A secret of salivary secretions: Multimodal effect of saliva in sensory perception of food

Overview of mouthfeel from the perspective of sensory scientists in industry

Mouthfeel is vital in consumer acceptance of foods and beverages. Despite the critical role mouthfeel plays in product development, the concept is often poorly understood and subject to various interpretations. Within this review, five topics of interest are discussed to provide a better understanding of the mouthfeel attribute-the definition, the perception, the importance, the influencing factors, and the methods of measurement of mouthfeel. Mouthfeel encompasses multiple attributes. Although mouthfeel attributes perceived through physical and chemical perceptions, such as cooling and heating, are understood as mouthfeel, attributes perceived through mechanoreceptors, such as creaminess and thickness, are more challenging due to varying opinions on texture and mouthfeel. Other factors, like food composition and temperature, are also vital in understanding the overall effect of mouthfeel in food and beverages. Including all perceived attributes and factors is important for consumer acceptance of products and for developing consistent evaluation of products. Other topics to consider include the dynamic aspects of oral processing and cultural backgrounds as these topics create additional intricacies in defining and understanding mouthfeel perception. Despite the lack of instrumental methodology available to measure mouthfeel attributes, trained panelists can be used to predict facets of mouthfeel in the eating experience. When designing sensory testing for trained panelists, experimental conditions and a product-specific lexicon are important factors to consider. Overall, understanding of the mouthfeel attributes and their role in consumer preference for different types of food and beverages continues to evolve.

The zinc receptor, ZnR/GPR39, modulates taste sensitivity by regulating ion secretion in mouse salivary gland

Reduced saliva secretion, dry mouth, and loss of taste are debilitating symptoms associated with zinc deficiency. A mechanism for zinc regulation of these processes is lacking. Here, we identified the Zn2+ sensing receptor ZnR/GPR39 as a mediator of ion transport in salivary gland epithelium. By monitoring transport of NH4 +, a surrogate for K+, we revealed that Zn2+ upregulates the Na+/K+ ATPase pump activity in parotid and submandibular salivary gland epithelium from wildtype (WT), but not from ZnR/GPR39 knockout (KO), mice. Since Na+/K+ ATPase activity is crucial for solute transport, we compared saliva composition in WT and ZnR/GPR39 KO mice and found impaired ionic concentration and reduced saliva secretion in ZnR/GPR39 KO mice. Moreover, mice deficient in ZnR/GPR39 exhibited decreased sensitivity to appetitive Na+ concentrations. Altogether, we demonstrate that salivary ZnR/GPR39 activity controls saliva ion composition and secretion, and provides a target for therapeutic approaches for dry mouth and taste disorders.

Volitional Control of Chewing Frequency Affects Food Oral Processing and Texture Perception

BACKGROUND

Although varieties in chewing patterns are essential for the transformation of food in mouth and thereby its sensorial perception, there are few reports that show the effect of chewing frequency on food oral processing and its properties.

OBJECTIVE

The current study tested whether consciously controlled chewing frequency influences the oral processing of habitually consumed foods and their sensory analysis.

METHOD

Chewing behaviour was analysed during the mastication of mushed potato samples by 20 participants in two separate test sessions, in which they were instructed to chew the sample in their habitual manner (free chewing test) or follow a preprogrammed video animation displayed on a screen, wich guided them to maintain a constant chewing frequency (F-const chewing test). Electromyography recording, sensory tests and rheological analysis of bolus properties were performed.

RESULTS

Oral processing in the F-const chewing test required longer chewing time due to the elongation of chewing cycle time, rather than an increased number of chews. The contribution of jaw muscle activity to chewing effort changed resulting in greater activity of temporalis muscle in the F-const chewing test. During volitional control of chewing frequency, the texture perception with respect to cohesiveness, adhesiveness and moisture scoring differed from that observed in habitual chewing, despite the similar physical properties of the bolus. These variabilities resulted in higher acceptability of the food sample.

