Interplay between bulk aggregates, surface properties and foam stability of nonionic surfactants.

In our previous study (Mustan et al. 2021) we showed that foams formed from two oil-soluble nonionic surfactants (Span 60 and Brij 72) can remain stable for more than 10 days at room temperature at high sugar concentration. The major aim of the current study is to reveal the interrelation between the surfactant structure and foam stability by investigating 6 polyoxyethelene alkyl ethers and 12 fatty acid esters with a wide variety of hydrophobic chain lengths (C12; C16; C18 and C18:1) and hydrophilic head-groups (sorbitol, glycerol, sucrose). Foams stable for more than 100 days at room temperature are obtained when sucrose palmitate or stearate (P1670 or S1670) are used as surfactants. This exceptional foam stability is related to the gelation of the aqueous phase and to the formation of solid adsorption layer with zero surface tension upon compression, thus preventing water drainage and decelerating the bubble Ostwald ripening. The foam stability decreases with (i) increasing the number of EO groups in polyoxyethylene alkyl ethers and in fatty acid sorbitan esters; (ii) decreasing the number of C-atoms in the surfactant tail for all studied surfactants; (iii) addition of double bond in the surfactant tail. The lower foam stability in all three cases is related to the worse packing of the surfactant molecules within the adsorption layer, leading to faster Ostwald ripening and subsequent bubble coalescence. The diesters present as admixture in the fatty acid esters play an important role in the foam stabilization by further compacting the adsorption layers and lowering the rate of Ostwald ripening. These conclusions can be used as a predictive tool for surfactant selection in the development of food or pharmaceutical foam concentrates that can be diluted before final use.

Fat emulsion intragastric stability and droplet size modulate gastrointestinal responses and subsequent food intake in young adults.

BACKGROUND: Intragastric creaming and droplet size of fat emulsions may affect intragastric behavior and gastrointestinal and satiety responses. OBJECTIVES: We tested the hypotheses that gastrointestinal physiologic responses and satiety will be increased by an increase in intragastric stability and by a decrease in fat droplet size of a fat emulsion. METHODS: This was a double-blind, randomized crossover study in 11 healthy persons [8 men and 3 women, aged 24 ± 1 y; body mass index (in kg/m(2)): 24.4 ± 0.9] who consumed meals containing 300-g 20% oil and water emulsion (2220 kJ) with 1) larger, 6-µm mean droplet size (Coarse treatment) expected to cream in the stomach; 2) larger, 6-µm mean droplet size with 0.5% locust bean gum (LBG; Coarse+LBG treatment) to prevent creaming; or 3) smaller, 0.4-µm mean droplet size with LBG (Fine+LBG treatment). The participants were imaged hourly by using MRI and food intake was assessed by using a meal that participants consumed ad libitum. RESULTS: The Coarse+LBG treatment (preventing creaming in the stomach) slowed gastric emptying, resulting in 12% higher gastric volume over time (P < 0.001), increased small bowel water content (SBWC) by 11% (P < 0.01), slowed appearance of the (13)C label in the breath by 17% (P < 0.01), and reduced food intake by 9% (P < 0.05) compared with the Coarse treatment. The Fine+LBG treatment (smaller droplet size) slowed gastric emptying, resulting in 18% higher gastric volume (P < 0.001), increased SBWC content by 15% (P < 0.01), and significantly reduced food intake by 11% (P < 0.05, equivalent to an average of 411 kJ less energy consumed) compared with the Coarse+LBG treatment. These high-fat meals stimulated substantial increases in SBWC, which increased to a peak at 4 h at 568 mL (range: 150-854 mL; P < 0.01) for the Fine+LBG treatment. CONCLUSION: Manipulating intragastric stability and fat emulsion droplet size can influence human gastrointestinal physiology and food intake.

Impact of bitter taste on gastric motility.

BACKGROUND: Unexplained nausea and vomiting is often associated with delayed gastric emptying in patients with functional dyspepsia. We hypothesized that the experience of an unpleasant, nauseating taste could lead to a delay in gastric emptying. METHODS: Sixteen healthy women consumed a bland liquid test meal on three separate study days. On two of the study days subjects sham fed either a bitter tasting, modified Slim-Fast bar or one with a pleasant strawberry flavour. The time for 50% gastric emptying (GE(50)) was non-invasively assessed by electrical impedance tomography and antral motility by electrogastrography (EGG). RESULTS: Gastric emptying was significantly delayed by sham feeding the bitter compared with the pleasant bar, GE(50) 24.7+/-3.9 versus 17.2+/-1.8 min, P<0.05. EGG power rose significantly during both the pleasant (basal 1.46+/-0.07 to 2.33+/-0.14 log(10) microV(2)/min, P=0.000) and the bitter sham feed (basal 1.64+/-0.09 to 2.35+/-0.11 log(10) microV(2)/min, P=0.000). CONCLUSION: An unpleasant bitter taste delays gastric emptying but does not significantly impair antral motility.