Milk has a neutral flavour and plays an important roll in the preparation of a great many dishes. Among other things milk can be used in the following preparations:
- In the preparation of batters for pancakes, waffles or beignets
- In sauces, for example béchamel sauce
- In soups
- In vegetable dishes such as pommes gratin
- In sweets such as custard (crème anglaise), flans, mousses and bavarois
- In the preparation of ice cream
- For drinking
In the preparation of certain meat dishes, milk is also used. For example the recipe for ‘rôti de porc au lait’ (roast pork with milk).
Milk can also be used for:
- Keeping vegetables and liver white
- Salt reduction for example with anchovy fillets (the fillets are steeped in milk)
Milk occupies among foods an almost unique position in that it is a substance specifically designed to satisfy the nutritive demands of rapid growth. Milk is therefore essential for children. A hundred grams of raw, unprocessed milk contains:
- 88 grams of water
- 3.4 grams of protein
- 4,3 grams of fat
- 4.4 grams of carbohydrate
As well as this, raw milk includes minerals such as calcium (an important mineral for teeth and bones), phosphorous, and the vitamins A and B- carotene (especially in the springtime), vitamins B1, B2, B6 and vitamins E, D and K. Proteins are in the form of casein (80%) and whey proteins (20%). Carbohydrate is present in the form of lactose or milk sugar, which gives the nice flavour to milk.
What happens to the proteins in milk?
As stated above, the proteins in raw milk are casein and whey. Casein is bound to the milk in the phosphor present. This bonding is broken if the casein comes into contact with acid or alcohol. This is the reason that tomato soup can sometimes curdle when cream is added. Since the tomatoes contain natural acids, the phosphor-casein binding is broken and the casein proteins are separated across the soup. The soup is then known to be curdled or separated. This separation in the soup does not affect the flavour but it looks a lot less appetising. It can however be avoided by adding the milk or milk product (cream perhaps) at room temperature.
In situations where the casein proteins encourage curdling, the whey proteins work in a completely opposite way – they avoid curdling. Only at high temperatures such as in cheese making will the whey proteins curdle.
When milk is being purchased, attention should be made to the following points:
- The type of milk or milk product being purchased
- The physical condition of the milk or milk product
- The quality hallmarks of the various types of milk and milk products
- The price of the various types of milk and milk products
- The types of milk and milk products available
A lot of cow milk is processed into other dairy products. Other types of milk such as goat and sheep milk are less widely used in the kitchen although in recent years there has been a big increase in the use of especially goats’ cheese. However in the rest of this chapter when milk is mentioned, it should be taken to mean ‘cow milk’.
Before going on to discuss the various milk products available it is important to understand the processes that raw milk undergo from the time fresh milk arrives at the milk factory or creamery to the moment that milk is purchased. The processes determine the flavour of the milk, the fat percentage and/or the storage life of the milk or milk product.
The following are a list of processes that milk can undergo:
- UHT (Ultra high treatment)
Standardisation is the first processing step whereby the various milk types such as full milk, skimmed milk and semi skimmed milk are brought to their minimum or maximum legal fat levels according to the Food Standards Agency for Milk and Dairy Products.
After standardisation, before pasteurisation it is clarified to remove any foreign matters. It is then heated to kill any harmful bacteria and to lengthen its’ storage life.
There are three types of heating processes:
- Ultra high treatment
During pasteurisation the milk is heated to a temperature of 78º C and then quickly cooled. The aim is to kill the dangerous micro organisms and to increase the storage life of milk. From a health point, the milk is then ready for consumption.
Pasteurisation is the most commonly used heat treatment method for fresh market milk. It is applied to a product with the aim of avoiding public health hazards arising from pathogenic bacteria in the milk. The level of heat treatment is determined by the need to reduce harmful micro organisms to a level, which does not constitute a significant health risk. In addition, the level of chemical, physical and sensory changes in the milk must be minimised.
Why is the bacteria percentage important?
