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H T Lawless

Publications and source records attributed to H T Lawless.

At least 19 recordsLinked to original sources
PubMed2002

The effect of microgravity and space flight on the chemical senses.

The effect of space flight and microgravity on the chemical senses is reviewed. Skylab-4 and Soyuz 30-31 studies revealed changes in taste thresholds while no effect was found in a Canadian investigation (41-G) and conflicting results were obtained on another Soyuz mission. Two simulated microgravity studies found no effect on taste or smell sensitivity; while 5 other studies found an effect. Microgravity induces physiological changes including an upward shift of body fluids toward the head, which may lead to an attenuation of the olfactory component in the flavor of foods. Chemosensory changes may also relate to space sickness, Shuttle atmosphere, stress, radiation, and psychological factors.

Adult↗
PubMed2001

Quantitative descriptive analysis and principal component analysis for sensory characterization of ultrapasteurized milk.

Quantitative descriptive analysis was used to describe the key attributes of nine ultrapasteurized (UP) milk products of various fat levels, including two lactose-reduced products, from two dairy plants. Principal components analysis identified four significant principal components that accounted for 87.6% of the variance in the sensory attribute data. Principal component scores indicated that the location of each UP milk along each of four scales primarily corresponded to cooked, drying/lingering, sweet, and bitter attributes. Overall product quality was modeled as a function of the principal components using multiple least squares regression (R2 = 0.810). These findings demonstrate the utility of quantitative descriptive analysis for identifying and measuring UP fluid milk product attributes that are important to consumers.

Animals↗
PubMed2000

Contrast and range effects for category, magnitude and labeled magnitude scales in judgements of sweetness intensity.

The labeled magnitude scale (LMS) is a verbally anchored quasi-logarithmically spaced response scale with properties similar to magnitude estimation. Three experiments examined whether the LMS showed context effects similar to those found with magnitude estimation and category scales. Two versions of the LMS were used, one anchored at the high end to the strongest imaginable sweetness and the other to the strongest imaginable oral sensation. In a simple contrast experiment, subjects judged the sweetness of a 10% sucrose fruit beverage in the context of a less sweet (5%) beverage or a more sweet (20%) beverage. Consistent with previous literature, the sweetness was judged more intense in the low context and less intense in the high context, for all scaling methods. In a second experiment, this effect persisted (although was smaller) when the contextual item preceded the to-be-rated item, a so-called 'reversed-pair' design. Once again, the effect was highly significant for all scaling methods. In a third experiment, a range effect was examined using wide and narrow ranges of concentration. Psychophysical functions were flatter in a wide context and steeper in a narrow context, consistent with previous observations on range-mapping bias. This result was obtained for all scales. In three common contextual effects, the labeled magnitude scale behaved similarly to other scaling procedures. Its application to comparisons across individuals may be limited if those individuals have different experiential contexts within which they make their judgements.

Female↗
PubMed1999

Combined effects of carbon dioxide addition and barrier films on microbial and sensory changes in pasteurized milk.

The growth of psychrotrophic microorganisms is an important factor in the deterioration of refrigerated pasteurized milk. Dissolved CO2 inhibits certain spoilage microorganisms in foods provided that the packaging offers a sufficient barrier to CO2 evolution. The objectives of this work were, first, to estimate the sensory threshold for dissolved CO2 in 2% milk and, second, to determine the relationship between microbial growth and package barrier properties for pasteurized milk to which CO2 had been added at concentrations near the flavor threshold. The sensory threshold, as determined by a trained panel, for CO2 in 2% pasteurized milk was > 2.8 mM and < 9.1 mM. Pasteurized milk was inoculated with a cocktail of spoilage microorganisms, packaged in different barrier film pouches, and stored at 6.1 degrees C for up to 28 d. The addition of CO2 at concentrations of 8.7 and 21.5 mM increased the time needed to reach 10(6) cfu/ml from 6.4 d (no CO2) to 8.0 and 10.9 d, respectively, in low barrier pouches. In high barrier pouches, the time needed to reach 10(6) cfu/ml was increased to 9.7 and 13.4 d, respectively, at CO2 concentrations of 8.7 and 21.5 mM. This increase represents an increase in shelf-life of approximately 25 to 200%. Microbial counts had longer lag times and lower growth rates and took longer to reach stationary growth as the concentration of CO2 increased in all films than did the control milk. The control milk curdled in less than 17 d, but the test milk in the high barrier packaging had not curdled at 28 d. These data suggest that the shelf-life of pasteurized refrigerated milk could be extended by at least 25 to 200% at CO2 concentrations near the sensory threshold. The major variables in shelf-life are the amount of added CO2 and the barrier properties of the package.

