Promising applications of cyclodextrins in food: Improvement of essential oils retention, controlled release and antiradical activity

Carbohydrate Polymers 131 (2015) 264–272

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Promising applications of cyclodextrins in food: Improvement of essential oils retention, controlled release and antiradical activity Miriana Kfoury a,b , Lizette Auezova a , Hélène Greige-Gerges a , Sophie Fourmentin b,∗ a Bioactive Molecules Research Group, Doctoral School of Science and Technology, Department of Chemistry and Biochemistry, Faculty of Sciences, Section II, Lebanese University, Lebanon b Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), ULCO, F-59140 Dunkerque, France

a r t i c l e

i n f o

Article history: Received 6 May 2015 Received in revised form 2 June 2015 Accepted 7 June 2015 Available online 15 June 2015 Keywords: ABTS• + scavenging Cyclodextrins Essential oils Food packaging Formation constant Retention

a b s t r a c t Essential oils (EOs) are gaining great interest as alternatives for harmful synthetic food preservatives. Due to their volatile nature, they could be applied in food packaging to improve food quality and extend shelflife. To provide long-term effects of EOs by increasing their retention and ensuring controlled release of their components, they could be encapsulated in cyclodextrins (CDs). Herein, the ability of six CDs to retain nine EOs and to bind their individual components was investigated. Retention capacities and binding abilities of CDs were assessed by static headspace-gas chromatography (SH-GC) using a new validated “rapid method”. The ability of CDs to generate controlled release systems was examined by multiple headspace extraction (MHE). Finally, radical scavenging activity of free and encapsulated EOs was evaluated. The highest retention capacity toward the studied EOs was obtained for ␤-CD and its derivatives (69–78%). Also, ␤-CD and its derivatives showed, with one exception, the highest Kf values for all the studied guests. In addition, encapsulation in CDs reduced the releasing rate of EO components (from 1.43 to 2.43-fold for ␤-CD/Satureja montana EO used as a model). Furthermore, the inclusion complexes showed higher ABTS• + scavenging capacity than the free EOs. Results confirmed the usefulness of CDs as encapsulant for EOs and should encourage their application in food and as part of active packaging systems. © 2015 Elsevier Ltd. All rights reserved.

1. Introduction Essential oils (EOs) are aromatic oily plant extracts and are gaining great interest as antioxidants and food preservatives due to their antioxidant and antimicrobial activity (Costa, Garcia-Diaz, Jimenez, & Silva, 2013; Jayasena & Jo, 2014). The use of EOs can preserve the quality of food products and extend their shelf life (Amorati, Foti, & Valgimigli, 2013). Furthermore, there is a demand to reduce the consumption of synthetic antioxidants like butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) because of their suspected carcinogenicity (Grice, 1988; Witschi, 1986). Being from natural origin, many EOs are classified as Generally Recognized As Safe (GRAS) by the Food and Drug Administration (Prakash, Kedia, Mishra, & Dubey, 2015) and are widely accepted by consumers. Moreover, EOs are eco-friendly and their use do not necessitate any toxicity data requirements by the Environment Protection Agency (Prakash

∗ Corresponding author. Tel.: +33 03 28 65 82 54; fax: +33 03 28 23 76 05. E-mail address: [email protected] (S. Fourmentin). http://dx.doi.org/10.1016/j.carbpol.2015.06.014 0144-8617/© 2015 Elsevier Ltd. All rights reserved.

et al., 2015). Thus, EOs and their components could be considered as alternative preservatives or processing aid as green technology (Tongnuanchan & Benjakul, 2014). Indeed, several studies have proved that EOs and their components could be effective in preservation of food products like roasted sunflower seeds (Quiroga, Asensio, & Nepote, 2014), chicken meat (Rimini, Petracci, & Smith, 2014), palm olein during repeated frying of French fries (Cardoso-Ugarte, Morlán-Palmas, & Sosa-Morales, 2013) and others. Adding EOs to packaging systems could be considered as active packaging due to their biological potencies (Llana-Ruiz-Cabello et al., 2015). For example, they could prevent the penetration of insect pests and the infection of packaged food due to their insect repellent capacity (Navarro & Finkelman, 2014). One of the critical points in the formulation of food packaging is that the organoleptic characteristics of the food should not be affected by the presence of the active agents. Thus, the use of EOs is often limited due to flavoring considerations (Zinoviadou, Koutsoumanis, & Biliaderis, 2009). Consequently, the development of EOs controlled release systems inside the packaging material should be performed to optimize the conditions of their application.

