Factors controlling flavors binding constants to cyclodextrins and theirapplications in foods

G. Astray a, J.C. Mejuto a, J. Morales a, R. Rial-Otero b, J. Simal-Gándara b,*

aDepartment of Physical Chemistry, Faculty of Science, University of Vigo, Ourense Campus, E32004 Ourense, SpainbDepartment of Analytical and Food Chemistry, Faculty of Science, University of Vigo, Ourense Campus, E32004 Ourense, Spain

a r t i c l e i n f o

Article history:Received 10 December 2009Accepted 18 February 2010

Keywords:CyclodextrinsFlavorsBinding constantsUV-Vis spectroscopy

a b s t r a c t

The binding constants of 14 different flavors (Maltol, Furaneol, Vanillin, Methyl Cinnamate, Cineole,Citral, Menthol, Geraniol, Camphor, Nootkatone, Eugenol, p-vinil Guayacol and Limonene) to cyclo-dextrins (a-cyclodextrin and b-cyclodextrin) have been determined by an UV–Vis spectrophotometrictechnique. In all cases the binding constant of flavors to b-cyclodextrin are bigger than the correspondingone to a-cyclodextrin. This fact is due to the different size of cyclodextrin cavity. As well as, a relationshipbetween log P of each flavor and the binding constants was found, proving that the driving force for host–guest complex formation is hydrophobic/hydrophilic interactions.

! 2010 Elsevier Ltd. All rights reserved.

1. Introduction

Cyclodextrins (CDs) are cyclic oligosaccharides composed ofglucose units (Bender & Komiyama, 1978; Saenger, 1980). Thebest-characterized forms are a-, b- and d-CD consisting of six, se-ven and eight D-glucose units, respectively. CDs are regulators ofchemical (Connors, 1997; Tee, Fedortchenko, Loncke, & Gadosy,1996; Wenz, 1994) and photochemical reactivity (Kalyanasunda-ran, 1987; Ramamurthy, Weiss, & Hammond, 1993). The CDs mol-ecule is often described as a torus, but in somewhat morerealistically pictures as a ‘‘shallow truncated cone”. Regardless ofthe finer details of theirs structure, the most important feature ofCDs is their cavity, because this enables then to form inclusioncomplexes with small molecular guests of an appropriate size,shape and polarity (Connors, 1997). Several classes of compounds,that can form inclusion complexes with natural cyclodextrin, havebeen subjected to systematic studies. These cover almost everyclass of compounds such aliphatic alcohols (Cabaleiro-Lago,García-Río, Hervés, Mejuto, & Pérez-Juste, 2006; García-Río et al.,2005), amines and acids (Gadosy, Boyd, & Tee, 2000), aminoacids(Tee, Gadosy, & Giorgi, 1997), ketones (Iglesias, 2003), surfactants(Dorrego et al., 2000; Fernández et al., 2000; Garcia-Rio et al.,2004) and other compounds (García-Río et al., 2006; Rekharsky &Inoue, 1998).

The formation of host–guest complexes occurs through desolv-ation of the species. Nevertheless, the stability of the complex is

related to the amount of water, which may be released by thecyclodextrin upon the encapsulation of the guest molecule(García-Río, Hall, Mejuto, & Rodríguez-Dafonte, 2007; García-Río,Mejuto, Rodríguez-Dafonte, & Hall, 2010; Inoue et al., 1993). Thedepths of cavities CDs are all the same (approximately 7.5 Å), beingdetermined by the width of a glucose unit, but the size o theircavities differ in diameter (a-CD about 5.0, b-CD about 7.0 andd-CD about 9.0 Å) given rise to a gradation in binding affinity(Connors, 1997), as it can be seen in the Fig. 1.

Different techniques such as NMR (Funasaki, Ishikawa, & Neya,2003), surface tension (Saito et al., 2000), potentiometry (Martínez,Junquera, & Aicart, 1999) and sound velocity (Gonzalez-Gaitano,Crespo, & Tardajos, 2000; Martínez et al., 1999) were used to deter-mine the host–guest binding constant (Ks). The binding constantand the change in the property for the host–guest complex forma-tion can be simultaneously estimated from the bulk thermody-namic properties like calorimetry (Castronuovo, Elia, Niccoli, &Velleca, 2003), density (Martínez et al., 1999) and heat capacity(De Lisi, Lazzara, Milioto, Muratore, & Terekhova, 2003).

There is much interest in manipulating the complex-formingability of CDs with a view to developing applications (Astray,Mejuto, Rial-Otero, Gonzalez-Barreiro, & Simal-Gándara, 2009;Szejtli & Osa, 1996). In the last years, several reviews describingthe use of CDs in food and flavor applications have been published(Astray et al., 2009; Cravotto, Binello, Baranelli, Carraro, & Trotta,2006; Hedges & McBride, 1999; Hedges, Shieh, & Sikorski, 1995;Qi & Hedges, 1995; Samant & Pai, 1991; Szente & Szejtli, 2004).CDs have been recommended for applications in food processingand as food additives with a variety of aims: (i) to protect

0963-9969/$ - see front matter ! 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.foodres.2010.02.017

* Corresponding author. Tel.: +34 988 38 70 60; fax: +34 988 38 70 01.E-mail address: jsimal@uvigo.es (J. Simal-Gándara).

Food Research International 43 (2010) 1212–1218

Contents lists available at ScienceDirect

Food Research International

journal homepage: www.elsevier .com/ locate / foodres

lipophylic food components that are sensitive to oxygen and light-or heat-induced degradation; (ii) to solubilise food colorings andvitamins; (iii) to stabilize fragrances, flavors, vitamins, and essen-tial oils against unwanted changes; (iv) to suppress unpleasantodors or tastes; and (v) to achieve a controlled release of certainfood constituents.

