Citrus by Pierre Laszlo: a book review

Citrus: A History by Pierre Laszlo

This fun little book from 2007 contains everything you ever wanted to know about the history, economics, and properties of oranges, lemons, limes, grapefruit, and other citrus fruit.

Somewhat unusually for a book of this kind, it even includes a number of recipes – for fried valencia orange slices, sea bass with tangerine juice, marmalade, tarte au citron, citrus sabayon, orange mousse, and a few other things. For example:


12 limes, halved
1 medium onion, peeled and quartered
4 hot green chilli peppers
1 inch ginger root
4 oz seedless raisins
7 green cardamom pods
1 tablespoon black peppercorns
1 tablespoon coriander seeds
1 tablespoon mustard seeds
4 dried red chilli peppers
1 1/2 cups cider vinegar
3 tablespoon coarse salt
1 lb light brown sugar

  • Juice the limes. Discard 6 lime halves.
  • In a food processor, combine remaining 18 lime halves, green chilli peppers, onion, ginger and raisins. Chop finely. Place mixture in a non-metal bowl.
  • Open cardamom pods. In a heavy skillet, toast peppercorns, cardamom seeds, mustard seeds, coriander seeds, and the dried red chillies for about 3 minutes, stirring constantly. Let the spices cool on a dry plate, then grind finely.
  • Add spices, lime juice, sugar, and vinegar to the chopped fruit mixture. Stir thoroughly, cover, and let steep at room temperature for 2 days.
  • On the third day, pour mixture into an enamelled pot (no stainless steel), add salt, and bring to a boil slowly. Simmer, uncovered, for 30 minutes.
  • Place in prepared clean jars. Close jars with a tight-fitting lid. Store in a cool place.

Still-Life, Jan Davidsz. de Heem, 1642

I found the chapter on art a little frustrating, though. There are many oranges in art and lemons in art, but authors who discuss such works should provide a few more illustrations. And equating oranges with “golden apples” in Greek mythology was rather dubious, I thought. But overall, I enjoyed reading this book.

Citrus: A History by Pierre Laszlo: 3½ stars


The dose makes the poison

Some time ago, someone pointed me at a “natural health” site which expressed shock that “Big Pharma” was putting “toxic copper” into baby formula. Those poor babies! Now the copper was there, all right, but only because copper is an essential mineral. Indeed, copper is present in human breast milk, at a concentration of about 0.36 milligrams per litre, and inadequate copper intake has terrible consequences, especially in premature babies. The copper was necessary. The key idea here, which the diagram below is intended to capture, is sola dosis facit venenum (“the dose makes the poison”).

Many essential vitamins and minerals, like copper, transition from a “no effect” dose (blue) to a beneficial dose (green) to a toxic dose (red). In the upper three bars of the diagram, the black dot indicates the recommended daily intake (which we should ingest), and the white bar marks the recommended upper limit, which we should not exceed (disclaimer: this diagram may contain inadvertent errors; please take your medical advice from official sources).

Something similar happens with medicines, like paracetamol (acetaminophen). Small amounts do nothing for your headache; in adults, one or two tablets (0.5–1 gram) safely ease mild pain; but exceeding the dosage indicated on the packet can cause liver failure and death.

Paracetamol tablets (photo: Mateus Hidalgo)

For toxic heavy metals like mercury, cadmium, lead, or silver, there is no beneficial level – the transition is from a “no effect” dose (blue) to progressively greater harm, up to and including death. In the lower four bars of the diagram, the white dot indicates the daily intake of the average person (which generally seems to have no observable effect), and the white bar marks the recommended upper limit.

When people are exposed to levels above the white bar, health authorities start to get worried. For example, shark meat can contain 1 mg of mercury per kg or more. Australian authorities recommend that if shark meat is eaten by pregnant women or children, it should be limited to 1 serve per fortnight (with no other fish eaten that fortnight). But even there, it is the dose that makes the poison.

Kitchen chemistry: fats and oils

Our previous kitchen chemistry post discussed esters. Fats and oils (triglycerides) are an important special case of esters. The alcohol in triglycerides is glycerol, a “triple alcohol” with three OH groups:

The glycerol combines with “fatty acids” (like the one on the right) which resemble acetic acid (left), but with a much longer hydrocarbon chain hanging off the COOH group:


The resulting triglyceride esters have three COO groups:

Fatty acids have important dietary implications, and they can be classified in dietary terms, but the most common classifications are chemical. The three main chemical classifications all refer to the presence of carbon-carbon double bonds:

One important classification is in terms of the number of carbon-carbon double bonds:

  • Saturated fatty acids have no carbon-carbon double bonds (they are “saturated” in the sense of containing as much hydrogen as possible). Fats made from saturated fatty acids (“saturated fats”) tend to be solid at room temperature, because the straight-line molecules stick to each other. Saturated fats are usually of animal origin (although coconut oil and palm oil are also mostly saturated).
  • Monounsaturated fatty acids have exactly one carbon-carbon double bond per molecule. Oleic acid (in e.g. olive oil) is an example.
  • Polyunsaturated fatty acids have two or more carbon-carbon double bonds per molecule. Linoleic acid (in e.g. sunflower oil) is an example.
Saturated fatty acid
Monounsaturated fatty acid   Polyounsaturated fatty acid

The position of carbon-carbon double bonds is also significant. A common classification counts the position of the first double bond, starting from the “omega” end of the molecule (the end furthest from the oxygen atoms). For example, there are omega-3, omega-6, and omega-9 fatty acids:

Omega-3 fatty acid  Omega-6 fatty acid  Omega-9 fatty acid

Finally, the orientation of double bonds is very important. In cis fatty acids, there are two hydrogen atoms on the same side of the double bond, giving a molecule with a “kink.” In trans fatty acids, the two hydrogen atoms are on the opposite sides of the double bond, giving a straight-line molecule (trans fats are usually synthetic, resulting from the partial hydrogenation of vegetable oils). Since the straight-line molecules tend to stick together, “trans fats” (made from trans fatty acids) tend to be solid at room temperature, while “cis fats” (made from cis fatty acids) tend to be liquid – that is, oils (such as olive oil) rather than fats:

Cis fatty acid   Trans fatty acid

Fatty acids can also be classified in dietary terms. The body needs fatty acids, but can manufacture most of them itself. Essential fatty acids are fatty acids that must be included in the diet. Both ALA and linoleic acid (found in vegetable oils) are essential. Adult men need about 13 grams of linoleic acid and 1.3 grams of ALA per day. Some omega-3 fatty acids from oily fish should also be included in the diet.

Fish oil capsules contain the omega-3 fatty acids EPA and DHA.

In contrast, trans fats are particularly unhealthy, and should be eliminated from the diet completely. This can be difficult in the USA, since pre-packaged foods there often contain trans fats (because of their long shelf life). Monounsaturated and polyunsaturated oils are also preferable to solid saturated fats.

Butter contains a large amount of saturated fat.