Monday, April 13, 2009

Curry Powder


Sara asked about curry powder.

There is absolutely nothing wrong with curry powder. It has been safely used for many centuries, following time honoured and well proven practices.

But what if those practices are not followed?

First, let's look at what curry powder is. It is the ground mixture of spices, seeds of a variety of plants. Seeds that have been exposed to the environment. There is nothing abnormal in that but, because of their origin, the seeds that go into curry powder will bring with them a variety of organisms from the environment. Notably Salmonella.

Now, how is curry traditionally prepared? You heat oil in a pan and cook the powder in this oil. Ostensibly to 'bring out the flavour' but, by a happy coincidence, it also sterilises the powder. You then add meat, vegetables, whatever and continue with making your curry.

What happens if you deviate from this long proven, survival enhancing, cooking practice? What if you are a new age cook and make a curried pasta salad where you just mix the warm (!) pasta, mayonnaise, vegetables, cream and curry powder and stir? Nothing much if you eat it straight away. But bacteria will double roughly every 20min at room temperature; what if you make your salad early and leave it for a few hours before eating? Not a good idea - the salad is warm, moist and protein rich - happy times for the bacteria.

Because of the risk, spices are one of the few things that are permitted to be irradiated to sterilise them. But this does not teach people safe handling practices for a potentially dangerous food. People will just be ignorant of the dangers and at risk from spices that are not irradiated.

Monday, April 6, 2009

Egg whites & Copper bowls

Woodfired asked: Whisking egg whites to the correct stiffness seems to challenge many. There is plenty of advice about how to make your whites stiff. An old one, and one that seems to be supported by professional chefs, is to whisk them in a copper bowl. Can you think of any likely reason why this would help?

Well, no, I had no idea. I thought it may be related to bowl cleanliness as this can influence whipping of egg whites. So I went hunting.

The bowl you use makes a difference when you are whipping egg whites. When air is whisked into egg whites, the mechanical action denatures the proteins in the whites. The denatured proteins coagulate, stiffening the foam and stabilizing the air bubbles.

A copper bowl assists in creating a tighter bond in reactive sulfur items such as egg whites. The bond created is so tight that the sulfurs are prevented from reacting with any other material. Copper bowls produce a yellowish, creamy foam that is harder to overbeat than the foam produced using glass or stainless steel bowls. When you whisk egg whites in a copper bowl, some copper ions migrate from the bowl into the egg whites. The copper ions form a yellow complex with one of the proteins in eggs, conalbumin. The conalbumin-copper complex is more stable than the conalbumin alone, so egg whites whipped in a copper bowl are less likely to denature (unfold).

If the foam is overbeaten in a non-copper bowl, eventually the proteins become completely denatured and coagulate into clumps. There is no going back from the clumpy mess to nice foamy whites, so overbeaten whites are usually discarded.

A silver plated bowl will have the same result as the copper bowl. Drawbacks of the copper bowl include the expense of the bowl itself, as well as the fact that the bowls are difficult to keep clean. Copper contamination from the bowl is minimal as a cup of foam will contain a tenth of one's daily normal intake level.

Although the iron and zinc found in other metal bowls also form complexes with conalbumin, these complexes don't make the foam more stable.

Cream of tartar (potassium bitartrate) is an acidic salt that can be used to change the pH of the egg white to an acidic range by boosting the number of free-floating hydrogen ions in the egg white. This has the effect of stabilizing the foam, and is therefore an alternative to using a copper bowl.


Onions as bacteria magnets.

Pauline asked: there is an email circulating claiming that cut onions are "magnets for bacteria" and should never be stored for later use (even in the fridge for a few days) as they will cause food poisoning. True?

Snopes (here) rates it as "undetermined".

I am willing to go out on a limb and say "false".

Reason 1: Nothing is a bacteria magnet. Firstly, bacteria have minimal mobility. They usually travel in water droplets, if at all. Sneezes, for example. Moulds can release spores which get blown around but bacteria usually grows in moist environments and are slimy, making getting airborne difficult. Secondly, if there was such a thing as a 'bacteria magnet' it would be enormously useful in the medical field for drawing bacteria away from the ill and infirmed. Not such use has been made of onions.

Contact with unclean hands can introduce bacteria to new surfaces but they need a surface that will support growth, otherwise they will just stay there without multiplying or die.

Reason 2: Bacteria like moist, neutral environments. Not many acidic things grow bacteria. That's why vinegar is used for preserving. The surface of a cut onion is acidic due to the production of sulphuric acid (this is what makes your eyes water). There are some moulds that will tolerate acidic conditions and grow on onions but they are not high risk, they are visible, and any normal person would cut them off or ditch the onion.

Reason 3: High risk foods are usually high in protein and available moisture. Onions are low protein, verging on nil, and what moisture they have is contained in their cellular structure. The surface, as well as being acidic, dries soon after cutting and will not support bacterial growth.

Reason 4: If onions are attracting bacteria, where are they coming from? Somewhere else in your fridge? Perhaps it is time to clean the fridge.

Reason 5: In the 20 odd years I worked in a food laboratory, onions were never mentioned as even a suspect in a food poisoning case.

Footnote: we did have some onions brought to the laboratory as a food poisoning complaint once. A guy had eaten them and ended up in hospital. Only problem was, they weren't onions.

They were daffodil bulbs.

