Saliva Incorporation Research Articles

Impact of saliva incorporation on the rheological properties of in vitro gastric contents formulated from sour cream.

Rheological properties of gastric contents depend on the food ingested, and on the volume and composition of secretions from the host, which may vary. This study investigates the impact of saliva regular incorporation in the stomach after a meal on the rheological properties of gastric contents, considering two levels of salivary flow (low = 0.5 and high = 1.5 mL/min). In vitro chymes were obtained by mixing sour cream, simulated gastric fluid, two different volumes of oral fluid (at-rest human saliva, SSF for Simulated Salivary Fluid or water) and adjusting pH at 3. Chymes samples were characterized at 37°C for their particle size and rheological properties. Overall, particle size distribution was not different between samples: incorporating a larger volume of saliva resulted in more heterogeneity, but the surface area moment D[3,2] and volume moment D[4,3] did not differ significantly with the oral fluid type. Shear viscosity of chyme samples was higher when saliva was incorporated, in comparison with water or SSF. In addition, as shown from data extracted at = 20 s-1 the higher the fluid volume the lower the shear viscosity, which is attributed to a dilution effect. However, this dilution effect was attenuated in the case of saliva, most likely due to its composition in organic compounds (e.g., mucins) contributing to the rheological properties of this biological fluid. In these in vitro conditions, both saliva and the salivation rate had a significant but slight impact on the rheological properties of gastric contents (of the order of 1-5 mPa s at = 20 s-1).

The influence of different cooking treatments on vegetables’ bolus properties

The influence of boiling, steaming, grilling and sous-vide treatments on bolus properties of vegetables was investigated. Cooking produced potato boluses with large particles or pasty boluses unsuitable for analysis. Celeriac preserved its brittleness and produced more small particles as mastication prolonged. Eggplant and zucchini were similar and both produced relatively large particles throughout the mastication. Saliva incorporation results showed an uncommon trend since boluses from the moment of swallowing did not have the highest moisture content. It was inferred that boiling had similar effects as steaming on one side, and grilling had similar effects as sous-vide on the other.

What is the food like that people choke on? A study on food bolus physical properties under different in vitro oral capacities

People with oral impairments, such as poor denture status, poor muscle strength, and poor salivary secretion, have more difficulties performing oral processes, which results in the risk of choking. In this study, we aimed to understand, in vitro, how different oral impairments can affect the oral processing of food reported as a choking hazard. Six foods that frequently cause choking were selected and studied, varying three in vitro factors at two levels—saliva incorporation amount, cutting activity, and compression action. The median particle size (a50) and the particle size heterogeneity (a75/25) of the food fragmentation, the hardness, and adhesiveness of the bolus formation, and the final cohesiveness of the bolus were studied. The results showed that all the parameters studied varied depending on the food product. High compression reduced a50 (except in mochi that increased) and a75/25 (except in eggs and fish) but increased bolus adhesion and particle aggregation (except for mochi). Regarding cutting activity, when performing a greater number of strokes, the particle size for sausage and egg, and the hardness of the bolus for mochi and sausage were lower. In contrast, for some food products, the bolus adhesiveness (bread) and particle aggregation (pineapple) were higher at a high number of strokes. The amount of saliva also played an important role in the creation of the bolus. When high amounts of saliva were added, the a50 values (mochi) and hardness (mochi, egg, and fish) decreased; and increased the adhesiveness (mochi) and particle aggregation (bread, pineapple, and sausage). When all oral factors are compromised (lack of muscle strength, denture status, and saliva secretion), some food products create a choking hazard as individuals cannot achieve the right particle size, bolus cohesiveness, and mechanical properties of the bolus to be safe to swallow, there is still a need to elaborate a guide, considering all the safety parameters.

The heat is on: Consumers modify their oral processing behavior when eating spicy foods

Food texture properties and consumer characteristics influence oral processing behaviors. Little is known about oral processing behavior of pungent spicy foods. In two experiments, we investigated how adding ground dried chilies to tomato soup or beef patties and curried rice altered oral processing behaviors. In Experiment One, tomato soups differing in concentration of added ground dried chilies (0.01, 0.03, 0.20 or 0.40% w/w) were consumed (n = 23). In Experiment Two, lunch meals that differed in added ground dried chilies consisting of beef patties (0.0, 0.6 or 1.2% w/w) and curried rice (0.0, 0.4 or 1.0% w/w) were consumed (n = 49). Sip/bite sizes were determined using hidden balances. Oral processing behavior was quantified using video recordings followed by post hoc annotations of specific behaviors. When eating tomato soup, increasing oral burn was associated with increasing number of water sips, water intake and total time between sips. For the solid meals (beef patties and curried rice), increasing oral burn was associated with increased time between bites and total sips of water; conversely, total oral exposure time, total number of chews and number of chews per bite all decreased with greater burn. Saliva content and rate of saliva incorporation into the solid food bolus increased with added ground dried chilies while oral exposure time decreased. We conclude consumers adapt their oral processing behaviors to oral burn of solid foods by reducing oro-sensory exposure time, chewing bites less, increasing time between bites, and consuming more water, potentially to mitigate the discomfort associated with the burn imparted by ground dried chilies.

