Past its 'Use-By'.

Don asks "How important are the 'sell by' dates on food? Clearly something like milk gets nasty. Bread can easily mold. But what about something like canned beans? Would that be more a textural issue; like they get soft or something? Some people in the U.S. stockpile food thinking something awful might happen. I don't agree but what would you expect of an out-of-date can of beans or even tuna?"

Researching it a bit, it seems there are lots of different date marking legislations.

In Australia, perishable food must have a USE-BY date.  Consumption beyond this date may present a health hazard.  But it presupposes that storage conditions have been complied with.  Leave your milk in the back of your car for a day and all guarantees are off.

Food that has a shelf-life of less than two years must have a BEST BEFORE date.  Consumption beyond this date may mean that the product is no longer of good marketable quality.  It may be stale or aged but does not imply a health hazard.  And it doesn't change from OK to dodgy on the BEST BEFORE date.  It is best before that date but can be passable for quite some time afterwards.  Again it depends on storage conditions.

Food expected to last beyond two years does not require a BEST BEFORE date but must have some identifiable marking to permit a recall (Batch code, manufactured date etc.).

So, where doe that get us with Don's question?

Canned beans will last a long, long time.  Canning produces a bacterially sterile product.  Enzymes are destroyed too.  Generally speaking changes happen at the time of cooking (flavour, texture) and then the product is in a kind of suspended animation.

With canned beans, assuming they were of good quality when canned, there is nothing much that can happen to them.  There is no mechanism for deterioration: free of bacteria and enzymes, protected from physical damage by a thick sauce, they are pretty indestructible.  That goes for most canned product.

The main issue will be the external deterioration of the can over time, resulting in the formation of small holes that permit the entry of bacteria or the possible failure of the lacquer or other coating on the inside of the can.  The only protection you really have from that is to buy good product.  If you are planning to cater for the end of civilization, don't do it with cheap, plain-wrap stuff.

If the people planning for disasters want to be safe they could rotate their stockpile, eating the oldest product and replacing it with fresh product, using it like a well-stocked pantry.
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At last, a different onion question!

Anonymous asks: "Would like to know if you can get sulphuric acid poisoning from rotting onions? Had a bag of onions in my cupboard for months and they had rotted now all I can smell is onions. Really strong at times. "

A few bits to this:

Firstly, sulphuric acid is not volatile, so you cannot smell it.   Heat it sufficiently and you will get sulphur trioxide fumes which you can definitely smell but I am talking 400degC, somewhat warmer that the average cupboard.

Secondly, it is corrosive rather than toxic.

But on to the onions.  When things rot, all manner of compounds are formed and released.  What compound and what level will be dependent on onion type and the organisms associated with the rotting.  Onions contain a lot of sulphur so the breakdown products will be smelly.  Unpleasant but not necessarily harmful.

Chuck them out and air the cupboard.  There is not much else you can do.
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Nuts to that!

Reading an article in Food Quality New I was a bit confused about the about photo (above), said to be of pecan shells.  Well, there may be pecans there at the back but the foreground is all almond and brazil nuts.

For the record, pecans look like this:

The gist of the article, though, was about the use of dried, powdered pecan shells as a natural, organic antibiotic, specifically against Listeria sp.

I would just like to point out that natural and organic are not the sole criteria for food safety.  Strychnine, cyanide, arsenic and aflatoxins are all well encompassed by the 'natural and organic' umbrella.  OK,  arsenic's not organic.  Just testing.  Lots (I mean lots of lots) of things contain organic compounds that exhibit antibiotic properties when concentrated and deposited of some unsuspecting bacteria.

But nothing beats having the bacteria not present in the first place.

No amount of powdered hoodoo dust will trump good manufacturing practices and plant hygiene.
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Coffee, Tea...

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Peter Bryenton asked "I was wondering how much caffeine there is on average in an ordinary cup of instant coffee?"

Not an easy question as the consumer is in control of how strong they make the coffee and how big a cup they use.  Generally instant coffee powder is about 2-3% caffeine and instant coffee is about 330mg/L (about 75mg per cup).  But I know my first cup of coffee in the morning is considerably stronger than my last of the day.

Tea is generally only about 80% of the caffeine levels of coffee but, again, this varies with type, cup size and steeping time.  Herbal teas generally have none but be careful of flavoured green teas, they have similar levels to black tea.

Colas are about 100mg/L; a third that of tea and coffee.

The much vaunted 'Energy Drinks' are only permitted a maximum of 320 mg/L in Australia and so are on a par with tea and coffee.  Not that they would want an image of a little old lady sipping her cuppa to be equated to the macho image of the heroic energy drink urban warrior-rapper-sportsman.
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Anticancer Spears

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Kevin Bell asked: "Any info on the email going around that Asparagus is good for curing cancer? This also seems incredulous, the pharma industry are not stupid and would be onto it quickly enough if there was any credibility in it."

Well, yes, I think you nailed it yourself, Kevin.

If there was any truth in it, it wouldn't be being sold at $4 a bunch at Woolworths.

As I understand it, cancers are initiated when your body loses the plot with regard to cell regeneration and starts an uncontrolled multiplication. 

I can see no reason why a food, any food, would stop this.  I would be more inclined to believe that eating excessive amounts of asparagus would cause problems rather than the reverse.

Too much of anything is bad.

But moderate amounts of asparagus with a good home-made hollandaise sauce is not bad for you and, indeed, can improve your emotional well-being no end.

By the way, I haven't seen the email that you mention, but I am sure that the miracle chemical in asparagus will be Rutin.  Love the name.  It is a naturally occurring flavonoid found in a number of foods.  As well as in asparagus, it is also in buckwheat, citrus peel, mulberries and cranberries.  In canned asparagus it appears as white or grey flecks in the spears.  Something about the canning process triggers crystallisation.  Quite beautiful crystals under the microscope.
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A load of old rhubarb

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I made mention on my home blog that my rhubarb was green and that I was adding elderberries to it to make it look more 'normal'.  I have seen recipes that added strawberries to give colour.  A few people asked if green rhubarb was safe.

Yes, it is.

The green stemmed rhubarb is a fast growing, thick stemmed hybrid.  Quite safe.

The poisonous element in rhubarb is a chemical called Oxalic Acid and it is found at high levels (0.5%) in the leaves, regardless of the stem colour.

Oxalic Acid is also found in many other plants but not at the levels found in rhubarb leaves.  Excessive Oxalic Acid consumption results in kidney stones (Calcium Oxalate).  A lethal dose of rhubarb leaves is about 5kg.
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Potomatatoes & Acidity

Anonymous asked "Do totatoes can acidity in the body?"

Well, that is not an easy question to answer, as such.

Are we talking potatoes or tomatoes?
Are we talking cancel or cause?

Never mind - I'm guessing that it relates to the much discredited acid-alkaline diet that lingers in the fringe diet circles.   In essence, it proposes that foods are good or bad depending on the pH of a solution of the ash of the food.  The notion that the acidity or alkalinity of the ash of a food will influence the impact that the food has on your body is just plain weird.

There is no scientific data to support the theory.  There is not even a coherent theory.

Your stomach is already 100-1000 times more acidic than a tomato or a potato, so any native acidity will have a negligible impact.  No foods are natively alkaline.

As you body never reduces food to its ash, the properties of the ash are immaterial to human nutrition.

Eat a varied, balanced diet.
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