Composition and characterization of soyabean and related products

Soyabean contains about 48 to 50% proteins. Among these, storage proteins are predominant. 7S and 11S globulins are two storage proteins that constitute 80% of the total protein content in soyabean. Moreover, there are other less abundant storage proteins such as 2S, 9S, and 15S globulins. In addition to globulins, enzymes, protease inhibitors (Kunitz and Bowman-Birk), lectin, and other complete the soya protein content. Different methods exist to characterize soya proteins. These methods involve (1) an isolation of proteins from soya commercial products and (2) the use of analytical techniques for protein determination. Soya proteins may interact with other soya components such as minerals, phytic acid, ascorbic acid, and fiber. These interactions, which depend on soya processing and treatment, can decrease the bioavailability of minerals and proteins. Swelling, solubility, viscosity, and capacity to form a gel, an emulsion, or a foam are the main functional properties of soyabean. They are responsible for the wide use of soya in industrial processes.

Strategies for the extraction and analysis of non-extractable polyphenols from plants

The majority of studies based on phenolic compounds from plants are focused on the extractable fraction derived from an aqueous or aqueous-organic extraction. However, an important fraction of polyphenols is ignored due to the fact that they remain retained in the residue of extraction. They are the so-called non-extractable polyphenols (NEPs) which are high molecular weight polymeric polyphenols or individual low molecular weight phenolics associated to macromolecules. The scarce information available about NEPs shows that these compounds possess interesting biological activities. That is why the interest about the study of these compounds has been increasing in the last years. Furthermore, the extraction and characterization of NEPs are considered a challenge because the developed analytical methodologies present some limitations. Thus, the present literature review summarizes current knowledge of NEPs and the different methodologies for the extraction of these compounds, with a particular focus on hydrolysis treatments. Besides, this review provides information on the most recent developments in the purification, separation, identification and quantification of NEPs from plants.

Analysis of soyabean proteins in meat products: a review

The use of soyabean proteins as meat extenders has spread significantly due to the interesting nutritional and functional properties that are present in soyabean proteins. Together with these, health and economical reasons are the major causes for the addition of soyabean proteins to meat products. Nevertheless, despite the good properties associated to soyabean proteins, there are many countries in which the addition of these proteins is forbidden or in which the addition of soyabean proteins is allowed up to a certain extent. Thus, the need of analytical methods enabling the detection of added soyabean proteins in meat products is obvious. Microscopic, electrophoretic, immunologic, and chromatographic methods are the most widely used for this purpose. However, the detection of soyabean proteins in meat products presents difficulties related to the composition (meat species, meat quality, soyabean protein source, presence of other non-meat proteins, etc.) and the processing of the meat products, and, although these analytical methods have tried to overcome all these difficulties, there is still not a method enabling quantitative assessment of soyabean proteins in all kinds of meat products.

Recent advances in the analysis of antibiotics by capillary electrophoresis

In this review, the main aspects related to the separation of different groups of antibiotics by CE as well as the different applications reported in the literature from the beginning 2003 till May 2005 will be provided to the readers. Firstly, the experimental conditions employed to achieve the analysis of antibiotics by CE are given. Then, the main applications performed in the pharmaceutical, clinical, food, and environmental fields have been reviewed making emphasis on sample preparation requirements needed in each case. Finally, the main conclusions and future prospects in this field are presented.

Perfusion chromatography: an emergent technique for the analysis of food proteins

Perfusion chromatography is a technique arised to overcome the problem associated with mass transfer in the separation of large molecules such as proteins by high-performance liquid chromatography (HPLC). Perfusion media are constituted by two set of pores: throughpores (6000-8000 A) and diffusive pores (800-1500 A) which enable better access of macromolecules to the inner of the particle by the combination of convective and diffusive flow. As a consequence, times required for a chromatographic separation are reduced. Perfusion media are available in different chromatographic modes: reversed-phase, ion-exchange, hydrophobic interaction, and affinity. From the theoretical models developed to explain the dynamic of retention of solutes in perfusive supports, it was derived that efficiency of a separation was independent of the flow-rate and only depended slightly on the particle diameter. Furthermore, loading capacity was also independent of the superficial velocity. All these advantages have promoted the use of this chromatographic technique for the separation of biomolecules both in analytical and preparative chromatography. Characteristics of perfusion chromatography make this technique very interesting for the analysis of food proteins. Perfusion chromatography enables the assessment of protein composition of a foodstuff at sufficient speed and low cost to be suitable in routine analysis.

