The effects of oil type, emulsifier type, and emulsion particle size on the texture, gel strength, and rheological properties of SPI emulsion-filled gel (SPI-FG) and TFSP emulsion-filled gel (TFSP-FG) were investigated. Using soybean protein isolate or sodium caseinate as emulsifiers, emulsions with cocoa butter replacer (CBR), palm oil (PO), virgin coconut oil (VCO), and canola oil (CO) as oil phases were prepared. These emulsions were filled into SPI and TFSP gel substrates to prepare emulsion-filled gels. Results that the hardness and gel strength of both gels increased with increasing emulsion content when CBR was used as the emulsion oil phase. However, when the other three liquid oils were used as the oil phase, the hardness and gel strength of TFSP-FG decreased with the increasing of emulsion content, but those of SPI-FG increased when SPI was used as emulsifier. Additionally, the hardness and gel strength of both TFSP-FG and SPI-FG increased with the decreasing of mean particle size of emulsions. Rheological measurements were consistent with textural measurements and found that compared with SC, TFSP-FG, and SPI-FG showed higher G\' values when SPI was used as emulsifier. Confocal laser scanning microscopy (CLSM) observation showed that the distribution and stability of emulsion droplets in TFSP-FG and SPI-FG were influenced by the oil type, emulsifier type and emulsion particle size. SPI-stabilized emulsion behaved as active fillers in SPI-FG reinforcing the gel matrix; however, the gel matrix of TFSP-FG still had many void pores when SPI-stabilized emulsion was involved. In conclusion, compared to SPI-FG, the emulsion filler effect that could reinforce gel networks became weaker in TFSP-FG.

Salmonella has been associated with numerous outbreaks from contaminated food products, including emulsions. Emulsions are influenced by emulsifier type and oil presence, which can have varying degrees of stress or protection on bacteria. Although our previous research has shown that emulsifier solutions, rather than emulsions, provide a protective effect on Salmonella typhimurium after thermal treatment, the underlying mechanism remains unclear. This study selected S. typhimurium as the model microorganism and utilized the same emulsifiers (Tween 20, Tween 80, Triton X-100) to create emulsifier solutions and emulsions with the same oil fraction (60% (v/v)) to examine their effect on the expression of nine selected genes (rpoE, rpoH, otsB, proV, fadA, fabA, dnaK, ibpA, ompC) associated with stress response. Specifically, the study observed variations in gene expression under normal and thermal stress at 55°C. After 20-h incubation, Triton X-100 emulsion caused an upregulation of stress-related genes, rpoE, otsB, and fabA, suggesting stressful environment. After thermal treatment, S. typhimurium in Triton X-100 solution showed a longer 5-log reduction time with increased proV and decreased fabA and ompC expression, suggesting enhanced thermal protection compared to its emulsion. Conversely, Tween 80 solution increased fabA and ompC expression, indicating greater membrane fluidity and passive diffusion, potentially reducing thermal resistance. However, according to the upregulation of ibpA, this effect was likely mitigated by the overproduction of heat shock proteins. Notably, Triton X-100 environments exhibited the most significant gene expression changes after heat treatment, whereas Tween 80 without oil was the most inhospitable for bacterial survival. These findings inform bacterial responses under various conditions, aiding food safety strategies.

Curcumin has a high inhibitory effect on many potential diseases caused by bacteria and fungi. However, its degradability and low water solubility limit its application. Loading curcumin with an emulsion delivery system can overcome these problems. Five different types of emulsifiers were used to prepare the curcumin-loaded nanoemulsions, namely, Tween 80 (T80), Span 80 (S80), sodium dodecyl sulfate (SDS), soybean protein isolate (SPI), and lecithin (LEC). The effects of emulsifier types and post-treatment methods on emulsion stability and curcumin-load efficiency were studied. In addition, photodynamic inactivation was used to test the antibacterial effect of nanoemulsions on Escherichia coli under blue light excitation. The five types of emulsifiers could form uniform emulsions with good storage stability and with antibacterial capacity on Escherichia coli. Among them, the T80 and LEC emulsions had good stability, coating effect, and sterilization performance under heating or room temperature. Both curcumin-loaded bactericidal emulsions had the potential for large-scale applications. A nanoemulsions delivery system could effectively improve the dispersion and chemical stability of curcumin in water. An emulsion loaded with antibacterial photosensitizer represents a new idea for the storage and preservation of food commodities.

