It's not so much a riddle, as a fact of commercial life. There are people, you see, who want black olives but don't like the taste of them. All black olives started life as green olives, vigorous, tough-skinned fruit. Then they ripened and turned pinkish-brown, gradually mauvish-purple and, finally, a glossy, wrinkled black; by now slippery with the savoury oil we love. But many find a ripe black olive unpalatable.
Thus, a design team would consign fat, wrinkled, old black olives with their slimy, decaying flesh to the bin. And, yuck, that taste, so strong, so bitter, earthy. Why can't a black olive be more like a green olive? The designer black olive would be as taut as a ripe cherry. Its taste would be unassertive. And, for the sake of convenience, it wouldn't have a stone to break your tooth on (pitting slippery, soft ripe black olives is one of life's less rewarding tasks).
Hmmm, sounds like a candidate for genetic engineering. In fact the Designer Black Olive was achieved by Californian cosmetic scientists. And today, using their techniques, olive factories in Spain are churning out tins of them in their hundreds of thousands.
I made my acquaintance with them one day when I was faced with a choice between an expensive jar of bottled olives, and this modestly priced, handsome-looking can, with the apparent bonus that the olives had been pitted.
I opened the can and found with some surprise that they did not taste of olives. Amazing. I drained them, drenched them in good olive oil (what a waste), and served them on a plate without comment. And, without comment, they were tasted and ignored. Can you imagine a bowl of juicy purple Kalamata olives being left untouched?
If you like the taste of black olives you wouldn't buy these, so why is there a market for them? Well, as a garnish. Even before the idea of the Mediterranean Diet, Americans sliced them onto millions of pizzas consumed every year. In salads too, night-black olives set off the green of salad leaves, the red of a slashed tomato.
They don't have any taste, agrees expert Anne Dolomore, author of several books on olives and olive oil. But she doubts if it's a scam any more than many food industry practices. Yes, she says, it is a charlatan, a green olive which has been "dyed" black.
How do they do that? Interesting. The green olive, as you will know if you've ever picked one off a tree, is supremely unpalatable. Yet its astringent, mouth-puckering bitterness can be drawn out by soaking it in water for weeks, or more effectively by leaving it in an alkaline solution of caustic soda.
That's the basic method. But there's more to producing say a gourmet olive, such as those giant, succulent green Queen Olives from Seville. These olives are first treated with with alkali to remove bitterness, then soaked in a brine which will produce lactic-acid fermentation and their characteristic flavour and texture. Throughout, it's essential to exclude air, or else the olive will oxidise and turn an offensive brown. Left too long, they will go black.
Go black? Green olives will turn black? So this is how they dye them. They plunge green olives into open tanks of caustic soda and agitate the mixture continuously for a week to 10 days, until they become a dark but not very lovely black. Then they wash the soda off and treat them with ferrous gluconate to fix the colour. Because of their firmness, they will stand up to machine-pitting and, finally, they are canned in brine. Black olives, of a sort. Forget about the flavour.
Favourite olives continue to be nutty Spanish green manzanillas, the savoury purply Greek Kalamata olives, and small sweet black Nicoise olives.
Stuffed olives are a charming alternative, green olives pitted and filled with anchovy, red pepper, almonds or - a new variety - smoked salmon. Alas, some choices are not what they seem, for in switching from hand- filling to machine-stuffing, something has been lost. Examine the pimiento stuffing and you will find it is a piece of extruded paste, not a morsel of red pepper.
The good news is the increasing range of olives offered in speciality shops and at deli counters; as it's possible to taste before buying, you can't go wrong. Many delis make up their own cracked green olives marinated in spiced and herbed mixtures, using anything from olive oil and lemon juice, lemon peel, cumin seed and coriander seed, to garlic and hot green peppers. There's no reason why you shouldn't buy bog-standard olives, green or black and do your own. Anne Dolomore suggests the following recipes:
CRACKED GREEN OLIVES
Rinse 1kg (2lb 4oz) of green olives and crack them with a hammer to break the flesh but not the stone. Put into a jar, layering with coriander seeds (6 tablespoons), dried oregano (4 tablespoons) and peeled garlic cloves (about three). When jar is full, top up with olive oil. Marinate for two to three weeks.
MARINATED BLACK OLIVES
Fill a deep jar with 500g (1lb 2oz) black olives, adding 30ml (2 tablespoons) red wine vinegar, two cloves of garlic, 15ml (1 teaspoon) paprika and one slice of lemon, topping up with olive oil. Leave to marinate for two or three weeks.
Drain brine from a jar of green olives, reserving half the brine. Return to jar with two crushed cloves of garlic and a pinch of oregano. Mix the reserved brine with enough white wine vinegar and olive oil to top up the jar. Leave for several weeks to mature.
