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Lime Correspondent: Science and Chemistry Behind Limes and Citrus

By Patrick Gallagher

The last few weeks have been bleak in the world of limes. With their not going down anytime soon, airlines have decided to ax the little citrus from their in-flight meals and are even replacing it with lemon. In fact, one article I found in my research has even proposed that lemons are just as fine a substitute for limes in most scenarios. This brings us to quite the junction in this horrific lime climate — limate, if you will — what truly differentiates a lime from a lemon? Physically, there are a multitude of differences. Limes are green and smaller, while lemons are slightly larger and yellow. But when it comes to cooking, how does one account for the differences in flavor? The answer to that lies in chemistry.

Before delving into the differences between limes and lemons, it is important to give a brief overview of the flavor chemistry involved with citrus in general. One of the most prevalent chemicals in lemons and limes is ostensibly citric acid. In the culinary arts, it is often used to give foods a more sour flavor. Of all citrus, lemons and limes have the highest concentration of citric acid, constituting up to about 8 percent of the fruit’s dry weight.

Both limes and lemons contain a compound mentioned on this blog once before: ascorbic acid, also known as vitamin C. This chemical has proved vital in preventing scurvy. Scurvy is a condition caused by a lack of vitamin C that inhibits the synthesis of collagen, a vital structural protein that constitutes a large percentage of connective tissue in the body. In fact, the connection between ascorbic acid and scurvy goes beyond the ties of science — ascorbic acid’s name is derived from the Latin name of scurvy, scorbutus.

Citral is one compound that gives citrus their scent, and is present in the oils of several plants, limes and lemons included. The scent given off is a strong lemon odor, and the compound is also known to have both powerful antimicrobial and pheremonal effects on insects. The main component of the citrus scent, however, stems from limonene, which takes its name from the rind of the lemon.

Having gone into this lengthy discussion on what chemical similarities limes and lemons have, what truly sets them apart? If they share such similar constituents, surely replacing one for another should not have much of a consequence on the taste bud. While they are similar, the subtle differences between limes and lemon are what  make our sense of taste so delicate and wonderful. In Harold McGee’s book, “On Food and Cooking, The Science and Lore of the Kitchen,” McGee presents a table outlining differences in acid and sugar content between lemons and limes.

 As made evident by the table, limes contain less sugar and more acid, which can explain the more bitter and tart flavor. While lemons are still acidic, their relatively higher sugar content makes them less bitter to the taste. But beyond the relative ratios of sugar and acid, there is something bigger at stake when replacing limes with lemons. Culinary cultures have been built alongside the lime, ranging from Mexico to Vietnam. To substitute limes for lemons is to actively ignore the years of culture derived from these dishes, as they were meant to be prepared. Times are hard for lime-enthusiasts, and some cannot avoid substitution. If this is the case, remember to honor the lime for what it has brought to the world, and, once this shortage is over, what it will continue to bring.


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