Water content of natural cyclodextrins and their essential oil complexes: A comparative study between Karl Fischer titration and thermal methods

The paper presents a comparative study regarding the water determination in natural cyclodextrins and in their essential oil complexes (Apiaceae, Liliaceae, and Cupressaceae families) by using Karl Fischer titration (KFT) and thermal methods. For the natural cyclodextrins, the influence of the solvent hydrophobicity and the preheating temperature on the water extraction process were evaluated. The water contents, estimated by KFT in both methanol and methanol–octanol solvent systems, were 10.6% and 14.4% for α- and β-cyclodextrin, respectively; the water content, estimated by KFT in a more hydrophilic solvent system, methanol–formamide, was 0.4–0.6% higher. Thermogravimetric evaluation of water conducts to lower values. For the essential oil/cyclodextrin complexes, the KFT water content were in the range of 6.4–8.1%, higher values being obtained in the case of Juniperus essential oil/β-cyclodextrin complexes (7.5–8.1%). With some exceptions, thermal analyses of complexes are in good agreement with the KFT results.     

Preparation and properties of phytosterols with hydroxypropyl β-cyclodextrin inclusion complexes

In order to enhance the solubility and bioavailability of phytosterols (PS), cyclodextrin–PS (CD–PS) inclusion complexes were prepared and the properties of PS-β-cyclodextrin (PS-β-CD) and the inclusion mechanism of its derivative hydroxypropyl β-cyclodextrin (PS-HP-β-CD) in solution were also evaluated. The effects of crucial parameters on cyclodextrin–sterol inclusion efficiency were optimized, including solvent type, β-CD/PS molar ratio, temperature, PS content and reaction time; 92–98?% inclusion efficiency was achieved under the conditions of HP-β-CD/PS ratio 3:1–4:1, PS concentration 15–20?mM, temperature 50–55?°C, reaction time 12?h. For β-CD host, butanol was a good solvent for PS inclusion reaction. The properties of CD–PS inclusion complexes were characterized by differential scanning calorimetric, scanning electron microscopy, UV–Vis scanning spectrophotometer (UV–Vis) and fourier transform infrared spectroscopy (FT-IR), which demonstrated that there are intermolecular hydrogen bonds between PS and HP-β-CD in inclusion complex, resulting in the formation of amorphous form. To clarify the mechanism of the increase in the solubility and bioactivity of HP-β-CD–PS inclusion complexes, the structure of CD as well as the interaction of the HP-β-CD–PS inclusion formation was elucidated. The conclusions indicated that PS-HP-β-CD showed higher water solubility with greater solubilizing and complexing capabilities than PS-β-CD and PS itself.     

Using flavonoids, phenolic compounds and headspace volatile profile for botanical authentication of lemon and orange honeys

This study evaluates the usefulness of flavonoids (naringenin, hesperetin, chrysin, galangin, kaempferol, luteolin, pinocembrin, and quercetin) and phenolic acids (caffeic acid and p-coumaric acid) together with 37 volatile compounds in the differentiation between lemon blossom honey (Citrus limon) and orange blossom honey (Citrus spp.). The total content of flavonoids and phenolic acids is twice as high in lemon honey (6.20 mg/100 g) as in orange honey (3.64 mg/100 g); naringenin and caffeic acid were the main compounds in all cases. Hesperetin, a floral marker of citrus honey, was not significantly different for the two types of honey. A multivariate PLS2 analysis showed that some volatile compounds such as, 4 lilac aldehydes and bencenacetaldehyde (all abundant in orange honey) were negatively correlated with 4 flavonoids: pinocembrin, chrysin, naringenin and quercetin, and caffeic phenolic acid (all abundant in lemon honey). Moreover, the last 5 compounds were positively correlated with: 6 alcohols, 2 ketones, acetaldehyde and furanmethanol. This is a first approach to employ all of these compounds together with appropriate statistical techniques to differentiate between two varieties of citrus honey, and therefore it could be an interesting tool for their authentication.     

