During eating, foods are submitted to two main oral processes-chewing, including biting and crushing with teeth, and progressive impregnation by saliva resulting in the formation of a cohesive bolus and swallowing of the bolus. Texture influences the chewing behavior, including mastication and salivation, and in turn, these parameters influence texture perception and bolus formation. During this complex mouth process, flavor compounds are progressively released from the food matrix. This phenomenon is mainly dependent on the food texture, the composition and in-mouth breakdown, and on saliva impregnation and activity, but an individual's anatomical and physiological aspects characteristics should also be taken into account. This article reviews the knowledge and progresses on in-mouth processes leading to food breakdown and flavor release and affecting perception. Relationships between food texture and composition, food breakdown, oral physiology, and flavor release are developed and discussed. This review includes not only the mechanical aspects of oral physiology but also the biological aspects such as the influence of saliva composition, activity, and regulation on flavor perception. In vitro and in silico approaches are also described.

The effect of textural modifications of solid milk gels on in vivo aroma release and aroma perception was investigated with a panel of 14 subjects. Great inter-individual differences were observed on aroma-release data, and the consequences of these differences on aroma perception were studied. From a hierarchical cluster analysis performed with several parameters extracted from release curves, the subjects were gathered into two groups, and a specific aroma-release profile was identified for each one. Then, by using a sensory profile, we showed that the intensity of the aroma perception was dependent on the release profile presented by the panelist. Second, we observed that, during the chewing phase, the aroma was perceived as more intense for the firmer gel and for panelists for whom the aroma release begins during the chewing of the product.

Using atmospheric pressure chemical ionization-mass spectrometry, aroma release was investigated in vivo and in vitro from three cheese-like gels with different hardnesses. In vivo, nosespace experiments were performed with 14 subjects. Results showed that the harder gel induced a greater and a faster release of all aroma compounds. In vitro, aroma release was followed in a mouth simulator where breakdown was mechanically produced. The same rate of stirring was applied to the three gels. In these conditions, we found that the amount of aroma released from the three gels was not discriminant. Thus, modification of gel structure had a strong impact on in vivo aroma release, but structural variations alone were not sufficient to induce a greater release. Natural breakdown provided by panelists during food consumption and adapted to the texture of the food was proposed to be the key parameter affecting in vivo aroma release.

International audienceIn humans, oral food consumption is by far the most important point where food's organoleptic properties can be perceived and can elicit sensory pleasure. It is also the ultimate stage of the food supply chain and the beginning of the food disintegration and digestion process. However, in regard to the influence of ageing on food oral processing, this topic has been mainly investigating through mastication, whereas salivation remains largely unexplored. The present experiment aimed at studying the impact of normal ageing on salivary flow taking into account the dental status and the number of drugs taken by the elderly people. This was achieved by comparing resting and stimulated salivary flows of young versus healthy elderly adults (i.e., autonomous elderly people without acute pathology). Ninety-three young adults (22-55 years old) and 84 elderly people (70-92 years old) underwent a measurement of resting and stimulated salivary flows and an oral examination (teeth counting; functional unit counting i.e., counting occluding tooth pairs). The present study showed an average 38.5% reduction of resting salivary flow and 38.0% reduction of stimulated salivary flow in healthy elderly people compared to young adults. This reduction was observed independently of the dental status and drug intake: elderly people presented reduced salivary flow even if they did not take any drugs or if their dental status was similar to the one of the young adults. The results also highlight a large inter-individual variability both in young and elderly adults.PRACTICAL APPLICATIONS During oral food consumption, saliva plays a key role in the acceptance of food and beverage by modulating the perception of texture, taste and aroma, as well as providing eating comfort by assisting the food breakdown process into a bolus that can be safely swallowed. However, in regard to the influence of ageing on food oral processing, the present results demonstrate a reduced salivary flow in healthy elderly people. Consequently, there is a need for developing foods tailored to the salivary capacities of elderly people aside from the efforts put into the development of foods tailored to the mastication and swallowing abilities of this population. In fact, in the context of an ageing population, the development of products meeting an elderly person's functional capacities becomes a major challenge for the food industry as well as for society

