A General Guide To Yoghurt

Introduction

Everyone should make their own yoghurt at least once, even if it seems far easier to just buy it. It almost always works, and it is an exciting thing to wake up to in the morning.

A Brief History

Yoghurt is a type of fermented milk. During the process, milk is soured by the bacterial production of lactic acid, which changes the protein structure, giving a smooth texture. Its name is derived from the Turkish Yoğurt and, with a history stretching back over thousands of years, it is one of the oldest and most prevalent fermented foods in the world. Its exact origins are unknown, but the birth of yoghurt was just waiting to happen. Without refrigeration, milk would frequently sour and separate into curds and whey. Presumably there were occasions when a particular batch of soured milk would taste better than others, and this would then be used to ‘seed’ another batch. Perhaps something fell into some warmed milk one day, and a delicious thickened yoghurt resulted.

Yoghurt.

Creamy yogurt being stirred with a ladle in a pot

In one of the earliest written records, Roman author Pliny the Elder wrote about certain barbarous nations, who ‘knew how to thicken the milk into a substance with an agreeable acidity’. It has been known since as early as 1700 that living microbes are present in raw milk and, by the end of the nineteenth century, LAB had been isolated by Louis Pasteur during his studies on wine spoilage. Their presence in the gut had also been verified In 1905, a type of Lactobacillus was isolated from yoghurt by Bulgarian researcher Stamen Grigorov, which became known as Lactobacillus bulgaricus.

Ilya Metchnikov, father of gut health. ADOBE

At the beginning of the twentieth century, Nobelprize winning scientist Ilya Metchnikov became particularly interested in the longevity of Bulgarian peasants. He had a theory that old age was an unnatural state, because of chronic intoxication by putrefactive bacteria in the gut. He made the link between the long life of the peasants and the L. bulgaricus microbes in the yoghurt they regularly consumed, suggesting that these good bacteria were preventing the putrefactive bacteria from prevailing.

Publishing his work in 1907, he made a great impact for a time, giving public presentations explaining that eating yoghurt could contribute to a long life. He consumed gallons of yoghurt himself, but sadly he did not live to a great age. He suffered a series of heart attacks and died in 1916, at the age of 71. On his deathbed, he is reputed to have suggested to a pathologist friend that he might like to examine his intestines carefully….

The production of yoghurt remained very much a home-based pursuit, until 1919, when a Greek Sephardic Jewish immigrant doctor, Isaac Carasso, based in Barcelona, began to be concerned about the poor digestive health of the local children. In Carasso’s view, the problems were due to a lack of hygiene. He knew of Ilya Metchnikov’s work and believed that yoghurt might strengthen the children’s bacterial flora and improve their resilience. He began production using original Bulgarian cultures, at a time when yoghurt was virtually unheard of in Western Europe. Initially, it was sold through pharmacies as a health tonic. Carasso named his brand ‘Danone’, or ‘Little Daniel’, after his son Daniel, who later took over the company, after training in microbiology at the Louis Pasteur institute in Paris.19

Today, the Turkish people have the highest annual average per capita consumption of yoghurt in the world, at 35 kilos per person. The UK manages a mere 12 kilos per person.20 Interestingly, consumption in Bulgaria has decreased over the years, and average life expectancy in that country is now one of the lowest in Europe. Do you know about harvest things? so firsly you have to learn more about preserving the best of the harvest.

The Health Benefits of Yoghurt

It is well known that consumption of live yoghurt (as opposed to yoghurt that has been heat-treated) improves lactose digestion and eliminates symptoms of lactose intolerance; the microbes responsible for making yoghurt generally produce high levels of the enzyme lactase.21 Reduction of gastrointestinal symptoms has also been recorded. Yoghurt bacteria have been recovered from human faeces, showing that survival through the GI tract is possible. Just as with kefir, there might also be an immunological role. In one randomized controlled trial, a year of live yoghurt consumption was found to decrease allergic symptoms.22 However, there is still some debate over whether all yoghurt starters can be considered to be probiotic, as health-giving properties could be specific to a particular strain. These days it is common for known probiotics to be added to yoghurt cultures.

All About Milk

Stirring fresh yogurt in a metal container with sunlight

Humans have been consuming milk for millennia as a wholesome source of proteins, fat and carbohydrates. Cow’s milk accounts for over 95% of all milk consumed worldwide, but it is not always all it seems: there are differences in nutritional value, depending on its origin. The most nutritious milk comes from animals that are fed their natural diet, and this does not include the grains used in factory feed. A recent paper by Newcastle University confirmed that organic, grass-fed dairy contained 50% more beneficial omega 3 fatty acids than conventional milk. This is important in the UK as the British diet is deficient in omega 3.23 It also has more conjugated linoleic acid, vitamin E, iron and carotenoids.

Cows producing organic milk must be fed predominantly on grass and reared outside most of the time. This is also ecologically advantageous, as they can nourish the soil with their own waste products. While it is possible to make yoghurt and kefir from conventionally farmed milk, it will often form weaker curds than milk produced by grass-fed cows, and may lack flavour. If you are going to the trouble of making your own yoghurt, it is worth choosing the best milk you can find.

