The answer to the conundrum is that neither is really "superior". Soy sauce is sold in two forms, light and dark - and Superior Soy is light, Soy Superior dark. That's one of the nuggets of wisdom provided by the renowned chef Ken Hom, presenter of the new TV series Hot Wok and one of the judges in our tasting of soy sauces to mark the start of the Chinese New Year (the Year of the Rat, incidentally).
Another judge, the New Zealand chef Mark Gregory - author of Cooking Japanese Style - confirms that choosing a soy sauce is a complex matter. The difference between a quality soy and a cheap one is a wide as that between grand cru wines and plonk. There are slow-fermented, fragrant, complex soy sauces, and salty, coarse and mouth-puckering ones. The innocent who buys cheap soy sauce, unable to decipher Chinese hieroglyphics, may be buying a crude chemical concoction.
With these pitfalls in mind, we organised a tasting of 20 different soy sauces, ranging from the traditional light and dark varieties (such as Kikkoman, Amoy and Sharwood's), to new ones flavoured with chilli, citrus and seasoning. These latter were not generally liked, but the supermarkets' own brands - and notably Sainsbury's - did well.
Even as we unpacked our samples, the semantic problems of soy sauce confounded us. We had ordered Pearl River Bridge, the brand most used by Chinese in Britain, but realised it was the wrong type - Soy Superior, the dark variety, rather than the light. Light soy sauce is a thin liquid, while dark is thicker and leaves a film on the glass when you shake the bottle (though the colour difference isn't always obvious since "dark" varies from medium brown to almost black).
For our third panellist, Mr Deh-Ta Hsiung, the author of several books on Chinese food, the distinction is most important. He gets through a bottle of light sauce every week, a bottle of dark sauce only every three months. He uses light soy, the saltier of the two, as a savoury seasoning in cooking. Dark soy, thicker and slightly milder and sweeter, he uses in a stew to add colour, or occasionally as a dip at the table. Mr Hsiung adds sugar, vinegar and chopped spring onions to make a seasoning that is in turn salty, sweet, sour and hot.
Soy sauce also has different uses in different Eastern countries. Ninety per cent of all soy sauce sold in China is used in cooking, for example. In Japan it is the opposite: 90 per cent of soy sauce (they use the dark type) is used as a dip, a table condiment into which you plunge deep-fried tempura pieces, sashimi (thin slices of raw fish), sushi (rice balls), or skewered, grilled fish, meat and chicken.
Our fourth panellist was the Thai food writer "Vatch" Bhumchitr, owner of the Chiang Mai restaurant in Soho, London. In Thailand, they use both light and dark varieties in cooking and in dips. A Thai dip, however, will be highly seasoned with grated ginger, garlic and chilli, and perhaps sugar and lemon or lime juice. Aromatics will occasionally be added, such as chopped lemongrass, kaffir lime leaves and peel, or Thai basil.
These are degrees of sophistication barely known to us in Britain. To most of us, soy sauce is an agreeably salty condiment that gives a lift to stir-fries (it's also very good on fish and chips, its acidity cutting into the oiliness). Since we buy soy sauce mainly from supermarkets - Amoy, Sharwood's or the own-brands now offered by Tesco, Sainsbury's and Safeway - there is no problem distinguishing between light and dark. Labels clearly state which is which.
Having got all this straight, it's time to taste the sauces. Mr Hsiung, however, introduces a further quibble. Soy isn't really a sauce, he says, it's an extract. But the tasters are agreed on what they are looking for: quality of aroma, complexity of taste, and a balance of sweet and salt on the tongue.
We taste light sauces first. Sainsbury's is the streets-ahead winner, everyone's first choice: mild, delicate and very salty (light soy sauces are saltier than dark ones). Kikkoman's was pronounced the best dark sauce: complex, with a lovely balance of sweet, salt and sharp flavours. A Thai soy sauce called Fat Boy (Dek Ohan) got my highest marks and it's the one that Vatch uses in his restaurant. Unfortunately, it is obtainable only from Thai stores, which are very few in number here.
Given the high prices of the supermarket sauces, Mr Hsiung suggests that it pays to know about Chinese labelling. Soy sauces sold in Asian and Chinese stores are often a fraction of the price - up to a 10th, or even a 20th if you buy in bulk. Even premium brands such as Kikkoman are much, much cheaper when bought in plastic one-litre containers rather than glass jars.
It also pays to know a little chemistry. Mark Gregory offered us a brief lesson. Non-brewed soy sauce, the cheapest variety, is made in just three days by a method familiar in the British food industry, that used to make hydrolised vegetable protein, a common savoury seasoning. Soya beans are first boiled with hydro-chloric acid, then cooled and neutralised with sodium carbonate. The mixture is pressed, mixed with active carbon, then filtered and blended with corn syrup, caramel colouring and salt, before it is refined and bottled. Voila! Soy sauce - of a sort.
Fermented soy sauce is a different matter, as I happen to know from visiting Kikkoman's giant plant in Noda, north of Tokyo. In Japan, there's really only one soy sauce, and this is it. The major companies merged 25 years ago to form a virtual monopoly. They took this well-liked domestic product and transformed it into a major export, so it now features as the brand leader in 94 countries, catapulting a 16th-century cottage industry (akin to wine making) into the 21st century.
Soy sauce is in fact a Japanese invention, a derivative of Chinese fermented beans (which are still used in Japan as miso, especially in soups). A Japanese Buddhist monk visiting China in the eighth century brought the bean curd recipe back, and it was initially prized as a preservative for meat and fish. Then they discovered they preferred the juice to the paste, and soy sauce was born.