COOKING WITH OLIVES
Green and black olives feature in some fine Mediterranean dishes; black in a French beef daube (a slow oven-cooked braise), a Portugese bacalao (dried salted cod with potatoes, onions and black olives); Moroccan black olive and orange salad; and green olives as in a Moroccan lamb tagine (very slow-cooked meat stew).
Here are the instructions on how to make two traditional olive pastes - a tapenade from France, and a green olive paste from Spain - and also the recipes for two dishes that include olives, all are taken from Anne Dolomore's Essential Olive Oil Companion (Macmillan pounds 10.95).
This Provencal spread is delicious on toasted bread and served as a canape, or it is often used to stuff hard-boiled eggs. Some recipes contain tuna but I think that just the flavour of the olives and anchovies is best.
200g/8oz black olives, stoned
2 cloves garlic
200g/8oz capers, drained
100g/4oz anchovy fillets
5ml/1 teaspoon mustard
15ml/1 tablespoon olive oil
If you think the anchovies are going to be too salty, soak them in milk for 10 minutes. Then place all the ingredients in a blender and mix to a smooth paste.
GREEN OLIVE PASTE
This paste is a mixture of typical Spanish produce which can be used as a spread on bread to serve as tasty tapas. It makes an ideal snack to hand round to your guests when you are having a barbecue.
Serves up to 12, as nibbles
40 green olives, stoned
5ml/1 teaspoon capers
5ml/1 teaspoon ground almonds
1 clove of garlic
60ml/4 tablespoons olive oil
12 teaspoon cumin
12 teaspoon paprika
14 inch slices of french bread
pimiento for garnish
Place all the ingredients, except the bread and pimiento, into a food processor and mix until you have a fine paste. Spread thinly on the slices of bread, decorate with pimiento pieces.
PASTA WITH BLACK OLIVES
500g/1lb penne or rigatoni
200ml/7fl oz olive oil
400g/14oz tin of tomatoes
2 cloves of garlic, crushed
300g/12oz tin tuna in oil, drained
1 tin anchovy fillets in oil, drained and chopped
12 black olives
salt and black pepper, to taste
Cook the pasta in plenty of salted, boiling water with a dash of olive oil. When it is al dente drain and tip into a serving bowl. While still hot pour over the olive oil and toss well.
Put the tomatoes with their juice and the garlic into a blender and process until you have a thick sauce, then stir this into the pasta, adding salt and black pepper. Add the flaked tuna and anchovies, then stir in the olives. Serve warm, or cold, but do not refrigerate.
The Spanish omelette is famous the world over. In this recipe, a small, plain omelette is combined with olives to make an unusual stuffing for beef. This is an old family recipe from Maria Jose Sevilla, the Spanish cookery writer.
600g/1lb 4oz skirt of beef
100g/4oz green olives, stoned
23ml/112 tablespoons flour
60ml/4 tablespoons olive oil
2.5ml/12 teaspoon thyme
120ml/4fl oz dry white wine
240ml/8fl oz beef stock
salt and pepper, to taste
Using the eggs, make three plain omelettes. Lay the skirt of beef flat and, using a sharp knife, cut a layer across the meat to within 2cm of the opposite side. Roll back the top layer and season. Place the omelettes and olives on top of the meat, covering the whole surface. Roll up the meat, secure with string and dust it with flour. Heat the olive oil and brown the meat. Add the thyme and wine and cook for a few minutes. Reduce the heat, add the stock and simmer for about an hour or until the meat is tender, adding more stock if necessary. Place on a large serving dish and remove the string. Allow the meat to rest for a few minutes, then slice. Pour the juices from the pan over the beef. Serve immediately.
Spain: The most renowned is the manzanilla (baby apple); a tight, meaty, juicy fresh olive with appealing pale green skin (the one that features in Martinis). The very big green ones are Gordals (gordo is Spanish for fat). Arbequinas are very small, tasty green olives from Cataluna.
Greece: Kalamata: purple, almond-shaped, dry-brined, packed in vinegar. Konservolia (also known as amphissa, atalanti, and salona): large, fruity, packed in brine. Thassos Throumba: small, wrinkled black olive. Elitses Koroneiki (elitses means little olive) from Crete: small, salty black olives. Naftlion: dark green, cracked for brining, chewy, packed in oil.
Italy: Liguria: small, acidic black olives cured in brine for eight months; best are called Taggiasca. Gaeta: mild, wrinkled black olives, dry-salted. Ponentine: mild, purplish-black olives, packed in vinegar. Ascolane: mild, large green olives, brine-cured.
France: Nicoise coquilles: very small, purple olives, brine-cured. Tanches (veritable de Nyons): large, plump, brown, oily. Tailladees: slit, plump, soft purple olives, lovely sour tang, brined, with orange pieces. Lucques Royales: from Carcassonne, early picked green olives, very pure, appley, fresh taste of oil. Picholine: long, green, early-picked, rather salty. (Fortnum & Mason, Selfridges or mail order from Fresh Olives Direct 0181 453 1918).