BOTANICAL EXTRACTS:

NEW USES OR NEW

EXTRACTION PROCESSES

MAY INDICATE

NEW INGREDIENTS*

NATURAL EXTRACTS

Natural extracts are more than a simple ingredient statement on a label, or the primary component for which the extract may be marketed, such as a citrus flavor note or the characteristic flavor and smell of rosemary from a rosemary extract. Natural botanical extracts are many times composed of hundreds of different individual chemicals, which may have a distinct impact on both the purported action of the extract, as well as the safety profile. This article discusses the many different aspects of natural botanical extracts, the basic composition of different extracts from different extraction processes, and the impact the extraction process may have on the resulting ingredient and the ability to determine the safety of the extract.

INTRODUCTION

Food formulators and food product manufacturers have a wide array of food ingredients available to incorporate into new and unique-tasting food products, due to the general understanding that many of the currently accepted ingredients that meet regulatory approval may be used according to current good manufacturing practice standards. That is, the large majority of food ingredients may be utilized at the minimum level to produce the desired effect, as long as the effect is still within the use for which the ingredient was approved. For example, rosemary oil has been concluded safe under the generally recognized as safe (GRAS) standard in the United States when used as a flavoring ingredient in foods generally. Therefore, as long as the intended use in food is to provide flavor and the concentrations used are similar to industry norms for flavoring ingredients, rosemary oil is approved for that intended use. However, if the use of rosemary oil in foods at concentrations much greater than typically found as a flavoring ingredient and for a use other than for flavoring (such as a preservative), then that use of rosemary oil is no longer “approved”, as the information on which to base the safety of rosemary oil may not be sufficient at much greater levels of intake. For example, anethole is found in many food and herbal plants, such as star anise, and fennel; certain extracts containing anethole are also utilized as flavors at low concentrations in foods (1, 2). However, previous studies in rats have reported that high intake of anethole results in a switch in metabolism to the formation of an epoxide metabolite that is both toxic and carcinogenic (3); this is a prime example that an excess intake of a food ingredient can change the safety of that generally accepted ingredient.

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FASCICOLO SPONSORIZZATO DA

The European Union is also concerned with current use and manufacture of approved food additives, and has set up a program for the re-evaluation of the safety of food additives that were previously permitted for use in the Union prior to January, 2009 (4). The re-evaluation process, being conducted by the European Food Safety Authority (EFSA) began with food colors, and is continuing with additional food ingredients, including botanical extracts. A guidance document providing a general framework for safety assessments focused on botanicals and botanical preparations was published by EFSA in 2009 (5) and included as one aspect of the safety assessment of these botanicals their proposed uses and use levels. The amount of a botanical consumed is one critical aspect to the evaluation of the safety of food ingredients under the intended conditions of use.

NEW ZEALAND BLACKCURRANT EXTRACT AND CARDIOVASCULAR FUNCTION AT REST

A different aspect of evaluating the safety of common food ingredients is in evaluating the current manufacturing process for that ingredient and determining if a new manufacturing process is supported by previous approvals. Many of the early botanical extract products were approved for use due to the long history of use of the specific extract. The U.S. Food and Drug Administration (FDA) concluded in 1977 that for a certain set of botanicals, the “essential oils, oleoresins (solvent-free), and natural extractives (including distillates)” were GRAS for their intended use. While the list of botanicals has been updated over the years, the reference to the types of extraction processes has not been altered (6), and various new extraction and distillation processes have been introduced into the ingredient manufacturing industry. For classic botanical extracts, new/novel extraction techniques may not result in the same chemical formulation of botanical extract that was produced from the original extraction process. In very general terms, the process of botanical extraction is the isolation of the chemicals of interest utilizing a solvent, from the ground or chopped plant material. Examples of common everyday extraction procedures includes the water extraction of Camellia sinensis leaves or of the ground, roasted seeds of the C. arabica L. plant, which provide us with tea and coffee, respectively.

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There are many different types of extraction solvents that have been historically used to produce botanical extracts, and the different solvents retain and isolate different chemicals. The solvent used is dependent on the specific polarity of the solute that is desired. Water (aqueous) extraction techniques and methanol:water or ethanol:water solutions isolate typically highly polar chemicals from plants, such as polyphenols (the phenolic ring results in higher hydrophilicity (7) and antioxidant substances (8). Ethanol is many times effectively used as a solvent for a wide variety of extracts, as residual levels of the ethanol solvent are relatively nontoxic at common use levels and are not considered adverse to most consumers. The type of ethanol used must be of a purity for use in food products and have a high purity. Polyphenol solubility depends mainly on the length and molecular size of constituent hydrocarbon chains and the presence and position of hydroxyl groups (9).