About the role of enantioselective selector-selectand interactions and the mobilities of diastereomeric associates in enantiomer separations using CE

It is generally accepted that the selective binding of enantiomers of the chiral analyte to a chiral selector is necessary for enantioseparations in CE, whereas the role of mobility differences between the temporary diastereomeric associates formed between the enantiomers and the chiral selector has been commonly neglected. One of the authors of this study suggested in 1997 that the mobility difference between the diastereomeric associates of two enantiomers with the chiral selector may be solely responsible for a separation of enantiomers in CE and enantioselective selector-selectand binding may be not necessarily required. Several indirect confirmations of this hypothesis have been described in the literature within the last few years but a dedicated study proving this concept has not been published yet. The present data obtained for the two chiral antimycotic drugs ketoconazole and terconazole by CE and NMR spectroscopy unequivocally support this concept.

Enantioseparation by Capillary Electrophoresis Using Ionic Liquids as Chiral Selectors

Capillary electrophoresis (CE) is one of the most widely employed analytical techniques to achieve enantiomeric separations. In spite of the fact that there are many chiral selectors commercially available to perform enantioseparations by CE, one of the most relevant topics in this field is the search for new selectors capable of providing high enantiomeric resolutions. Chiral ionic liquids (CILs) have interesting characteristics conferring them a high potential in chiral separations although only some of them are commercially available. The aim of this article is to review all the works published on the use of CILs as chiral selectors in the development of enantioselective methodologies by CE, covering the period from 2006 (when the first research work on this topic was published) to 2017. The use of CILs as sole chiral selectors, as chiral selectors in dual systems or as chiral ligands will be considered. This review also provides detailed analytical information on the experimental conditions used to carry out enantioseparations in different fields as well as on the separation mechanism involved.

Recent approaches in sensitive enantioseparations by CE

The latest strategies and instrumental improvements for enhancing the detection sensitivity in chiral analysis by CE are reviewed in this work. Following the previous reviews by García-Ruiz et al. (Electrophoresis 2006, 27, 195-212) and Sánchez-Hernández et al. (Electrophoresis 2008, 29, 237-251; Electrophoresis 2010, 31, 28-43), this review includes those papers that were published during the period from June 2009 to May 2011. These works describe the use of offline and online sample treatment techniques, online sample preconcentration techniques based on electrophoretic principles, and alternative detection systems to UV-Vis to increase the detection sensitivity. The application of the above-mentioned strategies, either alone or combined, to improve the sensitivity in the enantiomeric analysis of a broad range of samples, such as pharmaceutical, biological, food and environmental samples, enables to decrease the limits of detection up to 10⁻¹² M. The use of microchips to achieve sensitive chiral separations is also discussed.

Sensitive chiral analysis by capillary electrophoresis

In this review, an updated view of the different strategies used up to now to enhance the sensitivity of detection in chiral analysis by CE will be provided to the readers. With this aim, it will include a brief description of the fundamentals and most of the recent applications performed in sensitive chiral analysis by CE using offline and online sample treatment techniques (SPE, liquid-liquid extraction, microdialysis, etc.), on-column preconcentration techniques based on electrophoretic principles (ITP, stacking, and sweeping), and alternative detection systems (spectroscopic, spectrometric, and electrochemical) to the widely used UV-Vis absorption detection.

HPLC-Q-TOF-MS identification of antioxidant and antihypertensive peptides recovered from cherry (Prunus cerasus L.) subproducts

The processing of fruits, such as cherries, is characterized by generating a lot of waste material such as fruit stones, skins, etc. To contribute to environmental sustainability, it is necessary to recover these residues. Cherry stones contain seeds with a significant amount of proteins that are underused and undervalued. The aim of this work was to extract cherry seed proteins, to evaluate the presence of bioactive peptides, and to identify them by mass spectrometry. The digestion of cherry seed proteins was optimized, and three different enzymes were employed: Alcalase, Thermolysin, and Flavourzyme. Peptide extracts obtained by the digestion of the cherry seed protein isolate with Alcalase and Thermolysin yielded the highest antioxidant and antihypertensive capacities. Ultrafiltration of hydrolysates allowed obtaining fractions with high antioxidant and antihypertensive capabilities. HPLC-Q-TOF-MS together with bioinformatics tools enabled one to identify peptides in these fractions.

