Tomatoes on sale here during the winter don't taste as good as those available in summer. Does their nutritional value change too?

Mark Alberstat, Halifax, Nova Scotia, Canada

I've just opened a (paper) packet of flour that is 16 months past its sell-by date. It looks and smells OK and there are no visible signs of insect or fungus attack. What hidden dangers could lurk within it, or is it safe to eat?

I have noticed that when currys or chillies are frozen to eat later, they 'mature' and become noticeably hotter.  Can anyone expain this?

If you drop a piece of food on the floor, it is supposedly safe to eat it as long as you pick it up before 10 seconds has elapsed, because it takes that amount of time before it can be colonised by microbial life. Is there any truth in this whatsoever?

In his work "De Agri Cultura" the Roman author Cato the Elder describes recipes for making a drink called "Greek wine" (vinum graecum) or "Coan wine" (vinum coum). Basically, must (boiled shortly and then cooled) or grapes are mixed with salt water or sea water (Chapters 24, 105, 112, http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cato/De_Agricultura/home.html).

The resulting wine is kept in a dolium, a large ceramic vessel. The dolium is kept open for 15 or 30 days, and then sealed air tight and kept in a cool place for the rest of the winter (the process beginning in autumn when the grapes are harvested). In spring, the wine is filled into amphorae which are covered but not closed air tight and  placed into the sun for up to four years.

On of the recipes states that the amphorae should not be filled to the brim but only as high as the handles. I suspect this is to allow for the formation of foam. Probably there was a secondary fermentation. (This brings to mind the secondary fermentation of Belgian lambic beers, in which up to 80 different types of microorganisms are involved to create a complex flavour.)

What type of ferment would result from this process? Has anybody tried or studied this? If the initial fermentation yields alcohol, would this be turned into acetic acid later or would the salt prevent this. Would there be any alcoholic fermentation at all (I suspect that adding salt and closing the vessel air tight would result in a lactic acid fermentation instead)?

What kinds of microorganisms would be involved in the production of vinum coum (in an ancient Mediterranean farm environment), especially in the secondary fermentation?

My suspicion is that Vinum Coum was sour-salty refreshing drink with a complex flavour maybe in the direction of lambic beer or kombucha and that it was basically a lactic acid ferment. Has any scientific work been done on this?

I'm asking since there's a friend of mine, who states that thanks to "biotin", thay are basically harmless, so he eats them 2 in a row.

When I buy asparagus and keep it too long small beads of liquid appear on the tips. Why does it seem to decay preferentially from the tips, and what is the composition of the liquid that appears there? More importantly, can I still eat the asparagus after the liquid starts to appear?

Tyler Keaton, Bolton, Lancashire, UK

I'm aware of how it's done for dairy products and that, it being rather easy to tell when it's going bad. But I was just preparing some Charlotte Potatoes and I noticed it said "Display Until July 8th. Best Before July 10th". It's now October 22nd, but I wouldn't surprised to see them still good at 3 months given how they looked and felt.

They were stored in the veg drawer of a fridge that is at 2C +/- 1C, but even when we have gotten big bags and kept them in the garage they've kept for several weeks, though they did start sprouting (some were even got to by Field Mice before anything else).

So, just how did they come up with such a poor date for "Store in a cool, dry place"?

Sometimes for strengthening my hair, I make herb mixes or use single herbs  that are perfectly drinkable, like camomile or black tea. Only I make them stronger and let them stand for at least 30 minutes. Once I wanted to be quick and brewed the stuff just before washing my hair. Afterwards as I poured some into the palm of my hand in order to use it, it almost burned me. I found this strange and took a sip - it was not at all too hot to drink, only too strong.

Why does the mouth have no problem with temperatures that are too hot for the hand? I can guess part of the answer: we're used to it. Children get lukewarm food, and then we gradually increase the temperature. OK but when I try to let my hands get used to hot water - maybe the palms would, but the backs become rough and red...