Effect of compound sequence on bitterness enhancement.

The nature and occurrence of carry-over effects, i.e. the response to a stimulus is influenced by previous samples, were examined for selected bitter compounds. A time-intensity procedure was used to rate the bitterness of six compounds (caffeine, denatonium benzoate, limonin, naringin, quinine and sucrose octa-acetate). For each subject concentrations of these compounds were determined that were approximately equal in intensity to 1.18 x 10(-5) M limonin. To test carry-over effects of each compound the 36 paired sequences (pairs) were evaluated. Within a session three pairs were tested, between which two-stage rinses were used to remove any effects of the previous pairs. Within a pair only water rinses were used between stimuli. For all compounds carry-over or sensitization effects were observed in which values for maximum intensity, rate of onset and total area under the time-intensity curve were higher for a compound when tested in the second position than in the first. In addition, the degree of sensitization and susceptibility to sensitization were compound-specific. Caffeine increased the bitterness by the largest amount for all other compounds, while it was least affected. Regardless of the compound in the first position, the bitterness of quinine and denatonium were most enhanced.

Comparison of the effects of concentration, pH and anion species on astringency and sourness of organic acids.

The separate effects of concentration, pH and anion species on intensity of sourness and astringency of organic acids were evaluated. Judges rated sourness and astringency intensity of lactic, malic, tartaric and citric acid solutions at three levels of constant pH varying in normality and at three levels of constant concentration varying in pH. To assess the comparative sourness and astringency of the organic acid anions of study, binary acid solutions matched in pH and titratable acidity were also rated. As pH was decreased in equinormal solutions, both sourness and astringency increased significantly (P < 0.001). By contrast, as the normality of the equi-pH solutions was increased, only sourness demonstrated significant increases (P < 0.001) while astringency remained constant or decreased slightly. At the lowest normality tested, all solutions were more astringent than sour (P < 0.05). Although lactic acid was found to be significantly more sour than citric acid (P < 0.05), no other sourness or astringency differences among the organic acid anions were noted. This study demonstrates for the first time that astringency elicited by acids is a function of pH and not concentration or anion species, and confirms that sourness is independently influenced by concentration, pH and anion species of the acid.

The influence of acid on astringency of alum and phenolic compounds.

Astringency of aqueous solutions of phenolic compounds (grape seed tannins, tannic acid, catechin and gallic acid) increased upon addition of citric acid, whereas the astringency of alum was reduced. Astringency of alum was decreased equivalently by addition of equi-sour levels of lactic acid, citric acid or hydrochloric acid. The difference between alum and the phenolic compounds is speculated to result from chemical modifications affecting binding of the astringents with oral proteins rather than cognitive differences. Chelation of the aluminum ion in alum by acids reduces its availability for interacting with salivary proteins or epithelial proteins. In contrast, the increased astringency produced upon acidification of phenolic compounds is speculated to result from the pH driven increase in the affinity of the phenols for binding with proteins. These results suggest that alum cannot be used interchangeably with phenolic astringents in psychophysical studies.

Using sensory and instrumental data to interpret the effect of storage at elevated temperatures on aroma of Chardonnay wines.

The effect of elevated temperatures during storage on the aroma of commercial Chardonnay wines was monitored by sensory and instrumental methods. Aromas of wines stored at 40 degrees C for 0, 15, 30 and 45 days were profiled by descriptive analysis by a trained panel. Heated storage decreased intensity of fruity and floral notes, while increasing attributes such as honey, butter/vanilla, oak, and rubber. Volatiles recovered by solvent extraction from the same wines were separated by gas chromatography (GC) and identified by GC-mass spectrometry (MS). Principal component analysis of instrumental variables (PCAIV) was used to reduce the initial set of 67 quantified GC peaks. Six compounds, selected by PCAIV to yield the configuration closest to that of the principal component analysis of the sensory data, provided a highly significant fit with the sensory configuration, as shown by a permutation test. This solution was the statistically optimal one, but was not unique, as demonstrated by significant fits between the sensory and instrumental spaces upon use of other GC peaks, which were highly correlated with the original six variables.

Perceptual properties of benzoic acid derivatives.

Sensory properties of equimolar concentrations of benzoic acid derivatives were examined using time-intensity procedures. Significant differences in maximum intensities (P < 0.005) were found for astringency, bitterness, prickling, sourness and sweetness. Although these compounds differed only in the number and position of the hydroxy groups, they exhibited quite different profiles. Gentisic acid had the highest sourness and bitterness maximum intensity, salicylic and gentisic acids were highest in astringency, and m-hydroxybenzoic acid was the sweetest sample. Benzoic acid had the highest intensity of prickling feeling which lasted 20 s longer than salicylic acid and 40 s longer than the other samples which elicited lowest intensity of prickling sensation.