In this sense, we cannot forget that flavor plays an importantrole in consumer satisfaction and influences further consumptionof foods (Cuccovia, Schoroter, Montero, & Chaimovich, 1978). Man-ufacturing and storage processes, packaging materials and ingredi-ents in foods often cause modifications in overall flavor byreducing aroma compound intensity or producing off-flavor com-ponents (Arias et al., 2007; Lubbers, Landy, & Voilley, 1998). Tolimit aroma degradation or loss during processing and storage, itis beneficial to encapsulate volatile ingredients prior to use infoods and beverages. A variety of commercial encapsulation prac-tices are currently followed, however, those involving the forma-tion of flavor/CD molecular-inclusion complexes offer greatpotential for the protection of volatile and/or labile flavoring mate-rials present in a multicomponent food system throughout manyrigorous food-processing methods (cooking, pasteurization, etc.)(Bhandari, D’Arcy, & Young, 2001; Jouquand, Ducruet, & Giampaoli,2004; Pagington, 1987; Qi & Hedges, 1995). In the same way, CDscan eliminate some taste. In fact, a bitter taste is the main reasonfor the rejection of various food products although exceptions tothis rule are rooted in many cultures: in some foods and beverages,such as coffee, beer, and wine, a certain degree of bitterness is ex-pected (Binello, Cravotto, Nano, & Spagliardi, 2004; Binello, Robal-do, Barge, Cavalli, & Cravotto, 2008; Shaw, Tatum, & Wilson, 1984;Singh, Sharma, & Banerjee, 2002; Suzuki, 1975). Bitterness, how-ever, has proved a major limitation in the acceptance of commer-cial citrus juices. A commercial process is needed that removesbitter components without adding anything to the juice, while stillmaintaining the expected flavor and nutritional value of the prod-uct. CDs can be used for the removal or masking of undesirablecomponents. Some foods have a peculiar smell, but, when CDsare added in their manufacture, these components form CD inclu-sion complexes deodorizing the result product. For instance, thisprocess is used for deodorizing soybean milk and soy protein,and also for removing the peculiar fish odors, seafood and meat

products (Kuwabara, Takaku, Oku, & Kopure, 1988; Sakakibara,Sugisawa, Matsui, & Sengoku, 1985; Takeda Chem. Ind. Ltd., 1981).

On the other hand, the formation of inclusion complexes withCDs can protect some lipophylic food components that are sensi-tive to oxygen and heat- or light-induced degradation (Del Valle,2004). In addition, CDs protected phenolic compounds from enzy-matic oxidation by forming inclusion complexes. (López-Nicolás &García-Carmona, 2007; López-Nicolás, Núñez-Delicado, Sánchez-Ferrer & García-Carmona, 2007; López-Nicolás, Pérez-López, Car-bonell-Barrachina & García-Carmona, 2007a, 2007b).

In the present work we determine the binding constant of host–guest complex formation between different flavors and a-cyclo-dextrin and b-cyclodextrin. In addition, we will look for factorscontrolling flavors binding constants to cyclodextrins with theaim of selecting their appropriate applications in foods.

2. Material and methods

2.1. Reagents

All reagents with the highest commercially available puritywere supplied by Aldrich (Steinheim, Germany) and Fluka (Buchs,Switzerland). They were used without further purifications. Allsolutions were prepared in highly pure water (RP 18 MX) obtainsfrom a Millipore water purification system (Bedford, USA).

2.2. Apparatus and operating conditions

All spectrophotometric measurements were taking by means ofa Varian Cary 50 spectrophotometer (Palo Alto, CA). The systemwere thermostated at 25.0 ± 0.1 "C. The binding constant determi-nation experimental procedure using spectroscopy techniques hasbeen described in detail elsewhere (Arias et al., 2007; Cuccoviaet al., 1978). k values for each flavor are shown in Table 1. Basically,inclusion complexes were formed by adding to fix flavor concen-tration different aliquots of concentrated cyclodextrins solutions.In all cases the initial concentration of CD was at least 10 times big-ger than the flavor concentration to be sure that the free CD con-centration is approximately equal to the initial CD concentration.

Fig. 1. Geometric dimensions of a-CDs (a), b-CDs (b) and c-CDs (c).

G. Astray et al. / Food Research International 43 (2010) 1212–1218 1213

2.3. Structural determinations

MM2 (molecular mechanics) calculations were carried outusing a commercial software package (CS ChemBats3D Pro 4.0 sup-plied by the Cambridge Soft Corporation). MM2-Chem3D uses amodified version of the MM2 Allinger force-field (Allinger & Bur-ket, 1982).

3. Results and discussion

3.1. Factors controlling the cyclodextrins binding constants to flavors

The influence of the presence of CDs upon the UV–Vis spectra often different flavors has been measured. The flavors studied wereMaltol (3-Hydroxy-2-methyl-4-pyrone), Furaneol (2,5-Dimethyl-4-hydroxy-3(2H)-furanone), Vanillin (4-Hydroxy-3-methoxybenz-aldehyde), Methyl Cinnamate, Cineole (1-Isopropyl-4-methyl-7-oxabicyclo[2.2.1]heptane), Citral (3,7-Dimethyl-2,6-octadienal),Menthol (2-Isopropyl-5-methylcyclohexanol), Geraniol (trans-3,7-Dimethyl-2,6-octadien-1-ol), Camphor (1,7,7-thilmethylbicyclo[2,2,1] heptan-2-one), Nootkatone (4-a,5-dimethyl-1,2,3,4,4a,5,6,7-octahydro-7-keto-3-isoprenylnaphthalene), Eugenol (2-meth-oxy-4-(2-propenyl) phenol), p-vinil Guayacol (2-methoxy-4-vinylphenol) and Limonene (4-Isopropenyl-1-methyl-1-cyclohexene).Fig. 2 shows the different flavor structure and their geometric char-acteristics. Taking into account the size of the CD cavity (5.70 and7.80 Å for a-CD and b-CD, respectively) all flavors can accommo-date inside. In the present work we use two different CD: a-CDand b-CD. The determination of the binding constant of flavors toCDs is based in the fact that changes in the chemical environmentof flavor will modify their UV–Vis spectra (Arias et al., 2007;Bunton, Rivera, & Sepulveda, 1978; García-Río, Hervés, Mejuto,Parajó, & Perez-Juste, 1998). We can write then that the totalabsorbance measured (AT) corresponds with the sum of flavorsabsorbance in the absence of CDs (AG) and in the presence of CDs(AG–CD).

