P13: Saliva influences the rheological properties of semi-solid foods containing starch: a quantitative in vitro study

Anaïs Lavoisier, Sabrina Boudrag, and Marco Ramaioli

INRAE, France

Gelatinized starch is widely used as a texturing agent in foods and drinks, but starch molecules are rapidly hydrolyzed in the mouth by salivary α-amylase. This structural breakdown can modify the bolus rheology and influence texture perception, aroma release, and swallowing.

The objective of this study was to investigate quantitatively the dynamics of the destructuration and of the rheological evolution of semi-solids containing starch, a waxy maize starch suspension, and a commercial dairy custard, upon contact with saliva. Oral digestion was mimicked and followed using a rheometer. An insalivation ratio measured from spitted boli, was used in the in vitro oral digestion experiments with human saliva.

The initial viscosity of both samples was reduced by 80% after only 5 s of in vitro oral digestion. This decrease in viscosity was attributed to the breakdown of the starch granule structure by α-amylase and to a lesser extent to a dilution effect. The kinetics of this reaction are relevant for food oral processing and swallowing, particularly for individuals suffering from swallowing difficulties who may keep a bolus in the oral cavity for more than 5 s.

This work confirms that the shear viscosity of semi-solid foods containing gelatinized starch is significantly modified in the mouth, and during their transit from the mouth to the stomach. These changes should be considered carefully when formulating foods with specific textural attributes. The method developed in this study can be used to quantify the impact of food oral processing and evaluate rheological properties relevant for swallowing in the presence of saliva.


Key dates

Registration deadline:

31 January 2022


Organised by the IOP Food Physics Group