Can tribology be a tool to help tailor food for elderly population?

Introduction

From a food consumption perspective, aging brings about challenges related to eating ability, saliva production, sensory perception in the mouth, swallowing, and digestion, all of which impact overall nutrient intake. To address these issues, two primary food design strategies for older adults have been employed: first, fortifying foods with additional calories or bioactive compounds to enhance nutrient intake, and second, creating texture-modified foods or thickened liquids, focusing on rheology to accommodate issues like reduced dental function, decreased saliva production, and swallowing difficulties. Addressing oropharyngeal dysphagia has also become a significant area of research, as swallowing disorders commonly affect the health of the elderly.

Oral processing of food is a complex, dynamic process that spans multiple length and time scales, during which food undergoes a significant transformation from being dominated by rheology to being influenced by tribology, or friction and lubrication. While apparent viscosity measurements have been widely used to design texture-modified foods that ensure a “swallow-safe bolus,” the application of tribology—considering the interaction between food and oral surfaces affecting mouthfeel and safe swallowing—has not been extensively explored in food design for older adults.

Figure-1 Factors anticipated to influence the tribological properties of food designed for the elderly population

Although tribological studies on foods designed for older adults are currently limited, significant progress has been made in understanding the lubrication properties of hydrocolloid solutions commonly used in texture-modified foods. Research indicates that hydrocolloids with high molecular weights and expanded chains, such as λ-carrageenan and scleroglucan, exhibit excellent lubrication performance. Most studies have scaled friction data to viscosity, demonstrating that viscous lubrication is a crucial mechanism for separating tribo-contact surfaces in hydrocolloids, which is expected given their properties. Good lubrication performance, particularly the friction-reducing properties in the boundary regime where the tongue and palate are in close contact, is especially important for older adults. This is because many older adults experience reduced saliva production, which is a key intrinsic lubricant

Oral tribology can serve as a unique tool to establish new correlations between friction coefficients and the sensory properties of foods designed for older adults, ultimately enhancing safe swallowing. Although researchers have made significant efforts to mimic in vivo conditions, there are still many aspects to consider to bring food tribology closer to the actual characteristics of the elderly oral environment. For instance, customizing surfaces to closely resemble the deformability, wettability, and roughness (such as papillae height and density) of an older adult’s tongue could greatly benefit tribological research. Additionally, incorporating either model or ex vivo saliva could provide crucial insights into saliva-mediated lubrication, which is particularly important for older adults. This might lead to the development of new foods that do not require saliva incorporation, creating a new product line for patients suffering from dry mouth.

With the advent of 3D printing, translating in vivo knowledge into fabricating synthetic surfaces is expected to become much faster. These advancements will undoubtedly enable the rational design of tailored foods for aging populations, whether they have age-related health conditions or not. This should be achievable while maintaining ease of eating and swallowing, as well as sensory pleasure, without compromising nutritional quality—an often overlooked aspect that needs to be addressed to improve nutrient intake and tackle malnutrition issues among the elderly.

Reference

[1] Araiza-Calahorra, A., Mackie, A.R., Feron, G. and Sarkar, A., 2023. Can tribology be a tool to help tailor food for elderly population?. Current Opinion in Food Science, 49, p.100968.