Encapsulation of cinnamon and thyme essential oils components (cinnamaldehyde and thymol) in β-cyclodextrin: Effect of interactions with water on complex stability

Thymol and cinnamaldehyde formed inclusion complexes with β-cyclodextrin (β-CD) upon mixing the components in aqueous media and subsequent freeze–drying, as confirmed by differential scanning calorimetry. The samples were stored at constant relative humidities (RH) from 22% to 97%, at 25 °C. The release of encapsulated compounds was determined following the melting enthalpy of each guest. Water sorption isotherms for β-CD and the complexes showed constant and low water sorption at RH < 80%, then the uptake of water increased abruptly. The amount of sorbed water at each RH was smaller for the complexes than for β-CD. The guest molecules displaced water molecules from inside the cavity of β-CD. No thymol or cinnamaldehyde release was detected at RH < 84%, and it increased abruptly from 84% RH, coincidentally with the abrupt increase of sorbed water. Water sorption significantly affects β-CD complexes stability, which is thus governed by the shape of the water sorption isotherm.     

响应面法优化β-环糊精提取葡萄叶白藜芦醇工艺

研究水、50%甲醇溶液和β-环糊精溶液对葡萄叶中多酚和白藜芦醇提取效果的影响,并采用分子对接方法分析β-环糊精与白藜芦醇之间的相互作用。结果表明：50%甲醇溶液提取所得多酚的提取量最大,而β-环糊精所得白藜芦醇的提取量最大;β-环糊精的疏水性空腔可以容纳白藜芦醇分子,并通过氢键的形成维持复合物的稳定。通过单因素和响应面优化试验对β-环糊精提取葡萄叶中白藜芦醇的工艺参数进行分析和优化,结果表明,3 个因素对白藜芦醇提取量的影响主次顺序为提取温度＞β-环糊精质量浓度＞处理时间;白藜芦醇的最佳提取条件为β-环糊精质量浓度28 g/L、提取温度50 ℃、处理时间68 min,在此条件下,白藜芦醇提取量为152.2 μg/g。     

A comparative evaluation of methodologies for water content determination in green coffee

The main objective of this study was to compare methods for mass loss evaluation in green coffee to water content determination by Karl Fischer titration (KFT). The following methodologies were tested: (i) ISO 6673 (oven drying at 105 °C for 16 h); (ii) the reference method employed by the Brazilian Agriculture Ministry (oven drying at 105 °C for 24 h)—BRAMw, employing whole beans and BRAMg, employing ground beans; and (iii) infrared drying (IRD). Reference oven drying methodologies ISO 6673 and BRAMw presented results statistically equivalent (p>0.05) to those from KFT in the moisture content range that is of interest for green coffee commercialization (8-13 g/100 g), whereas IRD results were lower than those for KFT. ISO 6673 and BRAMw also presented the highest values of correlation coefficients to KFT. Differences in moisture content determination became more significant for lower moisture content values (4-7 g/100 g), probably due to loss of organic volatile substances during drying and occurrence of moisture loss during sample grinding.     

Effect of phenolic compounds on the properties of porcine plasma protein-based film

Properties of porcine plasma protein-based film incorporated with tannic acid, caffeic acid and ferulic acid at different concentrations (1–3% (w/w) of protein content) were studied. Film-forming solution (FFS) containing 3% protein (w/v) and 70% glycerol (w/w of protein content) was preheated at 70 °C for 30 min and adjusted pH to 10 followed by the addition of phenols and film casting. Tensile strength (TS) of resulting film increased by 123.3, 194.3 and 19.5% and elongation at break (EAB) increased by 71.1, 86.3 and 10.2%, respectively, compared with the control film, when tannic acid, caffeic acid and ferulic acid at a level of 3% was added. The use of all phenolic compounds slightly increased water vapor permeability (WVP) of resulting films (p < 0.05). The increases in a^∗- and b^∗-values of films were observed as the higher concentrations of tannic acid and caffeic acid were used. This was associated with the lowered transparency of resulting films. FFS containing 3% caffeic acid with prior oxygenation, especially with pH 10, yielded the film with increased TS but lowered EAB (p < 0.05). Oxygenation of FFS was associated with the lower L^∗-value and higher a^∗-value of resulting films. Therefore, phenolic compounds could be used as natural cross-linkers which affected the properties of porcine plasma protein-based film differently.     

