Cyclodextrins as additives in crops and flours
Cyclodextrins are cyclic oligomers formed by different units of glucose and characterized by having a truncated cone structure that contains a cavity in which small organic molecules can lodge forming inclusion complexes. The formation of these host-guest complex allows to "protect" these organic molecules, avoiding or slowing decomposition processes, solubilizing hydrophobic molecules formed aqueous solutions where cyclodextrins act as catalysts of phase transfer or capture molecules whose presence in a matrix is undesirable.
An example of this last property (the capture of undesirable molecules within a matrix) can be illustrated if we take into account that the rice stored for a long time acquires an unpleasant smell that harms its placing on the market and can be effectively eliminated by using CD. The same happens with the aroma of cooked rice that can be eliminated thanks to the formation of the maltosyl-CD complex.
figure 2: Chemical structure of 6-O-α-D-Maltosyl-β-cyclodextrina, from Li et al.
In the literature there are also examples of the use of CD with other cereals such as the case of the retention of unwanted flavours in corn. In this case, the formation of inclusion complexes allows the capture of cinnamaldehyde, eugenol, nonanoic acid or 3-octanone-.
figure 3: Chemical structure of cinnamaldehyde, eugenol, nonanoic acid and 3-octanone
This application can extend not only to cereals but also to flours and products processed from them. An example would be the case of cookies that when processed using butter that contains the aromas forming complexes with the cyclodextrins maintain the desired aroma 4 times longer than those that were prepared in the traditional way. 
Likewise, several authors proved a significant reduction in the recrystallization of amylopectin after the addition of cyclodextrins (in particular γ-cyclodextrin) after one week of storage of the dough of baked wheat flour.
On the other hand, we also find technological advantages of CDs in terms of their application to rice flours. This is due to the hydrophobicity of the proteins present in the masses of rice flour, which makes the use of traditional conditioners and improvers difficult. The ability of CDs as solubilizers plays an important role in this case. We must emphasize that this point is key for celiacs whose one way to combat the symptoms of their illness is to maintain a strict gluten-free diet . In this case, the enzyme cyclodextrin glycosyl transferase (CGTase) is confirmed as a good breeder for the quality of rice bread . Due to the properties of CDs, CGTase is used in the production of different foods . Its use reduces the hydrophobicity of the medium due to its ability to hydrolyse and cyclize the starch, generating in situ CDs that can form host-guest complexes with a different variety of compounds. This technology would make it possible to manufacture rice breads that meet and surpass the quality expectations of consumers with strict gluten-free diets .
figure 4: Crystal structure of cyclodextrin glycosyltransferase from Paenibacillus sp. (pCGTase) (PDB ID: 1UKS).
(a) pCGTase domains A–D are colored as green, cyan, magenta, and salmon, respectively.
(b) Substrate (cyan)/product (yellow) binding at the active site of pCGTase in domain A.
(c) Residues in substrate/product-binding site are shown as green sticks. Catalytic residues are as magenta sticks.
Taken from Li et al.
We must also take into account that starch is widely used in the food industry, in general to achieve a desired texture in many products. The use of starch is done through the preparation of a paste that in an aqueous medium will be used as a gelling agent, stabilizer, adhesive, for film formation, or thickening.
figure 5: Structure of (a) amylose and (b) amylopectin. From Amagliani et al. and Tester et al.
In the literature it has been shown that interaction of β-CD with α-amylase in wheat flour was much stronger than in wheat starch. Item plus, CDs are commonly used as carriers in spray drying and have demonstrate a high water solubility and low viscosity at low cost, likewise, improving the stability of bioactive components and increasing the performance and physicochemical properties of spray dried flours.
figure 6: Structure of α-amylase, from Sundarram et al.
As for the addition of lipids to commercial starch, it has been shown to cause delayed granule inflammation, but an increase in the extent of inflammation. Researchers report the anti-firming property of monoglycerides in baking, attributing it to the formation of complexes and amylose. Finally, a slight influence of β-CD on the sticking properties of rice starches has also been observed.