CONCLUSION

Since this study clearly shows how control of chewing frequency led to changes in oral processing of food and its sensorial properties, nutritionists can employ the findings to optimise the dietary recommendations decreasing eating rate and increasing palatability of the target products.

Aromatic Profiling of New Table Grape Varieties Using Gas Chromatography/Mass Spectrometry and Olfactometry

The aim of this study is the aromatic characterization of new table grape varieties, namely Guzun (V. vinifera), Melona (V. vinifera), Cotton Candy (V. vinifera), IVC SA3 (V. labrusca), and IVC SB1 (V. labrusca). The qualitative and quantitative analysis of odorant molecules present in the berries allows for the definition of the aroma profile of the grape. This analysis benefits from the progress of analytical techniques and sensory methodologies. Gas chromatography/mass detection enable the efficient detection of the substances present and their concentrations. Through the coupling of gas chromatography with sensory detection (gas chromatography-olfactometry), it is possible to correlate the compounds detected by gas chromatography with olfactory stimuli, exploiting the human olfactory system. Aroma, a significant flavor component, is an important attribute of table grape that contributes to defining their quality. This characteristic is highly valued by consumers, and consequently, the market asks for table grapes with a particular or new aroma. Aromatic characterization is a crucial step in the study of the table grape varieties to evaluate their potential at the commercial level or, for instance, in breeding programs focusing on organoleptic properties.

What Is Chalky? Investigating Consumer Language and Perception of Fine Particles in Beverages Containing Pea and Potato Starch

Despite its importance as an undesirable food texture, the phenomenon of chalkiness remains understudied. Chalky sensations presumably arise from fine particulates found in foods, but semantic overlap with other common descriptors of small particles, like gritty or sandy, is unclear. Here, we compare the usage of Chalky with related descriptors, and determine the effect of particle size, concentration, and xanthan content on Chalky ratings in a model beverage. A 23 factorial design with starch particle size (D90 = 33.8 and 64.6 µm), starch concentrations (10 and 20% w/v), and xanthan content (0.075 and 0.15% w/v) was used. Participants' salivary flow rate was also assessed. A multi-sip taste test was performed where naïve consumers (n = 82; 39% men, 60% women; age range = 18-79 years) rated the intensity of Chalky, Powdery, Gritty, Sandy, Mouthdrying, and Residual mouthcoating at 0, 30, and 60 s after each of three consecutive sips. All attribute ratings were highly correlated, with Chalky, Powdery, and Residual Mouthcoating being more closely correlated with each other than Gritty or Sandy. Although Chalky was still reported 60 s after consumption, no evidence of build-up was found with repeated sips. A larger size and higher concentration increased Chalky ratings, with the low-salivary-flow group reporting greater ratings for Chalky relative to the high-flow group. Our results suggest consumer percepts of small particles are overlapping but not entirely redundant. This suggests researchers and product developers should carefully distinguish between these descriptors when trying to understand consumer perception of food products containing fine particles.

Umami Altering Salivary Proteome: A Study across a Sensitivity Spectrum on Subjects

This study delved into the relationship between umami taste sensitivity (UTS) and variations in the salivary proteome among 12 healthy nonsmokers utilizing 4D data-independent acquisition-based proteomics. By assessing UTS through monosodium l-glutamate (MSG) detection thresholds, we discovered notable differences: individuals with high UTS detected umami at significantly lower MSG concentrations (0.20 ± 0.12 mM) compared to their low UTS counterparts (2.51 ± 1.21 mM). Both groups showed an upregulation of the S100A1 protein under MSG stimulation, indicating a potent biochemical response to umami stimuli. The high UTS group exhibited enhanced metabolic pathways including those for amino acid, lipid, and organic acid biosynthesis, essential for maintaining taste receptor functionality and enhancing signal transduction. This group also demonstrated increased activity in cytochrome P450 enzymes and ribonucleoprotein complexes, suggesting a readiness to manage metabolic challenges and optimize umami perception. In contrast, the low UTS group showed adaptive mechanisms, possibly through modulation of receptor availability and function, with an upregulation of structural and ribosomal proteins that may support taste receptor production and turnover. These findings suggest that varying biological mechanisms underpin differences in umami perception, which could significantly influence dietary preferences and nutritional outcomes, highlighting the intricate interplay of genetic, physiological, and metabolic factors in taste sensitivity.