Phase solubility studies and stability of cholesterol/β-cyclodextrin inclusion complexes

BACKGROUND: Cyclodextrins (CDs) are able to enhance the solubility, stability and bioavailability of several bioactive hydrophobic compounds by complex formation. They can also be used for removal of undesired components (such as cholesterol, off‐flavors or bitter components) present in foods. Although many patents account for the use of cyclodextrins for removal of cholesterol from dairy foods, there is no available information on the effect of water on encapsulation efficiency and on the stability of sterols in CDs. The aim of this work was to study the inclusion properties and the factors affecting the encapsulation and stability of cholesterol in β‐cyclodextrin (BCD). The optimum encapsulation conditions (ligand–CD molar ratio, stirring time and temperature), and stability of the complexes as a function of storage time and water content were analyzed. RESULTS: Phase solubility study pointed out the formation of 1:1 stoichiometric complexes between cholesterol and β‐cyclodextrin, which was influenced by temperature variations. The process was shown to be exothermic and energetically favored. The presence of cholesterol greatly modified the BCD water sorption curves, being the amount of adsorbed water smaller in the combined systems. The principal ‘driving force’ for complex formation is the substitution of the high‐enthalpy water molecules by an appropriate hydrophobic ligand. The freeze‐dried complexes probed to be stable at different storage conditions. CONCLUSION: The phase solubility and stability data obtained could be essential for selecting the most suitable conditions when CDs are employed either for removing cholesterol or to incorporate functional ingredients (i.e. sitosterol) in the development of innovative food products. Copyright © 2011 Society of Chemical Industry     

Karl Fischer Water Titration−Principal Component Analysis Approach on Wheat Flour

In this research, a new Karl Fischer water titration–principal component analysis (KFT–PCA) concept on wheat flour samples was introduced and studied. First, the evaluation of the performance of the determination of water content of wheat flour (Triticum aestivum L. subsp. aestivum) by using the KFT method was performed. The water content of white wheat flour, determined by KFT method, was in the range of 14.9–15.2 %, while for the whole-wheat and Graham flour samples, this concentration was lower (14.7 and 14.5 %, respectively) and was close to the limit of Romanian standards. The new approach on the KFT water reaction rates for wheat flour was performed. Thus, the “surface water” reaction rates of 1.2–2.1 mM/s and the “strongly bound water” reaction rates of 0.13–0.24 mM/s were obtained for flour samples. Further, these water reaction rates together with the primary KFT parameters (e.g., water concentration and normalized titration volume) were used in a multivariate statistical approach (PCA) in order to evaluate similarities–dissimilarities between samples. Among KFT parameters, the water content, the normalized titration volume, and the surface water reaction rate were important for a good classification of the flour products.     

Simultaneous determination of four phenolic components in citrus honey by high performance liquid chromatography using electrochemical detection

A sensitive and accurate method for simultaneous separation and determination of four phenolic compounds, including caffeic acid, p-coumaric acid, ferulic acid, and hesperetin in Chinese citrus honey by high performance liquid chromatography using electrochemical detection (HPLC-ECD) has been established. Chromatographic separation was performed using a reversed phase column and methanol/4% (v/v) aqueous acetic acid as the mobile phase. The detection and quantification limits of the four compounds with ECD were 6–14 times greater than those obtained with diode-array detection (DAD). All calibration curves of the four phenolic compounds showed good linearity (r ? 0.9994) within the test ranges, 1.10–66 μg/ml, 0.35–70 μg/ml, 0.16–16 μg/ml and 0.03–10 μg/ml, respectively. The recoveries ranged from 98.9% to 100.3%. The extraction process was very simple, because of the dissolution of honey only involving water. Taken together, the application of ECD in honey determination leads to a significant improvement in the quantification of phenolic compounds, whereby paying the way for the establishment of a better quality control of citrus honey.     

