This comes up occasionally, and below is a prevous post I did on the subject
The food standards agency advice has changed on this. It used to be that once unfrozen you should not re-freeze. Now they say that as long as the middle of the meat has reached 70 degrees c when eventually cooked.
The following thread shows this advice
http://community.babycentre
.co.uk
/post/a10078975/cooking_and_refreezing_meat_a_past_discussion.
in particular a letter from the FSA:
Dear madam,
Thank you for your recent request for information regarding thawing, cooking and refreezing. Your query has been passed to me for reply.
The Food Standards Agency advises that it is safe to thaw raw meat/chicken, and refreeze it.
When thawing raw meat, we advise that you do so overnight in a clean, covered container at the bottom of the fridge, to prevent any juices from dripping onto food which may be eaten without cooking. Once defrosted, you should keep the meat in the fridge and use it within two days. You could also defrost it using the “defrost” setting on a microwave, in which case you should use it immediately. We advise against thawing at room temperature, as doing so exposes food to the “danger zone” between 8°C and 63°C when harmful bacteria can grow quickly.
When cooking the meat, ensure that it is done thoroughly until the it is piping hot throughout, reaching a temperature of 70°C for 2 minutes and chicken should be cooked until no pink remains.
Before putting cooked food in the freezer, you should cool it thoroughly and quickly (ideally taking no more than 1-2 hours). To speed up the cooling process, you could divide the food up into smaller portions, place each portion in a clean container, and place the containers in a shallow dish of water. Once cool, you should transfer the food to the freezer immediately.
However, if the meat/chicken was already cooked prior to freezing, then we would advise that you do not keep any leftovers or refreeze. The reason we advise against refreezing cooked food more than once is because the more times food is frozen and thawed, the more chance there is for something to go wrong. Bacteria might grow and multiply because the food is not defrosted correctly, and might survive because the food isn't reheated properly. So it's best not to reheat and/or refreeze cooked food more than once.
Further advice on keeping food safe can be found on our Eatwell site:
http://www.eatwell
.gov.uk
/keepingfoodsafe
/I trust that you will find this information useful and that it answers your question.
Yours sincerely,
Grace Mukasa
Microbiological Food Safety Branch
Food Safety: Hygiene & Microbiology Division
However the FSA link then leads to this that says don't !
http://www.nhs
.uk
/Livewell
/homehygiene
/Pages/how-to-store-food-safely.aspx