AT ! AG " AG#CD $1%

Taking into account the Beer–Lambert law, Eq. (1) can berewritten as a function of total flavor concentration, [G]T, and therespective concentrations of flavor free, [G]f, and flavor-CD com-plex, [G–CD], where l is the light pathway (in a standard cell isequal to 1 cm), e corresponds with the attenuation coefficient orextinction coefficient.

eappl&G'T ! eGl&G'f " eG#CDl&G# CD' $2%

The three concentrations of Eq. (2) are related to the complexformation constant, Ks, defined as

Ks !&G# CD'&G'f &CD'

$3%

where [CD] is CDs concentration. Using Eq. (3) and the correspond-ing matter balance ([G]T = [G]f + [G–CD]), Eqs. (4) and (5) can be eas-ily deduced.

&G'f !&G'T

1" Ks&CD'$4%

&G# CD' ! &G'TKs&CD'1" Ks&CD'

$5%

Eqs. (4) and (5) imply

eappl&G'T !eGl&G'T " eG#CDl&G'TKs&CD'

1" Ks&CD'$6%

The initial CD concentration is at least ten times bigger than fla-vor concentration. Hence, we can assume that the free CD concen-tration is equal to the initial CD concentration. Because eappl[G]T isequal to the total absorbance (AT), eGl[G]T is the absorbance in theabsence of CDs (AG), and eG–CDl[G]T corresponds with the absor-bance when all the substrate is bound to CDs (AG–CD). Thus, Eq.(6) can be written as follows:

AT ! AG " AG#CDKs&CD'1" Ks&CD'

$7%

Moreover, Eq. (7) can be linearized like this:

AT # AG

AG#CD # AT! Ks&CD' $8%

If we measure the absorbance at various CDs concentrationskeeping constant the flavors concentration, the binding constantcan be calculated from Eqs. (7), (8). In Table 1, binding constantsobtained for the different flavors to CDs are shown. The Ks valuesobtained shows that all the studied flavors exhibit more affinityfor b-CDs than for a-CDs. This greater inclusion complexes stabilityof b-CD-G versus a-CD-G would be related to the larger cavity of b-CD, which can locate more comfortably the guest molecule.Whereas the main driving force for inclusion complex formationseems to be the hydrophobic/hydrophilic interactions. To demon-strate this aspect a relationship between log P (listed in Table 1)of each flavor and their binding constant to CDs was carried out.We must remember that log P is a parameter obtained from the ra-tio of distribution of substrate between water and 1-octanol and itis commonly used as a measure of the hydrophobicity of thesubstances.

Fig. 3 shows this correlation between hydrophobicity of the fla-vors (log P) and the binding constants with CDs (Ks). As it can beseen in this figure, correlation is satisfactory (R = 0.8548 andR = 0.8824, respectively for a-CD and b-CD), proving, as we quoteabove, that the main driving force behind the formation of thecomplex would include aspects related to the hydrophobic andthe hydrophilic character of the flavors. Any deviation from thiscorrelation could be allocated to the different geometry of the sub-strates, which in some cases may play a prominent role in the for-mation and stability of these inclusion complexes.

To evaluate the influence of the substrates geometry, a relation-ship between molar volume (listed in Table 1) of each flavor andhis binding constant to CDs was carried out. Fig. 4 shows this cor-relation which R-values are respectively of a-CD and b-CDR = 0.8041 and R = 0.8458. As in the previous case any deviationfrom this correlation is found, but they prove that the flavors

Table 1Binding constants of flavors to CDs obtained from Eq. (8), log P and Vm value for eachflavor.

Flavor k (nm) Ks Ks Log P Vm (cm3 mol#1)a-CD b-CD

Maltol 230 0.4 ± 0.1 2.1 ± 0.5 0.079 93.5Furaneol 285 1.1 ± 0.2 7 ± 1 0.339 102.5Vanillin 300 1.6 ± 0.3 17 ± 3 1.188 132.5Methyl cinnamate 391 4 ± 1 20 ± 4 2.177 166.9Cineole 250 6 ± 1 29 ± 4 2.821 167.1Citral 210 8 ± 2 31 ± 6 3.169 176.7Menthol 530 10 ± 1 35 ± 7 3.204 194.3Geraniol 240 9 ± 1 44 ± 9 3.274 177.9Camphor 280 3 ± 1 19 ± 6 2.131 154.8Nootkatone 254 7 ± 1 32 ± 5 2.872 192.3Eugenol 210 5 ± 1 23 ± 4 2.224 156.2p-Vinil guayacol 220 2.0 ± 0.5 17 ± 5 1.932 137.8Limonene 400 14 ± 3 55 ± 11 4.449 163.2

1214 G. Astray et al. / Food Research International 43 (2010) 1212–1218

geometry takes an important role in the inclusion complexformation.