Aroma perception is a determinant factor in food choices and acceptability by consumers. To be perceived, aroma compounds must be released in the mouth during food breakdown, transferred into the nasal cavity to reach the olfactory receptor and then be perceived. So, in order to control aroma perception, knowledge of the main factors that can influence in-mouth aroma release is of major importance. Focusing on dairy products, this review article investigates the factors due to: (i) food products, and mainly the influence of food composition and structure on aroma retention and release; (ii) the interindividual variability of subjects, mainly chewing behaviour, saliva rate and composition and their influence on aroma release; and (iii) the interactions between food products and subjects and their impact on aroma release and perception. We also discuss the various instrumental and sensory methodologies that are often used to study aroma-texture interactions in dairy products, with particular focus on articles that compare in vivo aroma release and perception in dairy products. This review emphasizes that the relationship existing between in vivo aroma release and perception in dairy products is strongly dependent on the type of texture relative to two mechanisms; physicochemical mechanisms based on the modification of aroma release and a cognitive mechanism based on aroma-taste-texture interactions. These two mechanisms exist simultaneously but have more or less impact on aroma perception, depending on the type of texture.

The aim of this work was to clarify the influence of the properties (firmness and fat content) of a solid processed model cheese on in vivo aroma release while considering the role of the in‐mouth process during both mastication and post‐swallowing steps, and the hydrophobicity of aroma compounds, on a large number of well characterized subjects. In vivo aroma release was studied on 44 subjects who freely consumed six processed model cheeses flavoured with the same concentration of nonan‐2‐one and ethyl propanoate. Globally, an increase in firmness induced an increase in chewing duration, amount of saliva incorporated into the food bolus, total amount of aroma released and rate of release. The kinetics of release clearly differed between the two aroma compounds. Ethyl propanoate presented a higher release rate for firmer cheese and was more released during the mastication step, whereas nonan‐2‐one was more released during the post‐swallowing step and more persistent in the mouth, due to its higher hydrophobicity. Consuming cheeses with a higher fat content led to a higher amount of product remaining in the mouth after swallowing, a lower amount of nonan‐2‐one released and a longer persistence of nonan‐2‐one in the breath. The results could be helpful to better understand the relative influence of the parameters related to products and subjects in order to reformulate foods with good sensory acceptability. Copyright © 2012 John Wiley & Sons, Ltd.

The chewing process transforms food into bolus for a safe swallow. It is known that humans adapt their chewing behavior to food product characteristics. This study aimed at identifying individual chewing strategies of healthy consumers and determining the respective consequences on bolus properties. For that purpose, the chewing activity of 50 subjects was recorded during consumption of five model cheeses. Boluses were collected at the swallowing threshold for rheological analyses. We found that 30% of subjects showed only slight adaptation of chewing activity to product characteristics and thus produced boluses with different rheological properties. Among the 70% of subjects who adapted their chewing behavior, 57% adapted their behavior via chewing time and 40% adapted their behavior via chewing time and muscular contraction amplitude. Among the bolus rheological parameters, only consistency was not influenced by chewing strategies. Hence, it seemed to be a determinant factor of the swallowing threshold for these products. PRACTICAL APPLICATIONS Flavor compounds are released during the oral processing of food. It is thus important to understand how consumers form a bolus and to analyze the consequences of chewing behaviors on bolus properties at the swallowing threshold, at the end of the oral stage of food, to clarify the role of mastication in the release of stimuli responsible for perception. Chewing strategies and bolus properties are some of the key factors of flavor release and product acceptability that is of interest for food manufacturers who can use these factors as additional parameters for new solid product design.

We hypothesized that food texture modifications might alter anticipatory reflexes, feeding behavior, and the postabsorptive consequences of ingestion. Two sets of complete meals with different textures but the same macronutrient composition were prepared. The first set was either a soup containing chunks of food (mixture) or the same soup blended until smooth (purée). The second set was either a rusk (R), a sandwich loaf (SL), or a liquid rusk meal (LR). We measured hunger and fullness feelings after ingestion of each food in a calibrated lunch, the ingestion rate, the duration between lunch and a spontaneous dinner request, the energy value, and the macronutrient composition of the ad libitum dinner. We also studied plasma modifications and respiratory gas exchanges from lunch to dinner. Feelings of hunger and fullness were not affected by texture modifications. The purée soup was consumed faster than the mixture (P < 0.05), and insulin, triacylglycerol, and energy expenditure were greater with the purée (P < 0.05). LR was less palatable than the other rusk lunch versions (P < 0.001), and R was ingested more slowly (P < 0.05). The lowest increase in plasma glucose occurred with SL, and the highest energy expenditure was seen with LR (P < 0.05). In humans, food texture modification affects not only eating patterns and palatability of ingestants but also metabolic management.