The higher the temperature that the milk has been heated to, the fewer the active bacteria. The fewer the bacteria, the longer the milk will stay fresh. In the preparation of milkshakes or pancake batter, it is essential that the bacterial levels are very low. If the percentage of bacterial is high, gas forming can take place in batter and it will very quickly turn rancid. In such a case, the milk should be boiled extra. Milkshakes can quickly have a high bacteria percentage anyway, so it is very important to use only milk with very few active bacteria when starting off preparation.
Sterilisation is a process whereby the milk is heated to a temperature of 110º C. Harmful bacteria and spores in the milk are killed at this heat. Sterilised milk has therefore a much longer shelf life. The heating process results in the milk sugars being caramelised and the milk having an unusual flavour and a darker colour.
d. Ultra high temperature (UHT)
Ultra high temperature milk is heated to a temperature of 142º C, even higher than the sterilisation temperature. The aim is similar to sterilisation that is improving the shelf life of the milk by killing off harmful bacterial and spores in the milk. It is however heated for a shorter period of time and therefore the sugars are not affected in the same way (they do not caramelise) and the colour is whiter than sterilised milk.
The aim of homogenisation of milk is to reduce the size of the milk fat globules in the milk and to give it a more homogenous structure. The milk is pushed under pressure through very small holes. In non-homogenised milk the fat floats to the surface. By reducing the size of the globules of fat, the fat is distributed evenly through the milk, so separation does not occur.
By condensing or evaporating the standardised milk, it becomes thicker as much of the water is evaporated off. The condensed milk is then sterilised. The high temperature combined with a higher sugar concentration browns the sugars to give the concentrated milk a particular nutty, caramel flavour. For sweet concentrated milk, extra sugar is added. In this type of environment, micro organisms cannot survive. Sweet concentrated milk is therefore for this reason not sterilised.
Drying is a technique whereby the slightly thickened standardised milk is heated with hot air to a temperature of 180 – 230 º C. This results in all the moisture being removed from the milk, while all the other properties remain in the form of powder. The remaining powder is called spray powder, which is used as a basic ingredient for making custards, puddings and ice creams, particularly for industrial kitchens.
Now that the various processes of raw milk have been discussed in a little detail, it can be said that milk and milk products are available for purchase in four ways:
- As milk and milk products with a short shelf life
- As milk and milk products with a long storage life
- As milk and milk products which are acidified
- As dried milk products
Milk and milk products with a short storage/shelf life
These are products that come on the market pasteurised. These include pasteurised full-fat milk and skimmed/semi skimmed milk and pasteurised custards and puddings.
Milk and milk products with a long storage life
These are products that come on the marked sterilised and /or condensed or evaporated. These include sterilised milk or evaporated coffee milk.
Acidified milk and milk products
These are products that are produced by the addition of a culture to pasteurised milk. A culture consists of bacteria that the milk sugars have converted to acids.
Dried milk products
These are products which have been relieved of all their moisture by the drying process. These include skimmed milk powders.
72-78°C, 15-40 sec
4-7 days at <8°C
135-150°C, 4-20 sec
6 months at a suitable temperature
110-120°C, 10-40 minutes
9 months at a suitable temperatures
Average Annual Milk Consumption in Europe: total 30 billion litres
Insert table consumption
- pasteurized: 42%
- UHT: 54%
- Sterilized: 4%
- The physical condition of the milk or the milk products
Milk and milk products are available in the following consistencies:
- Semi liquid
They are always purchased pre-packed.
Pasteurised and sterilised milk types are liquid. They are not thickened or bound by binding agents or emulsions.
- Semi fluid
Custards, to which flavourings and thickening agents have been added, are semi fluid. This group also includes yoghurt, which have been thickened with lactic acid bacteria. Bulgarian yoghurt is thickened with milk powder.
A dried milk product such as dried milk powder is milk which has all the moisture removed by an evaporation process.
3. The quality hallmarks of the various types of milk and milk products
It is very important that milk products be clearly labelled. The packaging must be undamaged and the contents clearly marked with regard to the composition and the use by date. The product regulations are stated in the Food Standards Agency for Agricultural quality regulations.
