At Chef Danhi & Co., for example, each time a recipe research project begins—it’s started with the end. That is to say, the final flavor profile desired for the shelf or the menu is the guide for what market form of a key ingredient, such as citrus, will be sought from suppliers. Often this means using a combination of ingredient sources. Some may be designed to be included in the manufacture of the product; others to be added by the operator or consumer.

There are some technical considerations necessary when choosing the right application of citrus to a food or beverage formulation.

“Citrus oil and citrus essence are among the most useful flavoring ingredients, especially in items such as soft drinks, dairy, candies and pastries,” acknowledges Anibal Concha-Meyer, Ph.D., a fruit technology scientist and research coordinator at the Centro de Estudios en Alimentos Procesados in Talca, Chile.

He explains that compounds called terpenes—specifically citral—are primary flavor and aroma consituents in lemon oil and lemon essence, as are other major chemical terpinoid components, including d-limonene, gamma-terpinene and alpha- and beta-pinenes.

However, Concha-Meyer notes, the high level of unsaturated fats and oxygen-functionalized compounds in citrus oil, specifically, make terpinoids highly susceptible to oxidation.

He further points out that changes in citrus peel oil constituents from such chemical reactions as oxidation have long been known to alter flavor in citrus oil and juice, especially during storage. Concha-Meyer cautions that oxidation is influenced not only by the presence of oxygen itself but by temperature, UV radiation and trace metals that can act as catalysts.

But, it is these chemicals that make citrus such a powerful flavor contributor. Concha-Meyer explains that airborne flavor molecules in the mouth pass back up through the nasopharynx and into the nose from the reverse direction from when they are inhaled. The mouth combines this olfactory sensation with both taste and textural sensations from a food for a complete sense of flavor. The characteristic citrus flavors themselves arise from volatile flavor materials, largely the aforementioned terpene compounds, which pass up through the back of the mouth and into the nose via the retronasal passages.

Citing research by Aldrich, et alia, Concha-Meyer illustrates that attempts to enhance sweetness of formulations, such as fruit-flavored candies by using sorbitol in combination with other natural sweeteners (for example hydrogenated starch polyol compounds,) typically fail. The researchers also pointed out that the citric acid contributing the needed sour/tart note to a fruit flavor will suppress sweetness and mask sweet fruit flavors, imparting “distinct citrus overtones in the case of non-citrus flavors, such as cherry and pineapple,” and imparting a “bland taste in the case of citrus flavors, such as lemon, lime, orange and grapefruit.”

When Life Hands You Lemons

A lemon is not just a lemon. Each variety has its own flavor story, and nuances of tastes within each family of citrus can be downright dramatic. Meyer lemons, believed to have developed as a hybrid of a lemon and a mandarin orange more than a century ago, are not quite as acidic as a standard lemon. They have trended markedly, being a great fit for desserts, and are the new “turn-to” lemon variety for a number of formulations.

Whole lemons, in general, are an underutilized fruit. The fragrant zest, bitter pith and juicy center all have their role in creating a flavorful marinade, dressing or dip. For example, when developing a marinade for grilled chicken, whole lemon pieces with garlic, pepper and oregano can be combined in a vacuum-tumbler and frozen. The result can be grilled and served on top of a salad or pasta.

There are a few manufacturers offering such a product, in small packages, to developers. But product developers need not bring in whole fruit to wash and prepare themselves. There are a number of providers of puréed whole citrus.

Lemon zest is one of the most commonly requested R&D ingredients and for good reason: Its bright flavor without the acid is more versatile. Plus, formulators don’t need to be concerned about the acid effecting color of pigmented vegetables, or the acid breaking down the animal proteins or changing the effectiveness of starches and gums. Orange and grapefruit also are easily employed and utilized. However, a suitable lime zest can still pose a challenge. There are dry forms of zests, but typically, they become too bitter and lack a lot of the specific aromatic characteristics that make them desirable.

Limes, on the whole, have an even more pronounced difference in flavor profile per variety. For example, the most common lime, the Persian lime, is the workhorse of the category. It possesses an archetypal lime aroma, acidic bite and a touch of sweetness.

Compared to the complex flavor of the more exotic Philippine lime, known also as the calamansi, the Persian lime is quite simplistic. Frozen calamansi juice is available, although expensive. It’s possible to approximate the flavor with a blend of Persian lime, lemon, orange, grapefruit, and a touch of red onion juice and salt.

Lime Time

Kaffir limes are a key component of many Southeast Asian cuisines, especially Thai, Malaysian and Indonesian. Kaffir leaves are used in a number of forms, but due to difficulties in importing citrus, coupled with a short growing season, availability (and therefore usage) of the peel and juice has traditionally been limited. The leaves are somewhat more available, often in whole, frozen form.

The kaffir lime has a powerful floral aroma and deep lime flavor. Recent cultivation in the U.S. has helped support demand in Southeast Asian restaurants and retail markets in the U.S., but until domestic production catches up to demand from other food operations, the fruit will remain a premium citrus.

Citrus juice is among the most commonly used and available forms of citrus in product development and production. It is in multiple market forms that fit any formulation need, including refrigerated, frozen or shelf-stable formats. These ensure a consistent acid level when prepared by manufacturers using the grams per liter of citric acid (GPL) rating system. Also the brix level (sugar content) is part of the specification and even pulp content. Concentrated forms of juice can be sourced and used when looking for the brightest flavor possible.

As processors scale-up recipes into formulas for larger volume production, it’s necessary to search for solutions to the variability of fresh lemons and other citrus. Fresh is still an option, yet sometimes a product such as frozen zest or a citrus powder is a better fit. A synergy of a few ingredient forms often are employed. For simpler citrus flavor, pasteurized lemon juice and frozen zest can come close approximating fresh.

 Often, R&D of more broad category formulations mandates reliance on a broader repertoire of citrus forms. Ease of use, microbial count and seeking a specific flavor element of the citrus without the entire flavor profile drive the form to be used. Fortunately, there are multiple options out there for the dedicated developer.