Physicochemical properties of lard-based diacylglycerols in blends with lard

The objective of the study was to investigate how blending of triacylglycerols and diacylglycerols affected the melting and crystallisation properties in a solid fat system. Lard-based diacylglycerols (DAGs) were blended with lard in various concentrations (0%, 1%, 5%, 10%, 20%, 50%, 60%, 70%, 80%, 90%, and 100%). The melting and crystallisation properties were investigated by the determination of dropping point (DP), solid fat content (SFC), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). In general, the effects of DAGs were found to be dependent on concentration. The DP was significantly (P < 0.0001) decreased when DAGs were added to the lard from 5–50%, whereas the DP was increased (P < 0.0001) when the blends contained more than 60% DAGs. The DSC thermograms showed that DAGs changed the melting and crystallisation profiles of lard. The crystallisation onset point increased (P < 0.05) with increasing the DAG concentrations (10–100%). The melting peaks and off-set points generally shifted slightly towards higher temperatures as the content of DAGs increased above 50%. DAG content of 5% and 10% resulted in lowering of the off-set point. The lard contained both β and β′ crystals. The β form was more pronounced in the blends with high concentrations of DAGs. Blending of TAGs and DAGs may serve as a solution to achieve specific functional properties in products containing solid fats.     

叶黄素浸膏的环糊精包合作用研究

目的:研究环糊精包合时叶黄素浸膏性能的改进效果.方法:HSCCC及HPLC分析浸膏成分,紫外法测定表观包合常数,研磨法制备包合物,以溶解性及稳定性指标考察包合效果.结果:色谱分析表明,叶黄素浸膏为成分复杂的混合物;叶黄素浸膏与环糊精存在较强的包合作用,且混合环糊精优于单一环糊精;单一环糊精的包合改进效果各异,p一环糊精的增溶效果较差,但稳定性好于羟丙基-β-环糊精;混合环糊精包舍的改进效果明显,尤以β-环糊精/羟丙基-β-环糊精9:1的混合包合性能效果最佳.结论:混合环糊精包合成分复杂的叶黄素浸膏可弥补单一环糊精的不足,包舍物的溶解度和稳定性均能得到明显改善.     

Optimisation,characterisation and quantification of phenolic compounds in olive cake

The phenolic compounds in extracts from pressed olive cake were investigated. Free phenolic compounds were extracted from olive cake using methanol. To liberate bound phenolic compounds, the olive cake was subjected to basic and acidic hydrolysis followed by methanol extraction. The individual phenolic compounds and antioxidant activity of the extracts were determined. The highest total phenolic content and antioxidant activity were obtained using methanol extraction for 12 h at 70 °C. The RP-HPLC profiles for full-fat and defatted olive cake showed that protocatechuic acid, hydroxybenzoic acid, sinapic acid, p-coumaric acid, rutin and hesperidin were the predominant free phenolic compounds. Meanwhile, syringic acid, sinapic acid, caffeic acid and protocatechuic acid were the predominant bound phenolic acids. A positive correlation was observed between total phenolic content and antioxidant activity. The results indicated that most of the phenolic compounds in olive products were present in their free forms (75–90% of total phenolic content), while bound phenolic compounds were only a small proportion (10–25%) of total phenolic content.     

Use of hollow fibre-based liquid–liquid–liquid microextraction and high-performance liquid chromatography–diode array detection for the determination of phenolic acids in fruit juices

This paper describes a simple method based on three-phase hollow-fibre liquid-phase microextraction (HF-LPME) for the determination of phenolic acids in fruit juices. Analytes including gallic acid, p-hydroxy benzoic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, and cinnamic acid were separated and determined using high-performance liquid chromatography–photodiode array detection (HPLC–DAD). Parameters affecting the enrichment factors (EFs) were investigated. These compounds were extracted from 5 mL aqueous samples (pH 2) to a thin layer of organic solvent (hexyl acetate) phase impregnated into the pores of the polypropylene hollow fibre wall, and then back extracted to a basic acceptor solution (0.02 M NaOH). EFs ranged from 15 (gallic acid) to 408 (cinnamic acid). The RSD of the method for the analysis of spiked water and fruit juice samples varied from 3.1% to 11.3%. The LODs ranged from 0.01 (cinnamic acid) to 2.0 (caffeic acid) μg/L.     

Pink grapefruit lycopene encapsulated in alginate-based beads: stability towards freezing and drying

Alginate-based beads containing lycopene extract were produced with the addition of various sugars and biopolymers. In present work, lycopene stability was studied on beads subjected to thermal treatments: continuous freezing (−18 °C, 30 days), four freezing/thawing (f/t) cycles, dehydration by vacuum- and freeze-drying. The progress of crystallisation was assessed using transversal relaxation times (T₂) obtaining isothermal curves at different temperatures. Alginate beads containing trehalose with β-cyclodextrin and arabic gum retained a high lycopene content (>80%) after freezing and drying, regardless of the freezing or drying method. Instead, beads containing only alginate showed sever lycopene decrease in all cases. Continuous freezing affected both lycopene content and stability to a higher extent than f/t cycles. Isothermal studies revealed the lower amount of crystallised water in beads containing trehalose (with or w/o other excipients), reducing also the time to arrive at the 50% of crystallisation during freezing.     

