The mysteries of fermenting milk
Humans have been fermenting milk from different types of cattle since early farming began. The process of fermentation commenced with wild air-borne bacteria and yeasts, but very rapidly early farmers began the process of deliberating inoculating batches of milk to make specific foods and drinks.
Preserving milk to make things that could be eaten many months to years later was one key motivation for early farmers, but so too was the production of foods that could be easily digested.
One of the most important bacteria found in milk fermentation is lactic acid bacteria, or members of the genus Lactobacillus. These tiny rod shaped bacteria can grow prolifically in milk and, as they spread, they produce lactic acid. These lactic acid bacteria (LAB) also produce huge amounts of bioactive compounds, some of which may be important for human health.
Yoghurt and other fermented dairy products contain many unusual and complex compounds. Many of these products have only been discovered and characterised in the past decade with the development of new chemical analysis technologies. These compounds are produced by the metabolic activities of the LAB.
Not everything these bacteria produce is good for human health. The LAB produce some compounds known as biogenic amines (including tyramine and histamine) that can cause allergies, increase blood pressure and headaches. Cheese is one type of fermented milk product that contains high levels of these biogenic amines.
Interestingly, LAB bacteria break down some of the proteins in milk to generate a range of encrypted proteins. These proteins are encrypted as they are fragments of the much larger milk proteins that the LAB have started to break apart.
Increasing amounts of experimental research is demonstrating how important these encrypted proteins might be for health.
The range of encrypted proteins is very large, although several key functions have been identified. Some of the encrypted proteins help the LAB and are antimicrobial, so they act to reduce the growth of competing bacteria. In keeping down spoilage microorganisms these antimicrobial proteins can help preserve the fermented product for longer.
The benefits to humans also include that these antimicrobial proteins slow the growth of potentially harmful bacteria, including E. Coli that can cause severe diarrhoea.
The range of encrypted proteins also includes those that bind minerals including the trace metals zinc, iron and copper. When the minerals are bound to the binding encrypted protein, the ability of the human body to absorb these minerals is increased.
Encrypted proteins can also carry out antioxidant functions and can modulate the human immune system. More recently there has been discovery of encrypted peptides that can bind onto human opioid receptors. These new ‘nutropioids’ may hold future promise for developing new functional foods with stress-management benefits.
Yoghurt is the most common form of fermented dairy product consumed in western culture. Although crafted to deliver a sweetened snack, many of these yoghurts will contain the encrypted proteins that have been produced by the beneficial LAB.
It’s unlikely that the doses are high enough in any single yoghurt serve to deliver enough of these encrypted proteins to have a major effect on health. However, future functional yoghurts may be developed to provide health benefits by delivering higher levels of the encrypted protein.
Last Reviewed: 25/02/2020
Norman Swan Medical Communications
Pessione E and Cirrincione S. Bioactive molecules released in food by lactic acid bacteria: encrypted peptides and biogenic amines. Frontiers in Microbiology 2016;7: 876. Doi: 10.3389/fmicb.2016.00876.
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