Animals↗
PubMed1998

Theoretical note: tests of synergy in sweetener mixtures.

Some methods for examining the additivity of sweeteners, and their synergy in mixtures depend upon setting component concentrations on the basis of sweetness equivalence, usually to a sucrose reference. These methods may under- or over-predict the sweetness of a mixture, leading to spurious claims of synergy or mixture suppression. This paper points out one problem with one such popular method, in that the method can lead to a conclusion that a substance would synergize with itself. To the extent that self-synergy is an illogical conclusion for a mixture comparison, such a method should be avoided in tests of synergy. The sweetness equivalence approach is contrasted with a simpler approach based on concentrations that does not lead to conclusions of self-synergy.

Drug Synergism↗
PubMed1996

Astringency of organic acids is related to pH.

Astringency and sourness of lactic, acetic and citric acids, each adjusted to pH 3, 5 and 7, were evaluated in two experiments, one starting at equal concentrations in wt/vol before neutralization and the second starting at equal molarity. Astringency and sourness decreased with increasing pH. However, acids were differentially sour at equal pH, consistent with previous findings. In contrast, the tactile attributes associated with astringency (drying, roughing of oral tissues and puckery/tightening sensations) were similar across acids; pH was the major influence on astringency. Strong dependence on pH suggests that astringency of these acids is a direct result of their acidic properties, and not solely due to the hydrogen bonding mechanisms previously suggested as an explanation of astringency in tannin interactions with salivary proteins.

Acetic Acid↗
PubMed1995

Variation in odor thresholds for l-carvone and cineole and correlations with suprathreshold intensity ratings.

Specific anosmias have been reported for l-carvone and cineole, two compounds of importance in food flavor perception. Detection thresholds were assessed in groups of 50+ individuals by ascending forced-choice tests conducted in quadruplicate. Wide individual differences in thresholds were observed. Within the same session, threshold correlations were in the range of +0.8 to +0.9, showing good short-term reliability. Correlations with suprathreshold ratings were moderate (in the range of r = -0.5) after subtraction of false positive ratings for blank samples. However, a cineole mixture experiment failed to show any differences between subgroups that were previously classified as high or low sensitivity on the basis of threshold measurements. Re-testing selected groups after a period of months showed considerable within-individual variation in the thresholds, especially for l-carvone. These results call into question the stability and utility of threshold classification for these two compounds.

Adult↗
PubMed1995

Astringent subqualities in acids.

Astringency, astringent subqualities (drying, roughing and puckering) and sourness were compared among six acids: hydrochloric, lactic, citric, acetic, fumaric and malic acids. The attribute profiles of organic acids were similar to each other but different from hydrochloric acid, the only inorganic acid, which was the most astringent and the least sour. In a second experiment, two inorganic acids (hydrochloric and phosphoric) and two organic acids (citric and malic) were tested at three concentration levels. At approximately equal levels of overall sensory impact, the inorganic acids were alike in astringency and sourness, receiving higher ratings for roughing and drying, and lower ratings for sourness than the organic acids. Interactions with concentration (differences in psychophysical functions) for the subquality of drying were noted, in addition to the differences in the astringent subqualities of roughing and drying seen across acids in both experiments. The higher level of astringency for inorganic acids suggests that the current model for tannin binding to salivary proteins as an explanation of astringency needs to be extended to include a direct pH-dependent effect.

Adult↗
PubMed1994

Interactions of astringent substances.

Two-component mixtures of astringent materials were rated for perceived intensity of astringent and taste attributes over time. Components included alum (a complex salt), gallic acid (the monomeric component of hydrolyzable tannins), catechin (the monomeric component of condensed tannins) and citric acid. Mixtures of alum and gallic acid showed mixture suppression, in that the 50/50 mixture was less intense than either component in astringency, drying, roughing and puckery/drawing sensations. Suppression was seen at concentration levels producing moderate to strong astringency but was absent or less pronounced at lower concentration levels. A similar pattern held for citric acid, although the suppressive effects were less pronounced. Catechin and gallic acid mixtures were additive. Sensory interactions between astringent materials appears to depend on the substances involved and their concentrations (or intensity levels).