An indication on the packaging stating that the milk is pasteurised is only allowed if the following points have been adhered to:
- The number of living micro organisms, the germ content, may not be higher than 50,000 per millilitre and in cream not more than 200,000 per millilitre.
- Living coli-types of bacteria should not be present in 1 millilitre
- Phosphates should not be present
An indication on the packaging stating that the milk is sterilised is only allowed if the product has undergone the following:
- A heat process to kill harmful bacteria
- It has been airtight packaged, at the point of sterilisation
- Controlled at a temperature of 30º C, in the original packaging that there are no more than 100 micro organisms per millilitre
The price of the various types of milk and milk products
The price paid for milk and milk products is dependent on a number of factors. Fat products are more expensive than those with little fat or no fat. Products where extra ingredients have been added are more expensive than those where nothing has been added. The type and size of packaging also plays a part. Boxes or crates with more products are often cheaper than individual products. The price paid for milk is also dependent on the use it is put to in the kitchen. Obviously a product that is sold well can be bought in larger (therefore cheaper) quantities than if it is not a good seller. However, thought should be given to the shelf life of milk. It is often better to have a good regular supply of fresh dairy products.
In this paragraph several aspects will be discussed:
- The transport
- The delivery
- The storage
- The use
There are three golden rules for the handling of milk and milk products in the kitchen.
- The transport
Golden rule 1: Do not break the cooling chain
From the cow to the user, milk is kept cool at a temperature of 4º C and is handled as hygienically as possible. It is important not to break this cool-hygienic chain and to place milk in the fridge or cooling as quickly as possible.
- The delivery
When milk is delivered, attention should be paid to the following:
- The type of milk delivered matches the milk ordered
- The amount of milk delivered matches the milk ordered
- The quality of the milk delivered matches the milk ordered
- The storage
Pasteurised and sterilised milk and milk products are packaged in various types of material from carton to synthetic materials and in sizes varying from one or several litres to 1/8th of a litre. Glass bottles have been almost replaced in recent years though there are environmental groups who would like returnable bottles to be re-introduced.
As well as smaller packaging there is also bulk packaging of milk available, dispensers of 18 litres for milk and buttermilk. Bulk packaging for cream, yoghurt and custard types in dispensers of 10 litres, mainly used in industrial kitchens. Desserts are available in packaging from 150 millilitres.
When milk and milk products must be stored, attention should be paid to the following points:
- Store pasteurised products cool and dark at a temperature of 2-4º C. Take careful note of the use by date.
- Sterilised milk packed in containers which allow light through, need not be stored in the fridge but in a dark store. Sterilised milk can be stored for a year. Again note should be made of the use by date, as the flavour will decrease after this date. Open containers must be stored in the fridge at a temperature of 2-4º C,
- UHT milk can be stored un-cooled for about three months.
- Acidified milk products must be stored cool and dark. Under ideal conditions they can be stored for about 7 days at a temperature of 2 - 4º C.
- Milk powder can be stored for about a year, un-cooled in a dry and dark store. Fat milk powder has a shorter shelf life than skimmed milk powder.
Short storage life means three to five days as long as the packaging is kept closed and the temperature a maximum of 4º C.
Long storage life of milk and milk products, sterilised and / or condensed or evaporated, means that the products will remain fresh in closed packaging for at least six months.
Golden rule 2: Store properly
- Do not store opened containers in the vicinity of products with strong smells such as fruit, onions, coffee, fish or fish products. Milk has the ability to absorb the flavour and smell of other products.
- Close opened containers properly. Irrespective of the use, milk and milk products should be stored cold and dark after opening. Depending on the type of product, they should be used between two and seven days.
Golden rule 3: Watch out for signs of decay
In general milk and milk products decrease in quality when stored.
- Yoghurt, buttermilk and other acidified products can begin to turn sour if stored too long. The product becomes bitter and acid and moisture separates to the top of the product.
- Milk products made from fruit, sugars and/or thickening agents can ferment. Fermented products can be recognised by the light tingling feeling on the tongue.
