I wanted to know how long oil can be re-used in a deep fryer since I'll have to fry (samosas, spring rolls, etc.) everyday, this month. Also, what is the most suitable container to store it in? Thanks.
There are no hard or fast rules on how many times you can re-use oil in deep fat frying as the number of times you can use it will depend on how long you are using it each time and what type of foods you are frying. The smoke point for oils is the temperature at which it starts to give off smoke and will start to burn. Each time the oil is heated the smoke point reduces slightly so ideally it is best to use a vegetable based oil with a neutral flavour. Safflower, sunflower, corn, canola/rapeseed and peanut/groundnut oils all have smoke points above 230c (450F), whereas most food is fried around 180-190c (350-375F), so they are more suitable for re-use than animal-based fats.
To get the best re-use from your oil you should filter it after each use as this will remove some of the small food particles that will have come off the foods you have been frying in the oil. Make sure the oil has cooled to room temperature then carefully filter it through a sieve or strainer lined with muslin or kitchen paper/paper towels or a coffee filter. The oil should be stored in an airtight container in a cool, dry place. Never pour hot oil into a container and store used oil separately from new oil.
There are some signs to look for to suggest that your oil should not be used any more. If the oil starts smoking before you reach cooking temperature, or around your target cooking temperature, then you should stop heating it and discard the oil as soon as it has cooled - there is a high risk that the oil will catch fire during cooking. If the oil has become very dark and thick then it is also past its best and if the oil starts smelling of the food cooked in it or smells rancid then it should also be discarded.
When deep fat frying never leave the pan unattended. Keep the lid of the deep fat fryer within reach so that if the oil catches alight you can cover the fryer quickly and extinguish the flames. Never pour water on a fryer that has caught alight.