Chiral Discrimination of DL-Amino Acids by Trapped Ion Mobility Spectrometry after Derivatization with (+)-1-(9-Fluorenyl)ethyl Chloroformate

A novel analytical method based on hybrid trapped ion mobility spectrometry-time-of-flight mass spectrometry (TIMS-TOFMS) has been developed to achieve fast enantiomeric separation of amino acids (AAs). Resolution of chiral AAs was achieved by forming diastereomers through derivatization with the chiral agent (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC), avoiding the use of reference compounds. Electrospray ionization (ESI) in positive mode yielded sodiated FLEC-AAs ions of which the diastereomers could be separated by TIMS. The effect of other alkali metal ions (such as Li and K) on the enantioselectivity was studied, but chiral discrimination was only observed for Na. TIMS conditions, including voltage ramp, ramp time, and accumulation time were optimized for each AA, and collision cross sections (CCSs) were determined for all diastereomers. The migration order of the DL enantiomers was found to be dependent on the structure of the AA. The resulting TIMS resolution (K0/ΔK0) for the FLEC-AA diastereomers on average was 115, requiring a mobility (K0) difference of about 0.009 cm²/(V s) to achieve 50%-valley separation. From the 21 AAs studied, enantiomer separation was achieved for 17 AAs with mobility differences ranging from 0.009 for lysine up to 0.061 cm²/(V s) for asparagine. Moreover, the presented methodology provided mutual separation of various AAs, allowing chiral analysis of multiple AAs simultaneously which may be challenging with previous enantioselective IMS approaches. It appeared possible to fully resolve all studied DL-AAs using three distinct TIMS methods, resulting in a total MS run time of about 3 min (1 min per method) and a total analysis time (including derivatization) of less than 15 min. The method demonstrated capable to determine enantiomeric ratios down to 2.5% with detection limits for the D enantiomers in the nanomolar range. This new TIMS-based methodology opens up possibilities for easy and fast analysis of AA enantiomers.

Amino acid chiral ionic liquids combined with hydroxypropyl-β-cyclodextrin for drug enantioseparation by capillary electrophoresis

Four amino acid chiral ionic liquids were evaluated in dual systems with hydroxypropyl-β-cyclodextrin to investigate the enantioseparation by CE of a group of seven drugs as model compounds (duloxetine, verapamil, terbutaline, econazole, sulconazole, metoprolol, and nadolol). The use of two of these chiral ionic liquids (tetramethylammonium L-Lysine ([TMA][L-Lys]) and tetramethylammonium L-glutamic acid ([TMA][L-Glu])) as modifiers in CE is reported for the first time in this work whereas tetrabutylammonium L-lysine ([TBA][L-Lys]) and tetrabutylammonium L-glutamic acid ([TBA][L-Glu]) were employed previously in CE although very scarcely. The effect of the nature and the concentration of each ionic liquid added to the separation buffer containing the neutral cyclodextrin on the enantiomeric resolution and the migration time obtained for each drug, was investigated. A synergistic effect was observed when combining each chiral ionic liquid with hydroxypropyl-β-cyclodextrin in the case of the five compounds for which the cyclodextrin showed enantiomeric discrimination power when used as sole chiral selector (duloxetine, verapamil, terbutaline, econazole, sulconazole). Buffer concentration and pH, temperature and separation voltage were varied in order to optimize the enantiomeric separation of these five compounds using dual systems giving rise to resolutions ranging from 1.1 to 6.6.

Potential of vancomycin for the enantiomeric resolution of FMOC-amino acids by capillary electrophoresis-ion-trap-mass spectrometry

The potential of the antibiotic vancomycin (VC) as chiral selector for the enantiomeric separation of amino acids by CE-ESI-MS/MS² was investigated for the first time in this work. Derivatization of amino acids with FMOC-Cl was carried out to enable their interaction with VC as well as the formation of precursor ions with larger m/z which were employed in MS² experiments. The partial filling of a coated capillary was employed to avoid the loss in MS sensitivity originated by the introduction of VC in the ionization source. Under optimized conditions, the simultaneous enantiomeric separation and unequivocal identification of 17 amino acids (two of them being nonprotein amino acids) took place in about 20 min with LODs in the micromolar range.

Separation of chiral polychlorinated biphenyls by micellar electrokinetic chromatography using beta- and gamma-cyclodextrin mixtures in the separation buffer

Chiral polychlorinated biphenyls (PCBs) 45, 84, 88, 91, 95, 132, 136, 139, 149, 171, 183 and 196 were separated each in its two enantiomers by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC). Mixtures of beta- and gamma-cyclodextrins were used as chiral modifiers in a 2-(N-cyclohexylamino)ethanesulphonic acid (CHES) buffer containing urea and sodium dodecyl sulphate (SDS) micelles. Separations of multicomponent mixtures of PCBs into their enantiomers were also performed. A mixture of PCBs 45, 88, 91, 95, 136, 139, 149 and 196 was separated into all sixteen enantiomers in an analysis time of approx. 35 min.