M. Kfoury et al. / Carbohydrate Polymers 131 (2015) 264–272

CDs have been described as potent encapsulant at the industrial level for food components (Astray, Gonzalez-Barreiro, Mejuto, Rial-Otero, & Simal-Gándara, 2009; Astray, Mejuto, Morales, RialOtero, & Simal-Gándara, 2010). CDs inclusion complexes with EOs could also act as a reservoir of encapsulated volatile components and allow their subsequent controlled release (Ciobanu et al., 2012; Yuan, Lu, & Jin, 2014). This permits EOs to reach effective concentrations in the food without exceeding organoleptically acceptable levels. Moreover, it is possible to modulate the quantity of entrapped substances in the CD inclusion complex and control the release-rate kinetics (Kfoury, Auezova, Ruellan, GreigeGerges, & Fourmentin, 2015; Yuan et al., 2014). Encapsulation with CDs could also protect EO constituents from the harmful environmental conditions (Pinho, Grootveld, Soares, & Henriques, 2014; Wang, Jin, & Xu 2014) allowing a preservation of their antioxidant activity (Kfoury, Landy, Auezova, Greige-Gerges, & Fourmentin, 2014; Medronho, Valente, Costa, & Romano, 2013; Zhao, Wang, Yang, & Tao, 2010). It has been suggested that, combined to other ingredients, CD/EOs inclusion complexes could be used as active food packaging material (Sun et al., 2014). CDs are non-toxic cyclic oligosaccharides derived from the enzymatic degradation of starch. They have a relatively hydrophilic external surface and a hydrophobic interior cavity allowing them to include hydrophobic guests. The interaction between guest and CD leads to the formation of non-covalent inclusion complexes, either in solution or solid state. Inclusion complex formation is a dynamic equilibrium allowing the guest to diffuse reversibly from the CD cavity. Commonly used native CDs are made up of six, seven or eight glucosyl units and called ␣-cyclodextrin (␣-CD), ␤-cyclodextrin (␤CD) and ␥-cyclodextrin (␥-CD), respectively. CDs cavity diameter is determined by the number of glucose units in the CD and control the size of the guest that can be encapsulated. CD derivatives with enhanced solubility and encapsulation performance are synthesized and widely used (Ciobanu, Landy, & Fourmentin, 2013; Decock et al., 2006). Many papers have reported the encapsulation of EOs as complex mixtures in CDs (Dima et al., 2014; Hadaruga, Hadaruga, Rivis, Gruia, & Pinzaru, 2007; Hadaruga, Hadaruga, & Isengard, 2012; Haloci et al., 2014). However, very few studies have attempted to investigate the binding ability of CDs with each EO constituent directly in the complex mixture (Kfoury et al., 2015). When adding CDs to EOs, a multitude of equilibriums could take place due to their heterogeneous composition. This leads to the formation of inclusion complexes with different stabilities owing to the nature and the concentration of each EO component. Thus, it is difficult to provide a single binding potential of CD to the whole EO mixture. The aim of this study was to investigate the capacity of three native CDs (␣-CD, ␤-CD and ␥-CD) and three ␤-CD derivatives: hydroxypropylated-␤-CD (HP-␤-CD), randomly methylated ␤-CD (RAMEB) and a low methylated-␤-CD (CRYSMEB) to retain the nine selected EOs of Cinnamomum camphora CT linalool (Hô Wood), Citrus reticulata Blanco (mandarin orange), Cymbopogon nardus (citronella grass), Eucalyptus citriodora (lemon eucalyptus), Origanum compactum (oregano), Origanum majorana CT thujanol (marjoram), Pimenta racemosa (bay rum tree), Rosmarinus officinalis cineoliferum (rosemary) and Satureja montana (winter savory) by static headspace-gas chromatography (SH-GC). These EOs are known for their antimicrobial, analgesic and anti-inflammatory properties (Bhalla, Gupta, & Jaitak 2013; Calo, Crandall, O’Bryan, & Ricke, 2015; Miguel, 2010; Shaaban, El-Ghorab, & Shibamoto 2012). For the first time, the binding potential of CDs toward individual EOs components present simultaneously in the complex mixtures was investigated. The ability of CD to generate a controlled release system of EOs components was also explored. Finally, the effect of CDs on the EOs radical scavenging activity was evaluated.