Taking into account both correlations, a multiparametric rela-tionship between log P and molar volume versus binding constantswas carried out for each CD (Fig. 5). In this case the normalized va-lue of log P and Vm (log P0 and V 0

m) were used. We take the normal-ized values as the ratio between each value log P and Vm and theaverage value of both of them (log P and Vm), as indicate Eqs. (9)and (10). The regression equation used is shown in Eq. (11).

log P0 ! log Plog P

$9%

V 0m ! Vm

Vm$10%

Ks ! aV 0m " b log P0 $11%

In this case, the regression coefficients (R) were R = 0.9124 andR = 0.9581, respectively for a-CD and b-CD. a and b values werea = 0.1 and b = 4.5. These values for the multiparametric regressioncoefficients are better than the corresponding one of separatedrelationships, probing that both parameters must be taken into ac-count to modelize the inclusion complex formation.

Camphor

nootkatone

Furaneol

Maltol Eugenol

limonene

Menthol Vanilline

Cineole

p-Vinyl Guayacol Methyl Cinamate

Citral Geraneol

Fig. 2. Chemical structure and geometric dimensions of flavours.

G. Astray et al. / Food Research International 43 (2010) 1212–1218 1215

3.2. Applications in food industry

Cyclodextrins have found numerous applications in food indus-try (Singh et al., 2002). They form inclusion complexes with a vari-

ety of molecules including fats, flavors and colors. For instance,they are used for the removal and masking of undesirable compo-nents and controlled release of desired food constituents (Prasad,Strauss, & Reichart, 1999). Moreover, cyclodextrins are used in foodformulations for flavor protection or flavor delivery (Kant, Linforth,Hort, & Taylor, 2004). Most natural and artificial flavors are volatileoils or liquids, and complexation with cyclodextrins provides apromising alternative to the conventional encapsulation technolo-gies for flavor protection. CDs act as molecular encapsulants, pro-tecting the flavor throughout many rigorous food-processingmethods such as freezing, thawing and microwaving. b-CD as amolecular encapsulant allows the flavor quality and quantity tobe preserved to a greater extent and longer period compared toother encapsulants and provides longevity to the food item(Muñoz-Botella, del Castillo, & Martín, 1995). In Japan, cyclodex-trins have been approved as ‘‘modified starch” for food applicationsfor more than two decades, serving to mask odors in fresh food andto stabilize fish oils. One or two European countries—for exampleHungary—have approved c-cyclodextrin for use in certain applica-tions because of its low toxicity. It was proved that CDs may alterthe sensory profile of a food and the flavor release depends of theCD type (Reineccius, Reineccius, & Peppard, 2002), the temperature(Reineccius, Reineccius, & Peppard, 2003) and also may be solvent-dependent (Reineccius, Reineccius, & Peppard, 2005). Their benefi-cial effects essentially derive from the ability to form stable inclu-sion complexes with sensitive lipophilic nutrients and constituentsof flavor and taste, making easy to prepare powdered flavor mate-rials (Liu, Furuta, Yoshii, Linko, & Coumans, 2000; Tobitsuka, Miura,& Kobayashi, 2005, 2006), and even to release such flavors duringcooking (Shiga et al., 2003). Toxicological data are examined andan assessment of CDs from the standpoint of safety for human con-sumption is made (Munro, Newberne, Young, & Bär, 2004). Regula-tions are covered, showing a general trend towards a wideracceptance of CDs as food additives. The growing health conscious-ness of consumers and expanding market for functional foods andnutraceutical products are opening up to CDs a promising future infood industry (Cravotto et al., 2006).

The complexation of CDs with sweetening agents such as aspar-tame stabilizes and improves the taste. It also eliminates the bitteraftertaste of other sweeteners such as stevioside, glycyrrhizin andrubusoside. CD itself is a promising new sweetener. Enhancementof flavor by CDs has been also claimed for alcoholic beverages suchas whisky and beer (Parrish, 1988). The bitterness of citrus fruitjuices is a major problem in the industry caused by the presenceof limonoids (mainly limonin) and flavanoids (mainly naringin).Cross-linked cyclodextrin polymers are useful to remove these bit-ter components by inclusion complexation (Szejtli & Szente, 2005).Cyclodextrins are also used to control bitterness in tannins, plantand fungal extracts, skim milk hydrolysates and overcooked teaand coffee (Hedges, 1998). They can also be used to keep the profileof oil volatiles in paste samples that were vacuum- or spray-dried(Bhandari, D’Arcy, & Padukka, 1999; Shiga et al., 2004), due to theirhigh encapsulation efficiency. The most prevalent use of CD in pro-cess aids is the removal of cholesterol from animal products suchas eggs or dairy products, like cheese (Kwak, Jung, Shim, & Ahn,2002). CD-treated material shows 80% removal of cholesterol. Freefatty acids can also be removed from fats using CDs, thus improv-ing the frying property of fat (e.g., reduced smoke formation, lessfoaming, less browning and deposition of oil residues on surfaces)(Hedges, 1998). Fruits and vegetable juices are also treated with CDto remove phenolic compounds, which cause enzymatic browning.In juices, polyphenoloxidase converts the colorless polyphenols tocolored compounds and addition of CDs removes polyphenoloxi-dase from juices by complexation. Sojo, Nuñez-Delicado,Garcia-Carmona, and Sanchez-Ferrer (1999) studied the effect ofcyclodextrins on the oxidation of o-diphenol by banana

Fig. 3. Relationship between log P versus the formation constant of the inclusioncomplex,Ks, for the target flavors. Symbols denote theuseofa-CDs (s) andb-CDs (d).

Fig. 4. Relationship between molar volume (Vm) versus the formation constant ofthe inclusion complex, Ks, for the target flavors. Symbols denote the use of a-CDs(s) and b-CDs (d).

