November 6, 2014

EAT A PEACH | Spice Trade

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Spices have been a part of international trade for all of human history. Commissioned by Kings and Queens of the Middle Ages, explorers like Marco Polo, Ferdinand Magellan and Christopher Columbus risked their lives and the lives of their crew members to establish all-water routes to India, a major spice trade center since 3000 B.C. European nations often tried to claim spice-growing countries, and their efforts precipitated several wars, all to obtain access to spices. Upon laying siege in Rome in 408 A.D., Alarich, a Gothic leader, demanded 3,000 pounds of pepper! In the Middle Ages, you could buy a sheep with a pound of ginger, or seven sheep with a pound of cloves! So why were spices so popular, so necessary?

Spices are composed of secondary compounds, or phytochemicals, produced by a plant to protect itself from parasites, pathogens or herbivores. Most spices contain dozens of these chemicals, and each spice’s unique aroma is attributed to its phytochemical cocktail. Secondary compounds are a plant’s natural defenses.

The obvious answer for the value of spices is they add flavor and color to food — an important benefit considering food wasn’t always so palatable. Yet why do we find the pungent, secondary compounds of plants so appetizing? And why are some spices so popular in some cultures, and non-existent in others?

In a time that lacked refrigeration, food spoiled quickly, or became inoculated with dangerous microbes before even showing signs of spoilage. Since food was often scarce, people were likely to be forced to eat things that weren’t exactly sanitary. Feeding oneself was a necessary, yet highly perilous, venture. Cooking methods helped to eliminate bacteria in raw foods, but once the food is cooked, it immediately becomes vulnerable. Spices, it seems, picked up where cooking left off. The same phytochemicals that protect plants from disease also protect us from food-borne illnesses. Phytochemicals are also generally thermostable, so their antimicrobial properties are not harmed by the high temperatures of cooking. Spices that are sensitive to temperature, such as parsley and cilantro, are typically added after cooking, so their antibiotic properties are not lost. Enjoying the flavor of spices is an evolutionary strategy that protected us from infection. The use of spices in cooking (or the use of parsley and cilantro after cooking) enhanced survival by reducing food-borne illnesses. Those who enjoyed the flavor of spices were more likely to survive, and then pass on their spice-preferring genes.

In a study by Cornell University in 1998, 43 spices from 36 countries with traditional cookbooks were examined for their antimicrobial properties, and their frequency in recipes across cuisines. Data on temperature and precipitation were also collected, to confirm a correlation between climate (a.k.a. susceptibility to bacteria) and spice use. They found that all 43 of the spices “inhibited or killed at least one-quarter of the [30] bacterial species tested, and half of the spices inhibited or killed three-quarters of these bacteria.” Furthermore, “the four most potent spices — garlic, onion, allspice and oregano — killed every bacterial species tested.” They also found a correlation between climate and spice use. The hottest climates, including India, Indonesia, Malaysia, Nigeria and Thailand, where food spoils most quickly, used the greatest quantity and the greatest number of spices per recipe. Comparing the hottest country (India) to the coldest (Norway) revealed a stark contrast. In India, which regularly uses 25 different spices, “the average meat-based recipe called for about nine [spices],” whereas in Norway, where a maximum of 10 spices are traditionally used, there were “usually less than two spices per recipe.” The most popular spices are the most powerful ones (their preference enhances survival), and the use of these spices increases as average temperatures rise.

In terms of susceptibility to pathogens, vegetables, just like the plants that produce spices, often contain inhibitory compounds that fight off pathogens. Plants also have modified cell walls, and maintain a more acidic pH level (4.3 to 6.5). These modified cell walls, composed of cellulose and lignin, are difficult for aerobic bacteria to decompose, and bacteria prefer a higher, more neutral pH (6.6-7.5). Meat, on the other hand, loses the natural defenses it once had (the animal’s immune system) when the animal dies. Meats are therefore extremely susceptible to bacteria. In keeping with the antimicrobial hypothesis, meat-based recipes should exhibit greater use of spices than vegetable-based ones. Sure enough, this is exactly what the Cornell researchers found. Across all cultures, meat based dishes called for an average of 3.9 spices per recipe, whereas vegetable dishes called for an average of 2.4.

Although food is much safer these days, our evolutionary history explains why dishes are so much more palatable when they’re seasoned. We come from a long line of ancestors who survived because they added nature’s antibiotics to their meals. So go ahead — douse your oatmeal in cinnamon, cover your vegetables with curry, or sauté everything with a little bit of garlic. With flu season coming up — history has shown—it can’t hurt.

Ella Nonni is a junior in the College of Human Ecology. She may be reached at [email protected]. Eat a Peach appears alternate Fridays this semester.