Titration protocols for vitamin A

1) Take 1g of food (with particle < 1mm of diameter) in bottle protected of the light, and add 15ml of hexane. Mix it.
2) Add again 15ml of hexane and shake during 5-10 minutes (do the same time, if you want compare two food sample).
3) In an other bottle protected of the light, do a filtration (coarse cellulose filter) of the previous solution.
4) Take the batter who don't pass the filter, and 15ml of hexane, shake 5 minutes, and filtered it like previously, to take all B-caroten as possible from the food sample.
5) Put in the fridge at -20°C to conserve it.
6) Obtain the result with a spectrophotometer with wavelenght of 450 nm (with a blank of hexane).