assessment-spatial-lingual-tactile-sensitivity-using-gratings

Assessment of Spatial Lingual Tactile Sensitivity using a Gratings Orientation Test

Individual thresholds by R-index estimates are calculated using a gratings orientation test (6 different tools of increasing grating size from 0.20-1.25 ...

University of Nottingham

Thermal taster status refers to the finding that, in some individuals, thermal stimulation of the tongue elicits a phantom taste. Little is known regarding the mechanism for this, it is hypothesised to be a result of cross-wiring between gustatory and trigeminal nerves whose receptors co-innervate papillae on the tongue. To address this, we use functional magnetic resonance imaging to perform the first study of whether the cortical response to gustatory-trigeminal samples is altered with thermal taster status. We study the response to cold (6°C) gustatory (sweet) samples at varying levels of trigeminal stimulation elicited by CO2 (no CO2 , low CO2 , high CO2 ) in thermal taster (TT) and thermal non-taster (TnT) groups, and evaluate associated behavioural measures. Behaviourally, the TT group perceived gustatory and trigeminal stimuli significantly more intense than TnTs, and were significantly more discriminating of CO2 level. fMRI data revealed elevated cortical activation to the no CO2 sample for the TT group compared to TnT group in taste, oral somatosensory and reward areas. In TnTs, a significant positive modulation in cortical response with increasing level of CO2 was found across taste, somatosensory and reward areas. In contrast, in TTs, a reduced positive modulation with increasing level of CO2 was found in somatosensory areas (SI, SII), whilst a significant negative modulation was found in taste (anterior insula) and reward (ACC) areas. This difference in cortical response to trigeminal stimuli supports cross-modal integration in TTs, with gustatory and trigeminal nerves highly stimulated by cold gustatory samples due to their intertwined nature. Hum Brain Mapp 37:2263-2275, 2016. © 2016 Wiley Periodicals, Inc.

Thermal taster status: Evidence of cross-modal integration.

Determination of the number of fungiform papillae (FP) on the human tongue is an important measure that has frequently been associated with individual differences in oral perception, including taste sensitivity. At present, there is no standardised method consistently used to identify the number of FP, and primarily scientists manually count papillae over a small region(s) of the anterior tip of a stained tongue. In this study, a rapid automated method was developed to quantify the number of FP across the anterior 2cm of an unstained tongue from high resolution digital images. In 60 participants, the automated method was validated against traditional manual counting, and then used to assess the relationship between the number of FP and taste phenotype (both 6-n-propylthiouracil (PROP) and Thermal Taster Status). FP count on the anterior 2cm of the tongue was found to correlate significantly with PROP taster status. PROP supertasters (PSTs) had a significantly higher FP count compared with PROP non-tasters (PNTs). Conversely, the common approach used to determine the number of FP in a small 6mm diameter circle on the anterior tongue tip, did not show a significant correlation irrespective of whether it was determined via automated or manual counting. The regional distribution of FP was assessed across PROP taster status groups. PSTs had a significantly higher FP count within the first centimetre of the anterior tongue compared with the PNT and PROP medium-tasters (PMT), with no significant difference in the second centimetre. No significant relationship was found with Thermal Taster Status and FP count, or interaction with PROP taster status groups, supporting previous evidence suggesting these phenomena are independent. The automated method is a valuable tool, enabling reliable quantification of FP over the anterior 2cm surface of the tongue, and overcomes subjective discrepancies in manual counting.

An automated method to detect and quantify fungiform papillae in the human tongue: Validation and relationship to phenotypical differences in taste perception.

Thermal tasters (TTs) perceive thermally induced taste (thermal taste) sensations when the tongue is stimulated with temperature in the absence of gustatory stimuli, while thermal non tasters (TnTs) only perceive temperature. This is the first study to explore detailed differences in thermal taste responses across TTs. Using thermal taster status phenotyping, 37 TTs were recruited, and the temporal characteristics of thermal taste responses collected during repeat exposure to temperature stimulation. Phenotyping found sweet most frequently reported during warming stimulation, and bitter and sour when cooling, but a range of other sensations were stated. The taste quality, intensity, and number of tastes reported greatly varied. Furthermore, the temperature range when thermal taste was perceived differed across TTs and taste qualities, with some TTs perceiving a taste for a small temperature range, and others the whole trial. The onset of thermal sweet taste ranged between 22 and 38°C during temperature increase. This supports the hypothesis that TRPM5 may be involved in thermal sweet taste perception as TRPM5 is temperature activated between 15 and 35°C, and involved in sweet taste transduction. These findings also raised questions concerning the phenotyping protocol and classification currently used, thus indicating the need to review practices for future testing. This study has highlighted the hitherto unknown variation that exists in thermal taste response across TTs, provides some insights into possible mechanisms, and importantly emphasises the need for more research into this sensory phenomenon.

