Dairy

Cows' milk

Cows' milk is by far the most commonly consumed milk in Britain. Fresh milk will keep for 3-5 days, once opened, in the fridge. 'Long-life' (or UHT, which stands for 'ultra heat treated') is milk that has been heated at a high temperature (135C for one second) to destroy all bacteria in it. It lasts much longer than fresh milk (several months) but cooks should only use UHT milk if they really have to, because it has a peculiar flavour that may mar your finished dish.

Milk scorches easily if heated to a high temperature. To reduce the likelihood of scorching, wet the bottom of the milk pan first. The water will help stop adhesion and minimise scalding. Milk forms a 'skin' when heated which, annoyingly, is impossible to stir back in once it's formed. To help prevent a skin forming, heat milk at the last possible moment, or whisk the surface to a light foam when heating.

Whole milk has a fat content of 3.9 per cent. It's deal for making white sauces, including the kitchen essential, béchamel. Add whole milk to vegetable soups and chowders for smoothness without too much richness.

Semi-skimmed milk has a fat content of 1.7 per cent co it's useful for people following a lower-fat diet. It can generally be substituted for whole milk in most recipes because it still has some creaminess. Skimmed milk has a fat content of 0.3 per cent. It lacks the creamy texture of whole milk and shouldn't be considered as an alternative to whole milk in baking and cooking, particularly in recipes that specify 'whole milk'.

Buttermilk is becoming more widely available in the UK. Traditionally it's a by-product of butter-making. These days, what's sold as 'buttermilk' is usually a cultured skimmed milk with a similar acidic quality. It's traditionally used in American-style pancakes and is great for making scones and breads, giving a pleasantly acidic 'bite'.

Don't confuse 'condensed milk' and 'evaporated milk'. Although both are made by heating milk in a partial vacuum to remove much of the water, condensed milk is usually sweetened at the end of production, so read the label before substituting. Condensed milk is great for homemade fudge or toffee. Use evaporated milk in making rich, creamy puddings.

Goats' and sheep's milk

Goats' and sheep's milk are a useful alternatives for people who have an intolerance to cows' milk. Both are becoming more widely available and can be found in many supermarkets and in health food shops. Goats' milk has a similar fat content to whole cows' milk, but sheep's milk has a higher fat content, of about 7.5 per cent.

You can also buy sheep's milk and goats' milk cream in some supermarkets and in health food stores. Use these instead of cow's milk in sauces and in baking. If you chill them well, they will whip, but look for creams with the highest fat content you can if that's what you're planning to do.

Dairy-free alternatives

If you're not able or choose not to eat dairy products, there are plenty of options to choose from that are completely dairy-free. Soya milk is probably the most versatile (and it's also very nutritious). It's made from soya beans and has a texture that's very similar to cows' milk, although many brands of soya milk can have a slightly sweet or bitter edge. Try a number of brands to find one that suits your taste and your needs. You can use soya milk as a straight substitution for cows' milks in recipes. Most supermarkets sell soya milk; otherwise look in health food stores.

As well as soya milk, there are other non-dairy alternatives, such as oat milk, almond milk and rice milk, which are available in some supermarkets and in health food stores. These tend to work better with sweet dishes than with savoury. Again, each brand tastes different, so do experiment.

Coconut milk can be substituted for cows' milk in some recipes, where it can add its own distinctive sweet flavour. Its flavour won't work in every recipe, though, so choose your recipe carefully.

Cream

Cream is the ultimate texture food - the word itself conjures up images of smooth velvety richness. Cream is the basis or the crowning glory of innumerable desserts from panna cotta to cream cakes and adds richness and depth to creamy stews and pasta dishes. Fat content is the key to learning how best to cook with cream. Types of cream with higher fat contents are more 'stable', are easier to whip and are less likely to curdle when cooking.

Single cream has too low a fat content (18 per cent) for whipping, but is useful as a topping for desserts or enriching soups, savoury dishes or sauces. Be careful when adding it to hot dishes (let the dish cool slightly first) and don't allow it to boil as this will cause it to curdle.

Whipping cream has a fat content of 38 per cent. As its name suggests, it whips well (to twice its original volume - although it will separate after a time) and isn't overpoweringly rich, so consider it as a lighter alternative to double cream in cooking. You can pipe sweetened whipped cream onto cold desserts such as trifle and fold it into mousses or puddings for a light texture.

Double cream has a fat content of 48 per cent. It can be spooned over desserts, to give richness to puddings and sweets and gives texture and richness to sauces. It can also be whipped and piped or used as a topping. Be careful when whipping double cream. It can quickly be over-whipped and start to turn to butter. Chill the cream and the bowl first and whip by hand.