Understanding relations between rheology, tribology, and sensory perception of modified texture foods.

The aim of this work was to examine relations between instrumental and sensory parameters in a texture modified food matrix, with and without saliva. Nine pureed carrot samples (eight thickened and a control) were developed with starch (0.4 and 0.8% wt/wt), xanthan (0.2 and 0.4% wt/wt) or starch-xanthan blends that met International Dysphagia Diet Standardisation Initiative (IDDSI) Level 4 guidelines using fork and spoon tests. Rheological and tribological tests were conducted on the food and simulated bolus prepared by adding fresh stimulated saliva to the food (1:5, saliva:food) to mimic oral processing. Perceived sensory properties were identified using a temporal dominance of sensations (TDS) test (n= 16) where panelists were given a list of nine attributes. The area under the curve was extracted from TDS curves for each attribute/sample and this was correlated with rheological (viscosity at 10s-1 , G', G″, and tan δ at 1 Hz) and tribological (friction coefficient in three regimes) data. The viscosity of the control sample decreased after adding hydrocolloids (except Starch_0.8%) and with saliva incorporation. G' and G″ either increased or were similar for xanthan and blends and decreased for starch-thickened samples. Hydrocolloid addition increased friction for all samples and was higher with saliva addition. Sensory results showed that samples with starch were perceived as thick and grainy while xanthan was perceived as smooth and slippery. A greater number of sensory attributes correlated with viscoelastic parameters compared to friction coefficients. Correlations were highest with the saliva added samples, further highlighting the importance of including saliva during instrumental testing.

Analysis of Pungency Sensation Effects from an Oral Processing, Sensorial and Emotions Detection Perspective—Case Study with Grilled Pork Meat

Pungency is an interesting sensory stimulus analyzed from different perspectives, in particular the underpinning mechanisms of its sensation and perception. In this study, grilled pork meat coated with three types of hot sauces were investigated regarding its main food oral processing characteristics and evaluated using time-intensity and temporal dominance of pungency sensations methods analyzing the pungency descriptors and intensities. Besides these methods, facial expressions obtained from video capturing were subject to emotion detection. Mastication parameters showed a slight, but not statistically significant, trend of an increased number of chews and consumption time associated with pungency intensity, while saliva incorporation indicated an increasing trend depending on the pungency intensity, especially after 25 strokes and before swallowing. Both time intensity and temporal dominance of pungency sensations showed that the complexity of understanding these sensations is in relation to intensity and type. Finally, the use of emotion detection software in analyzing the faces of panelists during mastication confirmed the increase in non-neutral emotions associated with the increase in pungency intensity.

Relationship between masticatory variables and bolus characteristics of meat with different textures.

The physiological transformations that happen during oral processing are complex and challenging to capture and measure; however, their knowledge can help design new products for people who struggle with mastication and swallowing. Here we relate chewing, saliva incorporation and bolus properties with initial meat texture. Three different textures (T1-tender, T2-intermediate, T3-tough) were created by cooking meat in different temperature time combinations and "ready-to-swallow" meat boluses were collected from 10 healthy individuals. Masticatory variables, saliva incorporation, and bolus mechanical and geometrical characteristics were analyzed. Meat texture showed significant effect on masticatory variables (number of chews and chewing duration) but not on saliva incorporation. Bolus mechanical characteristics (hardness, cohesiveness and adhesiveness) varied significantly (p< .05) with meat texture, where meat with a harder texture resulted in a harder bolus. Number of bolus particles changed significantly (p< .05) with increasing meat hardness, where harder meat produced more bolus particles. Significant (p< .05) intersubject variability was recorded for masticatory parameters and saliva incorporation. Mechanical and geometrical characteristics of "ready-to-swallow" meat bolus did not vary among subjects.