Fig. 5. Multiparametric relationship between normalized molar volume (V 0m) and

normalized log P (log P0) versus the formation constant of the inclusion complex, Ks,for the target flavors. Symbols denote the use of a-CDs (s) and b-CDs (d).

1216 G. Astray et al. / Food Research International 43 (2010) 1212–1218

polyphenoloxidase and found that cyclodextrins act as activator aswell as inhibitor. By combining 1–4% CD with chopped ginger root,Sung (1997) established that it can be stored in vacuum at coldtemperature for 4 weeks or longer without browning or rotting.

Other studies describes the development of a gas chromatogra-phy–mass spectrometry (GC–MS) library to identify optically ac-tive compounds in the flavor and fragrance field usingenantioselective GC with cyclodextrin derivatives (CDs) as chiralselectors in combination with MS (Bicchi et al., 2008; Libertoet al., 2008), but also olfactometry can be used for detection tohave extra information about flavors (Wüst & Mosandl, 1999).The ability to separate and quantitify enantiomers at low levelsshould be useful for detecting adulterated products, for evaluatingfermentation processes, and for the accurate characterization ofenantiomeric flavor components, growth regulators, pesticides,and herbicides as well as their chiral environmental degradationproducts and metabolites (Armstrong, Chang, & Li, 1990).

Flavonoids and terpenoids are good for human health becauseof their antioxidative and antimicrobial properties but theycannot be utilized as foodstuff owing to their very low aqueous sol-ubility and bitter taste. Sumiyoshi (1999) discussed the improve-ment of the properties of these plant components (flavanoids andterpenoids) with cyclodextrin complexation. CDs are used in prep-aration of foodstuffs in different ways. For example, highlybranched CDs are used in flour-based items like noodles, piedoughs, pizza sheets and rice cakes to impart elasticity and flexibil-ity to dough (Fujishima, Kusaka, Umino, Urushinata, & Terumi,2001). They are also used in the preparation of antimicrobial foodpreservatives containing trans-2-hexanalin in apple juice prepara-tion (Takeshita & Urata, 2001) and in the processing of medicinalmushrooms for the preparation of crude drugs and health foods.CDs are used in the preparation of controlled release powdered fla-vors and confectionery items and are also used in chewing gum toretain its flavor for longer duration, a property highly valued bycustomers (Mabuchi & Ngoa, 2001). CDs are also used in the detec-tion of aflatoxin in food samples (Chiavaro et al., 2001).

4. Conclusions

The ability to hold, orient, conceal and separate guest moleculestogether with CDs’ chirality and low toxicity place cyclodextrins ina unique class of building blocks for constructing novel moleculararchitecture. Cyclodextrins are not merely another group of excip-ients, extenders or bulking agents, but they are multipurpose tech-nological tools that can be finely honed by chemical modification.CDs act as molecular chelating agents of growing importance infood and agriculture, but also in pharmaceuticals, and chromato-graphic techniques. The versatility of CDs and modified CDs isdemonstrated in their range of applications from cosmetics andfood to drugs. The inclusion and release of flavors is one of theirmajor applications. CDs have also widened the presently limitedscope of various compounds by acting as powerful toxicitymodifiers. CDs broaden the horizons of catalysis by increasingenantioselectivity. In conclusion, owing to a unique architecture,cyclodextrins are now becoming an important part of the scien-tists’ options in drug development, as enzyme mimics, in chiralseparations and as complexing agents in the food, cosmetics andpharmaceutical industries.

Acknowledgements

G. Astray thanks the Government of Galicia for a training re-search grant (P.P. 0000 300S 14008). R. Rial-Otero is funded by aParga Pondal contract (Galician Council of Innovation andIndustry).

References

Allinger, N. L., & Burket, U. (1982). Molecular mechanics. Washington, DC: AmericanChemical Society.

Arias, M., García-Falcón, M. S., García-Río, L., Mejuto, J. C., Rial-Otero, R., & Simal-Gándara, J. (2007). Binding constants of oxytetracycline to animal feed divalentcations. Journal of Food Engineering, 78(1), 69–73.

Armstrong, D. W., Chang, C.-D., & Li, W. Y. (1990). Relevance of enantiomericseparations in food and beverage analyses. Journal of Agricultural and FoodChemistry, 38, 1674–1677.

Astray, G., Mejuto, J. C., Rial-Otero, R., Gonzalez-Barreiro, C., & Simal-Gándara, J.(2009). A review on the use of cyclodextrins in foods. Journal Food Hydrocolloid,23, 1631–1640.

Bender, M. L., & Komiyama, M. (1978). Cyclodextrin chemistry. Berlin, Germany:Springer.

Bhandari, B. R., D’Arcy, B. R., & Padukka, I. (1999). Encapsulation of lemon oil bypaste method using b-cyclodextrin: Encapsulation efficiency and profile of oilvolatiles. Journal of Agricultural and Food Chemistry, 47, 5194–5197.

Bhandari, B., D’Arcy, B., & Young, G. (2001). Flavour retention during hightemperature short time extrusion cooking process: A review. InternationalJournal of Food Science and Technology, 36, 453–461.

Bicchi, C., Liberto, E., Cagliero, C., Cordero, C., Sgorbini, B., & Rubiolo, P. (2008).Conventional and narrow bore short capillary columns with cyclodextrinderivatives as chiral selectors to speed-up enantioselective gas chromatographyand enantioselective gas chromatography–mass spectrometry analyses. Journalof Chromatography A, 1212, 114–123.

Binello, A., Cravotto, G., Nano, G. M., & Spagliardi, P. (2004). Synthesis of chitosan–cyclodextrin adducts and evaluation of their bitter-masking properties. FlavourFragrance Journal, 19(5), 394–400.

