Prebiotic Potential of a New Sweetener Based on Galactooligosaccharides and Modified Mogrosides.

This study was conducted to investigate the sweetness intensity and the potential fecal microbiome modulation of galactooligosaccharides in combination with enzymatically modified mogrosides (mMV-GOS), both generated through a patented single-pot synthesis. Sweetness intensity was performed in vivo by trained sensory panelists. The impact on the human fecal microbiome was evaluated by in vitro pH-controlled batch fermentation, and bacterial populations and organic acid concentrations were measured by qPCR and GC-FID, respectively. Significant growth (p ≤ 0.05) during the fermentation at 10 h of bacterial populations includes Bifidobacterium (8.49 ± 0.44 CFU/mL), Bacteroides (9.73 ± 0.32 CFU/mL), Enterococcus (8.17 ± 0.42 CFU/mL), and Clostridium coccoides (6.15 ± 0.11 CFU/mL) as compared to the negative control counts for each bacterial group (7.94 ± 0.27, 7.84 ± 1.11, 7.52 ± 0.37, and 5.81 ± 0.08 CFU/mL, respectively) at the same time of fermentation. Likewise, the corresponding significant increase in production of SCFA in mMV-GOS at 10 h of fermentation, mainly seen in acetate (20.32 ± 2.56 mM) and propionate (9.49 ± 1.44 mM) production compared to a negative control at the same time (8.15 ± 1.97 and 1.86 ± 0.24 mM), is in line with a positive control (short-chain fructooligosaccharides; 46.74 ± 12.13 and 6.51 ± 1.91 mM, respectively) revealing a selective fermentation. In conclusion, these substrates could be considered as novel candidate prebiotic sweeteners, foreseeing a feasible and innovative approach targeting the sucrose content reduction in food. This new ingredient could provide health benefits when evaluated in human studies by combining sweetness and prebiotic fiber functionality.

High-Yield Synthesis of Transglycosylated Mogrosides Improves the Flavor Profile of Monk Fruit Extract Sweeteners.

Luo Han Guo fruit extract (Siraitia grosvenorii), mainly composed of mogroside V (50%), could be considered a suitable alternative to free sugars; however, its commercial applications are limited by its unpleasant off-notes. In the present work, a central composite design method was employed to optimize the transglycosylation of a mogroside extract using cyclodextrin glucosyltransferases (CGTases) from three different bacteriological sources (Paenibacillus macerans, Geobacillus sp., and Thermoanaerobacter sp.) considering various experimental parameters such as maltodextrin and mogroside concentration, temperature, time of reaction, enzymatic activity, and pH. Product structures were determined by liquid chromatography coupled to a diode-array detector (LC-DAD), liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Sensory analysis of glucosylated mogrosides showed an improvement in flavor attributes relevant to licorice flavor and aftereffect. Consequently, an optimum methodology was developed to produce new modified mogrosides more suitable when formulating food products as free sugar substitutes.

Transglycosylation of Steviol Glycosides and Rebaudioside A: Synthesis Optimization, Structural Analysis and Sensory Profiles.

To improve flavor profiles, three cyclodextrin glucosyltransferases (CGTases) from different bacteriological sources, Paenibacillus macerans, Geobacillus sp. and Thermoanaerobacter sp., were used with an extract of steviol glycosides (SVglys) and rebaudioside A (RebA) as acceptor substrates in two parallel sets of reactions. A central composite experimental design was employed to maximize the concentration of glucosylated species synthesized, considering temperature, pH, time of reaction, enzymatic activity, maltodextrin concentration and SVglys/RebA concentration as experimental factors, together with their interactions. Liquid chromatography coupled to a diode-array detector (LC-DAD), liquid chromatography-mass spectrometry (LC-ESI-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were used to characterize and identify the chemical structures obtained along the optimization. To assess the impact on the sensory properties, a sensory analysis was carried out with a group of panelists that evaluated up to 16 sensorial attributes. CGTase transglucosylation of the C-13 and/or C-19 led to the addition of up to 11 glucose units to the steviol aglycone, which meant the achievement of enhanced sensory profiles due to a diminution of bitterness and licorice appreciations. The outcome herein obtained supposes the development of new potential alternatives to replace free sugars with low-calorie sweeteners with added health benefits.