Detection of bovine whey proteins by on-column derivatization capillary electrophoresis with laser-induced fluorescence monitoring

1-Anilinonaphthalene-8-sulfonic acid (1,8-ANS), 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) and 2-(p-toluidino)naphthalene-6-sulfonic acid (2,6-TNS) were evaluated as additives in different buffers for the detection of bovine whey proteins using laser-induced fluorescence (LIF) monitoring in capillary electrophoresis (CE). These N-arylaminonaphthalene sulfonates furnish a large fluorescence emission when associated to some proteins whereas their emission in aqueous buffers, such as those used in CE separations, is very small. To select the best detection conditions, the fluorescence of these probes was first compared using experiments carried out in a fluorescence spectrophotometer. Using bovine serum albumin (BSA) as a model protein, it was demonstrated that 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer (pH 8 and pH 10.2) and the fluorescent probe 2,6-TNS gave rise to the highest increase in fluorescence for BSA. When the composition of these separation buffers was optimized for the electrophoretic separations, CHES buffer, pH 10.2 was chosen as the most suitable buffer to detect bovine whey proteins. The limit of detection obtained for some whey proteins in CE separations was about 6.10(-8) M for BSA, 3.10(-7) M for beta-lactoglobulin A (beta-LGA), 3.10(-7) M for beta-lactoglobulin B (beta-LGB), and 3.10(-6) M for alpha-lactalbumin (alpha-LA). These detection limits were compared to those achieved using UV detection under the same separation conditions. The results showed that the detection limits of BSA, beta-LGA and beta-LGB were twice as good using LIF than with UV detection. However, the limit of detection for alpha-LA was better when UV was used. The applicability of LIF detection to CE separation of whey proteins in bovine milk samples was also demonstrated.

High performance liquid chromatography and capillary electrophoresis in the analysis of soybean proteins and peptides in foodstuffs

The increasing interest in functional and healthy food products has promoted the use of soybean in the manufacture of foods for human consumption. Soybean basic products (soybeans, textured soybean, soybean flour, soybean protein concentrate and soybean protein isolate) as well as soybean derivatives (soybean dairy-like products, soybean drinks with fruits, meat analogues, etc.) are commercially available. In addition, due to the interesting nutritional and functional properties of soybean proteins, they are usually employed as ingredient in the elaboration of a large number of food products such as bakery or meat products among others. In spite of the good characteristics of soybean proteins, their addition to some products is forbidden or allowed up to a certain limit. Therefore, analytical methodologies to achieve the determination of soybean proteins in foods are necessary in order to make possible adequate quality control and to prove that legal regulations controlling their addition are accomplished. However, this is not an easy task due to the diversity and complexity of the food matrices and the technological treatments to which some of these foods are submitted during their elaboration. This article presents for the first time a comprehensive review on the analytical methodologies developed using HPLC and CE to characterize soybeans and to analyse soybean proteins in meals. Moreover, the use of HPLC and CE in the characterization of soybean protein fractions and their hydrolyzates, and a study of their relationships to nutritional, functional and biomedical properties are included. Finally, the application of proteomic methodologies in soybean food technology is also reviewed.

Influence of mobile phase composition on electroosmotic flow velocity, solute retention and column efficiency in open-tubular reversed-phase capillary electrochromatography

The effects of some experimental parameters, such as the volume fraction and type of organic modifier in the mobile phase, and the concentration, type and pH of the buffer on the electroosmotic flow velocity, the retention behavior of test solutes, and the column efficiency have been investigated in capillary electrochromatography (CEC) using an open-tubular column of 9.60 microm I.D. with a porous silica layer chemically modified with C18 as stationary phase. The retention of a group of polycyclic aromatic hydrocarbons (PAHs) used as a test mixture varied significantly by changing the organic modifier content in the hydroorganic mobile phase according to the reversed-phase-like selectivity of the stationary phase. In addition, an increase in the percentage of organic modifier resulted in a slight increase in the linear velocity of the EOF. On the other hand, when the phosphate buffer concentration was increased over the range 1-50 mM, the electroosmotic mobility fell dramatically, the retention of the solutes decreased steadily, and the plate height showed a significant increase. The results obtained with phosphate, trishydroxymethylaminomethane or 2-morpholinoethanesulfonic acid as buffers were similar when pH remained constant. Optimization in CEC was essential to achieve further enhancement of separation performance, because the analysis time and separation resolution are essentially affected when varying operating parameters. Separations of seven PAHs with more than 100000 plates are presented within 4 min analysis time.