- Fungus forming or protein splitting can take place.
- Under the influence of light, fats can oxidise causing the milk to have a rancid flavour. This is not so common nowadays as the packaging is light proof
4. The uses
Milk is a product that is used in a great many different ways. However before using milk it is important to take a look at the properties of it.
- Milk has a high fat content and fat is a good flavour distributor. This is one of the reasons that milk or cream is such a good product in bringing the flavour of a dish to the forefront but also to reduce strong flavours and odours.
- Milk contains milk sugars. Milk sugars have the tendency to caramelise when heated. For this reason milk is used with products that do not colour naturally when heated to give them a nice brown crust. Fish is often dipped in milk, flour and seasoning before frying.
- Milk can also be used to lighten products that would normally discolour quickly. When boiling salsify or mushrooms a little milk will ensure that they stay white.
When boiling milk, care should be taken that it does not boil over and burn. If protein particles stick to the bottom of the pan and burn, the milk is ‘burnt’. The milk becomes unpleasant in flavour and aroma and cannot be use. The lower the fat content of the milk, the easier it is to burn as the milk fat has a sort of protective function. This is a reason why full milk cannot always be substituted for semi-skimmed or skimmed milk in a recipe.
Burning milk can be avoided by:
- Using a pan with a thick bottom
- Heating the milk slowly
- Bringing the milk to the boil by stirring with a wooden spoon or a milk whisk
Milk will not boil over if it is removed from the heat or the heat simply turned off the minute it begins to increase in volume.
There are various types of milk products:
- Cream types
- Sweet milk products
- Acidified milk products
1. Cream types
Cream is a collective name for products that contain no other fat than milk fat. The fat is separated and removed from the milk in a special centrifuge. Among other things this separated fat is used for making butter.
The following types of cream will be discussed in this paragraph:
- Whipping cream
- Coffee cream
- Single cream
- Sour cream
- Chefs cream, diet cream
- Clotted cream
- Whipping cream
Whipping cream is a very important ingredient in any kitchen. It is used in many dishes or as garnish with various sweets such as:
- Ice cream dishes
Whipping cream is a lighter version of double cream which contains at least 35% fat (double cream 48% fat). It whips up very well without being as rich as double cream.
Whipping cream is available both pasteurised and sterilised.
It is possible that cream can be difficult to whip. This can be caused by:
- The temperature being too high
- The cream is not sufficiently ripened
- The cream has not been homogenised properly
- The cream is from a particular type of grassland
Cream can be whipped in three ways: thick pouring, half whipped and fully whipped. The chance that cream will curdle in warm dishes is quite small.
- Coffee cream
Coffee cream is a product with a fat content of at least 20%, but less than 35%. Like single cream, it is homogenised and sterilised in the creamery and has therefore a long shelf life.
Coffee cream is used not only for coffee but also for finishing off soups and sauces. If coffee cream is added to very hot coffee and/or hot dishes, it can curdle. The curdling can be caused by:
- An instable salt balance of the coffee cream/single cream
- The cream not being homogenised properly in the factory
- Too high acidity of the cream
According to the Food Standards Agency, the wording ‘coffee creamer’ can be replaced with kitchen cream. It cannot be whipped.
c. Single cream (sometimes known as half-cream)
Single cream is a product with a milk fat percentage of at least 10% but less than 20%/ This product is homogenised and sterilised and is therefore a long storing commodity. Single cream is used as coffee cream.
d. Soured cream
Soured cream is a cream that has been fermented by a culture similar to that of yoghurt. This is a natural process and occurs after 2-3 days. It is due to the lactic acid bacterial constituents of the cream itself.
Sour cream is divided into three groups:
- Soured half cream
- Soured cream
- Soured whipped cream or crème fraiche
e. Chefs’ cream or diet cream
These products must contain a fat percentage of minimal 25%. Thickening agents and emulsions are added. In principle they are not really dairy products but since they are used more and more nowadays, they have been included in this section.
f. Clotted cream
Clotted cream is a traditional English cream. It has a very high fat content of 55% butterfat. It is made by heating cream to evaporate some of the liquids – it is concentrated. It has a pale yellow colour and is used in England to serve with scones and jam.
