MODELING OF THICKNESS FOR SEMISOLID FOODS

A Review of In Vitro and In Silico Swallowing Simulators: Design and Applications

Swallowing is a primary and complex behaviour that transports food and drink from the oral cavity, through the pharynx and oesophagus, into the stomach at an appropriate rate and speed. To understand this sophisticated behaviour, a tremendous amount of research has been carried out by utilising the in vivo approach, which is often challenging to perform, poses a risk to the subjects if interventions are undertaken and are seldom able to control for confounding factors. In contrast, in silico (computational) and in vitro (instrumental) methods offer an alternate insight into the process of the human swallowing system. However, the appropriateness of the design and application of these methods have not been formally evaluated. The purpose of this review is to investigate and evaluate the state of the art of in vitro and in silico swallowing simulators, focusing on the evaluation of their mechanical or computational designs in comparison to the corresponding swallowing mechanisms during various phases of swallowing (oral phase, pharyngeal phase and esophageal phase). Additionally, the potential of the simulators is also discussed in various areas of applications, including the study of swallowing impairments, swallowing medications, food process design and dysphagia management. We also address current limitations and recommendations for the future development of existing simulators.

Rheological and tribological characterization of different commercial hazelnut and cocoa-based spreads

Five commercial hazelnut/cocoa spreads with different compositions were tested by rheology/tribology. The impact of each formulation on the structural/lubricant performances was investigated. Rotational/oscillatory rheology was chosen to assess material behavior during flow. Viscosity variation as a function of temperature and chamber geometry was evaluated. Oscillatory mode tests were carried out to obtain information on product viscoelasticity. Tribological analysis was performed at different temperatures aiming at simulating the chewing/swallowing process. All samples were categorized as pseudo-plastic and viscoelastic materials, with the elastic component prevailing over the viscous one. Major differences were detected in terms of consistency index, depending on the total lipid content. Temperature increase enhanced spread fluidity with a decreasing viscosity according to the Arrhenius model (R² > 0.942) and greater values of activation energy reflecting higher sensitivity to microstructural changes. An inverse relationship between Casson viscosity η c and sugar/fat ratio highlighted additional correlations between structural parameters and spread formulation. Tribological measurements at 25°C highlighted that, at the initial eating stage, the friction factor (0.112 - 0.262 at sliding velocity of 8∙10^-6 m/s) was strongly affected by either the amounts of solid fat or hazelnut percentage. Tribological data corroborated the theory for which tribology and rheology cover different domains. This article is protected by copyright. All rights reserved.

Effect of Dietary Fiber and Thermal Conditions on Rice Bran Wax-Based Structured Edible Oils

In this work, extra-virgin olive oil (EVO)- and sunflower oil (SFO)-based oleogels were structured using rice bran wax (RBW) at 10% by weight (w/w). Bamboo fiber milled with 40 (BF₄₀), 90 (BF₉₀) and 150 (BF₁₅₀) µm of average size was added as a structuring agent. The effect of fiber addition and cooling temperature (0, 4, and 25 °C) on thermal and structural parameters of achieved gels was assessed by rheological (both in rotational and oscillatory mode), texture, and differential scanning calorimetry tests. Oleogelation modified the rheological behavior of EVO and SFO, thus shifting from a Newtonian trend typical of oils to a pseudoplastic non-Newtonian behavior in gels. Moreover, oleogels behaved as solid-like systems with G′ > G″, regardless of the applied condition. All samples exhibit a thermal-reversible behavior, even though the presence of hysteresis suggests a partial reduction in structural properties under stress. Decreasing in cooling temperature negatively contributed to network formation, despite being partially recovered by low-granulometry fiber addition. The latter dramatically improved either textural, rheological, or stability parameters of gels, as compared with only edible oil-based systems. Finally, wax/gel compatibility affected the crystallization enthalpy and final product stability (gel strength) due to different gelator–gelator and gelator–solvent interactions.

Predicting thickness perception of liquid food products from their non-Newtonian rheology

The "mouthfeel" of food products is a key factor in our perception of food quality and in our appreciation of food products. Extensive research has been performed on what determines mouthfeel, and how it can be linked to laboratory measurements and eventually predicted. This was mainly done on the basis of simple models that do not accurately take the rheology of the food products into account. Here, we show that the subjectively perceived "thickness" of liquid foods, or the force needed to make the sample flow or deform in the mouth, can be directly related to their non-Newtonian rheology. Measuring the shear-thinning rheology and modeling the squeeze flow between the tongue and the palate in the oral cavity allows to predict how a panel perceives soup "thickness". This is done for various liquid bouillons with viscosities ranging from that of water to low-viscous soups and for high-viscous xanthan gum solutions. Our findings show that our tongues, just like our eyes and ears, are logarithmic measuring instruments in agreement with the Weber-Fechner law that predicts a logarithmic relation between stimulus amplitude and perceived strength. Our results pave the way for more accurate prediction of mouthfeel characteristics of liquid food products.