Binello, A., Robaldo, B., Barge, A., Cavalli, R., & Cravotto, G. (2008). Synthesis ofcyclodextrin-based polymers and their use as debittering agents. Journal AppliedPolymer Science, 107, 2549–2557.

Bunton, C. A., Rivera, F., & Sepulveda, L. (1978). Micellar effects upon the hydrogenion and general acid catalyzed hydration of 1,4-dihydropyridines. Journal ofOrganic Chemistry, 43(6), 1166–1173.

Cabaleiro-Lago, C., García-Río, L., Hervés, P., Mejuto, J. C., & Pérez-Juste, J. (2006).Characterization of alkane diol-CD complexes. Acid denitrosation of N-methyl-N-nitroso-p-toluenesulphonamide as a chemical probe. Journal of InclusionPhenomena, 54(3–4), 209–216.

Castronuovo, G., Elia, V., Niccoli, M., & Velleca, F. (2003). Study of the effects ofcosolvents on the complexation of b-cyclodextrin with alkanols by calorimetryat 298 K. Journal of Inclusion Phenomena, 45(1–2), 91–97.

Chiavaro, E., Dallasta, C., Galaverna, G., Biancardi, A., Gambarelli, E., Dossena, A.,et al. (2001). New reversed-phase liquid chromatographic method to detectaflatoxins in food and feed with cyclodextrins as fluorescence enhancers addedto the eluent. Journal of Chromatography A, 937, 31–40.

Connors, K. A. (1997). The stability of cyclodextrin complexes in solution. ChemicalReviews, 5, 1325–1357.

Cravotto, G., Binello, A., Baranelli, E., Carraro, P., & Trotta, F. (2006). Cyclodextrins asfood additives and in food processing. Current Nutrition Food Science, 2(4),343–350.

Cuccovia, I. M., Schoroter, E. H., Montero, P. M., & Chaimovich, H. (1978). Effect ofhexadecyltrimethylammonium bromide on the thiolysis of p-nitrophenylacetate. Journal of Organic Chemistry, 43, 2248–2252.

De Lisi, R., Lazzara, G., Milioto, S., Muratore, N., & Terekhova, I. V. (2003). Heatcapacity study to evidence the interactions between cyclodextrin andsurfactant in the monomeric and micellized states. Langmuir, 19(2003),7188–7195.

Del Valle, E. M. M. (2004). Cyclodextrins and their uses. Process Biochemistry, 39,1033–1046.

Dorrego, A. B., García-Río, L., Hervés, P., Leis, J. R., Mejuto, J. C., & Pérez-Juste, J.(2000). Micellization versus cyclodextrin–surfactant complexation. AngewandteChemie, 39(16), 2945–2948.

Fernández, I., García-Río, L., Hervés, P., Mejuto, J. C., Pérez-Juste, J., & Rodríguez-Dafonte, P. J. (2000). b-Cyclodextrin-micelle mixed systems as areactionÙmedium. Denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide. Physical Organic Chemistry, 13, 664–669.

Fujishima, N., Kusaka, K., Umino, T., Urushinata, T. & Terumi, K. (2001). Flour basedfoods containing highly branched cyclodextrins. Japanese Patent JP 136, 898.

Funasaki, N., Ishikawa, S., & Neya, S. (2003). Proton NMR study of a-cyclodextrininclusion of short-chain surfactants. Journal of Physical Chemistry B, 107(37),10094–10099.

Gadosy, T. A., Boyd, M. J., & Tee, O. S. (2000). Catalysis of ester aminolysis bycyclodextrins. The reaction of alkylamines with p-nitrophenyl alkanoates.Journal of Organic Chemistry, 65(21), 6879–6889.

García-Río, L., Hall, R. W., Mejuto, J. C., & Rodríguez-Dafonte, P. (2007). Thesolvolysis of benzoyl halides as a chemical probe determining the polarity of thecavity of dimethyl-b-cyclodextrin. Tetrahedron, 63(10), 2208–2214.

García-Río, L., Hervés, P., Leis, J. R., Mejuto, J. C., Pérez-Juste, J., & Rodríguez-Dafonte,P. (2006). Evidence for complexes of different stoichiometries betweenorganic solvents and cyclodextrins. Organic Biomolecular Chemistry, 4,1038–1048.

García-Río, L., Hervés, P., Mejuto, J. C., Parajó, M., & Perez-Juste, J. (1998). Associationconstant of crystal violet in micellar aggregates: Determination byspectroscopic techniques. Journal of Chemical Research, 11, 716–717.

G. Astray et al. / Food Research International 43 (2010) 1212–1218 1217

Garcia-Rio, L., Leis, J. R., Mejuto, J. C., Navarro-Vazquez, A., Perez-Juste, J., &Rodriguez-Dafonte, P. (2004). Basic hydrolysis of crystal violet in b-cyclodextrin/surfactant mixed systems. Langmuir, 20, 606–613.

García-Río, L., Mejuto, J. C., Nieto, M., Pérez-Juste, J., Pérez-Lorenzo, M., & Rodríguez-Dafonte, P. (2005). Denitrosation of N-nitrososulfonamide as chemical probe fordetermination of binding constants to cyclodextrins. Supramolecular Chemistry,17(8), 649–653.

García-Río, L., Mejuto, J. C., Rodríguez-Dafonte, P., & Hall, R. W. (2010). The role ofwater release from the cyclodextrin cavity in the complexation of benzoylchlorides by dimethyl-b-cyclodextrin. Tetrahedron. doi:10.1016/j.tet.2009.12.005.