Friday, April 3, 2009

A non-cancer mouse death.


One neatly sliced mouse. Too much bread killed him.

Thursday, April 2, 2009

The case for tougher rats.


Chairman Bill, in a comment to the last post, deemed hydrogenated fats to be carcinogens.

While I took some issue with the broadness of the statement, I do agree in a broader sense.

At a different level, I believe EVERYTHING causes cancer. You just need more of some things than others.

In a broad sense cancers occur when the body's systems are overwhelmed by a particular compound or radiation. Even shift work is implicated in cancers nowadays. It is a case of the body getting swamped in someway and losing the plot when it comes to cell growth.

Tests in the labs have shown that if you swamp a lab rat's diet with a chemicals it will develop cancers but, in order to speed up the process the labs feed the rats enormous amount of the compound being tested. If you want to see what they went through, make a mix of a food of your choice and include 5% saccharin. Inedible. Now do it all meals for an extended time. Unbearable. No wonder the poor rat developed cancer. But how does swamping a rat's genetic processes translate into the long term effect of low levels of a saccharin on humans?

Bill talked about trans fats in margarines but they are naturally occurring in most fats.

In low levels.

It is generally accepted that smoking causes cancer; this is due to the compounds in the tars. Theoretically these compounds are first cousins of the charring of any plant matter. Smoking marijuana is just as dangerous as tobacco in this sense - different psychoactive substances, same tar.

But burnt plant matter is common in our diet - browned meat, roasted coffee, toast, cakes, biscuits, fries/chips. All theoretically foreign and carcinogens.

I argue that all chemicals, taken in excess for extended time will swamp the system.

I also argue that the system is designed to cope with a multitude of chemicals that are naturally in our food. The analogy would be sand. If I drop a stream of sand on your shoulder, it will bounce off and not be a problem. If I drop a ton of sand on you all at once, it is a big problem.

It is all a matter of recognising and managing risk.

Margarine & Butter

Sara asked for a run down on Margarine.

Normally the image sold to us with margarine is like the one above.

Mother Nature at her most adorable best.

In reality, canola seeds, the main source of oil for most domestic margarine and a close relative of rapeseed and mustard seed, looks like this:

Wholemeal margarine

For convenience, I will limit myself to the manufacturing steps to make canola-based margarines. The process is largely as follows:

1. Grind the seeds and extract the oil using petroleum solvent, usually hexane. Remove as much as possible of the hexane from the oil. The oil at this stage is a greeny-brown colour and has a nutty odour.

2. Treat the oil with caustic soda to neutralise free acids and precipitate gums.

3. Heat the oil with clay to bleach it to a pale yellow colour.

4. Deodorise the oil to remove unpleasant tastes and smells – this is usually done with steam and vacuum.

At this point you have vegetable oil, as you would buy it in the shops. Now...

5. Heat the oil under pressure and heat with finely divided nickel and hydrogen gas to saturate the double and triple bonds in the oil and create a fat that is solid at room temperature. Attempt to minimise the production of trans fats while doing this. The product is now solid, white and bland.

6. Add about 20% water or milk plus emulsifier (typically lecithin) to keep the water-oil suspension stable.

7. Add flavours (usually milk and/or milk solids) to give taste. Salt may also be added.

8. Add vitamins A & D to fortify it.

9. Add colour to make it look more appealing.

10. Put a lid on it.


Margarine has the same fat content (80-85%) as butter.

Margarine has the same calories as butter.

Margarine use was widely adopted when someone said butter was bad. No-one stopped to wonder if margarine was good. It just wasn't butter and butter was bad. Presumably butter was bad because it contained cholesterol. Now the notion that dietary cholesterol is a problem has been largely discredited. The concern now centres on the saturated fats in the diet.

Butter does have higher saturated fat levels than margarine.

The other thing to be aware of is that there is table margarine and cooking margarine. Cooking margarine is used in the biscuit and cake industry and is a harder (more saturated) fat than table margarine.

Is margarine bad?
No, not bad in the 'avoid at all costs' sense but nor is it 'natural' in the way the advertisers and their sunny yellow fields would like us to believe.

Wednesday, April 1, 2009

Locked away in a room full of celery...

I used to be intrigued by a story I was told as a kid, that hard boiled eggs use more energy to digest than they contain and so you loose weight if you eat them.

Sounded dodgy to me, even then. It implied that if you were locked in a room with nothing but water and hard boiled eggs, you would starve to death.

But apparently that is the case with celery.

The calories in food are a measure of energy content. For something we eat to be a source of "negative calories," it must provide fewer of these units of energy than we expend in consuming it. Yet everything contains calories, so at first this concept appears impossible.

Therefore, the hunt is on for ingestibles whose energy content is not released into our bodies because we humans lack the ability to break them down — it doesn't matter how many calories these goodies have, provided we can't extract them.

Cellulose in plants is one such substance: although it contains a goodly amount of carbohydrates, they are packaged in a form we cannot digest, so we fail to absorb their calories.

Celery has about 6 calories per 8-inch stalk, making it a dieter's staple.

Its ingestion can result in negative calories, but it is a fallacy to believe that effect has to do with energy expended in chewing. Though chewing might feel like a somewhat strenuous activity, it burns about the same amount of energy as watching paint dry. It is the bodily energy devoted to the digestion of the green stalks that exhausts calories.