Influence of masticatory side switch frequency on masticatory mixing ability and sensory perception in adults with healthy dentitions: A randomized crossover trial

STATEMENT OF PROBLEM

The advantages and disadvantages of frequently changing sides while masticating remain unclear.

PURPOSE

The purpose of this clinical study was to determine the effect of varying the frequency of masticatory side switches on masticatory mixing ability and sensory perception in dentate adults.

MATERIAL AND METHODS

This nonblinded, randomized 12-period crossover study, conducted at Barcelona Dental School from January to March 2022, included 36 healthy adults with natural dentitions (median age, 23.5 years; 26 women). Participants were randomly allocated to 12 sequences and performed 12 masticatory assays masticating a 2-colored gum for 40 cycles each using the following masticatory styles as interventions: freestyle, unilateral right, unilateral left, and switching sides 5%, 15%, and 25%. The primary outcome was the mixing ability index (MAI), defined as the standard deviation of the red channel intensity of the masticated gum in the color-histogram plugin of the ImageJ software program. Participants also rated the perceived flavor intensity and salivary flow on a visual analog scale. Data were analyzed by repeated measures analysis of variance (α=.05).

RESULTS

The MAI was similar for all masticatory styles (P=.63). Participants perceived greater flavor intensity (mean difference: 8%, 95% CI: 1% to 15%) and salivary flow (mean difference: 11%, 95% CI: 0% to 21%) with 25% side switching compared with freestyle or unilateral mastication.

CONCLUSIONS

Frequently switching the masticatory side while masticating gum does not alter the mixing ability, but it appears to enhance salivary flow and flavor intensity.

Resolution enhancement of tongue tactile image based on deconvolution neural network

To reproduce the tactile perception of multiple contacts on the human tongue surface, it is necessary to use a pressure measurement device with high spatial resolution. However, reducing the size of the array sensing unit and optimizing the lead arrangement still pose challenges. This article describes a deconvolution neural network (DNN) for improving the resolution of tongue surface tactile imaging, which alleviates this tradeoff between tactile sensing performance and hardware simplicity. The model can work without high-resolution tactile imaging data of tongue surface: First, in the compression test using artificial tongues, the tactile image matrix (7 × 7) with low resolution can be acquired by sensor array with a sparse electrode arrangement. Then, through finite element analysis modeling, combined with the distribution rule of additional stress on the two-dimensional plane, the pressure data around the existing detection points are calculated, further expanding the tactile image matrix data amount. Finally, the DNN, based on its efficient nonlinear reconstruction attributes, uses the low-resolution and high-resolution tactile imaging matrix generated by compression test and finite element simulation, respectively, to train, and outputs high-resolution tactile imaging information (13 × 13) closer to the tactile perception of the tongue surface. The results show that the overall accuracy of the tactile image matrix calculated by this model is above 88%. Then, we deduced the spatial difference graph of the resilience index of the three kinds of ham sausages through the high-resolution tactile imaging matrix.

Effects of TUG-891, a potent GPR120 agonist, on the physical and oral lipid- coating properties, and secretion of saliva

GPR120 agonists were recently shown to enhance the fatty orosensation in humans when added to vegetable oil or a low-fat food system, but did not evoke it by themselves. Furthermore, an emulsion prepared from vegetable oil had a stronger fatty orosensation than that prepared from mineral oil even though the physical properties of both emulsions were similar. To clarify the mechanisms underlying the enhancement of the fatty orosensation by GPR120 agonists, the present study investigated the effects of TUG-891, a potent GPR120 agonist, on physical and oral lipid-coating properties and the secretion of saliva. The addition of TUG-891 to a vegetable oil emulsion did not significantly change its physical properties, such as viscosity, particle distribution, interfacial tension, contact angle, frictional load, and ζ-electric potential, or the amount of the lipid coating remaining in the oral cavity. These results indicate that TUG-891 enhanced the fatty orosensation without changing the physical or oral lipid-coating properties of the emulsion. The addition of TUG-891 to a vegetable oil emulsion and whipped cream significantly increased the amount of saliva secreted. Therefore, TUG-891, a potent GPR120 agonist, may enhance the fatty orosensation by increasing the amount of saliva secreted.