Gonzalez-Gaitano, G., Crespo, A., & Tardajos, G. (2000). Thermodynamicinvestigation (volume and compressibility) of the systems b-cyclodextrin + n-alkyltrimethylammonium bromides + water. Journal of Physical Chemistry B,104(8), 1869–1879.

Hedges, A. R. (1998). Industrial applications of cyclodextrins. Chemical Reviews, 98,2035–2044.

Hedges, A. R., & McBride, C. (1999). Utilization of b-cyclodextrin in food. CerealFoods World, 44(10), 700–704.

Hedges, A. R., Shieh, W. J., & Sikorski, C. T. (1995). Use of cyclodextrins forencapsulation in the use and treatment of food products. In S. J. Risch & G. A.Reineccius (Eds.). Encapsulation and controlled release of food ingredients (Vol.590, pp. 60–71). Washington DC, USA: ACS Symposium Series.

Iglesias, E. (2003). Nitrosation of 2-acetylcyclohexanone. 2. Reaction in water in theabsence and presence of cyclodextrins. Journal Organic Chemistry, 68,2689–2697.

Inoue, Y., Hakushi, T., Liu, Y., Tong, L., Shen, B., & Jin, D. (1993). Thermodynamics ofmolecular recognition by cyclodextrins. 1. Calorimetric titration of inclusioncomplexation of naphthalenesulfonates with a-, b-, and c-cyclodextrins:Enthalpy–entropy compensation. Journal of the American Chemical Society,115(2), 475–481.

Jouquand, C., Ducruet, V., & Giampaoli, P. (2004). Partition coefficients of aromacompounds in polysaccharide solutions by the phase ratio variation method.Food Chemistry, 85, 467–474.

Kalyanasundaran, K. (1987). Photochemistry in microheterogeneous systems. NewYork, USA: Academic Press.

Kant, A., Linforth, R. S. T., Hort, J., & Taylor, A. J. (2004). Effect of b-cyclodextrin onaroma release and flavor perception. Journal of Agricultural and Food Chemistry,52, 2028–2035.

Kuwabara, N., Takaku, H., Oku, S., & Kopure, Y. (1988). Japan Kokai, JP 88 267 246.Kwak, H. S., Jung, C. S., Shim, S. Y., & Ahn, J. (2002). Removal of cholesterol from

cheddar cheese by b-cyclodextrin. Journal of Agricultural and Food Chemistry, 50,7293–7298.

Liberto, E., Cagliero, C., Sgorbini, B., Bicchi, C., Sciarrone, D., D’Acampora-Zellner, B.,et al. (2008). Enantiomer identification in the flavour and fragrance fields by‘‘interactive” combination of linear retention indices from enantioselective gaschromatography and mass spectrometry. Journal of Chromatography A, 1195,117–126.

Liu, X.-D., Furuta, T., Yoshii, H., Linko, P., & Coumans, W. J. (2000). Cyclodextrinencapsulation to prevent the loss of L-menthol and its retention during drying.Bioscience Biotechnology and Biochemistry, 64(8), 1608–1613.

López-Nicolas, J. M., & García-Carmona, F. (2007). Use of cyclodextrins as secondaryantioxidants to improve the color of fresh pear juice. Journal of Agricultural andFood Chemistry, 55, 6330–6338.

López-Nicolas, J. M., Nuñez-Delicado, E., Sánchez-Ferrer, A., & García-Carmona, F.(2007). Kinetic model of apple juice enzymatic browning in the presence ofcyclodextrins: The use of maltosyl-beta-cyclodextrin as secondary antioxidant.Food Chemistry, 101, 1164–1171.

López-Nicolas, J. M., Pérez-López, A. J., Carbonell-Barrachina, A., & García-Carmona,F. (2007a). Use of natural and modified cyclodextrins as inhibiting agents ofpeach juice enzymatic browning. Journal of Agricultural and Food Chemistry, 55,5312–5319.

López-Nicolas, J. M., Pérez-López, A. J., Carbonell-Barrachina, A., & García-Carmona,F. (2007b). Kinetic study of the activation of banana juice enzymatic browningby the addition of maltosyl-beta-cyclodextrin. Journal of Agricultural and FoodChemistry, 55, 9655–9662.

Lubbers, S., Landy, P., & Voilley, A. (1998). Retention and release of aromacompounds in food containing proteins. Journal of Food Technology, 52, 68–74.

Mabuchi, N., & Ngoa, M. (2001). Controlled release powdered flavour preparationsand confectioneries containing preparations. Japanese Patent JP 128, 638.

Martínez, N., Junquera, E., & Aicart, E. (1999). Ultrasonic, density, andpotentiometric characterization of the interaction of gentisic and gallic acidswith an apolar cavity in aqueous solution. Physical Chemistry Chemical Physics,20, 4811–4817.

Muñoz-Botella, S., del Castillo, B., & Martín, M. A. (1995). Cyclodextrin propertiesand applications of inclusion complex formation. Ars Pharmaceutica, 36,187–198.

Munro, I. C., Newberne, P. M., Young, V. R., & Bär, A. (2004). Safety assessment of c-cyclodextrin. Regulatory Toxicology and Pharmacology, 39, S3–S13.

Pagington, J. S. (1987). Beta-cyclodextrin – The success of molecular inclusion.Chemistry in Britain, 23, 455–458.

Parrish, M.A. (1988). Cyclodextrins—a review. Available from sterling organics.Newcastle-upon-Tyne NE3 3TT, England.

Prasad, N., Strauss, D., & Reichart, G. (1999). Cyclodextrins inclusion for food,cosmetics and pharmaceuticals. European Patent 1084, 625.

Qi, Z. H., & Hedges, A. R. (1995). Use of cyclodextrins for flavours. In C. T. Ho, C. T.Tan, & C. H. Tong (Eds.). Flavour technology: Physical chemistry, modificationand process (Vol. 610, pp. 231–243). Washington DC, USA: ACS SymposiumSeries.