Influence of ligand structure and water interactions on the physical properties of β-cyclodextrins complexes

The water sorption and physical properties of freeze-dried β-cyclodextrin (BCD) and 2-hydroxypropyl-β-cyclodextrin (HBCD) were studied. The stability of the inclusion complexes of these cyclodextrins with different hydrophobic ingredients, such as myristic acid and α-terpineol, was investigated as a function of the storage time and water content of the systems. Besides increasing its solubility, BCD ring modification with hydroxypropyl groups conferred amorficity to the dehydrated matrices, and modified the sorption properties and their ability to form hydrates.     

Experimental design to optimization of beta cyclodextrin production from ungelatinized sago starch

The aim of this study is to produce beta cyclodextrin (β-CD) from ungelatinized, but annealed (65 °C) sago starch using cyclodextrin glucosyltransferase (CGTase). The optimization processes were conducted at three stages using Response Surface Methodology. Preliminary data have shown that the three (3) highest points for each of the studied parameters were pH, concentration of sago starch and enzyme, and also agitation. In the second stage, two level full factorial design (2ⁿ FFD) was applied to determine the significant parameters affecting the production of β-cyclodextrin. Statistical analyses showed that pH, enzyme and sago starch concentration were the significant parameters. The final stage of optimization involved the use of Central Composite Design to determine and predict the optimum yield of β-cyclodextrin. The optimum condition for production cyclodextrin was at pH 8.62 (Glycine–NaOH buffer 0.05 M), 0.65% v/v sago starch and 15% w/v enzyme concentration, where 8.43 g β-cyclodextrin/L was produced after 4 h of reaction.     

Factors controlling flavors binding constants to cyclodextrins and their applications in foods

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 cyclodextrins (α-cyclodextrin and β-cyclodextrin) have been determined by an UV–Vis spectrophotometric technique. In all cases the binding constant of flavors to β-cyclodextrin are bigger than the corresponding one to α-cyclodextrin. This fact is due to the different size of cyclodextrin cavity. As well as, a relationship between 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.     

Empirical,thermodynamic and quantum-chemical investigations of inclusion complexation between flavanones and (2-hydroxypropyl)-cyclodextrins

The inclusion complexation of (2-hydroxypropyl)-cyclodextrins with flavanones was investigated by phase solubility measurements, as well as thermodynamic and quantum chemical methods. Inclusion complexes were formed between (2-hydroxypropyl)-α-cyclodextrin (HP-α-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), (2-hydroxypropyl)-γ-cyclodextrin (HP-γ-CD) and β-cyclodextrin (β-CD) and four flavanones (naringenin, naringin, hesperetin and dihydromyricetin) in aqueous solutions and their phase solubility was determined. For all the flavanones, the stability constants of their complexes formed with different CDs followed the rank order: HP-β-CD (MW 1540) > HP-β-CD (MW 1460) > HP-β-CD (MW 1380) > β-CD > HP-γ-CD > HP-α-CD. Experimental results and quantum chemical calculations showed that the ability of flavanones to form inclusion complex with (2-hydroxypropyl)-cyclodextrins was determined by both the steric effect and hydrophobicity of the flavanones. For flavanones that have similar molecular volumes, the hydrophobicity of the molecule was the main determining factor of its ability to form inclusion complexes with HP-β-CD, and the hydrophobicity parameter Log P is highly correlated with the stability constant of the complexes. Results of thermodynamic study demonstrated that hydrophobic interaction is the main driving force for the formation process of the flavanone–CD inclusion complexes. Quantum chemical analysis of the most active hydroxyl groups and HOMO (the highest occupied molecular orbital) showed that the B ring of the flavanones was most likely involved in hydrogen bonding with the side groups in the cavity of the CDs, through which the inclusion complex was stabilised.