Untargeted analysis to monitor metabolic changes of garlic along heat treatment by LC-QTOF MS/MS.

Black garlic is increasing its popularity in cuisine around the world; however, scant information exists on the composition of this processed product. In this study, polar compounds in fresh garlic and in samples taken at different times during the heat treatment process to obtain black garlic have been characterized by liquid chromatography coupled to tandem mass spectrometry in high resolution mode. Ninety-five compounds (mainly amino acids and metabolites, organosulfur compounds, and saccharides and derivatives) were tentatively identified in all the analysed samples and classified as a function of the family they belong to. Statistical analysis of the results allowed establishing that the major changes in garlic occur during the first days of treatment, and they mainly affect to the three representative families. The main pathways involved in the synthesis of the compounds affected by heat treatment, and their evolution during the process were studied.

HS-GC/MS volatile profile of different varieties of garlic and their behavior under heating.

Garlic is one of the most used seasonings in the world whose beneficial health effects, mainly ascribed to organosulfur compounds, are shared with the rest of the Allium family. The fact that many of these compounds are volatile makes the evaluation of the volatile profile of garlic interesting. For this purpose, three garlic varieties-White, Purple, and Chinese-cultivated in the South of Spain were analyzed by a method based on a headspace (HS) device coupled to a gas chromatograph and mass detector (HS-GC/MS). The main temperatures in the HS were optimized to achieve the highest concentration of volatiles. A total number of 45 volatiles were tentatively identified (among them 17 were identified for the first time in garlic); then, all were classified, also for the first time, and their relative concentration in three garlic varieties was used to evaluate differences among them and to study their profiles according to the heating time. Chinese garlic was found to be the richest variety in sulfur volatiles, while the three varieties presented a similar trend under preset heating times allowing differentiation between varieties and heating time using principal component analysis. Graphical Abstract HS-GC/MS analysis of the volatile profile of garlic.

Development and application of a quantitative method for determination of flavonoids in orange peel: Influence of sample pretreatment on composition.

Peel, a part of the citrus rich in compounds with high-added value, constitutes the bulk of the waste generated in citrus juice industries. Flavonoids are a class of these high-added value compounds characterized by their bioactivity. In this research, a method for analysis of flavonoids, based on LC-MS/MS by using a triple quadrupole detector, has been developed and applied to the quantitative analysis of 16 flavonoids in extracts obtained by maceration of citrus peel. The parameters involved in the ionization and fragmentation of the target analytes were optimized to develop a selected reaction monitoring (SRM) method, which reported detection and quantitation limits ranging from 0.005 to 5 ng/mL and from 0.01 to 10 ng/mL, respectively. The raw materials for flavonoids extraction were fresh, oven-dried and lyophilized peel of 8 different orange varieties, and the proposed quantitation method was applied to the analysis of the obtained extracts. Evaluation of the two methods of water removal showed that lyophilization preserves the concentration of the flavonoids, while oven-dried peel presented a decrease of glycosylated flavonoids and an increase of aglycone forms.

Ultrasound-assisted emulsification-extraction of orange peel metabolites prior to tentative identification by LC-QTOF MS/MS.

An optimized method for extraction and characterization of compounds present in orange peel has been developed. The extraction method allows the simultaneous extraction of polar and non-polar compounds by using two immiscible extractants (a polar extractant-an 80:20 (v/v) methanol-water mixture, and a non-polar extractant-n-hexane). The method is ultrasound-assisted, thus facilitating both formation of a stable emulsion between the two immiscible extractants and favoring mass-transfer from the solid sample to the liquid phases by a wide contact surface. Optimization of the ultrasound-assisted emulsification-extraction (USAEE) led to the following values as desirability conditions for both extracts: 32% amplitude, 0.75s/s duty cycle and 7.5min of extraction time. The extracts obtained under these conditions were analyzed by LC-QTOF MS/MS in positive and negative ionization modes. Tentative identification of the most significant compounds present in each extract allowed their characterization by using high resolution tandem mass spectrometry. The optimum extracts provided by USAEE were compared by using Principal Component Analysis to those obtained by conventional extraction based on maceration. Thus, the composition of the polar extracts obtained after 7.5min ultrasonication was similar to that of conventional maceration for 4h in both the ionization modes. On the contrary, the analysis of non-polar extracts led to different results depending on the ionization mode: the ultrasound-assisted extract was similar to those of conventional maceration for 10h in negative and positive ionization. This behavior could be explained by the contribution of different groups of compounds to each ionization mode.