A Comparative Analysis of Lime Species and Flavor Relevance in

Chapter 10

A Comparative Analysis of Lime Species and Flavor Relevance in Hispanic Food Suzanne C. Johnson

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The flavor of lime is prevalent throughout Hispanic food and food products but until recently has found somewhat limited application within the U.S. market. The increasing U.S. Hispanic population has driven a rapid increase in the number and variety of lime flavored food products introduced to the U.S. market. This includes products flavored with lime alone or in combination with other flavors. While some products are targeted to the Hispanic consumer, many are more mainstream. The typical profile of lime flavor found in U.S. products is quite different from the typical Hispanic limon flavor. It is a critical distinction that must be understood when formulating products to appeal to a particular market segment.

© 2007 American Chemical Society

In Hispanic Foods; Tunick, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2006.

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118 There are many reasons why we eat and why we choose to eat the way we do. Our basic nutritional needs could be covered by a diet far different from that consumed by most of us. The preference for certain foods and flavors is a relatively complex matter affected by our emotions and memories as well as our basic senses. There is also the undeniable cultural influence that greatly influences our choices. It can be said that familiarity leads to preference. When a food product that has been familiar and consumed frequently is removed from our diet, we have a tendency to crave that flavor. When this happens, only the exact product will satisfy our craving, and in fact a substitute that is similar is often rejected as undesirable. While an individual may develop a fondness for the new version, inevitably it will never be as good as the original. Similarly, when someone has a great fondness for a particular food product (mango, for example), it is not uncommon that they find an artificially flavored mango product to be offensive. This concept translates directly to the typical Hispanic vs. typical American expectation of lime flavor.

Lime Flavor Lime has always been a prevalent flavor within the Hispanic food market, from beverages to candy, chips to snacks and cakes, and of course alcoholic beverages as evidenced by the popular corona with a wedge of lime and the ever present margarita. Within the last few years the U.S. market has seen a huge growth in the number of products flavored with lime, either stand-alone or in combination with other flavors. Beverages, potato and tortilla chips, yogurts, and candy are just the beginning. Some have targeted the growing Hispanic population, while others are mainstream products with a twist. As the U.S. becomes more exposed to Hispanic products and foods there is a growing demand not only for authentic Hispanic products but also for fusion type products to appeal to the mass market. One critical prerequisite for successfiil product development in this arena is an understanding of flavor profile and its appeal to the target market. Lime is a prevalent flavor throughout Hispanic culture and until recently has found relatively little application in the U.S. market. It is also a great example of the difference in flavor expectations. The typical Hispanic lime profile is acidic and zesty, and is often served in combination with heat or spice in both food and candy applications. Even the Hispanic lime-flavored beverages are much different in flavor from the sweeter, candy-like profile typically found in the U.S. This is due in part to the prevalent variety of lime (Table I). In a product such as lime, both acidity (tartness) and sweetness, as well as salt i f applied, are as critical to the flavor perception as the aroma chemicals which inherently make a lime taste like lime. A lime flavor that tastes naturally tart and juicy in combination with acid and sugar can become sweet and candy-


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Table I. Comparison of Common Lime Varieties Citrus aurantifolia

Citrus latifolia

Key Lime Mexican Lime West Indian Lime

Persian Lime Tahitian Lime Bearss Lime Limon persa (Mexico) Limon sutil (South America)

Grown in Mexico, Peru, Haiti

Grown in Florida, Brazil

Smaller fruit, contains seeds

Larger seedless fruit

Yellow when ripe

Higher acid content, stronger flavor

Green when ripe, except Bearss turns yellow under appropriate ripening conditions Lower acid content, weaker flavor

Sensitive to cold

Enhanced resistance to cold

like when the acid is decreased. With lime being especially susceptible to this phenomenon, the composition of aroma chemicals can be contradicted by incorrect acid type and level in the final product.

The Lime Fruit The fruit itself is composed of three distinct parts, two of which are important to flavor. The outer skin, otherwise known as the epicarp or flavedo, contains not only carotenoids that give the fruit its distinct color but also the oil sacs containing characteristic essential oils. These essential oils are typically extracted and used in flavor manufacture. The white spongy layer immediately under the outer skin is referred to as the mesocarp or albedo and does not play an important role in flavor except perhaps for some occasional bitterness. The inside of the fruit, the endocarp, is composed of membrane-separated segments. Inside these segments are vesicles containing the juice.