- Departamento de Química Física, Facultad de Ciencias, Universidad de Vigo, Campus de Ourense, 32004-Ourense, SPAIN
- Area de Bromatología, Facultad de Ciencias, Universidad de Vigo, Campus de Ourense, 32004-Ourense, SPAIN
- L. García-Río; P. Herves; J. R. Leis; Jorge Perez-Juste; Pedro Rodriguez-Dafonte; Juan C. Mejuto; Evidence for complexes of different stoichiometries between organic solvents and cyclodextrins. Organic & Biomolecular Chemistry 2006, 4, 1038, 10.1039/b513214b.
- Celia Cabaleiro-Lago; Luis Garcia-Rio; Pablo Herves; Juan C. Mejuto; Jorge Pérez-Juste; Characterization of Alkane Diol-CD Complexes. Acid Denitrosation of N-Methyl-N-Nitroso-p-Toluenesulphonamide as a Chemical Probe. Journal of Inclusion Phenomena and Macrocyclic Chemistry 2006, 54, 209-216, 10.1007/s10847-005-7379-4.
- L. García-Río; Juan C. Mejuto; M. Nieto; Jorge Perez-Juste; M. Pérez-Lorenzo; Pedro Rodriguez-Dafonte; Denitrosation of N-Nitrososulfonamide as Chemical Probe for Determination of Binding Constants to Cyclodextrins. Supramolecular Chemistry 2005, 17, 649-653, 10.1080/10610270500231824.
- García-Río, L.; Hervés, P.; Iglesias, E.; Leis, J.R.; Mejuto, J.C.; Influence of cyclodextrins on chemical reactivity in water and micellar systems. Recent Research Developments in Physical Chemistry 2000, 1, 101-133, http://scholar.google.com/scholar?cluster=11693346887971388026&hl=en&oi=scholarr.
- Gonzalo Astray; C. Gonzalez-Barreiro; Juan C. Mejuto; R. Rial-Otero; Jesus Simal-Gandara; A review on the use of cyclodextrins in foods. Food Hydrocolloids 2009, 23, 1631-1640, 10.1016/j.foodhyd.2009.01.001.
- Ganesh Narayanan; Jialong Shen; Ramiz Boy; Bhupender Gupta; Alan Tonelli; Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes. Polymers 2018, 10, 428, 10.3390/polym10040428.
- Ganesh Narayanan; Ramiz Boy; Bhupender S. Gupta; Alan E. Tonelli; Analytical techniques for characterizing cyclodextrins and their inclusion complexes with large and small molecular weight guest molecules. Polymer Testing 2017, 62, 402-439, 10.1016/j.polymertesting.2017.07.023.
- Bin Li; Benguo Liu; Jiaqi Li; Huizhi Xiao; Junyi Wang; GuiZhao Liang; Experimental and Theoretical Investigations on the Supermolecular Structure of Isoliquiritigenin and 6-O-α-D-Maltosyl-β-cyclodextrin Inclusion Complex. International Journal of Molecular Sciences 2015, 16, 17999-18017, 10.3390/ijms160817999.
- Anantha N.R. Kollengode; Milford A. Hanna; Cyclodextrin Complexed Flavors Retention in Extruded Starches. Journal of Food Science 1997, 62, 1057-1060, 10.1111/j.1365-2621.1997.tb15037.x.
- Szejtli, J.. Proceedings of the First International Symposium on Cyclodextrins; Szejtli, J., Eds.; Springer Netherlands: Amsterdam, 1982; pp. 469-480.
- L. Duedahl-Olesen; Wolfgang Zimmermann; J. A. Delcour; Effects of Low Molecular Weight Carbohydrates on Farinograph Characteristics and Staling Endotherms of Wheat Flour-Water Doughs. Cereal Chemistry Journal 1999, 76, 227-230, 10.1094/cchem.19220.127.116.11.
- Yu Li; Likun Wei; Zhangliang Zhu; Songtao Li; Jian-Wen Wang; Qinglong Xin; HongBin Wang; Fuping Lu; Hui-Min Qin; Rational design to change product specificities and thermostability of cyclodextrin glycosyltransferase from Paenibacillus sp.. RSC Advances 2017, 7, 13726-13732, 10.1039/C7RA00245A.
- Veeran Gowda Kadajji; Guru V. Betageri; Water Soluble Polymers for Pharmaceutical Applications. Polymers 2011, 3, 1972-2009, 10.3390/polym3041972.
- Luca Amagliani; Jonathan O’Regan; Alan L. Kelly; James A. O’Mahony; Jonathan O'regan; James A. O'mahony; Chemistry, structure, functionality and applications of rice starch. Journal of Cereal Science 2016, 70, 291-300, 10.1016/j.jcs.2016.06.014.