265

2. Materials and methods 2.1. Materials Essential oils (EOs) were purchased from Herbes et Traditions (Comines, France). ␣-pinene 1, camphene 2, ␤-pinene 3, myrcene 4, limonene 5, eucalyptol 6, p-cymene 7, ␥-terpinene 8, linalool 9, citronellal 10, ␤-caryophyllene 11, 2,2 -azino-bis(3ethylbenzothiazoline-6-sulphonic acid), potassium persulphate (K2 S2 O8 ) and Trolox were purchased from Aldrich. ␣-CD, ␤-CD, ␥CD, HP-␤-CD (DS = 5.6) and RAMEB (DS = 12.6) were provided from Wacker-Chemie (Lyon, France). CRYSMEB (DS = 4.9) was provided from Roquette Frères (Lestrem, France). All products were of analytical grade and were used as received. Distilled deionized water was used all over the study. 2.2. Static headspace-gas chromatography (SH-GC) analysis EOs were added to 10 mL of water or aqueous CD solutions placed in 22 mL headspace glass vials. Vials were then sealed by using a silicone septa and aluminum foil and thermostated at 25 ± 0.1 ◦ C. After the equilibrium between aqueous and gaseous phases had been established (30 min), 1 mL of vapor presents above the solution was withdrawn from the vial by using a gas-tight syringe and injected directly in the chromatographic column via a transfer line (250 ◦ C) for chromatographic analysis. All measurements were conducted with an Agilent headspace autosampler and a Perkin Elmer Autosystem XL equipped with a flame ionization detector using a DB624 column gas chromatography. Temperature conditions were as follows: initial temperature of 50 ◦ C for 2 min, increased to 190 ◦ C at 2 ◦ C/min giving a total runtime of 30 min. Nitrogen was used as carrier vector. Main volatile components in EOs were identified on the basis of gas chromatographic retention times, determined by using standards of EOs components in the same conditions. 2.3. Retention of EOs by CDs The percentage of retention (r) of EOs by CDs was determined by SH-GC at 25 ◦ C for a 2 mM CD solution and expressed as follows:



r(%) =

1−



  A  CD × 100 A0

(1)



A0 and ACD stand for the sum of peak areas of each EO where component in the absence and the presence of CD, respectively. For each CD, measurements were done in triplicate. 2.4. Formation constants (Kf ) determination EO (10 ppm) was added to 10 mL of water or 2 mM CDs aqueous solutions previously introduced in 22 mL headspace glass vials. Vials were equilibrated and analyzed as described in Section 2.2. Peak areas relative to each individual component of the EO were determined. Kf values were calculated based on the ratio A0 /ACD (A0 and ACD are the peak areas of each component in the absence and the presence of CD, respectively) as follows (Fourmentin, Ciobanu, Landy, & Wenz, 2013): Kf =

(A0 /ACD ) − 1 [CD]0

(2)

where [CD]0 stands for the initial concentration of CD. This method is called the “rapid method”. Kf values for the standard molecules were determined using a SH-GC titration method as described previously (Ciobanu, Landy, & Fourmentin, 2013; Decock, Landy, Surpateanu, & Fourmentin, 2008).

266

Table 1 Chemical structures, calculated molecular volumes, retention times (RT) of the identified volatiles and their relative percentage in the studied EOs.

1

2

3

4

5

6

7

8

9

10

11

264 11.04 –

266 11.62 –

251 12.55 –

286 12.94 –

266 13.8 –

278 14.15 –

259 14.29 –

266 15.05 –

294 17.28 97.95

298 18.88 –

377 25.57 –

16.37

0.08

–

–

1.92

–

1.40

1.8

73.81

–

0.64

–

–

–

–

1.50

–

–

–

–

10.91

3.57

1.32

–

1.04

–

0.45

0.38

0.83

–

0.29

74.77

0.93

1.02

1.07

–

1.24

–

0.41

13.81

13.15

–

–

–

0.80

–

0.38

1.98

1.07

0.10

3.85

10.81

2.07

–

1.27

–

–

–

–

–

–

–

–

–

–

4.23

8.77

1.53

2.22

0.93

–

0.77

–

3.02

–

–

1.71

0.59

1.23

–

–

10.75

1.03

25.79

46.85

–

11.82

13.86

a V = M/dNA , with M: molecular weight, d: density, NA : Avogadro’s number. 1: ␣-pinene; 2: camphene; 3: ␤-pinene; 4: myrcene; 5: limonene; 6: eucalyptol: 7: p-cymene; 8: ␥-terpinene; 9: linalool; 10: citronellal; 11: ␤-caryophyllene.

