**2. Essential oils**

controlled release of desired food constituents [17]. Moreover, CDs are used in food formulations for flavor protection or flavor delivery [18]. Most natural and artificial flavors are volatile oils or liquids, and complexation with CDs provides a promising alternative to the conventional encapsulation technologies for flavor protection. CDs act as molecular encapsulants, protecting the flavor throughout many rigorous food-processing methods such as freezing, thawing and microwaving. β-CD as a molecular encapsulant allows the flavor quality and quantity to be preserved to a greater extent and longer period compared to other encapsulants and provides longevity to the food item [19]. In Japan, CDs have been approved as "modified starch" for food applications for more than two decades, serving to mask odors in fresh food and to stabilize fish oils. One or two European countries—for example, Hungary—have approved γ-CD for use in certain applications because of its low toxicity. It was proved that CDs may alter the sensory profile of a food and the flavor release depends of the CD type [20], the temperature [21] and may depend the solvent nature that is, water, water/alcohol mixtures, etc. [22]. Their beneficial effects essentially derive from the ability to form stable inclusion complexes with sensitive lipophilic nutrients and constituents of flavor and taste, making easy to prepare powdered flavor materials [23–25] and even to release such flavors during cooking [26]. Toxicological data are examined and an assessment of CDs from the standpoint of safety for human consumption is made [27]. Regulations are covered, showing a general trend toward a wider acceptance of CDs as food additives. The growing health consciousness of consumers and expanding market for functional foods and nutraceutical products are opening up to CDs a promising future in food industry [11].

264 Cyclodextrin - A Versatile Ingredient

The complexation of CDs with sweetening agents such as aspartame stabilizes and improves the taste. It also eliminates the bitter aftertaste of other sweeteners such as stevioside, glycyrrhizin and rubusoside. CD itself is a promising new sweetener. Enhancement of flavor by CDs has been also claimed for alcoholic beverages such as whisky and beer [28]. The bitterness of citrus fruit juices is a major problem in the industry caused by the presence of limonoids (mainly limonin) and flavonoids (mainly naringin). Cross-linked CD polymers are useful to remove these bitter components by inclusion complexation [29]. CDs are also used to control bitterness in tannins, plant and fungal extracts; skim milk hydrolyses and overcooked tea and coffee [30]. They can also be used to keep the profile of oil volatiles in paste samples that were vacuum- or spray-dried [31, 32], due to their high encapsulation efficiency. The most prevalent use of CD in process aids is the removal of cholesterol from animal products such as eggs or dairy products, like cheese [33]. CD-treated material shows 80% removal of cholesterol. Free fatty acids can also be removed from fats using CDs, thus improving the frying property of fat (e.g., reduced smoke formation, less foaming, less browning and deposition of oil residues on surfaces) [30]. Fruits and vegetable juices are also treated with CD to remove phenolic compounds, which cause enzymatic browning. In juices, polyphenol oxidase converts the colorless polyphenols to colored compounds and addition of CDs removes polyphenoloxidase from juices by complexation. Sojo et al. [34] studied the effect of CDs on the oxidation of *o*-diphenol by banana polyphenoloxidase and found that CDs act as activator as well as inhibitor. By combining 1–4% CD with chopped ginger root, Sung [35] established that it could be stored in vacuum at cold temperature for 4 weeks or longer without browning or rotting.

Other studies describes the development of a gas chromatography-mass spectrometry (GC-MS) library to identify optically active compounds in the flavor and fragrance field using enantioselective GC with CD derivatives (CDs) as chiral selectors in combination with MS Both *in vitro* and *in vivo* studies have demonstrated the important applications of essential oils, such an antioxidant or antibacterial activity, even antitumor or anti-inflammatory, with important technological applications in food science and pharmacology [60–64]. Indeed the presence of eugenol, carvacrol or thymol as main component of these oils guarantee their properties both antioxidants and antibiotics (**Figure 1**).

**Figure 2.** (2-Hydroxypropyl)-β-CD.

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**Figure 3.** Main components of black pepper [68, 70].

**Figure 4.** Main components of guava [78, 79].

**Figure 1.** Main components of essential oils [60].

As example, in the present chapter we have selected some essential oils to characterize their inclusion complex in (hydroxypropyl-β-CD) (**Figure 2**). They were black pepper essential oil, guava essential oil and yarrow essential oil.

Black pepper (*Piper nigrum* L.) is considered the king of spices because of its pungent of piperine [65]. It can be used for different purposes such as medicine, human dietaries, preservatives and bio control agents [65–67]. It has been already reported that essential oil from black pepper possess antioxidant [68] and antimicrobial activities [69]. Black pepper oil is basically composed of terpenes, which have been found to be β-caryophyllene, limonene, δ-3-carene and pinene (**Figure 3**) [68, 70]. The major composition of black pepper oil was found to be β-caryophyllene [68, 70]. Nevertheless, some active compounds in essential oils are sensitive toward the chemical modification under effect of some external factors such as temperature, light, oxygen, etc. [71]. Besides, to apply in foods, an extremely low flavor threshold of essential oils can drastically change the sensory properties of foods, and highly water insoluble may have limited contact with pathogens [72].

Guava (*Psidium guajava* L.) has been used as a traditional medicine because of its biological properties [73–75]. Essential oil from guava leaves contains several bioactive compounds, which are responsible for anti-proliferation, antioxidant and antimicrobial activities [76, 77]. Limonene, β-caryophyllene, 1,8-cineole and α-pinene are the major constituents (**Figure 4**) [78, 79]. However, essential oils have some limitations for food applications. Their low solubility in water limits contact with food pathogens in aqueous matrices [72]. Besides, some active compounds in essential oils are sensitive to chemical modifications under the effect of external factors such as temperature, light or oxygen [71].