- Richard F. Tester; John Karkalas; Xin Qi; Starch—composition, fine structure and architecture. Journal of Cereal Science 2004, 39, 151-165, 10.1016/j.jcs.2003.12.001.
- W. D. Li; J. C. Huang; H. Corke; Effect of β-cyclodextrin on pasting properties of wheat starch. Food / Nahrung 2000, 44, 164-167, 10.1002/1521-3803(20000501)44:3<164::aid-food164>3.0.co;2-x.
- Zhen Peng; Jing Li; Yufang Guan; Guohua Zhao; Effect of carriers on physicochemical properties, antioxidant activities and biological components of spray-dried purple sweet potato flours. LWT 2013, 51, 348-355, 10.1016/j.lwt.2012.09.022.
- Jaruporn Rakmai; Benjamas Cheirsilp; Juan Carlos Mejuto; Jesús Simal-Gándara; Ana Torrado-Agrasar; Antioxidant and antimicrobial properties of encapsulated guava leaf oil in hydroxypropyl-beta-cyclodextrin. Industrial Crops and Products 2018, 111, 219-225, 10.1016/j.indcrop.2017.10.027.
- Jaruporn Rakmai; Benjamas Cheirsilp; Ana Torrado-Agrasar; Jesús Simal-Gándara; Juan Carlos Mejuto; Encapsulation of yarrow essential oil in hydroxypropyl-beta-cyclodextrin: physiochemical characterization and evaluation of bio-efficacies. CyTA - Journal of Food 2017, 15, 1-9, 10.1080/19476337.2017.1286523.
- Jaruporn Rakmai; Benjamas Cheirsilp; Juan Carlos Mejuto; Ana Torrado-Agrasar; Jesús Simal-Gándara; Physico-chemical characterization and evaluation of bio-efficacies of black pepper essential oil encapsulated in hydroxypropyl-beta-cyclodextrin. Food Hydrocolloids 2017, 65, 157-164, 10.1016/j.foodhyd.2016.11.014.
- Nick Kalogeropoulos; Konstantina Yannakopoulou; Aristea Gioxari; Antonia Chiou; Dimitris P. Makris; Polyphenol characterization and encapsulation in β-cyclodextrin of a flavonoid-rich Hypericum perforatum (St John's wort) extract. LWT 2010, 43, 882-889, 10.1016/j.lwt.2010.01.016.
- J. A. Grabowski; V.-D. Truong; C. R. Daubert; Spray-Drying of Amylase Hydrolyzed Sweetpotato Puree and Physicochemical Properties of Powder. Journal of Food Science 2006, 71, E209-E217, 10.1111/j.1750-3841.2006.00036.x.
- Ngan King Chok; Peter Swedlund; Siew Young Quek; The physicochemical properties of spray-dried watermelon powders. Chemical Engineering and Processing - Process Intensification 2007, 46, 386-392, 10.1016/j.cep.2006.06.020.
- Duduku Krishnaiah; Rajesh Nithyanandam; Rosalam Sarbatly; A Critical Review on the Spray Drying of Fruit Extract: Effect of Additives on Physicochemical Properties. Critical Reviews in Food Science and Nutrition 2013, 54, 449-473, 10.1080/10408398.2011.587038.
- Sundarram, A.; Murthy T.P.K.; α-Amylase Production and Applications: A Review. Journal of Applied & Environmental Microbiology 2014, 2, 166-175, 10.12691/jaem-2-4-10.
- XiaoMing Liang; Joan M. King; Fred F. Shih; Pasting Property Differences of Commercial and Isolated Rice Starch with Added Lipids and β-Cyclodextrin. Cereal Chemistry Journal 2002, 79, 812-818, 10.1094/cchem.2002.79.6.812.
- A.-C. Eliasson; N. Krog; Physical properties of amylose-monoglyceride complexes. Journal of Cereal Science 1985, 3, 239-248, 10.1016/s0733-5210(85)80017-5.
- Roach, R.R.; Hoseney, R.C.; Monocaprin and Tricaprin in Breadmaking. Cereal Chem. 1996, 73, 197-198, https://www.aaccnet.org/publications/cc/backissues/1996/Documents/73_197.pdf.