Congener-specific determination of hydroxylated polychlorinated biphenyls by polar-embedded reversed-phase liquid chromatography-tandem mass spectrometry.

This paper reports the development of an LC-ESI-MS2 method for the sensitive determination of hydroxylated polychlorinated biphenyls (OH-PCBs) in human serum samples. Congener-specific separation was achieved by using a polar-embedded stationary phase, previously optimized for the working group, which provided better separation of isobaric compounds than the common octadecylsilane phases. MS fragmentation patterns and energies showed differences among OH-PCB congeners, mainly depending on the position of OH-group and the number of chlorine atoms in the molecule, although the most intense transitions were always those corresponding to the neutral loss of an HCl group from the quasi-molecular ion cluster. The method allowed the determination of OH-PCBs with good linearity (dynamic linear range of four orders of magnitude with R2 higher than 0.995) and precision (relative standard deviations of absolute areas lower than 10%), and with better sensitivity than other similar methods previously described in the literature. Matrix effect has been evaluated and reduced to less than 10% by the addition of isotopically labeled standards and a 10-fold dilution of the final sample extract. The low iLODs provided by the developed method (from 1.2 to 5.4 fg µL-1 for all the OH-PCBs studied, except 4'-OHCB108, whose iLOD was 61 fg µL-1) allows dilution without losses of detected peaks. Finally, the applicability of the method has been demonstrated by analyzing human serum samples belonging to an interlaboratory exercise.

Characterization and optimization by experimental design of a liquid chromatographic method for the separation of hydroxylated polychlorinated biphenyls on a polar-embedded stationary phase.

Traditionally, the determination of hydroxylated polychlorinated biphenyls (OH-PCBs) has been carried out by gas chromatography (GC). However, the gas chromatographic behavior and sensitivity of this type of hydroxylated compounds are not always satisfactory, hence a prior derivatization of the OH-PCBs must be performed. Therefore, the development of liquid chromatographic methods should prove to be a very interesting task aimed at dealing with the instrumental determination of OH-PCBs. Taking into account that octadecylsilane stationary phases are not the most adequate for the separation of isobaric compounds, an amide-type column has been tested. For the development of the method, the Response Surface Methodology was used, based on a Box-Wilson Central Composite experimental design. The initial content of methanol in the mobile phase, the gradient time, and the concentration and the pH value of the buffer were chosen as relevant experimental parameters. A global optimum was obtained by selecting the elution time, the sensitivity and the overall resolution as responses to optimize. The developed method for liquid chromatography presented a very good resolution and sensitivity, and a reasonably short analysis time. In addition, a retention study was conducted in order to survey the different interactions that take place in the separation process, showing that hydrogen bonding is the main interaction between OH-PCBs and the amide-type stationary phase. However, a substantial contribution of dispersion forces was present in methanol contents in the mobile phase below 65%. Besides, the pH value of the mobile phase was found to be the most important parameter to control the hydrogen bond forces and therefore, to regulate the OH-PCBs separation.

Improving the sensitivity of liquid chromatography-tandem mass spectrometry analysis of hexabromocyclododecanes by chlorine adduct generation.

It is well documented and experimentally confirmed that hexabromocyclododecanes (HBCDs) tend to associate with several anions forming different adducts that can affect the sensitivity and the accuracy of the determinations. In the present work, two different approaches for HBCD determination have been optimised and characterised based on their repeatability and intermediate precision, linear calibration ranges, sensitivity, limits of detection and quantification and application to commercial food samples. Both methods involve the use of a triple quadrupole mass spectrometer coupled to a liquid chromatograph and the addition of different ammonium salts to the mobile phase, i.e. ammonium chloride or ammonium acetate, in order to encourage (Cl method) or try to inhibit (Ac method), respectively, the formation of the chlorine adducts of the molecular ion. Precision of the two methods investigated was similar and both approaches presented a comparable behaviour for the analysis of food samples. However, the Cl method showed higher sensitivity and the limits of detection (0.23-0.41 pg on column) and quantification (0.77-1.35 pg on column) were up to 14 times lower than those obtained applying the Ac method. All these facts make the Cl method the best choice for the quantification of HBCDs in food samples with low concentration levels.