Chew on it: Consumer and food characteristics steer oral processing behavior and sensory perception

Food oral processing refers to the oral manipulations of food upon ingestion (i.e. oral behavior), the production of a bolus safe to swallow and simultaneously the sensory responses evoked from the structural transformation of the bolus. Deeper understanding of the factors involved in oral processing can facilitate the creations of food products that are goal-specific (e.g. controlling eating rate) and population-specific (e.g. elderly consumers) besides being nutritive and palatable. The main factors determining oral processing are the consumer and food being eaten. Therefore, in this thesis both factors were explored and their contribution to oral behavior, bolus properties and sensory perception determined.

 

Chapter 2 explored whether or not consumers exhibit different oral behaviors for a specific food product and how these differences in behavior might impact sensory perception. The results confirmed that consumers used different oral behaviors which differed in consumption time. Vigorous protocols (chewing and natural style) required shorter consumption time than passive protocols (melting). Furthermore, changes in oral behavior also influence dynamic sensory perception. For instance, changing oral behavior influenced significantly aroma and taste attributes, where upon applying an active oral behavior aroma attributes were detected earlier and for longer time than when a passive protocol was applied. On the other hand, if a passive protocol was applied, taste perception was perceived earlier and for longer time whereas aroma perception was delayed. Additionally, this chapter highlighted the existence of attribute chronology during oral processing and that consumers adopt an oral processing behavior that is optimized in terms of oral efficiency and sensory perception.

Chapter 3 explored a broad range of commercial foods and the effect of their rheological and mechanical properties on oral behavior parameters. The results showed that consumers adapted their bite size, consumption time and eating rate to food properties and that this adaptation was consistent within each food category. Overall, consistency (K) of liquids and semi-solids and stress at 15% strain of solid foods have a negative relationship with bite size, and positive relationship with consumption time. Together, these variables contribute to modulate eating rate. Thus, this chapter highlighted that oral behavior can be steered by modifications on food properties.

Chapters 4 demonstrated that not only food properties but also consumers characteristics can influence oral behavior. For instance, elderly exhibited longer consumption times and lower eating rates than their younger counterparts. Amongst genders, females took smaller bite sizes, and had lower eating rates than males. Finally, between ethnicities, Dutch-Caucasians exhibited larger bite sizes and faster eating rates than Asian-Chinese. Generally, the observed differences between consumer groups was relatively constant across food categories.

Chapter 5 investigated how the changes in oral behavior between consumer groups affected bolus properties and dynamic sensory perception. The results showed that consumers differing in age, gender or ethnicity adjust their consumption time in a way that allows them to form a bolus with optimized textural properties that guarantee them a safe and comfortable swallow. Also, these results show that the swallowing threshold is not universal but that it differs between consumers. Possibly due to the inherent physiological and cultural differences. Additionally, this chapter showed that dynamic sensory perception varied only in middle stages of oral processing maybe providing input to determine if further bolus degradation or saliva incorporation was needed.

Finally, chapters 6 and 7, demonstrated that when eating heterogeneous foods, oral processing behavior can be steered by modification in either food matrix or the embedded particle and that these results may be applicable to different consumer groups. The results of chapter 6 showed that the mere addition of peach particles to yogurts slowed down eating rate up to 60%, regardless of the particles’ characteristics (size, fracture stress or concentration). Similarly, in chapter 7 the addition of bell pepper pieces to cream cheeses also showed an impact on oral processing behavior although this was to a lower extent. Hence, we suggest that the bigger is the perception of contrast, between the disperse matrix and the added particle, the grater the impact on oral processing behavior. Moreover, not only the mere addition of particles but also the fracture stress of the embedded particle can influence oral behavior. For instance, embedding particles of high fracture stress, leads to longer consumption times and lower eating rates than when the particles have low fracture stress. Furthermore, it was observed that the perception of the solid component overruled the sensations arouse from the softest component. Thus, when designing heterogeneous foods, attention should be given to the hardest component since it will likely overrule the influence of the softest component.

In conclusion, consumer and food characteristics shape oral behavior which in turn affects bolus properties and consequently sensory perception. Therefore, new product development aiming for a more tailored sensory experience should take not only food characteristics into account but also the fact that consumer groups differ in oral processing behavior.