Cross-cultural differences in lingual tactile acuity,taste sensitivity phenotypical markers,and preferred oral processing behaviors

Cultural and genetic differences in consumer populations across the world are important determinants for food preferences. The present study investigated differences in preferred oral processing behaviors between Chinese Asian and Danish Caucasian consumers and the possible relationship to lingual tactile acuity and the two most well-researched phenotypic markers of taste sensitivity, such as 6-n-propylthiouracil (PROP) responsiveness and Fungiform Papillae Density (FPD).A total of 152 consumers (75 Chinese, 77 Danish) were enrolled in the study and categorized by their preferred oral processing behaviors. Lingual tactile acuity was assessed according to responses to stimulation with von Frey filaments. The responsiveness to PROP and the FPD were also determined.Cross-population differences were found in preferred food oral processing behaviors in these two cohorts, as Chinese consumers were characterized by a larger number of ‘Soft processing likers’ (77% of the population) who preferred soft food processing in the mouth. Contrarily, Danish consumers mostly belonged to the ‘Firm processing likers’ group (73% of the population) who had preferences for foods that needed firm processing on biting and chewing. Moreover, the group of ‘Firm processing likers’ appeared to be more sensitive to touch at the apex of the tongue compared with the ‘Soft processing likers’ in both population cohorts. Cross-population differences in lingual tactile acuity were not significant. Differences in FPD and PROP responsiveness were found between these two population cohorts, with Chinese consumers generally characterized by greater FPD and PROP responsiveness compared with the Danish subjects.This study provides evidence on cross-cultural differences in preferred oral processing behaviors and in the two phenotypic marker of taste sensitivity. However, further studies are needed to draw conclusive relationships between preferred oral processing behavior and oral tactile acuity, PROP responsiveness and tongue anatomy.     

Individual differences in oral tactile sensitivity and gustatory fatty acid sensitivity and their relationship with fungiform papillae density,mouth behaviour and texture perception of a food model varying in fat

Fat provides multimodal stimulation, particularly through mouthfeel and as a taste stimulant via free fatty acids. Individuals vary in perception of both mouthfeel and taste sensations from fat. Papillae number on the tongue can influence oral tactile and taste sensitivity. In addition, mouth behaviour (how foods are manipulated in the mouth during eating before swallowing) varies between individuals, and may influence mouthfeel perception. Limited research has explored the relationships between these factors.Fatty acid (FA) taste sensitivity was measured at two levels of oleic acid. Oral tactile sensitivity was measured using von Frey filaments. Fungiform papillae density (FPD) was measured on the tongue anterior. Mouth behaviour (MB) was measured by Graphic Jeltema/Beckley Mouth Behaviour (JBMB) classification tool. Mouthfeel perception (hardness, crunchiness, and greasiness) in a biscuit model was measured to examine the influence of FPD, tactile sensitivity and MB on mouthfeel perception.Higher FPD was significantly related to higher taste sensitivity to fatty acid and to higher oral tactile sensitivity. FPD and oral tactile sensitivity both significantly influenced mouthfeel perception of biscuits. The results demonstrate the need to characterise individual differences in oral sensory perception by more than one method, and suggest oral tactile sensitivity can be used as a marker of FPD. Further studies are required to understand the impact of MB on sensory perception. The BMI of participants in this study was negatively related to oral tactile sensitivity and the perception of greasiness.     

Interrelations among physical characteristics,sensory perception and oral processing of protein-based soft-solid structures

Oral processing is essential in breaking down the physicochemical structure of the food and thus important to the sensory perception of food in the mouth. To have an understanding of protein-based, soft-solid texture perception, a multidisciplinary approach was applied that combined studies of food microstructure with mechanical properties, sensory evaluation, and oral physiology. Model foods were developed by combining ion-induced micro-phase separation and protein-polysaccharide phase separation and inversion. Activities of masseter, anterior temporalis and anterior digastric muscles during oral processing were recorded by electromyography (EMG), while jaw movement amplitudes, durations, and velocities were simultaneously collected by a three-dimensional jaw tracking system (JT-3D). Changes in the microstructure of mixed gels significantly altered the characteristics of the chewing sequence, including the muscle activities, number of chews, chewing duration and chewing frequency. Mechanical attributes related to structural breakdown and sensory perception of firmness were highly correlated with the amount of muscle activity required to transform the initial structure into a bolus ready for swallowing. Chewing frequency was linked to mechanical properties such as recoverable energy, fracture strain and water holding capacity of the gels. Increased adhesiveness and moisture release also resulted in slower chewing frequency. Evaluation of oral processing parameters at various stages (i.e., first cycle, first 5 cycles, and last 3 cycles) was found to be a useful method to investigate the dynamic nature of sensory perception at first bite, during chewing and after swallowing. The study showed that muscle activity and jaw movement can be used to understand the links between physical properties of foods and sensory texture.     