M. Kfoury et al. / Carbohydrate Polymers 131 (2015) 264–272

Volume (A˚ 3 )a RT (min) Cinnamomum camphora CT linalol Citrus reticulata Blanco Cymbopogon nardus Eucalyptus citriodora Origanum compactum Origanum majorana CT thujanol Pimenta racemosa Rosmarinus officinalis cineoliferum Satureja montana

M. Kfoury et al. / Carbohydrate Polymers 131 (2015) 264–272

267

Fig. 1. Representation of the variation of the chromatogram of Satureja montana EO in the presence of various CDs.

2.5. Release studies The dynamic release of EOs components was studied using the multiple headspace extraction (MHE) method described by Kolb and Ettre (2006). This method carried out successive extractions for the vial’s headspace at different time intervals. At each individual extraction, 1 mL of the vial’s headspace was withdrawn and the amount of each EOs component present in the gaseous phase was determined by GC analysis. Successive extractions of the headspace eventually lead to a decrease in the quantity of volatiles present in the gaseous phase. The rate of this decrement reflected the retention efficacy of each EOs component in solution. GC settings were set as described in Section 2.2. Aliquots of EOs were added to water or CD solution (2 mM) previously placed in 22 mL headspace glass vials. Vials were sealed and four successive extractions were realized at 60 ◦ C. At each time interval (45 min), remaining percentages of each free or encapsulated EO component were determined using the following equation: remaining EO component (%) =

A  t

A0

× 100

(3)

where At and A0 stand for the peak area of each EO component at time t and time 0. 2.6. ABTS radical scavenging method The radical scavenging activity of EOs alone or in the presence of CD was determined by using ABTS radical cation (ABTS•+ ) (Prior, Wu, & Schaich, 2005). The method is based on the ability of an antioxidant to scavenge and reduce ABTS•+ into its colorless form. The ABTS•+ was generated by mixing 7 mM of ABTS salt with 2.45 mM of K2 S2 O8 in water at room temperature in the dark for 16 h. The ABTS•+ solution was then diluted with water to obtain an initial absorbance of 0.75 ± 0.2 at 730 nm using UVvisible dual-beam spectrophotometer (Perkin Elmer Lambda 2S) with a 1 cm thick quartz cuvette. Aliquots of EOs alone or in the

presence of 10 mM of CD were added to 2 mL of ABTS•+ . Mixtures were shaken for 1 h and allowed to stand at dark at 25 ± 0.1 ◦ C. The absorbance was measured at 730 nm. Blank samples contain ABTS•+ alone or in the presence of 10 mM of CD. The antioxidant activity was expressed as Trolox equivalents TEAC (␮mol Trolox/g of EO) by using a Trolox calibration curve prepared for a concentration range of 2.5–25 ␮M. All analyses were done in triplicate.

3. Results and discussion 3.1. Identification of the volatile composition of EOs The nine analyzed EOs present a large variety of components. Volatile components were identified by comparing their retention times in EOs to those of the standards analyzed under the same conditions. The major volatile components identified in the selected EOs were the following: the monoterpene hydrocarbons (␣-pinene 1, camphene 2, ␤-pinene 3, myrcene 4, limonene 5, p-cymene 7 and ␥-terpinene 8), the oxygenated monoterpenes (eucalyptol (1,8-cineol) 6, linalool 9 and citronellal 10) and the sesquiterpene hydrocarbon (␤-caryophyllene 11). Chemical structures and properties of identified volatiles, their retention times and their relative percentage in the EOs are listed in Table 1. Some of the components were common for different EOs while others were more specific. Moreover, some components were present in large amounts in some EOs and as trace elements in others. However, the high volatility of the identified components allows their detection even when they were present in very low concentrations. The identified compounds account for 97.95%, 96.02%, 15.98%, 80.01%, 30.7%, 22.33%, 25.79%, 79.07% and 30.24% of C. camphora, C. reticulata, C. nardus, E. citriodora, O. compactum, O. majorana, P. racemosa, R. officinalis and S. montana EOs, respectively. Among studied EOs, some ones showed typical monoterpene hydrocarbon pattern (C. reticulata, O. majorana, R. officinalis). Oxygenated compounds dominated in C. camphora (alcohol) and C. nardus, E. citriodora (aldehyde) and O. compactum, P. racemosa, S. montana (phenols). Phenols were not

