Food oral processing is not only important for the ingestion and digestion of food, but also plays an important role in the perception of texture and flavor. This overall sensory perception is dynamic and occurs during all stages of oral processing. However, the relationships between oral operations and sensory perception are not yet fully understood. This article reviews recent progress and research findings on oral food processing, with a focus on the dynamic character of sensory perception of solid foods. The reviewed studies are discussed in terms of both physiology and food properties, and cover first bite, mastication, and swallowing. Little is known about the dynamics of texture and flavor perception during mastication and the importance on overall perception. Novel approaches use time intensity and temporal dominance techniques, and these will be valuable tools for future research on the dynamics of texture and flavor perception.

The relationships between food structure, texture perception and bolus properties during bolus formation are poorly understood. This preliminary single‐subject study on three biscuit recipes investigated the links between bolus macrostructure, perceived texture (using temporal dominance of sensations), and mechanical and rheological properties (using back extrusion and consecutive double compression) throughout mastication. The fracture properties of the biscuits dominated textural perception in the early stages of mastication. As mastication progressed, a sensory transition from dry to sticky was accompanied by an increase in “cohesiveness” and decreases in the consistency coefficient, peak force and “adhesiveness.” At the point of swallow, the boluses were shear thinning pastes and sticky dominated perception. Consistency coefficient and “cohesiveness” indicated different swallowing thresholds for the different recipes. This study found back extrusion to be a suitable method for characterizing biscuit bolus rheology in the later stages of mastication as it is unaffected by bolus dimensions. Practical Applications Mastication of a solid food involves the breakdown of the food and reassembly with saliva into a deformable bolus that can be swallowed safely. The relationships between the perceived texture and structural, mechanical and rheological properties throughout mastication are not well understood. An understanding of these relationships could aid in the design of foods that can be swallowed safely by the elderly or those with dysphagia, or foods that follow a desired oral processing path and thus have a desired texture profile or flavor release.

Sensory trajectories of foods can be described using the temporal dominance of sensations method (TDS). This study aims to investigate the influence of TDS on oral processing variables and understand the optimum number of subjects required for oral processing studies. The work was carried out with a solid model food system (biscuits). Formulation differences in the model biscuits influenced texture perception but did not affect oral processing parameters apart from chewing frequency. Completing the TDS task influenced both mastication duration and the number of chews, although the different natural chewing behaviors observed between products were not affected. Training of subjects resulted in quicker attribute selection and greater dominance rates being observed even though the resulting TDS curves were similar. Analysis using a correlation technique suggests that 15-20 untrained subjects may be required to generate useful TDS curves for oral processing research assessing food properties. PRACTICAL APPLICATIONSThe dynamic and simple nature of temporal dominance of sensations (TDS) has given the technique great potential for use while simultaneously measuring oral processing parameters such as jaw movement, muscle activity and food bolus assessment. This study shows the differences in basic oral processing behavior between subjects who are, and are not, using the TDS technique. It shows that TDS can influence oral processing, but it has also potential for use with oral processing research. The research shows that slightly greater number of subjects than those commonly used in oral processing trials may be needed to generate a TDS curve effectively. bs_bs_banner A journal to advance the fundamental understanding of food texture and sensory perception Journal of Texture Studies ISSN 1745-4603 409 Journal of Texture Studies 45 (2014) 409-419

This study explored links between texture perception and breakdown path throughout oral processing. Five subjects chewed a short dough biscuit recipe. Dynamic textural perception was followed using Temporal Dominance of Sensations. Subjects expectorated at three stages of bolus formation (early, mid, and point of swallow). Visual inspection and moisture content (MC) provided a description of breakdown path.Interindividual differences in perceived texture and breakdown paths were observed. This study indicated differences between how individuals used sensory texture terms to describe bolus structure. The dry-to-sticky dominance transition corresponded to increased mixing and MC. However, there was not a significant change in MC for all subjects.A panel-level analysis agreed with the "Mouth Process" model but there were interindividual differences at the point of swallow. This study suggests that there may not be a universal swallowing threshold for this biscuit recipe in terms of the measured properties but does indicate it may be possible to group consumers using bolus structure swallowing thresholds. PRACTICAL APPLICATIONSOral processing of a solid food involves food breakdown and reassembly with saliva into a deformable bolus that can be swallowed safely. The relationships between masticatory behavior, perceived texture, bolus structure, and mechanical and rheological properties throughout oral processing are still not fully understood. This study provides evidence of the subjective nature of oral processing and texture perception but indicates that each individual is not necessarily unique. Consumers may be able to be categorized into different groups based upon sensory dominance, bolus structure, and moisture content swallowing thresholds. Understanding these groupings could aid in the design of foods that follow a desired oral processing path and therefore provide consumers with a specific sensory experience.

This study explored links between texture perception, breakdown path, and bolus properties throughout oral processing. Five subjects chewed biscuits to three stages of bolus formation (early, mid, and point of swallow). Bolus properties were measured using back extrusion (BE) (yield stress) and a modified texture profile analysis, consecutive double compression (CDC) (peak force, "adhesiveness", and "cohesiveness"). The validity of the testing methods was discussed and BE was found to be better suited than CDC for testing boluses of varying size. In addition, results indicated that a greater understanding of the properties being measured by the CDC parameters is required. The bolus properties were linked to texture perception and breakdown path results presented in Part 1 of this study.At a panel-level, yield stress and peak force decreased and "adhesiveness" and "cohesiveness" increased throughout oral processing. Interindividual differences were found in bolus mass, yield stress, peak force, "adhesiveness", "cohesiveness", and description of bolus properties using texture terms. A panel-level analysis agreed with the "Mouth Process" and "Optimum Swallow" models. However, not all individuals' results were consistent with the latter model. A universal swallowing threshold for this biscuit recipe in terms of the measured properties was not found. Results suggest consumers can potentially be grouped by sensory experience, breakdown path, or bolus properties. PRACTICAL APPLICATIONSThe relationships between masticatory behavior, perceived texture, bolus structure, and mechanical and rheological properties throughout oral processing are still not fully understood. This study applies modified texture profile analysis and back extrusion methods for the testing of boluses at different stages of oral processing and discusses their validity. This study indicates that analyzing texture-bolus property relationships at a panel -rather than individual -level may not provide a full picture of consumer experience. Although there are differences between consumers, they can potentially be grouped by sensory experience, food breakdown path, or bolus properties (including bolus moisture content and rheology). These groupings could be used to design studies that are more applicable to a general population and may be useful in tailoring foods to specific target groups.Journal of Texture Studies 00 (2016) 00-00 V C 2016 Wiley Periodicals, Inc.