Variation in thermally induced taste response across thermal tasters.

Water-in-oil-in-water emulsions containing an internalised salt solution were stabilised with non-chemically modified waxy rice starch (WRS), and octinyl succinic anhydride (OSA) as reference, to release salt during oral processing due to amylase-induced destabilisation. Salt levels were 1.5 g salt and 0.47 g salt per 100 g external and internal aqueous phases, respectively. Variables were the starch content (2, 3, 4 g per 100 g emulsion; 20 g oil per 100 g emulsion), level of polyglycerol polyricinoleate (PGPR) as a lipophilic emulsifier (0.29, 0.57 g per 100 g emulsion) and ambient-pressure processing temperature for WRS gelatinisation, the non-chemical modification process, (75 ± 3, 88 ± 5 °C). OSA starch was used under previously applied conditions (2, 3, 4 g starch, 0.57 g PGPR per 100 g emulsion, 25 ± 5 °C). Emulsions were stable for three months, except OSA and lower level PGPR low temperature processed WRS emulsions lost salt into the external emulsion phase. One day after processing, encapsulation efficiency (EE) was as predicted from the composition for OSA emulsions, while at the same PGPR content an external aqueous phase was incorporated into the oil droplets of the WRS emulsion increasing EE. Salt release was assessed in vitro and through sensory evaluation using paired comparison testing. The results revealed that the efficacy of this salt reduction approach was enhanced for gelatinised WRS compared to OSA starch stabilised emulsions. Consumer tests on a tomato soup, to validate this salt reduction approach for a real food, revealed a possible 25% salt reduction, compared to current UK products.

Non-chemically modified waxy rice starch stabilised wow emulsions for salt reduction.

Consumer sensory evaluation, aroma release analysis and biophysical protein analysis were used to investigate the effect of ethanol on the release and perception of flavour in beer (lager and stout) at different ethanol levels (0 and 5% ABV). Consumer study results showed no significant differences in orthonasal perception, yet retronasal results showed that 0% lager was perceived as maltier with reduced fruitiness, sweetness, fullness/body and alcohol warming sensation (p < 0.05). Whilst ethanol alone decreases the aroma release regardless of LogP, the presence of α-amylase selectively reduces the headspace concentration of hydrophobic compounds. It was found that ethanol has a subtle inhibitory effect on the binding of hydrophobic compounds to α-amylase, thereby increasing their headspace concentration in the 5% ABV as compared to the 0% beers. This synergistic ethanol * saliva effect is attributed to the changes in the conformation of α-amylase due to ethanol-induced denaturation. It is hypothesised that the partially unfolded protein structures have a lower number of hydrophobic pockets, leading to a lower capacity to entrap hydrophobic aroma compounds. This supports the hypothesis that ethanol * saliva interactions directly impact the sensory and flavour properties of beer, which would provide a basis for further investigations in reformulation of 0% ABV drinks.

Understanding the lost functionality of ethanol in non-alcoholic beer using sensory evaluation, aroma release and molecular hydrodynamics.

This study aimed to investigate the sensory and physicochemical differences of a range of commercial non-alcoholic lagers, as well as their influence on overall liking. Using physicochemical analysis and modified quantitative descriptive analysis (QDA) with a trained panel (n = 10) eighteen commercial non-alcoholic lagers, made using different production methods, were assessed. A subset (eleven), representing the sensory space were also assessed for hedonic liking using consumers (n = 104). Overall, it showed a clear variety of non-alcoholic lagers were selected, with different clusters of samples found with identifiable characteristics. Production methods were explored as a possible explanation for the differences in characteristics, however these did not fully explain the clusters and therefore other factors, such as pre or post processing methods are discussed. In terms of overall liking, five clusters of consumers were discovered with different patterns of liking, confirming that a wide range of non-alcoholic lagers are needed to satisfy all consumers.

Understanding the sensory and physicochemical differences between commercially produced non-alcoholic lagers, and their influence on consumer liking.

A pilot scale dealcoholisation unit fitted with reverse osmosis (RO) membranes was used to directly compare two beer matrices (stout, lager, ~ 5% ABV) and their dealcoholized counterparts (~0.5% ABV), for physicochemical properties (volatiles, pH, ABV, polyphenols, bitterness) and sensory profiles using a trained descriptive panel (n = 12). The efficiency and consistency of RO membranes were evaluated by replicate dealcoholisation trials (n = 3) for each beer. Statistical analysis revealed significant reductions (p < 0.05) in key volatile compounds with linear structures (ethyl octanoate, octan-1-ol) compared to those with increased levels of branching (3-methylbutyl acetate, 2-methylpropan-1-ol). Significant reductions (p < 0.0001) in 'fruity/estery', 'alcoholic/solvent', 'malty', 'sweetness' and 'body' sensory attributes were also discovered. Finally, longer processing times for the stout across replicate trials suggested membrane clogging, whilst differences in volatile reduction suggested membrane fouling. This novel research proposes compound structure, rather than compound size, impacts RO membrane permeability and resulting sensory quality.