268

M. Kfoury et al. / Carbohydrate Polymers 131 (2015) 264–272

Table 2 Percentage of retention (r %) of EOs by CDs. Standard deviation values are <10%.

Cinnamomum camphora CT linalol Citrus reticulata Blanco Cymbopogon nardus Eucalyptus citriodora Origanum compactum Origanum majorana CT thujanol Pimenta racemosa Rosmarinus officinalis cineoliferum Satureja montana

␣-CD

␤-CD

␥-CD

HP-␤-CD

CRYSMEB

RAMEB

1 33 38 11 17 9 – 50 28

68 81 87 83 75 84 27 86 86

– 4 3 – 18 20 – 40 40

57 76 7 69 70 74 46 78 80

69 83 77 83 75 86 59 87 78

61 82 83 75 76 87 61 85 87

Average retention (%)

detected in SH-GC under the analytical conditions due to their poor volatility. 3.2. Retention of EOs by CDs For retention experiments, the same amount of each EO was analyzed by SH-GC with or without CDs. Fig. 1 shows as example the effect of different CDs on the chromatographic profile of S. montana EO. EO retention by CDs was quantified by comparing the sum of the chromatographic peaks areas of EO components in the presence of CDs to that of the blank experiment. Retention values were calculated according to Eq. (2) and listed in Table 2. Except for P. racemosa with ␣- and ␥-CDs, the peak areas of all EOs components decreased in presence of CDs. This decay was attributed to the retention of guests upon inclusion complex formation (Ciobanu, Mallard, et al., 2013; Kfoury, Auezova, Greige-Gerges, Ruellan, & Fourmentin, 2014). This also reflected the reduction of the vapor pressure and volatility of EO due to its inclusion within CD cavity (Fourmentin et al., 2013). As for P. racemosa, ␣- and ␥-CDs did not show a remarkable retention capacity. The main volatile compound present in this EO is myrcene 4. A previous study showed that myrcene 4 is not well recognized by ␣- and ␥-CDs with Kf values of 212 and 138 M−1 , respectively (Ciobanu, Landy, & Fourmentin, 2013). Moreover, P. racemosa is highly rich in phenols (eugenol and chavicol) which are barely volatile and more soluble in water than the studied volatiles. The combined effect of these two factors could induce a salting-out effect of volatile EO components from CD solution to the vapor phase. Negative retentions were also reported in the literature (Jouquand, Ducruet, & Giampaoli, 2004; Reineccius, Reineccius, & Peppard, 2005). In all other cases, r % values showed that EOs were efficiently retained by CDs. This reflected the tendency of their components to form inclusion complexes with CDs. The comparison of the retention capacities of CDs toward the nine EOs showed that ␤-CD and its derivatives were more efficient than ␣- and ␥-CDs; the CD retention capacities can be ranked in the following order: CRYSMEB ≈ RAMEB ≈ ␤-CD > HP-␤-CD  ␣CD > ␥-CD. These results suggested that CDs, particularly ␤-CD and its derivatives, could efficiently retain EOs and consequently protect them from evaporation. Thus, CDs might be considered as efficient material to encapsulate and improve the release efficiency of volatile compounds enlarging the applications of EOs in food. 3.3. Determination of formation constants (Kf ) The “rapid method” used in this study allows a fast and simultaneous determination of Kf values of CD inclusion complexes with guests present in complex mixtures like EOs. Additionally, it doesn’t

