Is the food still safe to eat?

 For the past few days, New Zealand has suffered from high winds and extensive flooding as a result of Cyclone Gabrielle, which in some coastal areas has coincided with high tides.  Many areas have been without power for extended periods and thousands of people have had to leave their homes, in some cases being rescued from the roofs of their houses.

I was interviewed by a radio journalist who wanted to ask questions about the safety of food and water. Any food that has been contaminated by the flood waters is, of course, not fit to eat.  But what of foods that were in refrigerators and freezers?

This is a difficult question to answer.  If the power has been off for a few hours and the refrigerator has not been opened, the food will probably be safe to eat, however, some areas are not likely to have power restored for several days.  Some foods, such as yoghurt are naturally preserved by their acid content and will be shelf-stable even at room temperature for a few days.  Hard cheeses will also be safe.  Similarly, milk in sealed bottles will be OK for a couple of days.  Vegetables are also shelf-stable for several days at room temperature, provided that they have not been in the water.  Eggs have their shells to protect the contents, but it would be worth washing the shells to prevent contamination of the contents when they are cracked open.  Perhaps a good guide is to think of supermarket displays - if the food such as fruit, potatoes, tomatoes and cabbages is sold from open counters, it can reasonably be expected to last for several days.

The big concern will be fish and meat.  If the frozen food has thawed out completely, it may still be safe to eat if it is thoroughly cooked.  if the food still has ice crystals in it, refreezing is possible.  Beef and pork steaks are essentially sterile inside, so it is only necessary to cook the outside, remembering to cook the edges too.  Fish is normally sold in fillets, so again, frying or barbecuing will render it safe, however, the food cannot be stored for another few days before consumption.  I would be more concerned about chicken, which is always difficult to cook throughout because of the uneven thickness of drumsticks etc.  In all cases, the critical thing is to get the temperature of the food above about 75C throughout.  This will kill all vegetative (non-sporulated) bacterial cells.  If a thermometer is used, it must be clean and inserted into the thickest part of the food.  More care is required with minced meat.  During the mincing operation, the outside of the meat is mixed in with the interior portions, so thorough cooking is required - medium-rare hamburgers are out! 

Another, though not infallible guide is to look at the food and smell it - if it smells off, then don't eat it.  Things like bacon sometimes become a bit slimy as a result of bacterial growth on the surface.  If it is fried properly, it will be safe to eat, but may have off-flavours.

Of course, canned foods are safe, provided that there are no holes in the can. Similarly, sealed packages of snack foods, such as 'chippies' will be OK to eat and may make the kids feel a bit happier.  It is a good idea always to have a supply of canned foods in the cupboard so that they are available in emergency situations like ours.

Another major concern is water.  Some water treatment plants have been out of action for a couple of days as a result of power outages and some watersheds may have been swamped by flood waters.  A number of water supply authorities have said that the tap water is safe to drink.  However, if there is any doubt about its safety, it should be boiled.  I was asked about water for making up baby formula.  In that situation, I would always recommend using boiled water.  Rural households often collect water from the house roof and store it in large tanks.  In my opinion, this water will be safe, provided that the roof and tanks have not been inundated, but once again, if there is any doubt and the power is on, it should be boiled.

All of these questions will become more relevant when people are allowed to return to their dwellings. There may be a temptation to try to salvage food from refrigerators and cupboards.  If there is any doubt, the safest thing to do is to dump it, as food poisoning will put even more stress on health services at this time.

Our next concern will be resupply.  Many roads are impassable, leaving some towns completely cut off.  Supermarkets are very short on stock, even if they have power to operate the tills.  Foods may be in short supply for a while, but in addition, orchards and vegetable farms have been severely damaged, so shortages will continue for months.  There may be more reliance on imports.

Odd Spot:  if the cyclone were not enough to challenge the population, we also had a magnitude 6.3 earthquake yesterday.  It was centred about 50km NE of Paraparaumu in the North Island, so it was under the sea.  There have been no reports of injuries or damage, but it's something we could all have done without!