2. Sweet milk products
There are an enormous number of sweet milk products nowadays. They are available in many flavours and with a great variety of fat contents. They are available both sterilised and pasteurised and in many different types of packaging.
- Custard is made with buttermilk or milk, a binding agent and sugar: aroma, flavourings and colourings are added. It is available in full-milk or skimmed milk versions.
- Porridge is prepared similarly to custards. The binding agent is wheat, oats, rice, barley or semolina. It is available in full-milk or skimmed milk versions.
- Puddings are made similarly to custard but with different binding agents.
Since sweet milk products are not used so much in professional kitchens, the following is just a quick look at the preparation steps.
- The milk is standardised
- The milk is pasteurised
- The other ingredients are mixed with the milk
- The mixture is pre-heated
- The mixture is homogenised
- It is then either pasteurised or sterilised
- It is quickly cooled down and transported in a sterile manner, fresh.
The last procedure is also known as aseptic packaging since there is no chance of later contamination with micro organisms. There are many varieties of custards made in this way such as chocolate, vanilla, barley, semolina, chipolata and so forth.
3.Acidified milk products
The following acidified milk products will be discussed:
- Quark or fresh cheese
Kefir is a fermented dairy product something like yoghurt. Kefir culture is unique among fermented milk starters in that it is composed of a mixture of friendly bacteria and yeasts that harmoniously co-exist. The microbes break down the lactose in milk and the other chemical components, contributing to the taste and transformation of milk to kefir.
Kefir is a milk product with a fat content of 0.3 – 3,5%. According to the Food Standards Agency there is a distinction between:
- Skimmed kefir with a fat percentage of maximum 0,3%
- Semi skimmed kefir with a fat percentage of minimal 1.5% and maximal 1.8%
- Kefir with a fat percentage of at least 3.5%
Kefir can be made in two different ways:
- Via the direct method. Lactic acid bacteria and yeast is added to the milk. The flavour is slightly sour and prickles.
- Via the indirect method. Lactic acid bacterial and yeast are added to a minimum amount of milk. The milk particles clot together. This culture is then added to a larger amount of milk. The kefir produced, is softer in flavour and less prickly.
Buttermilk used to be a by-product of butter making, hence its name. Adding a culture to skimmed milk makes nowadays specially cultured buttermilk. It has the same acidic flavour as the original and is perfect for making extra-light scones, soda bread and American style pancakes.
Most commercial buttermilk is made by adding a lactic acid bacteria culture (a flora of Streptococcus lactic, Streptococcus diacetilactis and Betacoccus cremoris) to pasteurised whole milk or more commonly skimmed milk. It may or may not have added butter flecks.
After the addition of the culture, the milk is left to ferment for 12 to 14 hours at a low temperature.
Buttermilk contains 0.4 – 1% fat and will curdle at high temperatures.
The milk used in the preparation of yoghurt is homogenised and pasteurised at a temperature around 80 - 90º C and cooled back to a temperature of 31 - 32º C. At this temperature a yoghurt culture is added from two types of thermophilic lactic acid bacteria, the Streptococcus thermophilus and Lactobacillus bulgaricus. After ripening and regular stirring in a tank for 16 hours, the yoghurt is filled into containers and cooled. This product is called stirred yoghurt. It is thick but can still be poured. It has a limited shelf life. Depending on the standardisation of the milk, yoghurt can be full, skimmed or semi skimmed.
Whole milk yoghurt contains 3,4% fat, low-fat yoghurt contains 1-2%fat and diet, virtually fat-free yoghurt contains 0.2% fat.
Set yoghurt ripens in its containers or packaging. For the preparation of this product a culture is added to thickened milk at a temperature of 45º C. It is then filled into containers. After about 2 hours at 45º C the yoghurt is cooled down. The end product is thick, not easily poured and more acidic than stirred yoghurt. It is easily recognisable by its flat surface with a thick skin on top.