Interaction of salivary flow with temporal perception of sweetness, sourness, and fruitiness.

To explore the effect of salivary flow on perception of sweetness, sourness and fruitiness, 19 subjects continuously recorded perceived intensity from ingestion, through expectoration to extinction of the sensation, for each attribute in solutions sweetened with three levels of aspartame or sucrose at three levels of citric acid. Unilateral parotid flow was collected in response to the solutions at the medium acid level and used to assign subjects to low, medium and high-flow groups. For all three attributes, although the low-flow subjects reached maximum intensity later than high-flow, no significant difference in any time-intensity parameter for any attribute was found among salivary flow groups. No difference in salivary flow was elicited by equi-sweet solutions of aspartame or sucrose. Maximum intensity of sourness and salivary flow rate decreased as the level of sweeteners was raised (at a constant acid concentration) suggesting that salivary flow is mediated by cognitively processed taste response and not only the concentration of stimuli.

Bitterness in wine.

Bitterness in wine is elicited primarily by flavonoid phenols, which are bitter and astringent, and by ethanol. Monomeric flavonoid phenols are primarily bitter but as the molecular weight increases upon polymerization, astringency increases more rapidly than bitterness. The chiral difference between the two wine flavan-3-ol monomers produces a significant difference in temporal perception of bitterness: (-)-epicatechin is significantly more bitter and had significantly longer duration of bitterness than (+)-catechin. Ethanol enhances bitterness intensity and duration, whereas varying wine pH has little or no effect on perceived bitterness. Whereas PROP status had no significant effect on temporal perception of bitterness or astringency, subjects with low salivary flow rates took longer to reach maximum bitterness and astringency intensity and reported longer persistence of both attributes than high-flow subjects.

Human saliva and taste responses to acids varying in anions, titratable acidity, and pH.

Twenty subjects recorded perceived sourness of solutions of citric + fumaric and of citric + tartaric acids, at pH 3.5 and titratable acidity (TiA) of 4.0 g/l on a moving chart, while parotid saliva flow was recorded via a sialometer . Sourness intensity and flow were greater when citric was the minor acid than when it was dominant. Subjects varied widely in calculated volume of saliva reservoir, but not flow rate (time to 2/3 reservoir vol.). In tartaric-fumaric acid mixtures varying in pH (3.0-3.75) at a constant TiA of 4.0 g/l, and varying in TiA (3.7-4.6 g/l) at a constant pH of 3.5, sourness intensity and parotid flow increased with acidity and decreased with pH. However, eight subjects with a high flow (HF = 1.2 +/- 0.28 g/2 min) and nine subjects with a low flow (LF = 0.43 +/- 0.11 g/2 min) differed widely: (a) In response to variation in stimulus pH and TiA, HF demonstrated marked alteration in flow, but little change in sourness ; LF responded at a lower absolute level, but showed marked changes in sourness and little change in flow; (b) Salivary pH was higher and Na+ was three times greater for the HF than for the LF subjects; and (c) Salivary Ca++ showed a direct relationship with flow and pH among the HF, but an inverse relationship for the LF subjects.

Laparoscopic sterilization with spring-loaded clips: double-puncture technique.

The application of a spring-loaded clip to each fallopian tube using a second-incision clip applicator is a safe and effective method of laparoscopic sterilization. The operation is quick and easy to perform and is suitable for use with local anesthesia. The method avoids the dangers of hemorrhage, for the clip only alters 3 mm of the fallopian tube and does not transect the tube or mesosalpinx. No pregnancies have followed the sterilization procedure. An intrauterine pregnancy has occurred after a reversal procedure in one patient.

PIP: 533 women undergoing laparoscopic sterilization were studied in an effort to determine the feasibility and safety of a second-puncture clip applicator. The operation was done on an outpatient or overnight basis and a choice of general or local anesthesia was offered. Results indicated that 97.7% of the cases were uncomplicated while 1.2% resulted in bowel perforation; .4% in hematoma and .7% in tubal ligation. None of the complications were due to clip or applicator design. 85% of the cases had no complaints while 5% of the patients experienced abdominal discomfort lasting 48 to 72 hours. This was the only side effect related to the procedure with a spring-loaded clip. No pregnancies occurred at the 6-month follow-up and 1 reanastomosis occurred supporting existing evidence about successful reversal after sterilization with a spring-loaded clip.