Effect of salivary fluid characteristics on the physical features of in vitro bread bolus: From the absence of saliva to artificially simulated hypersalivation

• Published in: Food research international Vol. 175; p. 113753
• Main Authors: Avila-Sierra, Alejandro, Decerle, Nicolas, Ramaioli, Marco, Peyron, Marie-Agnès
• Format: Journal Article
• Language: English
• Published: Canada Elsevier Ltd 01.01.2024; Elsevier
• Subjects: alpha-amylase; Bolus particle size distribution; Bread; Bread oral processing; breads; digestion; enzyme activity; Food and Nutrition; Food engineering; food research; hardness; Humans; Life Sciences; Mastication; mouth; oral health; particle size; particle size distribution; Saliva; Saliva incorporation ratio; Saliva temperature; Salivary alpha-amylase; Salivary alpha-Amylases; sensation; Sialorrhea; temperature; water content; Bread oral processing; Saliva temperature; Mastication; Bolus particle size distribution; Salivary alpha-amylase; Saliva incorporation ratio; mastication; bolus particle size distribution; saliva temperature; bread oral processing; salivary alpha-amylase; saliva incorporation ratio
• ISSN: 0963-9969; 1873-7145; 1873-7145
• DOI: 10.1016/j.foodres.2023.113753

[Display omitted] •Saliva incorporation affects particle size and fluid content of in vitro bread bolus.•An excess of saliva fluid leads to bread boluses constituted by smaller particles.•A lack of saliva to form the bread bolus leads to extremely large particles.•The enzymatic activity of α-amylase favours bread particle size reduction.•Saliva temperature does not significantly affect bread particle size reduction. Saliva facilitates food oral processing, bolus formation, swallowing, and sensory perception, in addition to contributing to oral health and phonation. Ageing, health affections, and polymedication are among many causes altering salivary production, modifying the mastication process, the food impregnation ratio, and in turn altering the characteristics of the bolus, swallowing, and digestion. In this in vitro work, using the AM2 masticator apparatus, which replicates the mechanical actions taking place while chewing solid foods and produces realistic food bolus in various oral conditions, we investigated the effect of salivary fluid characteristics, i.e., composition, quantity (from absence to hypersalivation), temperature, and enzymatic action, on the physical characteristics (i.e., particle size distribution (PSD), bolus mass, salivary fluid content) of in vitro boluses of Traditional French baguette. A ready-to-swallow bolus of baguette displayed on average a d50 value (median particle size by mass) of 4.1 ± 0.4 mm, with saliva fluid constituting ∼ 35 % of the final bolus mass. The absence of saliva in mouth led to a deficient oral processing, forming bread boluses constituted by extremely big particles (ca. 80 % of particles had a size > 7.1 mm) that likely cannot be swallowed safely. On the contrary, an excess of saliva favoured an excessive breaking down of bread, leading to bread boluses constituted by smaller particles than those formed under healthy salivary conditions (d50 decreased from 4.1 mm to 3.1 mm), having a higher salivary fluid content (+10 %). On the other hand, the salivary fluid temperature did not affect PSD, d50, bolus mass, or salivary fluid content of in vitro bread boluses, however, the addition of human salivary α-amylase did, favouring particle size reduction (d50 decreased to 2.6 mm). Therefore, beyond the correlation between bolus hydration by saliva and food properties such as hardness and moisture content, our findings indicate that the quantity of salivary fluid present in the oral cavity and the enzymatic activity of salivary α-amylase during bread mastication significantly influence both the particle size distribution and the fluid content of bread boluses, ultimately determining the physical properties of the bolus and, therefore, potentially impacting the subsequent swallowing process.