require the knowledge of the guest’s concentration in the initial mixture. It should be noted that interference and competition for complexation of the various guests were negligible because of the large excess of CDs. The integrated GC peak area values of identified EOs components were individually collected. Kf values were calculated from the ratio A0 /A of the peak area of each component without and with CD, according to Eq. (2). Kf values are summarized in Table 3 in comparison with literature data. Values not found in the literature were determined using the algorithmic titration method described in previous studies (Ciobanu, Landy, & Fourmentin, 2013; Decock et al., 2008). High Kf values indicate a great binding potential of CD for the guest and thus an important stability of the subsequent inclusion complex. Kf values for the identified volatiles as standards or as components of EOs were identical for the great majority of guests with all CDs. Except for ␤-caryophyllene 11, Kf values fell in the ranges 5–1000 M−1 for ␣-CD and ␥-CD and 500–10,000 M−1 for ␤CDs. These are representative ranges for Kf values of volatile flavor compounds (Ciobanu, Landy, & Fourmentin, 2013). Furthermore, almost all Kf values are in the range 200–10,000 M−1 which is adequate to allow a controlled release of the guests (Aicart & Junquera, 2003). As we can obviously see in Table 3, ␣-CD showed marginal complexation capacity toward ␤-caryophyllene 11. This could be due to the smallest cavity of ␣-CD among the studied CDs. Being a sesquiterpene, ␤-caryophyllene 11 has a large volume that does not fit with the size of the ␣-CD cavity. ␥-CD in its turn showed no complexation ability for linalool 9 and citronellal 10 which present a linear structure. This proved that the performance of CDs largely depends on geometric complementarity (size and shape) between their cavity and the guest. The binding potential of the different CDs was compared. ␤-CD and its derivatives showed the highest Kf values for all the studied guests except for eucalyptol 6. In fact, eucalyptol 6 presents a bicyclic large structure that increases the steric hindrance and reduces the interaction with the ␤-CD cavity. Conversely, this favors the interactions between eucalyptol 6 and the bigger cavity of ␥-CD which showed the best complexation ability toward this guest. It should be noted that despite the fact that ␣-pinene 1, camphene 2 and ␤-pinene 3 have a bicyclic structure, their size is relatively smaller than that of eucalyptol 6. This allows them to fit better within the ␤-CD cavity. Considering ␤-CD and its derivatives (HP-␤-CD, CRYSMEB and RAMEB), we can obviously see that, except for eucalyptol 6, ␤-CD showed better or comparable complexation capacity toward all the studied EOs components. HP-␤-CD showed relatively weaker binding capacities than other ␤-CDs. This could be due to steric hindrance of the substitutive hydroxypropyl groups

M. Kfoury et al. / Carbohydrate Polymers 131 (2015) 264–272

269

Table 3 Formation constants (M−1 ) values of CD/EO components inclusion complexes obtained by the “rapid method” at 25 ◦ C in comparison with values from the literature. Standard deviation values are <10%.

1 2 3 4 5 6 7 8 9 10 11

␣-CD

␤-CD

␥-CD

HP-␤-CD

CRYSMEB

RAMEB

986(1778a ) 500(598a ) 921 (1018a ) 230 (212a ) 257 (486c ) 50 (13a ) 146 (140a ) 136 (37d ) 10 (32a ) 16 (137d ) 59 (–d )

2540 (2588a ) 4956 (4825a ) 4646 (4587a ) 1267 (1431a ) 2605 (3162a ) 512 (615a ) 2525 (2505a ) 1640 (1309d ) 1058 (368a ) 1523 (1268d ) 23,032 (28,674d )

223 (214a ) 389 (360a ) 417 (633a ) 172 (138a ) 130 (116a ) 990 (742a ) 82 (88a ) 86 (40d ) 5 (138a ) 7 (–d ) 3581 (4004 d )

1361 (1637a , 1842b ) 2556 (3033a ) 1742 (1671b ) 817 (575a ) 3076 (2787a , 1667b ) 1185 (1200b ) 2230 (2213a ) 1554 (1406d ) 675 (596a ) 815 (507d ) 4941 (4960d )

2651 (2999a ) 5049 (6625a ) 4803 (5140a ) 880 (959a ) 4154 (3668a ) 2361 (688a ) 2945 (2549a ) 2167 (1950d ) 1121 (816a ) 1700 (2141d ) 8545 (11,488d )

