Studies of the Oral Capabilities in Relation to Bolus Manipulations and the Ease of Initiating Bolus Flow

Bolus swallowing can be a difficult task and/or highly hazardous to people with dysphagia (swallowing impairment), involving a risk of choking and airway obstruction. Food and pharmaceutical industries are under growing pressure to design and provide quality food for safe consumption by these disadvantaged populations and urgently need knowledge and a proper understanding of the controlling mechanisms of bolus manipulation and swallowing. In this study, physiological capabilities related to oral food handling, including maximum isometric tongue pressure, the volume of oral cavity, optimum bolus size, and tongue pressures applied during bolus swallowing were investigated. A total of 106 healthy subjects of different ages, genders and ethnic groups were involved in the investigation. A wide range of maximum isometric tongue pressure (from as low as 10 kPa to as high as 70 kPa) and maximum oral volume (from as low as 25 mL to as high as 116 mL) were observed. Further analysis showed that gender had no significant influence on tongue pressure and oral volume capacities. For younger adults (22–64 years), age also appears to have little effect. However, for older adults (>65 years), both maximum isometric tongue pressure and the oral volume showed a gradual decrease with the increasing of age. By investigating basic factors of bolus swallowing, this project aimed to reveal critical controlling factors underlining the process and to test the hypothesis that, because tongue pressure provides the initial driving force for bolus flow, one's capability to generate tongue pressure could be related to the ease with which one can swallow. For this purpose, a selection of subjects with known maximum isometric tongue pressure was further invited to swallow food (bolus) of varying consistencies. A positive correlation was observed between maximum tongue pressure and the maximum consistency of bolus that one can swallow for those who had lower tongue pressure generation capacity ( 40 kPa), a tongue pressure reserve (around a third of their maximum capability) was observed during bolus swallowing. Practical Applications This article investigates a few interesting hypothesis on the bio-mechanics of food processing, especially tongue pressure for bolus management and transfer during oro-pharyngeal swallow. Swallowing is the final stage of food oral processing and is crucial for the transportation of orally processed food (the bolus) to the stomach for further digestion and nutrient absorption. As such, safe swallowing is a major concern for many disadvantaged populations, e.g., some elderly populations, infants, oral and/or pharyngeal dysphagia and cerebrovascular accident (stroke) patients, patients in the late-stage of Alzheimer's disease and other hospital patients. Food and pharmaceutical industries are under an increasing pressure to develop and provide foods that are not only healthy and tasty, but are also safe to consume by these disadvantaged populations. The information presented in this article could be a bridge between oral and food sciences, and also could be of interest to R&D researchers in both food manufacturing and pharmaceutical industries in trying to understand individuals' physiological capability of swallowing and the implications for food provision.