Bulgarian (or thick) yoghurt is made from milk that is thickened to 2/3 of its volume. Skimmed milk powder is added to this to increase the percentage of milk components. Bulgarian yoghurt has a limited shelf life.
There are also Bulgarian yoghurts on the market mixed with fruit or fruit pulp, sugar and other additives. Due to a special heating process, they are able to be stored longer
Greek yoghurt is yoghurt made from cows’ or sheep’s milk, which is boiled in open vats so that its liquid content is reduced. The result is a much thicker consistency giving more concentrated yoghurt with a fat content of 8 – 10%.
Low –fat Greek yoghurt is also available nowadays. This is a very useful ingredient in cooking since it can replace some of the cream when the aim is to lighten dairy desserts.
Umer is sometimes confused with yoghurt. It is made from thickened semi-skimmed milk whereby a concentrate of certain materials such as proteins, calcium and minerals are produced.
Umer can be whisked and is a good alternative to full yoghurt.
Drinking yoghurts are also available with various fruit flavours. They must contain at least 70% milk and at least 4% fruit juice. They have a short shelf life.
A few examples of yoghurt types:
- Yoghurt with standardised milk with a fat content of 2,95 – 4.4%
- Semi-skimmed yoghurt with a fat content of at least 1,5 % and no higher than 1,8%
- Skimmed yoghurt with a fat content of no higher than 0,5%
- Bulgarian yoghurt, made with thickened milk and fat content of at least 4.4%
- Skimmed Bulgarian yoghurt with a fat content of no higher than 0,5%
Beograd is a similar product to yoghurt but legally may not be called yoghurt. The culture that is used to make biogarde is different from yoghurt. This other culture ensures that biogarde is different to yoghurt because of the amount of dextrorotary lactic acid. This is the reason that biogarde products are softer and less bitter than the yoghurt cultures.
Dextrorotary and Levorotary Lactic Acids
Lactic acid bacteria or yoghurt bacteria make Dextrorotary and Levorotary Lactic Acids.
If these lactic acids are required in the body, Lactobacillus acidophilus or Lactobacillus bifidus can be taken in certain foods. This is thought to prevent and sometimes cure intestinal disorders, to protect the intestines from harmful microbes and toxins and to reduce allergic reactions. In the human body there is an enzyme that breaks down the dextrorotary lactic acids. For the levorotary lactic acid there is no specific enzyme, it therefore circulates longer in the blood but is in the end broken off. Some people see a low pH (acid content) of the blood as undesirable. Scientifically there is no definite proof that dextrorotary acids are better absorbed in the body.
Nowadays there is an extensive choice of these products, for example fermented milk and yoghurt drinks to which lactic acid bacterial has been added. The consistency and flavour vary considerably.
- Quark or fresh cheese
The beginning of all cheeses is a soft cheese called Quark in Germany, which is nothing but thickened milk. This thickening is caused by acidification (fermentation) with the help of milk bacteria. In this fermentation process the milk bacteria converts the lactose (milk sugar) into lactic acid (milk acid). Since most milk nowadays has been pasteurised, and all bacteria have been killed, the right bacteria must be added back into the milk by inoculating it with a starter culture.
Quark is, unlike cheese, not pickled or ripened.
The curds can be mixed with salt, herbs or fruit.
Depending on the amount of milk fat content, quark will be labelled:
- Cream quark with fat content in the dry materials of at least 50%
- Full quark with a fat content in the dry materials of at least 35% but less than 50%
- Semi skimmed quark with a fat content in the dry materials of at least 10% but less than 35%
- Skimmed quark with a fat content in the dry materials of less than 10%
Imitation products are made with other components than that of milk. Included in this group of products are:
- Diet products. These are made from evaporated, sterilised milk which has had the fat removed to 0.1% and to which 4 – 7% corn oil has been added
- Coffee whiteners or creamers
- Toppings or imitation cream powder
The last two groups are made from vegetable fats, mainly from coconut components and milk proteins.