Effect of varietal differences on the oral processing behavior and bolus properties of cooked rice

Abstract This research explored the impact of in-vivo oral processing on the bolus properties of three rice varieties [white ponni (WP), mappillai samba (MS), and basmati (B)] that were selected based on variations in the amylose content. The amylose and dry matter content of the WP, MS, and B were 4.67, 7.48, and 13.8(%) and 69.57, 60.09, and 70.47(%), respectively. Mastication features (bite-size, chewing time, and chew cycles), bolus properties (particle size distribution, bolus moisture content, rheology, and starch hydrolysis), time-dependent bolus features (rate of incorporation of saliva and saliva content) and, temporal dominance of sensation (TDS) of cooked rice were studied. Results confirmed the significance of oral processing on various bolus characteristics. Moreover, a pronounced correlation between the morphology of rice varieties and mastication features was observed. The structure and textural characteristics of the different rice varieties (MS, WP, B) showed considerable effects on the consumption time (25.7 s, 22.2 s, 17.8 s) and chewing cycles (34, 31, 23). Rate of saliva incorporation was relatively lesser for MS as compared with WP and B. Solid loss followed the trends WP &gt; MS &gt; B. The total starch content of cooked rice boluseswas WP (82.69 ± 0.01%), MS (79.49 ± 0.01%), and B (71.74 ± 0.01%). Further, texture – TDS and flavor – TDS of all varieties were found to be strongly dependent on textural attributes, composition, and oro-sensory perception. This study provides a significant understanding of the oral processing behavior of rice and its bolus, considering the effect of variations in amylose content, texture, and morphology.

How do culinary methods affect quality and oral processing characteristics of pork ham?

The influences of three different culinary methods: cooking, sous vide and grilling were studied with regards to quality and oral processing characteristics of pork ham. Besides instrumental analysis of color and textural properties of pork ham, sensory panel with 12 trained panelists participated in temporal dominance of sensations, oral processing analysis, boluses collection, particle size distribution analysis, and saliva incorporation. The results revealed that number of chews, mastication time and saliva incorporation are correlated with textural properties and cooking losses. In-mouth sensation was intertwined with juiciness, fibrousness and firmness depending on the culinary methods. Cooked pork ham showed highest results for hardness and cooking loss. Firmness and fibrousness were dominant sensory attributes. Sous-vide results show that firmness and juiciness dominated during the first third of consumption time. This corresponds with textural values for lowest values for hardness and cooking, number of chews and total exposure time. Sous-vide also resulted in lower values for number of chews and total exposure time associated with oral processing.

Influence of meat texture on oral processing and bolus formation

Changes that happen with aging have an effect on food texture perception and oral processing behaviour. Mastication and saliva incorporation are two major aspects of oral processing which can be used to evaluate the texture perception of food. This study aimed to investigate inter-oral responses of healthy individuals during chewing in relation to cooked meat texture. Mastication variables were recorded during the chewing process and boluses were collected and analysed for saliva impregnation and particle size distribution. Increasing hardness of meat did not change the number or duration of chewing cycles, but particle breakdown was significantly increased (P < 0.05) with the hardness of meat. As a result more saliva was required to agglomerate harder particles in order to make a safe swallow cohesive bolus. Two different groups were identified in relation to texture responses where one group was able to swallow samples with less saliva incorporated into it and cohesiveness was due to less fragmented muscle fibres and meat juice whereas other group had relatively higher saliva incorporation to obtain cohesiveness of particles.

Tribology and its growing use toward the study of food oral processing and sensory perception.

Here we provide a comprehensive review of the knowledge base of soft tribology, the study of friction, lubrication, and wear on deformable surfaces, with consideration for its application toward oral tribology and food lubrication. Studies on "soft-tribology" have emerged to provide knowledge and tools to predict oral behavior and assess the performance of foods and beverages. We have shown that there is a comprehensive set of fundamental literature, mainly based on soft contacts in the Mini-traction machine with rolling ball on disk configuration, which provides a baseline for interpreting tribological data from complex food systems. Tribology-sensory relationships do currently exist. However, they are restricted to the specific formulations and tribological configuration utilized, and cannot usually be applied more broadly. With a careful and rigorous formulation/experimental design, we envisage tribological tools to provide insights into the sensory perception of foods in combination with other in vitro technique such as rheology, particle sizing or characterization of surface interactions. This can only occur with the use of well characterized tribopairs and equipment; a careful characterization of simpler model foods before considering complex food products; the incorporation of saliva in tribological studies; the removal of confounding factors from the sensory study and a global approach that considers all regimes of lubrication.