Adult↗
PubMed1994

Limiting response alternatives in time-intensity scaling: an examination of the halo-dumping effect.

Time-related measurements pose some challenges to psychophysics and to applied sensory testing methods including control of psychological biases which have been found in single-point scaling. This research examined enhancement of ratings when response alternatives were limited in time-intensity scaling tasks using repeated category ratings. Panelists rated a pseudo-beverage containing sweetener and flavor and one with sweetener only over a 90-s period. The aromatic flavor caused an increase in sweetness intensity and especially so when the panelists were limited to sweetness responses only. The odor-induced enhancement of sweetness was smaller when panelists were given both flavor and sweetness response options than when the panelists were given only a sweetness scale. Prior use of both scales in a previous experimental session did not lessen the halo-dumping enhancement effect. In one study, sweetness ratings of sucrose alone were depressed when the additional scale for flavoring was provided, perhaps due to inappropriate partitioning of responses.

Adolescent↗
PubMed1987

Enhancement of responses to sequential presentation of oral chemical irritants.

The irritative flavor compounds, capsaicin and piperine, were presented in sequence to the oral cavity of human subjects and rated for perceived intensity of irritation. Marked increases in perceived irritation were reported when the second-presented irritant differed from the first, as compared with control conditions in which the same irritant was repeated. This cross-enhancement is explained most simply by recruitment of additional receptors or fiber types, and implies a greater degree of specificity (narrowness of tuning) of trigeminal receptors than previously suggested by desensitization studies.

Alkaloids↗
PubMed1985

An adjustment error in optimization of taste intensity.

In a currently popular method of adjustment for assessing optimal preferred levels of tastants in foods, a robust perceptual error was observed. When subjects concentrated a dilute beverage to optimal taste, the final (adjusted) concentration of the added tastant was reliably lower than when diluting a concentrated beverage. This discrepancy between ascending and descending runs was observed for both adjusted sucrose in a fruit beverage and for adjusted NaCl in tomato juice. The premature shift in perception from non-optimal to optimal judgment resembles the "error of anticipation" in the classical method of limits. The effect could not be attributed to sensory adaptation or perceptual insensitivity, and it persisted even when subjects were told to be sure to reach the same level in both directions of adjustment. The magnitude of the error was diminished by interweaving of ascending and descending trials, which altered the immediate stimulus context, and by enhancing the motivational level of subjects (through reward) to try to reach the same concentration in both ascending and descending adjustments.

Adult↗
PubMed1982

Aversions to bitterness and accidental poisonings among preschool children.

Individual differences in responsiveness to bitterness were studied among children with and without histories of accidental ingestion of toxic substances. The oral behaviors of 56 children between the ages of 12 and 41 months were videotaped during two minute test periods with lollipops containing different concentrations of bitter sucrose octaacetate (SOA). Videotapes were scored for mouthing times, numbers of oral contacts and latencies to mouthing for each stimulus. Mouthing time was the most sensitive dependent measure examined. Both groups rejected pops with added SOA, decreasing mouthing times as SOA concentration increased. Mouthing times for children with histories of accidental ingestion were slightly lower overall. These results suggest that lowered reactivity to tastes is not a predisposing factor in accidental ingestions, and that bitter substances have some value as deterrents to ingestion for this age group. Rejection of bitter pops by children closely paralleled ratings of bitterness by adult judges.

Adult↗
PubMed1979

Evidence for neural inhibition in bittersweet taste mixtures.

Three lines of evidence from psychophysical experiments implied that mutual suppression of bitter and sweet tastes is due to neural inhibition rather than chemical interactions in solution or competition of molecules for common receptor sites. Removal of sweetness from bittersweet mixtures caused the bitterness to increase. This was accomplished by adaptation to sucrose or by treatment with Gymnema sylvestre, neither of which affect the concentration of sucrose on the tongue. Such increases in the bitterness of mixtures, independent of the concentration of the sweet masking substance, are difficult to reconcile with suppression by means of chemical interactions. Similar dependence of suppression on perceived intensity (and independence from concentration) was observed with mixtures of phyenylthiocarbamide and sucrose. Tasters of phenylthiocarbamide showed stronger suppression of sweetness than nontasters. This result was also inconsistent with molecular interactions causing suppression, which would have resulted in the same degree of suppression for the two groups. Instead, these findings support neural explanations of mixture suppression, such as antidromic inhibition or occlusion.

Adaptation, Physiological↗