Temperature control for fridges

Your food may tell you if the temperature of your fridge or freezer needs tweaking. Meat and dairy products go off quicker if it’s too warm. Too cold means leafy greens freeze and turn into a jelly-like mess. If your ice cream develops crystals on the top, it's thawed a bit and refrozen. This will affect its texture and taste and may well affect the quality of other foods too.

You can buy fridge thermometers at hardware stores and some kitchenware stores. Or you can leave an ordinary thermometer in a glass of water in the fridge overnight and take a reading when you first open the door the next morning. Check temperatures in the doors, crispers, dairy compartments and several locations in the main part of the fridge. Use a fridge-freezer thermometer to check the freezer temperature.

The ideal temperature for the main fridge is 3°C, although this isn’t standard for all compartments. It should be slightly warmer than 3°C in the dairy compartment but closer to 0°C in the chiller. The freezer should be at least -18°C for longer-term storage of frozen food but -12°C to -15°C is acceptable for short-term storage (about 2 weeks).

A stand-alone freezer needs to be able to cope with extreme temperatures because they're often kept in a garage or shed. Freezers are designed to cope with ambient temperatures ranging from 10°C to 43°C. However, if your freezer is in a garage or shed, temperatures can easily get lower or higher than this, making it difficult to maintain the set internal temperature. It's best to use a thermometer to check, especially when the outside temperature changes significantly.

Keep the door or lid shut

• It sounds obvious, but time is critical for excluding warmth and moisture from the inside. Some models have an alarm, either sound or light, which tells you when the door is not properly shut. Any alarm light should be easy to see - some are poorly located beneath the freezer door and aren’t visible from a normal standing position.

Don't run on empty

• Keep a moderate amount of food in both the freezer and fridge at all times. This will help to limit temperature rise, and is particularly important on a hot day when the door is opened and warm air floods in.

• It's even more important with frost-free models, which defrost automatically using a heater. If the freezer is nearly empty, the compartment can warm too much during the defrost process.

• If your freezer is nearly empty, put in some plastic bottles, three-quarters filled with water. This will reduce temperature variation within the compartment, help to chill items quickly when you first put them in the freezer and prevent the temperature from climbing when the door is opened.

Pack correctly

• Don't pack food against the walls and to the top of each shelf of your fridge, particularly with a frost-free fridge, which needs space for the fan to circulate the cold air properly.

• The coldest part of a chest freezer tends to be on the compressor step at the bottom of the freezer; the coldest part of an upright tends to be the top shelf. Keep long-term storage items here.

• Moisture-proof packaging such as plastic containers, thick plastic bags and aluminium foil will preserve food quality by preventing dehydration and oxidation.

• Ideally, you shouldn't load a freezer with food that's at room temperature; cool it first in the fridge so it doesn't partially defrost the food already in the freezer.

Learn how the controls work

• Fridge-freezers that don't have separate controls for the 2 main compartments can struggle to maintain both at the right temperature. Even models with 2 controls don't always get it right. Where settings can be adjusted in steps (as with some electronic models), the steps may be too far apart, and the temperature you really want is in the middle.

• Check the manual to see how the controls work. If that explanation is not clear, you might need to experiment yourself. In a typical frost-free fridge, altering only one control will often change the temperature in both compartments. This is usually because one is the thermostat control that controls the overall cooling, and the second is a flap or baffle that controls the airflow between compartments.

• Markings can also be confusing, so you may be turning the controls the wrong way. Look out for graphics that say "cold" but mean "less cold" for the warmest setting. Also many controls are simply marked "temperature controls" and don't tell you how they work, or that they affect each other.

• Some freezers have a "fast-freeze" function, to ensure the rapid freezing of freshly loaded food. Remember to turn it off after a few hours, or running costs will be higher and constant noise could be a problem.