Polyethyleneimine and Chitosan Polymer-Based Mucoadhesive Liquid Crystalline Systems Intended for Buccal Drug Delivery

The buccal mucosa is accessible, shows rapid repair, has an excellent blood supply, and shows the absence of the first-pass effect, which makes it a very attractive drug delivery route. However, this route has limitations, mainly due to the continuous secretion of saliva (0.5 to 2L/day), which may lead to dilution, possible ingestion, and unintentional removal of the active drug. Nanotechnology-based drug delivery systems, such as liquid crystalline systems (LCSs), can increase drug permeation through the mucosa and thereby improve drug delivery. This study aimed at developing and characterizing the mechanical, rheological, and mucoadhesive properties of four liquid crystalline precursor systems (LCPSs) composed of four different aqueous phases (i) water (FW), (ii) chitosan (FC), (iii) polyethyleneimine (FP), or (iv) both polymers (FPC); oleic acid was used as the oil phase, and ethoxylated and propoxylated cetyl alcohol was used as the surfactant. Polarized light microscopy and small-angle X-ray scattering indicated that all LCPSs formed liquid crystalline states after incorporation of saliva. Rheological, texture, and mucoadhesive assays showed that FPC had the most suitable characteristics for buccal application. In vitro release study showed that FPC could act as a controlled drug delivery system. Finally, based on in vitro cytotoxicity data, FPC is a safe buccal drug delivery system for the treatment of several buccal diseases.

Eating behaviour explains differences between individuals in dynamic texture perception of sausages

Texture perception of foods has been demonstrated to be influenced by age, dental health and oral processing behaviour. Eating duration is a significant factor contributing to and determining food oral processing behaviour. The influence of eating duration on dynamic texture perception, oral processing behaviour and properties of the food bolus have not been investigated extensively. The aims of this study are (i) to determine the influence of naturally preferred eating duration on dynamic texture perception of sausages and (ii) to explain differences in dynamic texture perception between short and long duration eaters by chewing behaviour and bolus properties. Two groups of subjects were selected based on their natural eating duration for a controlled portion size of two sausages. The group of “long duration eaters” (n=11) took on average twice as long to consume a piece of sausage compared to the group of “short duration eaters” (n=12). Independent of eating duration, short and long eating duration subjects chewed sausages with the same chewing frequency (p=0.57) and muscle effort rate (p=0.15) during oral processing. Total muscle effort and total number of chews were significantly higher (p<0.05 for both) for long duration eaters mainly due to the longer eating time compared to short duration eaters. Bolus properties showed that short duration eaters did not break down the boli as much as long duration eaters resulting in fewer (p<0.001) and larger (p<0.05) sausage bolus fragments, firmer (p<0.001) and less adhesive (p<0.001) boli with lower fat content (p<0.05) and less saliva incorporation (p<0.001) at swallow compared to the bolus properties of long duration eaters. These differences in bolus properties influenced dynamic texture perception of the sausages as the bolus of short duration eaters revealed different properties than the bolus of long duration eaters. Temporal dominance of sensations (TDS) showed that short and long duration eaters perceived the same sausage similarly in the early stages of oral processing, but started to perceive the texture of the same sausage differently from the middle of oral processing towards the end. We conclude that short duration eaters did not compensate for their shorter eating duration by chewing more efficiently but were comfortable swallowing a less broken down bolus than long duration eaters. Moreover, we conclude that differences in eating behaviour between subjects can lead to differences in bolus properties of sausages causing differences in dynamic texture perception of the same sausage.

Impact of formulation and saliva on acid milk gel friction behavior.

Rheological analysis is commonly used to evaluate mechanical properties in studies of food behavior. However, rheological analysis is often insufficient to describe food texture as evaluated by descriptive sensory analysis. Additionally, traditional rheometry does not account for changes in food behavior as a function of saliva incorporation into the food during mastication. The objectives of this study were to evaluate friction behavior of acid milk gels with and without the addition of saliva, and to determine relationships between frictional behaviors and mechanical and sensory behaviors. Acid milk gels were prepared with 12.5% total solids comprising nonfat dry milk, whey protein isolate, waxy maize starch, and gelatin in different ratios. The addition of starch was found to have significant impact on acid milk gel frictional behavior. Addition of saliva resulted in a change in frictional behavior over the entire sliding speed range measured. Correlations were found between rheological, tribological, and sensory behavior, suggesting that an underlying mechanism may impact both viscosity and friction behavior. Additional study is needed to further explore the links between food structure, rheology, tribology, and sensory texture. Application of tribology in food science allows measurement of friction behavior of foods. Matching both rheological and tribological behavior is important to creating reduced-fat or reduced-sugar products with similar mouthfeel to the original product.