Effect of Hogweed Pectin on Rheological, Mechanical, and Sensory Properties of Apple Pectin Hydrogel

This study aims to develop hydrogels from apple pectin (AP) and hogweed pectin (HP) in multiple ratios (4:0; 3:1; 2:2; 1:3; and 0:4) using ionotropic gelling with calcium gluconate. Rheological and textural analyses, electromyography, a sensory analysis, and the digestibility of the hydrogels were determined. Increasing the HP content in the mixed hydrogel increased its strength. The Young’s modulus and tangent after flow point values were higher for mixed hydrogels than for pure AP and HP hydrogels, suggesting a synergistic effect. The HP hydrogel increased the chewing duration, number of chews, and masticatory muscle activity. Pectin hydrogels received the same likeness scores and differed only in regard to perceived hardness and brittleness. The galacturonic acid was found predominantly in the incubation medium after the digestion of the pure AP hydrogel in simulated intestinal (SIF) and colonic (SCF) fluids. Galacturonic acid was slightly released from HP-containing hydrogels during chewing and treatment with simulated gastric fluid (SGF) and SIF, as well as in significant amounts during SCF treatment. Thus, new food hydrogels with new rheological, textural, and sensory properties can be obtained from a mixture of two low-methyl-esterified pectins (LMPs) with different structures.

Recent trends in aroma release and perception during food oral processing: A review

The dynamic and complex peculiarities of the oral environment present several challenges for controlling the aroma release during food consumption. They also pose higher requirements for designing food with better sensory quality. This requires a comprehensive understanding of the basic rules of aroma transmission and aroma perception during food oral processing and its behind mechanism. This review summarized the latest developments in aroma release from food to retronasal cavity, aroma release and delivery influencing factors, aroma perception mechanisms. The individual variance is the most important factor affecting aroma release and perception. Therefore, the intelligent chewing simulator is the key to establish a standard analytical method. The key odorants perceived from the retronasal cavity should be given more attention during food oral processing. Identification of the olfactory receptor activated by specific odorants and its binding mechanisms are still the bottleneck. Electrophysiology and image technology are the new noninvasive technologies in elucidating the brain signals among multisensory, which can fill the gap between aroma perception and other senses. Moreover, it is necessary to develop a new approach to integrate the relationship among aroma binding parameters, aroma concentration, aroma attributes and cross-modal reactions to make the aroma prediction model more accurate.

Retronasal Aroma of Beef Pate Analyzed by a Chewing Simulator

In retronasal aroma, the targeted aroma compounds are released from food during chewing. The changes in the food structures during chewing strongly influence the release of the compounds, therefore affecting the perception of food. Here, the relationship between retronasal aroma and food deliciousness based on the physicochemical properties of aroma compounds was examined. We considered the consumption of solid foods and the effect of oral parameters in elderly people. Beef pate was used as a model food sample to study the effect of the release of aroma compounds under controlled in vitro mastication and salivation conditions using a chewing simulator. We identified the effects of coexisting ingredients such as beef fat on the time course behavior of the release of aroma compounds. In particular, the release of the middle types of aromas was significantly faster with stronger chewing force, and higher with a high fat content of the sample. In addition, a larger release intensity was observed when soy proteins were partially substituted for beef proteins. Using an appropriate model saliva, a change in the salting-out effect from the saliva composition was found to be a factor, which could explain the lowering of aroma sensation in an elderly person.