Orthonasal and retronasal perception of some green leaf volatiles used in beverage flavors.

Orthonasal perception of six green leaf volatiles (GLVs) classified only hexanal, (E)-2-hexenal, and (Z)-3-hexen-1-yl formate as green. (Z)-3-Hexen-1-yl hexanoate and (Z)-3-hexen-1-yl 3-methylbutyrate were more floral, and (Z)-3-hexen-1-yl acetate fell between the two groups. For retronasal perception, classification along a bipolar green-fruity scale is proposed for describing these GLVs. Data from grouping and dissimilarity tests as well as from sensory profiling show green character for these compounds in standard beverage bases having low Brix or high acidity. As the Brix value increases (or acidity decreases) within the limits encountered in commercial beverages, the character becomes fruity. Several tastant-dependent changes in intensity scores for retronasal descriptors were shown to occur for mixtures of GLVs. The GLVs did not affect intensity scores for gustatory descriptors.

Sweetener/sweetness-induced changes in flavor perception and flavor release of fruity and green character in beverages.

Green leaf volatile (GLV) mixtures, commercial orange flavors, and commercial strawberry flavors were applied to beverage bases in which concentrations of citric acid as well as a sweetener (sucrose or aspartame/acesulfame-K) were varied. Sensory profiling showed that flavor-specific fruity character increased as perceptible sweetness increased, independent of whether the sweetness resulted from sucrose (a change from 9 to 12 Brix) or aspartame/acesulfame-K (a change from 0.2 to 0.4 Brix). Sweetness was affected only by the tastants in the base and not by the flavors, although flavor-specific interactions between sweetener type and sweetener level occurred. Flavor release from the sucrose bases was compared to flavor release from bases containing aspartame/acesulfame-K by static headspace measurements and by MS-Nose measurements using an artificial throat. These measurements showed greater flavor volatility from bases having low Brix (fewer soluble solids). This negative Brix effect was also evident in the sensory data for perception of some GLV green notes. The headspace data could not support a positive Brix effect, the typical salting out, which would correspond to the observed perceptual enhancement of fruity notes.

Factors affecting the perception of naturalness and flavor strength in citrus drinks.

In two profiling experiments and one grouping experiment, panelists evaluated orange drinks in order to measure the effects of design variables, especially color, on basic tastes as well as on more consumer-like attributes such as flavor strength and naturalness. Naturalness was increased in one experiment by lowering degrees Brix or increasing quinine HCl. Low sweet-sour ratios were generally perceived as more natural. Pectin had no effect on naturalness. Flavor strength was increased consistently by augmenting levels of quinine HCl, sucrose, citric acid or degrees Brix. Addition of Cochineal Red increased sweetness and flavor strength but decreased the perception of naturalness for the aromas studied.

Chemometrics in bioanalytical sample preparation. A fractionated combined mixture and factorial design for the modelling of the recovery of five tricyclic amines from plasma after liquid-liquid extraction prior to high-performance liquid chromatography.

A general systematic approach is described for the chemometric modelling of liquid-liquid extraction data of drugs from biological fluids. Extraction solvents were selected from Snyder's solvent selectivity triangle: methyl tert.-butyl ether, methylene chloride and chloroform. The composition of a mixture of the three extraction solvents was varied and the extraction yield (recovery) of a group of tricyclic amines was measured at all compositions selected. Two process variables, the extraction time and the extraction intensity, were varied simultaneously with the mixture variables to study their influence and their interaction with the mixture composition. The combined mixture and factorial design statistical techniques obtained in this way enabled the recovery to be modelled as a function of both the composition of the extraction liquid and the process variables. The models were assessed with regard to both descriptive and predictive capacities. The results showed that structurally related compounds may demonstrate different partitioning behaviour with regard to both mixture variables and process variables. It was concluded that mixtures of solvents result in higher extraction efficiencies for the amines. A positive effect on the extraction efficiency was demonstrated by the extraction intensity process variable and extraction time. A positive effect on the extraction efficiency was demonstrated by an interaction between extraction intensity and time. Mixture models in which process variables were introduced were recognized as being very suitable for modelling liquid-liquid extraction systems.