Food oral processing: Some important underpinning principles of eating and sensory perception

The oral processing of food is a dynamic process which involves a sequence of highly coordinated oral actions and gives desirable sensory experience. Even though this process is perceived to be routine, its governing principles are highly complicated and are still not fully understood. Based on some recent research findings, this paper reviews current understandings on some important issues associated with eating and sensory perception. The review begins with a short introduction to the background of eating studies. This is followed by four sections focusing on different aspects of eating and sensory perception: the important roles of saliva incorporation and implications; the basic features of oral dynamics and what does it mean to sensory perception; the underpinning physical principles of instrumental characterisation of food sensory properties; and finally the psychophysical principles of human sensation and perception.

パン摂食時における食塊への唾液の混入と嚥下誘発への関与

パン摂食時における食塊への唾液の混入と嚥下誘発への関与

Main individual and product characteristics influencing in-mouth flavour release during eating masticated food products with different textures: Mechanistic modelling and experimental validation

A mechanistic model predicting flavour release during oral processing of masticated foods was developed. The description of main physiological steps (product mastication and swallowing) and physical mechanisms (mass transfer, product breakdown and dissolution) occurring while eating allowed satisfactory simulation of in vivo release profiles of ethyl propanoate and 2-nonanone, measured by Atmospheric Pressure Chemical Ionization Mass Spectrometry on ten representative subjects during the consumption of four cheeses with different textures. Model sensitivity analysis showed that the main parameters affecting release intensity were the product dissolution rate in the mouth, the mass transfer coefficient in the bolus, the air–bolus contact area in the mouth and the respiratory frequency. Parameters furthermore affecting release dynamics were the mastication phase duration, the velopharynx opening and the rate of saliva incorporation into the bolus. Specific retention of 2-nonanone on mucosa was assumed to explain aroma release kinetics and confirmed when gaseous samples were consumed.

The dynamics of aroma compound transfer properties in cheeses during simulated eating conditions

In vivo aroma release during solid food consumption is a complex phenomenon that depends on food structure and composition, as well as on oral processing (combination of mastication and incorporation of saliva into the food product). The objective of this study was to understand and to predict the physico-chemical properties of aroma compounds through the dynamics of flavor release during in-mouth oral processing of food before bolus swallowing. Within this context, the evolution of two aroma compounds during bolus formation was explored by studying the two main properties that account for mass transfer: air/bolus partition and mass transfer coefficients. Four types of industrial cheese products (varying in fat and firmness) flavored with ethyl propanoate and 2-nonanone were chosen. Each matrix was mixed with various amounts of artificial saliva to mimic boluses at different stages of mastication. The air/bolus partition coefficient was determined by the static phase ratio variation method (PRV), while the mass transfer coefficient was obtained by non-linear regression from dynamic headspace experiments. Results showed that there is a dilution effect on the air/bolus partition coefficient and both a dilution and a product effect (firmness) on the mass transfer coefficient of ethyl propanoate in the bolus. These results were also validated with 2-nonanone for the low-fat cheeses.

In-mouth aroma compound release during cheese consumption: Relationship with food bolus formation

The present study describes the changes in mechanical properties and saliva incorporation for cheese samples with different composition and texture, and their influence on the rate of aroma release. Chewing work per cycle, salivary flow rate and chewing rate varied highly among subjects. Despite the differences in cheese hardness, at the end of mastication, bolus texture was the same for cheeses with the same lipid content. Low-fat cheeses gave harder bolus than high fat ones, despite being chewed longer, with higher work per cycle and more moisture. Salivary flow rate did not vary among cheese samples but, at the end of mastication, the amount of saliva in boluses differed depending on the hardness and fat content of cheeses. Differences in aroma release pattern between subjects could be explained by the combined effect of both chewing process and salivary flow rates.

Relationships between saliva and food bolus properties from model dairy products

During food consumption, complex oral processing occurs to transform the food into a bolus, ready to be swallowed. The objective of this study was to relate food, saliva and bolus properties, by using model dairy products, to better understand the role of saliva in bolus formation. Un-stimulated and stimulated saliva was collected from 5 subjects and biochemical and enzymatic properties were measured. Food bolus was then obtained from 8 different dairy products, varying in composition and ranging from liquid to gelled samples. The rate of saliva incorporation, pH, spreading ability and bolus rheological properties were determined. Some correlations seemed to exist between lysozyme activity and bolus properties. Subject and food product had a significant effect on almost all bolus properties. The rheology of bolus was highly correlated with food product texture. Even though preliminary, this approach could be used to better understand stimulus release and perception during food consumption.