Ramamurthy, V., Weiss, R. G., & Hammond, G. S. (1993). Photochemistryin organized and confining media: A model. Chemical Research, 26(10), 530–536.

Reineccius, T. A., Reineccius, G. A., & Peppard, T. L. (2002). Encapsulation of flavorsusing cyclodextrins: Comparison of flavor retention in alpha, beta, and gammaTypes. Journal of Food Science, 67(9), 3271–3279.

Reineccius, T. A., Reineccius, G. A., & Peppard, T. L. (2003). Flavor release fromcyclodextrin complexes: Comparison of alpha, beta, and gamma types. Journalof Food Science, 68(4), 1234–1239.

Reineccius, T. A., Reineccius, G. A., & Peppard, T. L. (2005). The effect of solventinteractions on a-, b-, and c-cyclodextrin/flavor molecular inclusion complexes.Journal of Agriculture and Food Chemistry, 53, 388–392.

Rekharsky, M. V., & Inoue, Y. (1998). Complexation thermodynamics ofcyclodextrins. Chemical Reviews, 5, 1875–1917.

Saenger, W. (1980). Cyclodextrin inclusion compounds in research and industry.Angewandte Chemie, 19, 344–362.

Saito, Y., Watanabe, K., Hashizaki, K., Taguchi, H., Ogawa, N., Sato, T., et al. (2000).Determination of stability constants for alkanol/a-cyclodextrin inclusioncomplexes using the surface tension method. Journal of Inclusion Phenomen,38(1–4), 445–452.

Sakakibara, S., Sugisawa, K., Matsui, F., & Sengoku, K. (1985). Japanese Patent JP 851248 075.

Samant, S. K., & Pai, J. S. (1991). Cyclodextrins: New versatile food additive. IndianFood Packer, 45(3), 55–65.

Shaw, P. E., Tatum, J. H., & Wilson, C. W. (1984). Improved flavor of navel orange andgrapefruit juices by removal of bitter components with b-cyclodextrin polymer.Journal of Agricultural and Food Chemistry, 32, 832–836.

Shiga, H., Yoshii, H., Ohe, H., Yasuda, M., Furuta, T., Kuwahara, H., et al. (2004).Encapsulation of shiitake (Lenthinus edodes) flavors by spray drying. BioscienceBiotechnology and Biochemistry, 68(1), 66–71.

Shiga, H., Yoshii, H., Taguchi, R., Nishiyama, T., Furuta, T., & Linko, P. (2003). Releasecharacteristics of flavor from spray-dried powder in boiling water and duringrice cooking. Bioscience Biotechnology and Biochemistry, 67(2), 426–428.

Singh, M., Sharma, R., & Banerjee, U. C. (2002). Biotechnological applications ofcyclodextrins. Biotechnology Advances, 20, 341–359.

Sojo, M. M., Nuñez-Delicado, E., Garcia-Carmona, F., & Sanchez-Ferrer, A. (1999).Cyclodextrins as activator and inhibitor of latent banana pulp polyphenoloxidase. Journal of Agricultural and Food Chemistry, 47, 518–523.

Sumiyoshi, H. (1999). Utilisation of inclusion complexes with plant components forfoods. Nippon Shokuhin Shinsozai Kenkyukaishi, 2, 109–114.

Sung, H. (1997). Composition for ginger preservation. Repub Korea KR 9707,148.Suzuki, J. (1975). Japan Kokai, JP 7 569 100.Szejtli, J., & Osa, T. (1996). Comprehensive supramolecular chemistry. Cyclodextrins

(vol. 3). New York, USA: Pergamont.Szejtli, J., & Szente, L. (2005). Elimination of bitter, disgusting tastes of drugs and

foods by cyclodextrins. European Journal of Pharmaceutics and Biopharmaceutics,61, 115–125.

Szente, L., & Szejtli, J. (2004). Cyclodextrins as food ingredients. Trends in FoodScience Technology, 15, 137–142.

Takeda Chem. Ind. Ltd. (1981). Japan Kokai, JP 81 127 058.Takeshita, K., & Urata, T. (2001). Antimicrobial food preservatives containing

cyclodextrin inclusion complexes. Japanese Patent JP 29,054.Tee, O. S., Fedortchenko, A. A., Loncke, P. G., & Gadosy, T. A. (1996). Binding of

aliphatic ketones to cyclodextrins in aqueous solution. Journal Chemical Society,26, 1243–1249.

Tee, O. S., Gadosy, T. A., & Giorgi, J. B. (1997). Effect of b-cyclodextrin on the reactionof a-amino acid anions with p-nitrophenyl acetate and p-nitrophenylhexanoate. Canadian Journal of Chemistry, 75(1), 83–91.

Tobitsuka, K., Miura, M., & Kobayashi, S. (2005). Interaction of cyclodextrins withaliphatic acetate esters and aroma components of La France pear. Journal ofAgricultural and Food Chemistry, 53, 5402–5406.

Tobitsuka, K., Miura, M., & Kobayashi, S. (2006). Retention of a European pear aromamodel mixture using different types of saccharides. Journal of Agricultural andFood Chemistry, 54, 5069–5076.

Wenz, G. (1994). Cyclodextrins as building blocks for supramolecular structures andfunctional units. Angewandte Chemie, 33, 808–822.

Wüst, M., & Mosandl, A. (1999). Important chiral monoterpenoid ethers in flavoursand essential oils – Enantioselective analysis and biogenesis. European FoodResearch and Technology, 209, 3–11.

1218 G. Astray et al. / Food Research International 43 (2010) 1212–1218