Q: "I often cook frozen chicken in a Ralta crock pot slow cooker. It is cooked in time for tea and after putting under the grill for 5 minutes is moist and tender. I was wondering: are we in danger of getting food poisoning through not cooking at high enough temperatures?"
A: We asked Caroline Gunn, Director of Food Safety Services Ltd in Napier, to respond:
"This was a fascinating question, as I couldn't find anything documented on what temperatures slow cookers reach, how long it takes to reach them and with what type of food.
As chicken is a high-risk food, it needs to be carefully handled and cooked. Recommendations are that it needs to be cooked at a minimum temperature of 75-80°C to give assurance of food safety. It is also recommended that we thaw meat, especially chicken, before cooking.
Poultry producers recommend you cook thawed chicken in a conventional oven at 180°C for about 30 minutes for every 500 grams, or in a microwave on high for 43 minutes (for size 20) plus 10 minutes standing time.
I could find no recommendations available for using a slow cooker so I decided to replicate what Vanessa does and test whether a frozen chicken reaches the required temperature using the slow cooker method myself.
To make the test as stringent as possible I used the largest chicken I could fit in my slow cooker (size 20) and the lowest setting (low). The lid couldn't fit on properly because the chicken was so big and frozen solid. I then took temperatures throughout the day. The results were as follows:
- 8.30am – began slow cook of frozen chicken
- 11.00am – still frozen <0°C
- 1.30pm – internal temp of chicken 70°C (still in unsafe zone)
- 2.00pm – internal temp of chicken 75°C (lower limit of safe cooking zone)
- 2.30pm – internal temp of chicken 82°C (safe cooking zone)
- 3.30pm – internal temp of chicken 91°C (safe cooking zone)
- 5.00pm – internal temp of chicken 97°C and chicken falling apart when removed from slow cooker
I tested this several times on both the low and high settings. On the basis of these results, with a size 20 chicken I would recommend that if you are cooking a chicken from frozen in a slow cooker it will take at least 5 1/2 hours on low (or 5 hours on high) just to reach the minimum safe cooking zone of 75°C inside the chicken.
I would then continue cooking a further 2 hours in the slow cooker. The chicken may be ready before this but I'm assuming you're not home to check exactly when the juices are clear so this timing allows a comfortable safety margin.
I would be confident the chicken is safe to eat after cooking at these temperatures for this time."