Characterization and discrimination of lamb with different breeds and muscle types using precursors and volatile compounds

The unique aromas of mutton stem from the chemical reactions between the characteristic precursors during cooking. This study aimed to establish the relationship of volatile compounds and aroma precursors (protein, fat, free amino acids and fatty acids) in lamb from different breeds and muscle types. Hong lamb was characterized by greater tenderness and water holding capacity, higher polyunsaturated fatty acids and higher essential/non-essential amino acids in comparison with Hu lamb. Aldehydes, such as heptanal, hexanal, octanal and nonanal were higher in Hong-ST compared with Hu-ST. Principal component analysis (PCA) showed that aroma precursors were closely related to volatile components of cooked lamb. Discriminant analysis results showed that precursors and volatile compounds could be used to identify the breeds and muscle types of lamb. These findings revealed the contributors of lamb aroma and might help understand the regulatory mechanism of aroma in lamb from different breeds and muscle types.

Kinetics of aroma formation from grape-derived precursors: Temperature effects and predictive potential

This study investigates the accumulation and degradation of aroma molecules released by acid hydrolysis of aroma precursors in winemaking grapes. A first-order kinetics model effectively interprets this accumulation, including subsequent degradation. Experimentation at three temperatures categorizes specific grape-derived aroma molecules into three stability-based groups: labile molecules from labile precursors, stable molecules from labile precursors, and stable molecules from stable precursors. While many grape-derived aromas exhibit similar patterns and levels of accumulation across temperatures, reaction rates significantly increase with temperature. The analysis of 12 samples of two grape varieties hydrolyzed at 50 °C for 5 weeks and 75 °C for 24 h confirms that fast hydrolysis accurately replicates varietal and between-sample aroma compositional differences. Moreover, the accumulated levels of 21 relevant grape-derived aromas strongly correlate with those at 50 °C, indicating that fast hydrolysis at 75 °C reliably predicts grape aroma potential.

Sensory, olfactometric and chemical characterization of the aroma potential of Garnacha and Tempranillo winemaking grapes

Reconstituted polyphenolic and aromatic fractions (PAFs) from 33 different Garnacha and Tempranillo grapes were incubated in strict anoxia (75 °C × 24 h). Obtained hydrolyzates were characterized by sensory analysis, gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Five different aroma categories emerged. Garnacha may develop specific tropical/citrus fruit, kerosene and floral and Tempranillo toasty-woody and red-fruit characteristics. Those notes seem to mask alcoholic and fruit-in-syrup descriptors and the common vegetal background. Twenty-seven odorants were detected by GC-O. GC-MS data showed a clustering closely matching the one found by sensory analysis, suggesting the existence of five specific metabolomic profiles behind the five specific sensory profiles. Overall results suggest that 3-mercaptohexanol is responsible for tropical/citrus fruit, TDN for kerosene, volatile phenols for woody/toasty, β-damascenone and massoia lactone, likely with Z-1,5-octadien-3-one for fruit-in-syrup and alcoholic notes. Nine lipid-derived unsaturated aldehydes and ketones may be responsible for the vegetal background.

New acyclic secondary metabolites from the biologically active fraction of Albizia lebbeck flowers

The total extract of Albizia lebbeck flowers was examined in vivo for its possible hepatoprotective activity in comparison with the standard drug silymarin at two doses. The higher dose expressed promising activity especially in reducing the levels of AST, ALT and bilirubin. Fractionation via liquid–liquid partition and reexamination of the fractions revealed that the n-butanol fraction was the best in improving liver biochemical parameters followed by the n-hexane fraction. However, serum lipid parameters were best improved with CHCl₃ fraction. The promising biological activity results initiated an intensive chromatographic purification of A. lebbeck flowers fractions. Two compounds were identified from natural source for the first time, the acyclic farnesyl sesquiterpene glycoside1-O-[6-O-α-l-arabinopyranosyl-β-d-glucopyranoside]-(2E,6E-)-farnesol (6) and the squalene derivative 2,3-dihydroxy-2,3-dihydrosqualene (9), in addition to eight compounds reported here for the first time from the genus Albizia; two benzyl glycosides, benzyl 1-O-β-d-glucopyranoside (1) and benzyl 6-O-α-l-arabinopyranosyl β-d-glucopyranoside (2); three acyclic monoterpene glycosides, linalyl β-d-glucopyranoside (3) and linalyl 6-O-α-l-arabinopyranosyl-β-d-glucopyranoside (4); (2E)-3,7-dimethylocta-2,6-dienoate-6-O-α-l arabinopyranosyl-β-d-glucopyranoside (5), two oligoglycosides, n-hexyl-α-l arabinopyranosyl-(1 → 6)-β-d-glucopyranoside (creoside) (7) and n-octyl α-l-arabinopyranosyl-(1 → 6)-β-d-glucopyranoside (rhodiooctanoside) (8); and ethyl fructofuranoside (10). The structures of the isolated compounds were elucidated based on extensive examination of their spectroscopic 1D and 2D-NMR, MS, UV, and IR data. It is worth mentioning that, some of the isolated linalol glycoside derivatives were reported as aroma precursors.

Modulation of coffee aroma via the fermentation of green coffee beans with Rhizopus oligosporus: I. Green coffee

Modulation of coffee aroma via the biotransformation/fermentation of different coffee matrices during post-harvest remains sparingly explored despite some studies showing their positive impacts on coffee aroma. Therefore, this is an unprecedented study aimed at modulating coffee aroma via the fermentation of green coffee beans with a food-grade fungus Rhizopus oligosporus. The objective of part I of this two-part study was to characterize the volatile and non-volatile profiles of green coffee beans after fermentation. Proteolysis during fermentation resulted in 1.5-fold increase in the concentrations of proline and aspartic acid which exhibited high Maillard reactivity. Extensive degradation of ferulic and caffeic acids led to 2-fold increase in the total concentrations of volatile phenolic derivatives. 36% of the total volatiles detected in fermented green coffee beans were generated during fermentation. Hence, the work presented demonstrated that R. oligosporus fermentation of green coffee beans could induce modification of the aroma precursors of green coffees.