Encapsulation of Essential Oils by Cyclodextrins: Characterization and Evaluation http://dx.doi.org/10.5772/intechopen.73589 267

**Figure 2.** (2-Hydroxypropyl)-β-CD.

As example, in the present chapter we have selected some essential oils to characterize their inclusion complex in (hydroxypropyl-β-CD) (**Figure 2**). They were black pepper essential oil,

Black pepper (*Piper nigrum* L.) is considered the king of spices because of its pungent of piperine [65]. It can be used for different purposes such as medicine, human dietaries, preservatives and bio control agents [65–67]. It has been already reported that essential oil from black pepper possess antioxidant [68] and antimicrobial activities [69]. Black pepper oil is basically composed of terpenes, which have been found to be β-caryophyllene, limonene, δ-3-carene and pinene (**Figure 3**) [68, 70]. The major composition of black pepper oil was found to be β-caryophyllene [68, 70]. Nevertheless, some active compounds in essential oils are sensitive toward the chemical modification under effect of some external factors such as temperature, light, oxygen, etc. [71]. Besides, to apply in foods, an extremely low flavor threshold of essential oils can drastically change the sensory properties of foods, and highly water insoluble

Guava (*Psidium guajava* L.) has been used as a traditional medicine because of its biological properties [73–75]. Essential oil from guava leaves contains several bioactive compounds, which are responsible for anti-proliferation, antioxidant and antimicrobial activities [76, 77]. Limonene, β-caryophyllene, 1,8-cineole and α-pinene are the major constituents (**Figure 4**) [78, 79]. However, essential oils have some limitations for food applications. Their low solubility in water limits contact with food pathogens in aqueous matrices [72]. Besides, some active compounds in essential oils are sensitive to chemical modifications under the effect of

guava essential oil and yarrow essential oil.

**Figure 1.** Main components of essential oils [60].

266 Cyclodextrin - A Versatile Ingredient

may have limited contact with pathogens [72].

external factors such as temperature, light or oxygen [71].

**Figure 3.** Main components of black pepper [68, 70].

**Figure 4.** Main components of guava [78, 79].

stabilize labile guests against oxidation, control volatility and sublimation, modify taste by masking off flavors, entrap odors and control the releasing of drugs and flavors [92]. Among those CDs, β-CD is the most widely applicable kind because of its suitable cavity size for common guests with molecular weights between 200 and 800 g/mol and its availability and reasonable price [93]. Although β-CD can be used with many guests, its solubility in water is low (1.8 g in 100 mL water at 25°C). In some cases, there is a need to enhance water solubility of β-CD by adding the hydroxyl-alkyl groups on the β-CD surface. A hydroxyl-alkylated or hydroxypropyl-β-CD derivative (HPβCD) is relatively high aqueous solubility (above 60 g in

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On the other hand, encapsulation of essential oils or their chemical components with CDs or CD derivatives for improvement of biological properties have been observed [5, 95–98] or

Indeed, a large amount of contributions about technologic applications of CD-inclusion complex of essential oils and their main components has been published in the last 10 years, some

**component**

Citronella oil β-CD [105] Barbigerone Hydroxypropyl-β-CD [106]

Carvacrol

Garlic oil β-CD [102, 111] Cinnamaldehyde β-CD [99, 103] Guava leaf oil Hydroxypropyl-β-CD [112] Citronellal β-CD [105] Lemon oil β-CD [113] Citronellol β-CD [105]

Olive leaf oil β-CD [114] Eugenol β-CD [99, 115–118]

**Table 1.** Contributions abut host-guest complex formation between CDs and CDs derivatives and essential oils.

β-CD [107, 119] Limonene β-CD [120]

β-CD [121, 122] 2-Nonanone β-CD [123]

β-CD [124] Thymol β-CD [103, 109,

Hydroxypropyl-β-CD [125] Vanillin β-CD [126, 127]

β-CD [71] Hydroxypropyl-β-CD [110]

Allyl isothiocyanate

**Guest References**

α-CD [101]

β-CD [101, 104]

β-CD [108, 109]

121]

100 mL water at 25°C) with low toxicity and satisfactory inclusion ability [94].

their antimicrobial activity [99].

of them are included in **Table 1**.

Black pepper essential oil

Cinnamon essential oil

Coriander essential oil

Oregano essential oil

Thyme essential oil

Yarrow essential oil

Sweet basil essential oils

**Essential oil Guest References Essential oil** 

β-CD [99, 102,

Clove bod oil β-CD [99, 107] Carvacrol

Hydroxypropyl-β-CD [100] Allyl isothiocyanate

103]

**Figure 5.** Main components of yarrow [87].

Yarrow (*Achillea millefolium* L. s. l.) has a broad spectrum of pharmacological activities. It is widely used in folk medicine [80]. In Europe, it has been used as a remedy to treat digestive problems, diabetes, hepatic-biliary diseases, amenorrhea, and consumed for its antitumor and anti-inflammatory properties [81–83]. In addition, antimicrobial and antioxidant properties of yarrow have also been reported [84–86]. Chemical components of yarrow essential oil have been found to be carvacrol, linalool, 1,8-cineole, camphor and thymol was mostly found as a major component (**Figure 5**) [87]. However, some active chemical components of yarrow oil (such as carvacrol and thymol) are sensitive to environmental factors such as, light, oxygen and temperature. Encapsulation of yarrow essential oil could offer possible solutions for the limitation.
