Many spice compounds slow the growth of bacteria in the laboratory. Whether that explains why hot countries use more spice, as Sherman and Billing proposed in 1998, remains an open question.
The question¶
Why do some cuisines use so much more spice than others? The food of southern India, Thailand, Ethiopia or Mexico is, on average, far more heavily spiced than that of Scandinavia or Britain. One explanation, which has attracted a good deal of attention, is that spices help keep food safe, and that cultures in hot climates, where food spoils fastest, came to value them for that reason.
The antimicrobial hypothesis¶
🔬 Sherman and Billing, 1998
The biologists Paul Sherman and Jennifer Billing of Cornell University analysed thousands of meat-based recipes from traditional cookbooks from several dozen countries. They reported that recipes from hotter countries used more spices, and more kinds of spice, and that the spices used most often were those with the strongest antibacterial activity in laboratory tests. They proposed that spice use is an evolved and culturally transmitted response to the risk of food-borne infection — sometimes called "Darwinian gastronomy". A follow-up study found vegetable recipes, which spoil less dangerously, were less heavily spiced than meat ones.
It is an elegant idea, and it is worth being clear about its status: it is a hypothesis supported by correlation, not an established fact.
What the laboratory shows¶
It is well established that many compounds in herbs and spices can inhibit or kill bacteria and fungi in the laboratory, often at quite high concentrations.
| Compound | Source |
|---|---|
| Allicin and related sulphur compounds | garlic, onion |
| Allyl isothiocyanate | Mustard, horseradish, wasabi (see mustard-oils) |
| Cinnamaldehyde | cinnamon, cassia |
| Eugenol | cloves, allspice |
| Thymol and carvacrol | thyme, oregano, savory, ajwain |
| Capsaicin | Chillies (modest activity) |
Some are used commercially. Rosemary extract, rich in the antioxidant carnosic acid, is a permitted additive (E392) that slows fats turning rancid, and mustard-derived compounds have been studied for use in food packaging.
Objections and complications¶
- Correlation is not cause. Hot countries differ from cool ones in many ways: the plants that grow there, trade routes, wealth, population density and culinary history. Spice plants themselves grow mostly in the tropics, so availability alone could explain much of the pattern.
- Dose. The concentration needed to inhibit bacteria in a laboratory dish is often higher than a cook would use, and food, with its fats and proteins, reduces the effect.
- Cooking does most of the work. Thorough cooking kills most food-borne bacteria regardless of spice, and many spices are added to food that is then cooked.
- Other explanations. Spices add flavour to bland staples, can make cheaper ingredients more appealing, and carry cultural meaning; these reasons are not exclusive.
Later researchers have tested the pattern with other data sets and methods, with mixed results, and the debate continues. The fairest summary is that spices probably contribute something to food safety in some traditional preparations, and that this may have played some part in shaping spice use, but it is unlikely to be the whole story.
The masking myth¶
A related claim — that medieval Europeans used spices to disguise rotten meat — is generally rejected by food historians. Spices were among the most expensive goods in medieval Europe, and those who could afford them could usually afford fresh meat; rotten meat would also have made people ill whatever it tasted of. Medieval spice cookery was about luxury, status and ideas of health, not concealment. See medieval-spice-cookery and spices-in-the-ancient-world.
What actually preserves food¶
In traditional preservation the heavy lifting is done by salt, sugar, acid, drying, smoking and fermentation, which lower water activity or pH to levels bacteria cannot tolerate. Spices play a supporting role in many of these foods — pickling-spice in pickles, pepper and nutmeg in cured sausages, chillies in fermented chilli pastes — contributing flavour and possibly a little extra protection.
⚠️ Spices are not a safety measure
Adding spice does not make unsafe food safe. Follow normal rules for cooking, chilling and storing food. Spices themselves, as dried agricultural products, can carry bacteria such as Salmonella, which is why most commercial spices are treated before sale; see spice-contamination.