance
- Reduce muscle wasting
- Improve bone health
- Help prevent cardiovascular diseases
According to a still-cited October 2011 study in the Journal of Environmental and Public Health, alkaline diets may also be able to improve the function of chemotherapeutic agents and improve the potassium-sodium balance. This balance can improve bone health, reduce muscle wasting and prevent cardiovascular diseases.
The benefits of this diet are not definitive, but alkaline diets are generally considered to be healthy for most people.
Yogurt and Healthy Diets
Although yogurt is technically a high-acid food, it is a recommended food for most people, including those consuming alkaline diets. This is because yogurt is generally considered to be less acidic than other animal proteins since it contains citrate from milk and lactate due to the fermentation process. Consumption of yogurt is even recommended for people who have chronic kidney disease.
The Dietary Guidelines for Americans recommends that most people who consume a 2,000 calorie diet ingest about 3 cups of dairy each day. Low-fat and fat-free dairy products like milk and yogurt are considered particularly healthy choices. Fermented food products like yogurt are even more beneficial for you, as probiotics are able to regulate various aspects of gastrointestinal function, like bowel movements.
Fermented foods and foods with probiotics can also help prevent various diseases, including cancer and bone diseases. They can also help manage problems like intestinal disorders and urinary infections, as well as maintain healthy cholesterol levels.
Milk Products and pH
If you're concerned about the pH of yogurt and its acidity, there are a variety of other healthy milk products that you can consume with a higher pH. The pH of milk on its own is between 6.2 and 7.3, and the pH of cream is around 6.5. Butter also has a higher pH that's much closer to neutral, ranging between 6.1 and 6.4.
- International Journal of Dairy Technology: "Chemical Composition of Naturally Fermented Buttermilk"
- Oklahoma State University: "The Importance of Food pH in Commercial Canning Operations"
- International Journal of Scientific and Research Publications: "The Evolution, Processing, Varieties and Health Benefits of Yogurt"
- Health.gov: "Dietary Guidelines for Americans 2015-2020"
- Journal of Renal Nutrition: "Reducing the Dietary Acid Load: How a More Alkaline Diet Benefits Patients With Chronic Kidney Disease"
- Journal of Environmental and Public Health: "The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health?"
- AboutYogurt.com: "Yogurt Varieties"
- Harvard Health Publishing: "The Benefits of Probiotics Bacteria"
- Colorado State University: "Food Source Information: Yogurt"
- Clemson University: "pH Values of Common Foods and Ingredients"
- Thermo Scientific: "pH of Yogurt (at Room and at Refrigeration Temperatures)"
- BMJ Open: "Systematic Review of the Association Between Dietary Acid Load, Alkaline Water and Cancer"