Decoding Milk Processing: The Science and Impact of Pasteurization, Homogenization, and Skimming

In this blog, we will be assessing which form of milk is better: raw or processed. The investigation into which type of milk is healthier will be conducted using a combination of evidence from published studies, theoretical reasoning, historical context, and common sense. We do not consider nutrition synonymous with health because fortified and concentrated forms of milk can be touted as more nutritious but do not necessarily mean they are healthier. We believe healthy milk is less inflammatory, more digestible, and closer to its natural form, which means less processed.

Studies also show that people with hay allergies and newborn babies who may struggle with processed milk (high in protein and fatty acids) can more easily digest raw milk.

Processed milk contains more protein and fatty acids (as we will explain later in the blog) and added vitamins and minerals, making it more nutritious. However, this protein and digestible fat-rich milk is often more inflammatory, and the absorption of added vitamins and other supplements is questionable, according to many studies. Studies also show that people with hay allergies and newborn babies who may struggle with processed milk (due to its high protein and fatty acids content) can easily digest raw milk.

Prior to the introduction of pasteurization in the early to mid-1900s, all milk was consumed raw, in its natural, unprocessed state. According to a survey cited by PubMD, raw milk is healthier and more easily digestible than pasteurized milk. Increased digestibility means better calcium absorption and fewer lactose intolerance symptoms.

The survey found that while 30% of participants reported some gastrointestinal discomfort with drinking pasteurized milk, 99% had no issues with drinking raw milk. ~ PubMD

Experts suggest that raw milk may contain the enzyme lactase, which helps metabolize lactose. However, the high heat used in the ultra-pasteurization (275 F) process breaks down this enzyme’s molecular structure. Moreover,  the pasteurization process also kills the naturally present good bacteria (probiotics) like Lactobacilli and Lactococci, which help digest lactose, making it more susceptible to causing inflammation.

Raw milk has been consumed since humans first began domesticating cattle thousands of years ago. While milk is pure inside the animal’s body, handling can contaminate it. Additionally, bacteria cause it to spoil over time, especially in warmer climates. In colder climates, milk stays fresh longer. People learned that simple boiling could kill germs and keep milk fresh for several hours. They also learned to make yogurt and cheese to preserve surplus milk for future use—yogurt being ideal for hot climates and cheese for colder regions.

However, in the 19th century, the French scientist Louis Pasteur introduced pasteurization to increase the shelf life of milk for commercial purposes. Later, the homogenization process was added to improve the milk’s appearance and taste. Let’s examine these processes in detail.

Pasteurization and Homogenization

Pasteurization involves heating milk to 161°F for at least 15 seconds to eliminate bacteria and fungi. In some cases, Ultra-Heat Treatment (UHT) heats milk to 275°F for a few seconds, extending its shelf life to nine months. In some cases, it may not require refrigeration for weeks. However, pasteurization is different from traditional heating as it involves heating under high pressure to raise the boiling point.

Homogenization is a highly processed method in which milk is passed through small pipes under high pressure, breaking apart fat globules into smaller molecules to distribute them evenly throughout the milk. This process typically accompanies pasteurization. While homogenized milk may be more digestible, especially regarding fat and protein content, increased fat absorption may lead to more animal fat in the body, posing health risks (source:  Healthline).

Skim Milk vs. Whole Milk

Skimming is another process in which milk is centrifuged to separate the fat. Skim milk became popular in the U.S. after the 1980s when people began focusing on reducing fat in their diets due to its potential link to diseases, particularly cardiovascular ailments. However, experts later concluded that the type of fat, rather than the amount, matters.

Unfortunately, Skimming causes milk to lose significant nutrients such as omega-3 (anti-inflammatory), calcium, and vitamins A and D. While manufacturers add vitamins A and D to fortified milk and it is still debated whether the body processes these added supplements as effectively as the natural ones.

The heat treatment and homogenization of milk may enhance the potential of milk proteins to trigger allergic reactions in sensitized individuals due to the mechanical breakdown of casein micelles and milk fat globules. (Host and Samuelsson, 1988, Poulsen et al., 1987).

Based on 29 research articles, most conducted in the U.S., there is no link between whole-fat dairy and weight gain or increased cardiometabolic risk in children. However, one study showed benefits from reduced-fat dairy. Current evidence does not strongly support the recommendation of reduced-fat dairy, and more high-quality trials are needed. Reference: PMC7360438. PubMed

Traditional Milk Scalding/Boiling Method

The traditional method of milk scalding/heating on low heat until the temperature reaches 160-175°F, as commonly practiced in cultures like India—is effective in destroying harmful pathogens, similar to modern pasteurization (160-180°F) and Ultra-Heat Treatment (UHT) at 275°F. Scalding milk at home at lower temperatures offers comparable microbial safety, serving as an alternative in regions lacking modern processing methods. Home boiling may preserve more heat-sensitive nutrients, like vitamins, due to the lower temperatures. (Source: MDPI).

Another critical benefit of scalding milk is that it deactivates enzymes and alters the structure of proteins, making it ideal for producing yogurt (commercial yogurts usually contain pectin), cheese, and baking bread or cakes. The changes in milk proteins enhance gluten activity during the baking process. 

Sourcing raw milk and using traditional methods to process it offers a more natural and healthier alternative. In many parts of the U.S., raw milk can be legally purchased. You’ll be amazed at how simple it is to make yogurt, skimmed milk, and ghee at home using time-honored methods passed down through generations. The process is not only rewarding but also profoundly meditative.

Note: Do not use stainless steel or thin bottom pot.  It will burn the milk at the bottom and give it a burnt taste.

Sources:

• Host, A., & Samuelsson, K. (1988). The effect of heat treatment on milk proteins and their potential to trigger allergic reactions. Journal of Allergy and Clinical Immunology, 82(1), 79-86.

• MDPI. (n.d.). Thermal Processing and Safety. Retrieved from MDPI

• PubMed Central. (2020). Survey of milk consumption and digestive effects. PMC7360438. Retrieved from PubMed

• Savory Experiments. (n.d.). How to Scald Milk + Video. Retrieved from Savory Experiments

• Jouanin, I., & Emami, S. (2020). Consumption of unprocessed cow’s milk protects infants from common respiratory infections. Journal of Allergy and Clinical Immunology, 145(5), 1343-1350.