Clotted cream is famously rich and thick, with a creamy-yellow colour and a fat content of 55 per cent. It's a must on scones, and is often served on top of ice cream in Devon and Cornwall (where it's a speciality).

Creme fraiche (39 per cent fat) is cream that has been treated with a culture that gives it a slight acidity. It's long been indispensable in French kitchens and is becoming more popular in Britain as an accompaniment to desserts or used in savoury dishes. It adds a welcome piquancy to casseroles, sauces and dips. It's great for cooking as it doesn't curdle easily.

Soured cream (18 per cent fat) is a single cream that's been soured using an added culture (similar to that in yoghurt); it's delicious spooned onto baked potatoes and is used to enrich and add an edge to soups and stews, such as goulash. It's sometimes used in baking - mixing sour cream with cream of tartar results in a very light, airy sponge cake. It's also used to add a desirable sourness to some cheesecakes and chocolate brownies.

Yoghurt

Although yoghurt has been made across eastern Europe, Asia and northern Africa for centuries, it's a relative newcomer to the kitchens of northern Europe. Yoghurt is made by fermenting milk (sheep's and goats' milk traditionally), which results in a thick, creamy-textured product with a characteristic tanginess.

Plain (also called natural) yoghurt is milk to which yoghurt cultures have been added; whole milk yoghurt contains about three per cent fat while low-fat yoghurt, made from concentrated skimmed milk, contains 1-2 per cent fat; plain yoghurts are available 'set' and can be used as dressings, in soups and savoury dishes, to make drinks or serve with fruit or cereal. 'Virtually fat-free' yoghurts have about 0.2 per cent fat.

Yoghurt can be added to soups and stews and used in sauces and dips and in sauces for northern Indian-style curries, where it helps to temper the fire of chillies. Add some finely chopped cucumber and some grated onion and you have raita, which is great as an accompaniment to Indian dishes, or as a dip with crudites.

It forms the basis of many drinks and can replace cream in some dishes. Be careful adding it to hot dishes though - it can easily curdle, although a teaspoon of cornflour mixed with water and stirred into the yoghurt first will help to stabilise it.

Flavoured yoghurts can be handy for using in desserts such as fruit fools. Keep an eye on the sugar though - some can be very sweet.

Greek-style yoghurt has a richer texture and higher fat content than plain yoghurt (about ten per cent fat). It can be made from either cows' or sheep's milk. It's delicious with honey, or served with fruit or desserts. Add a squeeze of fresh lemon juice or some ground cumin and you have a delicious accompaniment to roasted summer vegetables.

You can also find yoghurt made with goats' milk, which has a nice tangy flavour (and is good for people who are intolerant to cows' milk).

Butter

Butter is a kitchen essential. Without it, cakes, biscuits and pastries wouldn't have the same melting richness and tender texture. It's also used in many classic sauces, such as beurre blanc, beurre noisette, beurre meunier and hollandaise. Added at the end of cooking, it to gives richness and gloss to sauces. With a fat content of 80 per cent, butter isn't exactly diet food, but a little goes a long way.

Butter is, of course, made from churning cream. Because it contains milk deposits it can burn easily, so it can be a temperamental cooking medium. Adding some oil (which burns at a higher temperature) to the cooking pan with the butter can help get around the problem.

Flavoured butters are easy to make and delicious served with grilled meats, fish and vegetables. Just add some chopped herbs or other flavourings (such as mustard or anchovy paste) and roll into a 'sausage' shape and keep in the fridge, cutting off a disc or two as you need it. You can store flavoured butters in the fridge for up to a week or in the freezer for up to a month.

For baking, pale, creamy unsalted butter (sometimes called 'sweet' butter) is better than unsalted butter as it allows the cook to control the amount of salt going into the finished dish. Butter labelled as 'salted' contains three per cent or more salt; the salt was traditionally added to butter to help preserve it. Salted is best for spreading rather than cooking, allowing the cook to maintain control of the seasoning. 'Slightly salted' butter contains 1-2.5 per cent salt and is more versatile than salted.

Clarified butter is butter that's been heated to boiling point (so it separates), after which the water and milk solids are removed. It's good for cooking at high temperatures. Ghee is a type of clarified butter that originated in India; it's made in a similar way to clarified butter (but using a different kind of cream) although it's cooked for longer, producing a richer flavour. It's available in many supermarkets and in Asian stores and is great for cooking rich Indian dhals and some curries.