Cow, Sheep and Goat. Adobe

Goat’s Milk

Goat’s milk is gaining popularity as there is evidence that it is less likely to induce allergies. It is much whiter than cow’s milk, forms softer curds, and has smaller fat globules that are well incorporated, so it does not form cream. It also has higher levels of available iron.24

Lactose Intolerance

When a human baby is born, it produces the enzyme lactase in the small intestine to break down lactose in its mother’s milk. As humans grow up, production of this enzyme stops in some people, leading to problems of lactose intolerance. However, about 90% of the UK population experiences lactase persistence, where mutations in a section of DNA that controls how the lactase enzyme is produced, allows them to keep on drinking milk into adulthood. Although adults rarely drink as much milk as children do, they often enjoy cheese and yoghurt, which contain reduced levels of lactose.

Sheep’s Milk

Sheep’s milk is almost always used for cheese in the UK and there are only a handful of suppliers. It is interesting that it is not popular for drinking as it has a milder flavour than goat’s milk, is rich in protein and does not seem to cause allergies.

Milk Alternatives

There are several reasons for the growing market in non-dairy milk alternatives, including growing self-diagnosis of lactose intolerance, increasing dairy allergies (for which there is some evidence), disenfranchisement with the dairy industry, environmental concerns and veganism.

There is a wide variety of ‘mylks’ (EU law prevents use of the word ‘milk’ for a product that does not come from a lactating mammal) available in supermarkets today, including soy, almond, hazelnut, oat, coconut, cashew, peanut, tiger nut, walnut, hemp, quinoa and pea. Most are heavily processed and fortified to at least in part replicate the nutritional benefits of milk. There is little research at the moment on the effects of substituting mylks for milk in western societies, which could be a concern, especially for children. The most nutritious substitutes for cow’s milk are soya and almond milk.

Raw Milk

Raw milk may be sold in England and Wales, but not in Scotland, at the farm, or at farmers’ markets, or from a milk float. Unpasteurized and untreated, it comes straight from cow to bottle. Because of this, it carries a risk of bacterial contamination, and occasional outbreaks have been recorded. Milk is thought to be sterile until it leaves the udder cells, but then sources of possible contamination include the teat apex, milking equipment, grass, soil and the environment of the milking shed. Raw milk may be nutritionally superior, retaining the LAB, enzymes and vitamins that are lost through pasteurization. Making kefir is a way of putting that goodness back (and more) into pasteurized milk.

Milk alternatives: almond, oat, hazelnut, rice and coconut. ADOBE

Nutrient comparison table for different milks and mylks so Read up on milk kefir.

PASTEURIZATION AND HOMOGENIZATION

In order to help keep milk fresh and safe, it is still today subjected to the process of pasteurization, developed by Louis Pasteur in the 1880s. Investigating ways of preventing the spoilage of wine by acetic acid bacteria, Pasteur found that, by heating the wine to a certain temperature for a fixed time, he could destroy the bacteria and spoilage enzymes without affecting the flavour. The process was later applied to milk. At the time, the aim was to destroy the causal agent of tuberculosis, but it was found to kill all manner of other human pathogens too. The incidence of food poisoning from milk these days is usually due to contamination at other points in the food chain post-pasteurization, or when the correct timings for the process are not observed.

Pasteurization does not kill all of the microbes in milk. A species called Paenibacillus not only survives the process, but is also capable of growing at low temperatures, which is why treated milk will eventually turn, even in the fridge.

After pasteurization, milk is often homogenized. This is a mechanical process by which fatty globules of cream are broken up into tiny pieces, too small to coagulate, so they do not float to the top of a cup of tea, for example. This does not apply to skimmed milk, which has had the cream removed already. Many people feel that homogenization improves the consistency of milk and it certainly makes lovely smooth kefir and yoghurt. Some have concerns that the altered globule configuration could have health implications, but these are unsubstantiated.

  • HOW YOGHURT FORMS
  • Milk Proteins
  • Milk contains two types of protein: casein and whey proteins. These exist in an approximate 4:1 ratio, and make up about a third of the milk’s content. They contain all nine essential amino acids that are required by humans.

Casein micelles make up about 80% of milk proteins.

Casein proteins include several different types, each with a different amino acid composition. They are loosely folded, with open structures. They coagulate at pH 4.6 and are suspended in milk in micelles – little globules that water can freely move in and out of. Caseins have a random coil structure and are not susceptible to denaturation (bonds breaking) upon heating. They are stable.25

The whey protein elements form a compact spherical shape, because of disulphide bonds that link amino acids together. Upon heating to just below boiling point, these bonds can be broken, leading to loss of compact structure and denaturation. This enables the proteins to hold more water, which improves the texture of yoghurt.

The milk sugar lactose is a disaccharide comprising glucose and galactose. During fermentation by LAB (usually in the low-oxygen environment they prefer), it is cleaved into its two components. Further processing results in the production of lactic acid and acetaldehyde, which flavours the milk, giving the sour, tart taste, and lowers the pH. The acidity affects the milk casein, causing it to coagulate and precipitate. Whey proteins are denatured by temperatures of about 90 degrees, which is helpful when trying to make yoghurt, as their structure then enables them to bind more water. It also increases the cross linking between the whey and casein micelles, increasing gel strength. This forms the yoghurt curd, which can be described as a gel or a soft solid.

Leave a Reply

Your email address will not be published. Required fields are marked *