Assessing the sensory and physicochemical impact of reverse osmosis membrane technology to dealcoholize two different beer styles.

Food manufacturers are under increasing pressure to limit the amount of free sugars in their products. Many have reformulated products to replace sucrose, glucose and fructose with alternative sweeteners, but some of these have been associated with additional health concerns. Rare sugars are "monosaccharides and their derivatives that hardly exist in nature", and there is increasing evidence that they could have health benefits. This review aimed to scope the existing literature in order to identify the most commonly researched rare sugars, to ascertain their proposed health benefits, mechanisms of action and potential uses, and to highlight knowledge gaps. A process of iterative database searching identified 55 relevant articles. The reported effects of rare sugars were noted, along with details of the research methodologies conducted. Our results indicated that the most common rare sugars investigated are D-psicose and D-tagatose, with the potential health benefits divided into three topics: glycaemic control, body composition and cardiovascular disease. All the rare sugars investigated have the potential to suppress postprandial elevation of blood glucose and improve glycaemic control in both human and animal models. Some animal studies have suggested that certain rare sugars may also improve lipid profiles, alter the gut microbiome and reduce pro-inflammatory cytokine expression. The present review demonstrates that rare sugars could play a role in reducing the development of obesity, type 2 diabetes, and/or cardiovascular disease. However, understanding of the mechanisms by which rare sugars may exert their effects is limited, and their effectiveness when used in reformulated products is unknown.

Rare sugars: Metabolic Impacts and Mechanisms of Action - a Scoping Review.

Understanding the contribution of hop essential oil to the multisensory profile of beer is known to be challenging because of its chemical and sensory complexity. Limited research has been conducted investigating hop-derived volatiles' role in the modulation of taste and mouthfeel sensations. Supercritical CO₂ can be used to extract specific fractions from hop oil, thereby enabling the localisation of compounds responsible for different sensory impressions. Terpene alcohol and sesquiterpene fractions were extracted from a Magnum hop oil and further fractionated into seven sub-fractions and individual compounds. All extracts were evaluated in lager (4.5% v/v) by a trained panel (n = 10) using a newly developed attribute lexicon and following a sensory descriptive analysis approach. The sensory data was analysed using ANOVA, followed by Tukey's test (HSD) and correlated with chemical profile data obtained by gas chromatography-mass spectrometry (GC-MS) by Principal Component Analysis. The study revealed evidence for hop extracts to impart multisensory characteristics to beer due to sensory interactions within and across modalities. The monoterpene alcohols-rich fractions and particularly geraniol, added fruity- and floral aromas and flavours, modified the sweetness and induced a smooth bitterness in the beer matrix. Flavouring the beer with sesquiterpene fractions resulted in a harsh bitterness sensation. Contrary to previous findings, the humulene epoxides fraction appeared to have limited effects on lingering bitterness and astringency, illustrating the need for temporal sensory assessments in future studies. This research shows that splitting hop oil into fractions and sub-fractions provides a source of natural, sustainable flavouring preparations with distinct sensory characteristics.

Article	Year
Thermal taster status: Evidence of cross-modal integration. Human brain mapping\| PubMed ID: 26947429	2016
An automated method to detect and quantify fungiform papillae in the human tongue: Validation and relationship to phenotypical differences in taste perception. Physiology & behavior\| PubMed ID: 29223711	2018
Variation in thermally induced taste response across thermal tasters. Physiology & behavior\| PubMed ID: 29410235	2018
Non-chemically modified waxy rice starch stabilised wow emulsions for salt reduction. Food & function\| PubMed ID: 31259325	2019
Understanding the lost functionality of ethanol in non-alcoholic beer using sensory evaluation, aroma release and molecular hydrodynamics. Scientific reports\| PubMed ID: 33257785	2020
Understanding the sensory and physicochemical differences between commercially produced non-alcoholic lagers, and their influence on consumer liking. Food chemistry: X\| PubMed ID: 33532724	2021
Assessing the sensory and physicochemical impact of reverse osmosis membrane technology to dealcoholize two different beer styles. Food chemistry: X\| PubMed ID: 34189455	2021
Rare sugars: Metabolic Impacts and Mechanisms of Action - a Scoping Review. The British journal of nutrition\| PubMed ID: 34505561	2021
Exploring the multisensory perception of terpene alcohol and sesquiterpene rich hop extracts in lager style beer. Food research international (Ottawa, Ont.)\| PubMed ID: 34507743	2021

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