It is hard to imagine Mexico without thinking of hot chili peppers or of India without curry. But what gastronomic sensations come to mind when we think of Norway, Sweden, or Finland? For some reason, spices are prevalent in the hotter, southern-most countries instead of cooler, northern countries. Why is it that some like it hot—and others do not?

Four centuries ago, spices were so difficult to procure that the trading of spices drove the world's economy much as oil does today. For centuries, the Arabs held a monopoly on the spice trade. Marvelous tales of a paradise protected by fierce monsters kept the weak at heart from searching for the source of the highly celebrated spices. However, the lure of these valuable spices eventually became too great for Europeans to ignore, and despite initial fears, large expeditions were eventually funded by the Portuguese, Spanish, Dutch, and English.

Historian Wolfgang Schivelbusch, in his book Tastes of Paradise, reveals an 11th century Europe that treasured spices as symbols of wealth—the higher the rank of a household, the greater its use of spices. The ruling classes had an unusual preference for strongly seasoned dishes, and individual spices were displayed on elegant trays and served to guests much like an aperitif would be offered today. Heavily spiced beverages were commonplace. By the 17th century, wars raged in Europe over the control of the fabled Spice Islands.

Spices as an Antidote to Spoilage

But modern-day scientists suspect a more practical appeal to spices: food preservation. Although today we have many methods to prolong the shelf life of food, including strict food handling guidelines developed by food manufacturers and the Food and Drug Administration (FDA), preserving precious food stores was a critical issue in the days before refrigeration. The most common type of food spoilage is caused by microorganisms, and contamination starts immediately after produce is harvested or meat is slaughtered. Techniques such as cooking, smoking, drying, salting, or spicing were the only reliable options.

Two Cornell researchers, Jennifer Billing and Paul Sherman, wondered if heavy use of spices might be related to the more pronounced need of food preservation in hotter climates. They focused on 43 spices used in the meat-based cuisines of 36 countries for which they could locate traditional cookbooks—a total of 4,578 recipes. Their goal was to test the age-old hypothesis that spices act as food preservatives, extensively used throughout the ages to keep food from spoiling.

Billing and Sherman only considered recipes that were based on meat, poultry, or fish because research shows that these dishes stored at room temperature for more than a few hours, especially in tropical climates, typically show massive increases in bacterial counts. Bacterial growth occurs on the surface of the meat, where spices would provide the most antimicrobial benefit.

Which Spices Provided the Best Protection Against Bacteria?

The researchers findings were significant. Out of the 43 spices, they found sufficient data to indicate antimicrobial properties on 30. The most effective were garlic, onion, allspice, and oregano, which inhibited 100% of the bacterial species they were tested against. Thyme, cinnamon, tarragon, cumin, cloves, lemon grass, bay leaf, capsicums (hot peppers), and rosemary all inhibited more than 75% of the bacteria they were tested against.

Of the recipes they tested, Billing and Sherman found that traditional recipes from the hottest climates used the greatest number of powerful antimicrobial spices, such as cinnamon, cumin, onion, garlic, and hot peppers. In fact, all recipes from the tropics called for at least one spice, whereas one-third of the recipes from the north were spice-free.

Spice Mixtures Enhance Food Preservation

Some spices were found to have enhanced antimicrobial effects when combined with other spices. Maybe this is the original basis for spice combinations like chili powder (typically a mixture of chili peppers, onion, paprika, garlic, cumin, and oregano) and curry powder (typically containing cumin, coriander, fenugreek, ginger, turmeric, dill seed, black pepper, red pepper, mace, cardamom, and cloves). This may also explain why fewer spices in combination are needed to prevent food spoilage, as opposed to single spices.

Based on their findings, the researchers concluded that adding spices to traditional meat-based dishes, especially in the hotter climates, was probably based on their ability to keep dangerous organisms at bay, and therefore, spices were originally used to preserve food.

The Biggest Spice Users

Interestingly, Billings and Sherman found that of the 36 countries investigated, ten stood out as the heaviest spice users—Ethiopia, Kenya, Greece, India, Indonesia, Iran, Malaysia, Morocco, Nigeria, and Thailand. This supports the theory that the countries with hotter climates relied heavily on spices to prevent food spoilage; however, these 10 countries have always been easily accessible by sea from the Spice Islands.

One possible explanation for the lighter use of spices in the northern countries could be due to the difficulty these countries had in obtaining them. It is possible that when traditional recipes were being developed, spices were not available in the northern regions of the world. However, upon review of all 43 spices, Billing and Sherman could find no discernible connection between proximity to the locale where spices were grown and spice usage.

Why Do Spices Work as Preservatives?

Scientists believe that the essential oils produced by plants, which give spices their distinct flavors, evolved to protect plants from attack by insects, bacteria, parasites, and other harmful organisms. Humans are affected by many of these same organisms, such as bacteria and fungi, that live on and in dead plant and animal tissue. If spices kill microorganisms or inhibit their production of toxins, then spice use might reduce the chances of contracting foodborne illnesses or food poisoning. The same chemicals in a plant that protect it from invading organisms might also be beneficial to humans.

Food microbiologists are still investigating spices for their potential as food preservatives. Researchers at Delta State University in Abraka, Nigeria are looking for inexpensive, simple, and reliable ways to preserve tropical fruits and vegetables, which supply much needed vitamins and minerals to inhabitants of developing countries. Despite the fact that these fruits and vegetables are abundant in these countries, the fruits become scarce soon after harvest due to limited storage facilities. The researchers are combining minimal heat treatment with the addition of the antimicrobial spices ginger and nutmeg with good results.

Today, health-conscious consumers are demanding that producers offer more foods that are less "processed" and have less added preservatives. Who knows? Maybe food microbiologists will bring us full circle and reintroduce the use of spices or other natural plant compounds—combined with minimal processing—to bring us foods that are closer to "fresh" and safer to eat.