Citrus latifolia Citrus latifolia, also known as the Tahitian Lime or Persian Lime, is the primary lime grown in the U.S. and it sold simply as lime. It was developed as a hybrid for its resistance to disease, pests, and climate. It is similar in size and


120 shape to a lemon. Although it is typically sold when green, it does turn yellow when fully ripe. It has a thick rind, is quite hardy, and has very few if any seeds.


Citrus aurantifolia Citrus aurantifolia is also known as Key Lime, West Indian Lime, or Mexican Lime. Most of the Key Limes found in the U.S. are currently imported from Mexico where it is grown year round. Within the U.S., they are grown in Florida, Texas, and California where they are seasonal. The fruit is smaller and seedier than Citrus latifolia with a thinner rind but also is more acidic and has a stronger more complex aromatic flavor profile. This lime is also sold and used when green but ripens to a yellow color. It lends its name to key lime pie and is also the lime of choice for margaritas. This lime predominates not only in Mexico but also in many other parts of the world.

Lime Processing There are three basic alternatives when processing citrus fruit for juice and essential oils: extraction of the essential oil from the whole fruit prior to juice extraction, extraction of the essential oil from the peel following juice extraction, and simultaneous extraction of juice and essential oil. If the essential oil is extracted before the juice, the juice is less likely to be contaminated by noticeable levels of essential oil, which must be removed to produce juice with an acceptable flavor profile. The quality of the essential oil however, is judged to be higher when separated from the peel following juice extraction.

Lime Essential Oils Lime essential oils generally fall into two categories: expressed (or cold pressed) and distilled. Expressed oil is washed out of the skin with water once the skin is ruptured due to a grating or pressing process. The oil is separated from the water by centrifuge. Due to limited processing, the flavor of expressed oil is close to that of the natural fruit. It is mid to dark green in color and can be cloudy. In contrast, distilled oil is purified after extraction by distillation producing a clear colorless oil. Many of the components that characterize the flavor of distilled lime are formed during the distillation process, while some volatiles and all non-volatiles are removed. While the distillation process is applied equally to both Tahitian and Key Limes, the majority of commercially available expressed lime is of the Tahitian variety.


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Analysis of Lime Oils A lime oil is a complex mixture consisting of a volatile and non-volatile fraction. The volatile fraction makes up 85-90% of the oil and consists primarily of monoterpene and sesquiterpene hydrocarbons and their oxygenated derivatives along with aldehydes, alcohols, and esters. The non-volatile fraction makes up the additional 10-15% and contains fatty acids, sterols, carotenoids, waxes, coumarins, psoralens, and flavonoids. In a distilled oil, the non-volatile fraction is removed, therefore a comparative analysis considers only the volatile portion of the oil. There are numerous reports of lime oil analysis utilizing a variety of methods and producing a variety of results (1-3). A thorough review of citrus oil analysis is available (4). The current comparison focuses from the perspective of flavor.

Expressed Lime Oil Comparison The comparison of expressed Tahitian and Mexican lime oils shows surprisingly little differences. The most prominent differences are the content of β-pinene and γ-terpinene (Fig. 1). The β-pinene content is higher in Mexican or Key lime oil than in the Tahitian or Persian variety. Its taste is described by Mosciano (5) as "Fresh, piney and woody, terpy and resinous with slight minty, camphoraceous and spicy nuance." In contrast, γ-terpinene is higher in expressed Tahitian Lime Oil. The taste of γ-terpinene is described as "oily, terpy, musty and citrus like" in taste (5).

Distilled Lime Oil Comparison During the distillation, process the composition of lime oil changes significantly. It is these changes that lead to the characteristic flavor and aroma of distilled lime (Table II). a- and β-pinene concentrations decrease along with neral, geranial, and sabinene leading to the formation of 1,4-cineole, 1,8-cineole, terpinolene, α-terpineol, fenchol, borneol, γ-terpinene, a-terpinene, and /?cymene. The primary differences in distilled Mexican or Key Lime and Tahitian lime can be seen in Figure 2. Key Lime is higher in quantities of terpinolene ("woody, terpy, lemon and lime-like with a slight herbal and floral nuance"), aterpineol ("citrus woody with a lemon and lime nuance"), and β-pinene ("fresh, piney and woody, terpy and resinous with slight minty, camphoraceous with a spicy nuance") (J).



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• Key s Tahitian

β-pinene

γ-terpinene

nerai

sabinene

neryl acetate

Figure 1. Expressed lime oil composition.

