Effects of barium sulfate on rheological properties and IDDSI flow consistency of liquid stimuli prepared using commercial thickening powders.

During videofluoroscopic swallowing study (VFSS), barium sulfate (BaSO4 ) is commonly added into food samples as a radiopaque contrast media for bolus visualization and examination. Accordingly, the consistency and flow behavior of barium stimuli can differ significantly from their non-barium counterparts. Such differences may have a subsequent impact on the validity of VFSS. Therefore, in this study, effects of barium sulfate on the shear and extensional rheological properties and IDDSI (International Dysphagia Diet Standardization Initiative) flow consistency of liquids prepared using various commercial thickening powders were investigated. Results showed that all barium stimuli exhibited shear thinning behavior but with significantly higher shear viscosity compared to the non-barium counterparts. A shift factor of viscosity at shear rate 50 s-1 with values in range of 1.21-1.73 could be used to describe the increase in the viscosity for samples thickened with gum-based thickeners. However, the change in the viscosity was not invariant for the stimuli prepared starch-based thickener. The addition of BaSO4 had a negative impact on extensional properties of samples by demonstrating a faster filament rupture. The extent of impact on the decrease in filament breakup time was more pronounced in xanthan > guar gum ≈ tara gum-based thickeners. Based on the IDDSI flow test, no significant effect of BaSO4 was found on the gum-based thickeners, whereas there was a marked effect in the starch-based sample. These results can be used beneficially to assist clinicians in the dysphagia diagnosis for matching rheological properties of the barium stimuli to enhance effectiveness dysphagia interventions.

Effects of gellan gum and calcium fortification on the rheological properties of mung bean protein and gellan gum mixtures.

In this study, the effects of gellan gum types and CaCl2 addition on the rheological characteristics of mung bean protein (MBP)-gellan gum mixtures at varying protein contents (1-7 wt%) were investigated. Two types of gellan gum, high acyl gellan (HAG) and low acyl gellan (LAG), at 0.5 wt% were used. MBP-HAG system showed soft and elastic gels at below 3 wt% MBP content, but gel became weaker due to protein network disruption at higher MBP content. In contrast, MBP-LAG system exhibited a liquid-like behavior and a synergistic interaction between LAG and MBP. High calcium concentration can cause proteins to aggregate leading to protein precipitation. However, such phenomenon could be retarded by both types of gellan gum in the MBP-gellan gum mixtures studied herein. The calcium addition of up to 50 mM did not significantly alter the overall viscoelastic property of MBP-HAG system. In contrast, MBP-LAG system fortified with calcium formed solid gel at low protein content (1 wt%), but excessive calcium ions were required to maintain the strong gel characteristic at higher protein concentration (≥ 3 wt%) due to the competitive binding of calcium between the protein and gellan gum. These results were also supported by their microstructure observed through CLSM and SEM experiments. PRACTICAL APPLICATION: The application of hydrocolloids as rheology modifiers is useful to improve the stability and textural properties of plant-based protein drinks. Results from this study are helpful for the industry to understand the textural properties of mung bean protein at varying concentrations in the presence of gellan gum and calcium. Especially, at high calcium fortification which is desirable in plant-based protein drinks, protein aggregation could be retarded by gellan gum. Overall, the finding demonstrated that a range of rheological characteristics of mung bean protein and gellan gum mixtures could be manipulated as desired to meet both nutritional quality and product stability.

Roles of viscosity, applied load and surface wettability on the lubrication behaviour of model liquid/semi-solid foods: Measurements with a bespoke tribo-cell fixture and rotational rheometer.

Thin film sliding and friction phenomena of food bolus confined between tongue-palate surfaces during oral processing can be explored using tribological measurements. However, these measurements are still limited within the food industry due to the requirement of expensive commercial instruments which are not commonly used in the food industry. This work has designed and manufactured a modular "tribological cell" (tribo-cell) that can simulate lubricated soft-hard contact interfaces and can be mounted on a rotational rheometer to perform tribological measurements. The tribo-cell was validated by performing tribological measurements using a range of corn syrup solutions as model liquid foods. It was shown that the Stribeck curve describing the change in friction behaviour with entrainment speed or with the product of entrainment speed and liquid viscosity could be obtained. Since tribology deals with surface property, the cell was then used in the further studies to demonstrate the effects of applied normal load and surface wetting on the tribological response of lubricated hard-soft contact of the designed fixture. These parameters were shown to have a marked influence on in the boundary and mixed-lubrication regimes. The designed tribo-cell was also used to illustrate the impact of fat content on the lubrication properties of commercial liquid and semi-solid foods with different fat contents, thus, pointing out to the importance of tribology as a vital tool for product formulation designs in food and beverage industry.

Food polysaccharides and roles of rheology and tribology in rational design of thickened liquids for oropharyngeal dysphagia: A review.

In today's market environment, an aging society is recognized as one of the megatrends in the world. The demographic change in the world population age structure has driven a huge demand in healthcare products as well as services that include the technological innovation for the health and wellness of the elderly. Dysphagia or swallowing difficulty is a common problem in the elderly as many changes in swallowing function come with aging. The presence of a strong relationship between swallowing ability, nutritional status, and health outcomes in the elderly leads to the importance of dysphagia management in the population group. Modification of solid food and/or liquid is a mainstay of compensatory intervention for dysphagia patients. In this regard, texture-modified foods are generally provided to reduce risks associated with choking, while thickened liquids are recommended for mitigating risks associated with aspiration. In this review, we discuss thickened liquids and other issues including the importance of their rheological and tribological properties for oropharyngeal dysphagia management in the elderly. The review focuses on both commercial thickeners that are either based on modified starch or xanthan gum and other potential polysaccharide alternatives, which have been documented in the literature in order to help researchers develop or improve the characteristic properties of thickened liquids required for safe swallowing. Furthermore, some research gaps and future perspectives, particularly from the nutrition aspect related to the interaction between thickeners and other food ingredients, are suggested as such interaction may considerably control the rate of nutrient absorption and release within our body.

Studies on chemical composition, rheological and antioxidant properties of pectin isolated from Riang (Parkia timoriana (DC.) Merr.) pod.

Although synthetic antioxidant food additives are widely used in a variety of food products, some of them are suspected of having a noxious effect on human health. As a consequence, much research attention has been focused on developing natural antioxidant compounds from plants. Riang (Parkia timoriana (DC.) Merr.) is known as a traditional medicinal plant in which its various parts have been reported to exhibit antioxidant and numerous biological activities. In this study, pectins from Riang pod husk and pod powder were extracted, and their physico-chemical, rheological, and antioxidant properties were characterized. The extracted pectins showed high uronic acid content (> 65%) and high molecular weight (200-250 kDa) and the yields were approximately 15 and 36%w/w (dry basis), for Riang husk pectin (RHP) and Riang pod powder pectin (RPP), respectively. Furthermore, both pectins were classified as a high methoxyl with their DE of ~66%. Rheological measurements revealed a pseudoplastic behavior above 2% w/v. RHP contained higher content of total phenolics, flavonoids and tannin, compared with RPP. Antioxidant activities of RHP were consequently higher than RPP in all studied assays. The highest antioxidant activities of RHP and RPP, obtained from ABTS assay, were 0.95 and 0.24 mmol Trolox equivalents/g, respectively.