Linking oral processing behavior to bolus properties and dynamic sensory perception of processed cheeses with bell pepper pieces

The addition of food particles to food matrices is a convenient approach that allows to steer oral behavior, sensory perception and satiation. The aim of this study was to determine the influence of physical-chemical properties of heterogenous foods on oral processing behavior, bolus properties and dynamic sensory perception. Bell pepper gel pieces varying in fracture stress and concentration were added to processed cream cheese matrices differing in texture. Addition of bell pepper gel pieces to processed cheeses increased consumption time, decreased eating rate and led to harder and less adhesive bolus with more saliva incorporated. Addition of bell pepper gel pieces to processed cheeses decreased dominance rate and duration of creaminess, smoothness, melting and dairy flavor and increased graininess and bell pepper flavor. Increasing fracture stress of bell pepper gel pieces from 100 to 300 kPa resulted in longer consumption time and lower eating rate. For hard/non-adhesive processed cheese matrices increasing gel pieces fracture stress lead to a boli with larger particles and more saliva. These changes were accompanied by decreased dominance perception of creaminess and bell pepper flavor and increased dominance of graininess. Increasing the concentration of bell pepper gel pieces from 15 to 30% did not affect oral behavior but led to the formation of harder and less adhesive bolus with larger particles and less saliva that were perceived with reduced dominance of creaminess, meltiness and dairy flavor while dominance of graininess and bell pepper flavor increased. Changing the texture of the cheese matrix from soft/adhesive to hard/non-adhesive decreased consumption time, increased eating rate, did not influence bolus properties and decreased dominance rate of creaminess, smoothness and melting sensations. Number of chews and total consumption time were positively correlated with saliva content of the bolus, number of bolus particles, bolus hardness, dominance of firmness, chewiness and graininess. We conclude that the modification of physical-chemical properties of processed cheeses and embedded bell pepper gel pieces can be a strategy to steer oral behavior and bolus properties which consequently determine dynamic sensory perception.     

Acoustic emission measurement of rubbing and tapping contacts of skin and tongue surfaces in relation to tactile perception

The application of acoustic emission measurement (“acoustic tribology”) is explored for in vivo characterization of rubbing and tapping contacts of the biological tissues of skin and tongue. This acoustic signal originates from physical processes that are closely related to the rapid force fluctuations that are sensed by the rapidly-adapting mechanoreceptors involved in the sensation of touch. Demonstrated is the recording and analysis of sound produced by rubbing and tapping the skin against various surface textures of common materials and by rubbing the tongue against the palate or against food material in the mouth for 1 individual. The technique is shown to be sensitive to skin pre-treatment and pre-meals, and is also shown to discriminate between various surface textures and food materials in a way that relates to perception. The main advantages of the technique are its time-resolution, ease of operation and the fact that it is a direct in vivo measurement of processes that are closely related to texture perception.     

Genetic influences on oral fat perception and preference: Presented at the symposium "The Taste for Fat: New Discoveries on the Role of Fat in Sensory Perception, Metabolism, Sensory Pleasure and Beyond" held at the Institute of Food Technologists 2011 Annual Meeting, New Orleans, LA, June 12, 2011

Research suggests that dietary fat is perceived not only by texture, but also by taste. However, the receptors for chemosensory response to fat have not been identified. We report on 2 genes,TAS2R38 and CD36, that may play a role in fat perception and preference in humans. TAS2R38 is a taste receptor for bitter thiourea compounds, including 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC). Nontasters of these compounds tend to be poor at discriminating fat in foods, even though they prefer higher fat versions of these foods. CD36, a fatty acid translocase expressed on multiple cell types including taste cells, plays a critical role in fat preferences in animals. In studies conducted in our laboratory with African-American adults, we identified a variant in the CD36 gene, rs1761667, that predicts oral responses to fat. Individuals who have the A/A genotype at this site tend to find Italian salad dressings creamier than those who have other genotypes at this site. In addition, A/A individuals report higher preferences for added fats, oils, and spreads (for example margarine). Assuming these data are confirmed in other populations, screening for CD36 genotype may provide helpful information to food companies for developing fat-modified products.     

Implications of recent research on microstructure modifications,through heat-related processing and trait alteration to bio-functions,molecular thermal stability and mobility,metabolic characteristics and nutrition in cool-climate cereal grains and other types of seeds with advanced molecular techniques

ABSTRACT

The cutting-edge synchrotron radiation based and globar-sourced vibrational infrared microspectroscopy have recently been developed. These novel techniques are able to reveal structure features at cellular and molecular levels with the tested tissues being intact. However, to date, the advanced techniques are unfamiliar or unknown to food and feed scientists and have not been used to study the molecular structure changes in cool-climate cereal grain seeds and other types of bio-oil and bioenergy seeds. This article aims to provide some recent research in cool-climate cereal grains and other types of seeds on molecular structures and metabolic characteristics of carbohydrate and protein, and implication of microstructure modification through heat-related processing and trait alteration to bio-functions, molecular thermal stability and mobility, and nutrition with advanced molecular techniques- synchrotron radiation based and globar-sourced vibrational infrared microspectroscopy in the areas of (1) Inherent microstructure of cereal grain seeds; (2) The nutritional values of cereal grains; (3) Impact and modification of heat-related processing to cereal grain; (4) Conventional nutrition evaluation methodology; (5) Synchrotron radiation-based and globar-sourced vibrational (micro)-spectroscopy for molecular structure study and molecular thermal stability and mobility, and (6) Recent molecular spectroscopic technique applications in research on raw, traits altered and processed cool-climate cereal grains and other types of seeds. The information described in this article gives better insights of research progress and update in cool-climate cereal grains and other seeds with advanced molecular techniques.