Table II. Lime O i l Comparison Distilled lime

Expressed lime

Character

Terpeny, fresh, sharp citrus note

Fresh, heavy, sweet, earthy, peel-like, smooth citrus note

Character impact compounds

1,4-cineole, 1,8-cineole, a-terpineol, γ-terpinene

High citral content balanced with β-pinene, γterpinene and neryl acetate

Main use

Cola or lime soft drinks

Lemon-lime soft drinks


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20

A

B

C

D

E

F

G

H

Figure 2. Distilled lime oil comparison. A = γ-terpinene, Β = terpinolene, C = a-terpineol, D = a-terpinene, Ε = β-pinene, F= p-cymene, G = β-bisabolene, H = myrcene.

Tahitian lime has higher levels of γ-terpinene ("terpy, citrus, lime-like, oily, green with a tropical fruity nuance"), α-terpinene ("terpy, woody, piney, citrus lemon and lime with spice and mint nuances"), and p-cymene ("terpy and rancid with slightly woody oxidized citrus notes") (5).

Lime Juice Lime juice, rind, zest, or essential oils may all be used in different recipes, whether industrially or in the home kitchen. Therefore, both must be considered in a flavor profile comparison. From an aroma chemical standpoint, lime juice is considerably less complex in nature than the essential oil (Table III). Freshly squeezed Mexican lime juice was compared to freshly squeezed Persian lime juice. Organoleptic evaluation (Table IV) correlates well with the analytical results (Table V ) . Mexican Lime is higher in γ-terpinene (herbaceous-citrus, terpene-like) (6) and β-pinene (resinous-piney odor, turpentine-like) (7).


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Table III. Number of Compounds Identified in Lime Juice and Lime O i l Juice

Cold Pressed Peel Oil

Distilled Peel Oil

Hydrocarbons Alcohols Aldehydes Ketones

13 18 6 4

36 32 19 8

27 17 7 3

Esters Sulfur compounds Ethers

5 1 1

12 0 2

2 0 2

Phenols Epoxides, pyrans, coumarins

0 4

2 12

1 0

Total

52

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59

SOURCE: Reference 11.

Table I V . Lime Juice Comparison Key Lime Juice

Tahitian Lime Juice

Character

Terpeny, piney, musty notes, balanced lime flavor

Fresh, tart, lime flavor, acid spike, less balanced

Significantly higher in

γ-terpinene, β- pinene, 4terpineol, bisabolene, geranial

a-terpineol


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Conclusion Natural extracts of lime have different characteristic profiles and differing compositions of aroma chemicals due to lime species, extraction methods, and processing. The appropriate combination of juices, essential oils, and aroma chemicals can be used to simulate typical lime flavor profiles in various applications.


Table V . Major Character Difference Contributors Aroma Chemical a-Terpineol

Description Sweet, floral (lilac), lime odor; very sweet taste in dilution; major impact component for lime

Higher in Tahitian

γ- Terpinene

Refreshing herbaceous-citrus-like terpene odor

Mexican

β-Pinene

Dry, woody, resinous-piney odor; turpentine-like taste

Mexican

β-Bisabolene

Sweet, balsamic odor, citrus, woody, myrrh, tropical, floral

Mexican

Geranial

Powerful lemon note

Mexican

4-Terpineol

Sweet, earthy-green, musty; slightly peppery woody notes

Mexican

SOURCE: References 6-10.

References 1. 2. 3: 4. 5. 6.

Shaw, P.E. J. Agric. Food Chem. 1979, 27, 246-257. Haro, L.; Faas, W.E. Perfumer Flavorist 1985, 10(5), 67-72. Guenther, E. The Essential Oils; D. Van Nostrand Co.: New York, 1949. Citrus; Dugo, G.; D i Giacomo, Α., Eds.; Taylor and Francis: London, 2002. Mosciano, G . Perfumer Flavorist 2000,25(2), 1-12. Mosciano, G. Perfumer Flavorist 1993, 75(1), 43-45.


126 Mosciano, G . Perfumer Flavorist 1993, 18(2), 39-41. Mosciano, G . Perfumer Flavorist 1993, 75(3), 53-45. Mosciano, G . Perfumer Flavorist 1993, 75(4), 51-53. Mosciano, G . Perfumer Flavorist 1993, 75(5), 39-41. Volatile Compounds in Food: Qualitative and Quantitative Data, 7th ed.; Maarse, H . ; Visscher, C . A . ; Willemsens, L . C . ; Nijssen, L . M . ; Boelens, M . H . , Eds.; T N O C I V O Food Analysis Institute: Zeist, The Netherlands, 1994.


7. 8. 9. 10. 11.


A Comparative Analysis of Lime Species and Flavor Relevance in

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