2203 (2395b ) 4005 (6057a ) 4445 (4450a ) 1244 (1286a ) 4042 (4386a ) 1580 (672a ) 3341 (3543a ) 1984 (1778d ) 793 (833a ) 994 (1235d ) 9744 (14,274d )

a

Ciobanu, Landy, and Fourmentin (2013). Kfoury, Auezova, Fourmentin, and Greige-Gerges (2014). Decock et al. (2008). d This study. 1: ␣-pinene; 2: camphene; 3: ␤-pinene; 4: myrcene; 5: limonene; 6: eucalyptol: 7: p-cymene; 8: ␥-terpinene; 9: linalool; 10: citronellal; 11: ␤-caryophyllene. b c

leading to weaker binding of the guest. The better complexation abilities of CRYMEB and RAMEB as compared to HP-␤-CD could be explained by the higher hydrophobic character of their cavity due to the methylation of hydroxyl groups of the native CD that favors inclusion complex formation (Danel et al., 2013). The assessment of the binding ability of CDs toward EOs components allows a better comprehension of interactions between CDs and EOs. This could allow a versatile selection of the CD. In other terms, it leads to a discrepancy in the release of EOs components: guests with high Kf values will be released more slowly than those with low Kf values. Here, we should note that, in addition to Kf value, guest amount, volatility and solubility should also be taken into consideration during the formulation of controlled release systems (Shiga et al., 2003). Our findings showed that steric considerations control the space filling of CD cavity and are important factors influencing the inclusion complexes formation (Valente & Söderman, 2014). These results suggested that CDs, could be considered as biomaterial for encapsulation of active agents like EOs in food packaging. It should

be noted that ␤-CD has been recommended by the Joint FAO/WHO Committee of Food Additives (JECFA) with an Acceptable Daily Intake (ADI) of 5 mg/kg/day and included in the GRAS list of the FDA (Kurkov & Loftsson, 2013). 3.4. Release studies ␤-CD and S. montana EO were chosen to perform the release studies by the means of MHE. At each extraction corresponding to a 45 min time interval, the remaining percentages of identified volatiles found in S. montana were determined based on their individual chromatographic peak areas using equation 3. Results are illustrated in Fig. 2. The release of S. montana EO components (␣-pinene 1, myrcene 4, limonene 5, p-cymene 7 and ␥-terpinene 8) revealed exponential asymptotic trends indicating that they followed apparent first-order kinetic whether they were examined in their free or encapsulated forms. The calculated release rate constants were 0.0017, 0.0029, 0.0031, 0.0010 and 0.0028 min−1 for free ␣-pinene

Fig. 2. Residual rates of free and encapsulated S. montana EO components.

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M. Kfoury et al. / Carbohydrate Polymers 131 (2015) 264–272

Fig. 3. Effect of ␤-CD on the Trolox equivalents TEAC of EOs (␮mol Trolox/g of EO) by using ABTS assay. (a) Rosmarinus officinalis cineoliferum, Cinnamomum camphora CT linalol, Origanum majorana CT thujanol, Eucalyptus citriodora, Citrus reticulata Blanco and Cymbopogon nardus and (b) Satureja montana, Origanum compactum and Pimenta racemosa EOs.

1, myrcene 4, limonene 5, p-cymene 7 and ␥-terpinene 8, respectively. Encapsulation within ␤-CD reduced the release rate of these EOs components by 2.43, 1.53, 1.72, 1.43 and 1.87-fold, respectively. At each time interval, the remaining percentage of each component in the inclusion complex solution was considerably higher than that of its relative free form. After 135 min, remaining percentages of ␣-pinene 1, myrcene 4, limonene 5, p-cymene 7 and ␥-terpinene 8 were 79, 69, 67, 87 and 69% when they were in their free form against 91, 77, 79, 91 and 81% when they were encapsulated, respectively. This indicated that encapsulation within ␤-CD, considerably improved the retention of EOs components, reduced their volatility and allowed their sustained release in agreement

with literature (Ciobanu et al., 2012; Yuan et al., 2014). The results obtained could not be only correlated with Kf values because the release of the volatile could be also affected by its intrinsic volatility and solubility. CDs could therefore be considered as ideal candidate to retain EOs components for example during heat processes. 3.5. Radical scavenging capacity The ABTS•+ assay was used to evaluate the radical scavenging activity of EOs and their inclusion complexes with ␤-CD in respect to Trolox as reference antioxidant. Results were expressed as TEAC (␮mol Trolox/g of EO) and illustrated in Fig. 3. EOs with higher