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Less polar solvents utilized in extraction processes include hexane, chloroform, ethylacetate and acetone. These solvents extract a wider array of phytochemicals, including terpenoids and alkaloids. However, these solvents are toxic at increased levels of use and therefore must be removed for use of the resulting extract in food. A modern solvent being utilized in more extraction processes is supercritical carbon dioxide (CO2), in which the CO2 is pressurized to a sub-critical or supercritical state, then is passed through a chamber that contains the ground botanical. Once the extraction process is complete, the pressure is lessened and the CO2 evaporates, leaving the plant extract. Supercritical CO2 may result in isolation of a composition of plant chemicals substantially different than an aqueous or ethanolic-based extract. Lima et al. (10) found that the supercritical CO2 extraction of potato peels resulted in a high concentration of caffeic acid in the resulting extract, although chlorogenic acid is the major phenolic acid in peels.

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Microwave-assisted extraction (MAE) is a relatively new technique being employed to extract phytochemicals, in which electromagnetic waves (both electric and magnetic) are applied to the plant material (11). The MAE process heats the plant material to increase subsequent extraction efficiently, and has been shown to increase antioxidant and phenolic content from extraction (12). Similar to MAE, ultrasound-assisted extraction (UAE) increases extraction efficiency by increasing the ability of the extract to reach phytochemicals within the cell walls and other cellular compartments (13, 14).

NEW ZEALAND BLACKCURRANT POWDER AND SKIN VOLATILE ORGANIC COMPOUNDS

Distillation methods (hydro and steam) are also utilized in the extraction of volatile oils and other relatively non-polar plant constituents. Distillation processes are utilized to produce many different food ingredients, from herbal essential oils to the production of spirits from a mash mixture of fermented grains (alcohol production distilleries) and have been utilized for thousands of years, but enhancements in the distillation process (e.g., molecular distillation) have increased the concentration of phytochemicals in the distillates (15).
Vacuum distillation (i.e., distillation under reduced pressure) lowers the liquid boiling point and exposure to oxygen, reducing the potential degradation of temperature-sensitive phytochemicals, as well as reducing oxidation processes. However, if relatively heat-resistant, highly polar phytochemicals are desired, pressurized hot water extraction (PHWE) is a relatively new extraction technique that utilizes super-heated water and pressure to decrease extraction time.

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Isolation techniques must also be able to differentiate between different but similar chemicals that may have different attributes and safety profiles. To return to the example of anethole above, anethole is a molecule that can be produced in a trans- or a cis- formation in plants; most anethole-containing plants have the trans-isomer in greater concentrations than the cis-isomer (2).
The trans-isomer has a licorice flavor, while the cis-isomer has an unpleasant flavor; the cis-isomer is also much more toxic than the trans-isomer (16, 3). In addition, cis- isomer can be formed from the trans- form if exposed to ultraviolet radiation, or in acidic conditions that may occur during the extraction process if not conducted appropriately (1). Therefore, one must be aware of the potential chemical modifications that may occur to a botanical extract if new/modern extraction/distillation techniques are employed.

NEW ZEALAND BLACKCURRANT POWDER AND SKIN VOLATILE ORGANIC COMPOUNDS

Changes in extract use levels and overall intake, or the utilization of different extraction processes can result in the increased consumption of phytochemical components that were previously consumed at much lower levels that were previously concluded to be safe, either through history of use or through scientific safety studies. Regulatory agencies recognize that technologies evolve, as these new technologies are put to use, the ingredient formulations also change. Therefore, periodic evaluation of the safety of the components of extracts made using new extraction processes must also occur, to confirm that the ingredients being made by novel processes still meet safety requirements for incorporation into food under federally stated intended conditions of use. Uses and use levels that do not meet regulated limitations also need to go through a full safety review to confirm that the current set of safety information supports those new uses and/or use levels. Only in this way can food ingredient manufacturers provide the assurance that ingredients being added to food also meet consumer confidence standards for safe food.

CONCLUSION

*Article previously published in Agro Food Industry Hi Tech 32(2) 2021.