These days Kikkoman uses American soy beans (steamed until they are soft) and Canadian wheat (crushed and roasted). These are combined with Japanese salt and yeast to make a paste, which is liquefied and piped into pendulous overhead vats to ferment. In earlier centuries, the soy paste would have been pressed through cotton cloths. Today they use a fine nylon net four metres wide, folded over to make an envelope or bag, which is filled with layers of paste. Every four metres the layer is doubled back over itself, until two miles of continuously woven net have been fed into the press frame, a height of eight metres.
A hydraulic compressor then starts to squeeze out the extract. After five hours the contents are transferred to a second press, and the process continues for another 10 hours. The four presses each yield 80,000 litres of concentrated soy a day. During the six months of fermentation, proteins in the soy beans turn into amino acids, developing the savoury taste. The starch in the wheat turns to sugar, then alcohol, then acid, each stage in turn contributing sweetness, fragrance, tartness, colour.
This is what we mean by fermented soy sauce. Most of it is pasteurised and bottled, then whizzed off around the world. For home consumption, however, Kikkoman also produces premium extracts (like single malts) that can genuinely be called "superior soy sauce".
The three recipes below - Chinese, Japanese and Thai - represent the way the respective cultures use soy sauce.
RED-COOKED LEG OR SHOULDER OF PORK
A Chinese New Year special, this dish is a must for every feast and is the nearest equivalent to the British Sunday joint. Leg of mutton or shin of beef, cut into large chunks, can also be cooked this way. This recipe comes from Deh-Ta Hsiung's The Festive Food of China (just reprinted by Kyle Cathie, pounds 4.99).
1.35-1.5kg/3-312lb leg or shoulder of pork, cleaned
4-5 spring onions
3-4 slices of fresh ginger root
3 tablespoons light soy sauce
100ml/4fl oz dark soy sauce
3 tablespoons brandy
115g/4oz brown sugar
Make sure the pork skin is free of bristles and score the rind and meat with a few cuts.
Place the meat with spring onions and ginger in a large saucepan, skin side down. Cover with cold water and bring to the boil rapidly, skimming constantly. Add the soy sauces and brandy, reduce the heat and simmer, covered, for 30 minutes. Turn the meat over, add the sugar, cover, and continue cooking for about 112 hours. Now reduce the liquor by boiling rapidly, uncovered, for five to 10 minutes.
To serve: lift out the meat and put it on to a deep serving dish, skin side up. Discard the ginger and the spring onions and pour the gravy over the pork. The meat should be so tender that it can be torn into shreds with chopsticks.
MARK GREGORY'S SALMON TERIYAKI
4 salmon fillets, 175g/6oz each, skinned and boned
1 tablespoon sunflower oil
4 sprigs of watercress
2 tablespoons grated daikon (giant white radish)
For the teriyaki sauce:
1 teaspoon caster sugar
1 teaspoon sake or dry white wine
1 tablespoon mirin or sweet sherry (optional)
2 tablespoons Kikkoman soy sauce
Grilled salmon tastes fabulous with teriyaki sauce. It is simple to prepare, and makes a wonderfully healthy meal for all the family.
Mix the teriyaki sauce ingredients together until the sugar dissolves. Marinate the salmon in it for 10-15 minutes. Drain, reserving sauce.
Brush the marinated fillets with sunflower oil. Place on a rack skin side up and grill for four to five minutes until slightly golden. Turn over and grill for a further four to five minutes.
Serve immediately on warm plates. Garnish the salmon with the watercress and serve with grated daikon as a condiment in a small bowl.
STEAMED SCALLOPS WITH GARLIC
A typical Thai recipe from Vatch's Thai Cookbook (Pavilion, pounds 19.99)
6 scallops on the shell, cleaned
3 tablespoons oil
3 garlic cloves, finely chopped
1 small red or green chilli, sliced into fine rings
3 tablespoons light soy sauce
2.5cm/1in piece ginger, finely chopped
1 teaspoon sugar
1 small red chilli, finely chopped
2 tablespoons spring onion, sliced into fine rings
6 coriander leaves
Set the scallops on their shells in a steamer over 2.5-5cm/1-2in hot water. In a small frying pan, heat the oil, add the garlic and fry until golden brown. Pour a spoonful of garlic and oil over each scallop, add a little sliced chilli, cover, and steam over medium heat until the scallops are cooked (10-15 minutes). While the scallops steam, mix together all the sauce ingredients.
When the scallops are cooked, remove them from the steamer, place on a serving dish and garnish with the sliced spring onion and coriander leaves. Serve the sauce on the side. !
A REALLY SUPERIOR SAUCE
Of our 20 soy sauces, the following are the top four in each of the two categories. They were awarded star ratings on the basis of aroma, complexity of taste, and the balance of sweet and salt sensations on the tongue.
LIGHT SOY SAUCES
****Sainsbury's Light Soy Sauce, 150ml, 42p
**Safeway Light Soy Sauce, 150ml, 49p
*Amoy Light Soy Sauce, 150ml, 51p
***Pearl River Bridge Superior Soy Sauce (light), 1 litre, 59p. This one was missing from our tasting, but sampled afterwards; it's the brand favoured by Chinese cooks in Britain.
DARK SOY SAUCES
*****Kikkoman All-purpose, 250ml, 59p
****Safeway Rich Dark Soy Sauce, 150ml, 42p
***Amoy Premium Dark Soy Sauce, 150ml, 65p
**Sharwood's Rich Soy Sauce, 150ml, 65p
Another strong contender was Fat Boy (Dek Ohan), available only from specialist Thai shops, which are few and far between.