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monoterpenic abundance (R. officinalis, C. camphora, O. majorana, E. citriodora, C. reticulata and C. nardus) (Fig. 3a) were less effective than those with high phenolic content (S. montana, O. compactum and P. racemosa) (Fig. 3b). This proved that antioxidant activity of EOs is directly attributed to their phenols content (Miguel, 2010). Before investigating the encapsulation effect on the radical scavenging activity of EOs, we should note that a decrease in the absorbance of the ABTS•+ solution was also observed when ␤CD was added alone at the same concentration used with EOs. This could be due to the inclusion of the radical inside the CD cavity (Lucas-Abellan, Mercader-Ros, Zafrilla, Gabaldon, & NunezDelicado, 2011). Fig. 3 shows the radical scavenging activity of EOs in their free and encapsulated forms. EOs inclusion complexes showed higher radical scavenging activity than free EOs. This could be due to the formation of inclusion complexes between EOs components and ␤-CD (Lucas-Abellan et al., 2011) or to the fact that ␤-CD could act as a secondary antioxidant and enhance the antiradical capacity of guests (Lopez-Nicolas, Perez-Lopez, Carbonell-Barrachina, & Garcia-Carmona, 2007; Nunez-Delicado, Sanchez-Ferrer, & Garcia-Carmona, 1997). These results suggest that CDs could enhance the antioxidant activity of EOs in food. 4. Conclusion The ability of CDs to retain EOs and reduce their volatility was demonstrated. The “rapid method” based on SH-GC technique was successfully applied and validated for studying the interactions between CDs and individual components present simultaneously in EOs. Kf values of inclusion complexes between six CDs and eleven volatile compounds present in nine EOs were determined. The assessment of Kf values for CD inclusion complexes with EOs components is of major interest for choosing the well-suited CD. In addition, encapsulation within CDs reduced the volatility and allowed the controlled release of EOs components as demonstrated by MHE. Moreover, in the presence of CD, EOs showed higher radical scavenging efficacy. Our results suggested that CD inclusion complexes could overcome limitations of EOs application in food by reducing their volatility and lost during storage or food process and enhancing their radical scavenging ability. Thus, they could generate controlled release systems for food packaging use as well as for improved aroma differentiation and aroma burst. Acknowledgment Authors are grateful to Lebanese National Council for Scientific Research (CNRS-L) for the financial support of M. Kfoury’s PhD thesis. References Aicart, E., & Junquera, E. (2003). Complex formation between purine derivatives and cyclodextrins: A fluorescence spectroscopy study. Journal of Inclusion Phenomena, 47(3–4), 161–165. Amorati, R., Foti, M. C., & Valgimigli, L. (2013). Antioxidant activity of essential oils. Journal of Agricultural and Food Chemistry, 61(46), 10835–10847. Astray, G., Gonzalez-Barreiro, C., Mejuto, J. C., Rial-Otero, R., & Simal-Gándara, J. (2009). A review on the use of cyclodextrins in foods. Food Hydrocolloids, 23(7), 1631–1640. Astray, G., Mejuto, J. C., Morales, J., Rial-Otero, R., & Simal-Gándara, J. (2010). Factors controlling flavors binding constants to cyclodextrins and their applications in foods. Food Research International, 43(4), 1212–1218. Bhalla, Y., Gupta, V. K., & Jaitak, V. (2013). Anticancer activity of essential oils: A review. Journal of the Science of Food and Agriculture, 93(15), 3643–3653. Calo, J. R., Crandall, P. G., O’Bryan, C. A., & Ricke, S. C. (2015). Essential oils as antimicrobials in food systems – A review. Food Control, 54, 111–119. Cardoso-Ugarte, G. A., Morlán-Palmas, C. C., & Sosa-Morales, M. E. (2013). Effect of the addition of basil essential oil on the degradation of palm olein during repeated deep frying of French fries. Journal of Food Science, 78(7), 978–984. Ciobanu, A., Landy, D., & Fourmentin, S. (2013). Complexation efficiency of cyclodextrins for volatile flavor compounds. Food Research International, 53(1), 110–114.

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