Butter substitutes such as margarine and 'non-dairy spreads' vary in fat content, water content and flavour. 'Hard' margarine has the same fat content as butter, so is the best 'substitute' for butter - although your baked goods won't taste the same. Because it has the same fat content as butter, it isn't a low-fat option. Low-fat spreads cannot be used as butter substitutes in cooking.

Cheese

Cheese has been described as 'one of the great achievements of mankind'. No one knows how cheese-making was 'discovered' centuries ago, but it was probably a happy accident, one that allowed them to concentrate and preserve highly perishable milk for long periods.

There are innumerable kinds of cheese, but they can be categorised into broad types, including fresh cheeses (such as mascarpone); natural-rind cheeses (these are often made with goats' milk); soft white-rind cheese (such as Camembert and Brie); semi-soft cheeses and washed-rind cheeses (such as Fourme d'Ambert and Epoisses); semi-hard and hard cheeses (such as cheddar or parmesan); and blue cheese (such as Stilton).

In Britain cheeses are most commonly made from cows', sheep's and goats' milk (or a combination of these). Over the last couple of decades there's been a revival in cheese-making across Britain, so there's an ever-growing number of cheeses to choose from. Specialist cheese shops and farmers' markets are the best places to find interesting artisanal cheeses. A good cheesemonger will let you taste before you buy and can tell you about where each cheese came from and how it was made.

Cheese is a great cooking ingredient, whether it's a mere sprinkling of grated parmesan over pasta or the main player in a light cheese souffle. It's sensitive to heat though, so be careful not to burn cheese if grilling or it will taste acrid. Be careful reheating melted cheese, because it can separate into a single hard lump and a pool of oil.

Cheese shouldn't be stored in vacuum-sealed plastic, which can damage its texture. It's best to buy cheeses cut for you from a whole piece if you can. When you get it home, wrap it in waxed paper or aluminium foil and store, away from meat products, in the fridge. Buy small pieces frequently rather than buying too much at once. They'll taste best if you take them out of the fridge about 30 minutes before serving.

Pasteurising milk and cream

Virtually all milk and cream sold in Britain is pasteurised. Pasteurisation is a heat treatment that kills virtually all bacteria present in milk.

It is possible to buy unpasteurised (raw) cows' drinking milk, but it needs to meet 'bacteria count' standards before it can be sold and must carry warnings to advise people it may contain harmful bacteria. If you choose unpasteurised milk or cream, be especially careful to keep them properly refrigerated because they both have a short shelf-life.

Food poisoning outbreaks have been associated with unpasteurised milk and cream, mainly due to salmonella, campylobacter and Escherichia coli O157 (E. coli O157). The Food Standards Agency strongly advises children, pregnant women, older people and those who are unwell or have chronic illness, not to consume unpasteurised milk or cream.

Storing and freezing dairy

Store dairy products in the fridge well away from meat products to lessen the chance of cross-contamination. If your fridge has a dedicated cheese drawer, this is the best place to store your cheese.

Always observe the 'use-by' dates on dairy products, particularly milk and cream and don't use those that are out-of-date. Milk can easily pick up aromas from the fridge, so it's best to buy milk in containers that can be easily resealed. Tightly cover part-used cream with cling film and or aluminium foil.

You can freeze pasteurised milk before the 'Use by' date. Defrost it in the fridge, allowing about 24 hours for it to thaw, and try to use the milk within a few days of defrosting - it will go off in the same way as fresh milk. Be aware that when milk is frozen it expands and this can rupture the packaging, so check that the packaging is intact before you defrost it and if it has ruptured, it's best not to use the milk. Freezing can affect the quality of some milk.

All cream should be kept in the fridge and used within two to three days. UHT creams should be treated as fresh cream once opened. Creams, in their 'raw' state, are generally unsuitable for freezing but clotted cream can be frozen for up to a month and double cream and whipping cream can be frozen for a month if lightly whipped first. When incorporated with other ingredients, such as when making ice cream, cream freezes well.

Hard cheeses will keep for longer than soft cheeses, but it's best to buy in small batches and consume them quickly. If a cheese develops an ammonia-like aroma, don't eat it; it will be over-ripe.

Most cheeses can be frozen, but freezing can affect the flavour and texture of the cheese. Wrap portions of cheese in a layer of cling-film then aluminium foil and freeze for up to three months. Defrost cheese in the fridge for 24 hours.

Recipes

Macaroni cheese by Paul Merrett (video recipe)

Victoria sponge with strawberry jam by Lesley Waters (video recipe)

Eggs Benedict by Paul Merrett (video recipe)

Salmon en croûte (with all-butter puff pastry) by Lesley Waters (video recipe)

Salmon with green butter by Sophie Grigson (video recipe)