This paper is part of a series examining the impact of the main factors influencing lipid digestion and nutraceutical bioaccessibility in β-carotene-loaded oil-in-water emulsions using the harmonized INFOGEST simulated gastrointestinal model. Here, the impact of emulsifier type was examined since food emulsions and nutraceutical delivery systems are often stabilized by various types of emulsifier. The INFOGEST method was adopted to investigate the in vitro gastrointestinal fate of emulsions stabilized by five kinds of food-grade emulsifier representing different classes: synthetic surfactants (Tween 20); natural surfactants (quillaja saponin); proteins (caseinate); polysaccharides (gum arabic); and phospholipids (soy lysolecithin). Microfluidization produced emulsions with small droplet sizes for all emulsifiers, except soy lysolecithin. Within the gastrointestinal model, the caseinate-coated oil droplets had the worst gastric stability, with severe droplet flocculation and coalescence occurring in the stomach. The fraction of the lipid phase that had been digested by the end of the gastrointestinal model was considerably lower for the emulsions stabilized by soy lysolecithin (93%) or caseinate (93%), than those stabilized by gum arabic (99%), quillaja saponin (111%) or Tween 20 (117%). This effect was attributed to lower surface area of lipids available for lipase to attach to for the lysolecithin and caseinate emulsions. The overall bioaccessibility of the β-carotene increased in this order: lysolecithin (25%) < gum arabic (51%) < caseinate (55%) < quillaja saponin (56%) < Tween 20 (62%). The impact of emulsifier type on carotenoid bioaccessibility was ascribed to various factors: (i) some emulsifiers inhibited lipid digestion and so a fraction of the β-carotene remained inside the undigested droplets and the mixed micelle phase had less solubilization capacity, i.e., lysolecithin, and caseinate; (ii) some emulsifiers protected β-carotene from chemical degradation, i.e., lysolecithin and caseinate; and (iii) some emulsifiers promoted sedimentation of the β-carotene-loaded micelles, i.e., lysolecithin. These results suggest that food emulsion behavior in the human gut may be influenced by the nature of the emulsifier employed, which is important knowledge when creating functional food and beverage products.

Human breast milk is a natural emulsion containing relatively large triacylglycerol droplets coated by a distinct interfacial layer known as the milk fat globule membrane (MFGM). The unique properties of the MFGM impact the release of nutrients from breast milk in an infant\'s gastrointestinal tract (GIT), but the membrane architecture is susceptible to disruption by industrial processes. To formulate infant formula that simulates the gastrointestinal behavior of breast milk, food manufacturers require knowledge of the impact of the interfacial properties on the gastrointestinal fate of fat globules. In this study, a simulated GIT was utilized to monitor the gastrointestinal fate of emulsified corn oil with different dairy emulsifiers, including sodium caseinate, lactoferrin (LF), whey protein isolate (WPI), and milk phospholipids (MPL) isolated from MFGM. The influence of droplet size on the gastrointestinal fate of the MPL-stabilized emulsions was also examined. Our findings provide valuable information for the optimization of infant formula and dairy-based nutritional beverages.

Oral ingestion of curcumin is claimed to be effective against several diseases, including inflammation and cancer. However, its utilization in food, supplement, and pharmaceutical products is often challenging due to its poor water solubility, high chemical instability, and limited oral bioavailability. Emulsion-based delivery systems can be designed to overcome these challenges, but their composition and structure must be optimized to ensure they function appropriately. This study examined the impact of emulsifier type on the formation and stability of curcumin-loaded oil-in-water emulsions: sodium caseinate; Tween 80; quillaja saponin; gum arabic. The effectiveness of these food-grade emulsifiers at forming emulsions by microfluidization was characterized in terms of their surface load, i.e., the mass of emulsifier per unit surface area. The surface loads decreased in the following order: gum arabic (55.3 mg/m2) > > saponins (2.0 mg/m2) > Tween 80 (1.6 mg/m2) > caseinate (1.5 mg/m2), which indicated that much more gum arabic was required to form emulsions than the other emulsifiers. Curcumin-loaded emulsions were then prepared under conditions where there was just enough emulsifier to cover the droplet surfaces (\"critical\"), and under conditions where there was an excess of emulsifier in the aqueous phase (\"excess\"). Initially, both critical and excess emulsions were physically stable and had similar appearances. In all emulsions, curcumin degradation during storage occurred more rapidly at pH 7 than at pH 3, and was faster at 55 °C than at 37 °C. The physical and chemical stability of the curcumin-loaded emulsions also depended on emulsifier type. After storage at 55 °C for 15 days, the extent of curcumin degradation decreased in the following order: saponins > > gum arabic ≈ casinate ≈ Tween 80. Moreover, droplet creaming was observed in the critical Tween 80 and saponin emulsions, but not in the other emulsions. These results suggest that saponin accelerated curcumin degradation, possibly due to its ability to promote peroxidation reactions. Emulsifier concentration did not significantly affect curcumin degradation. These results suggest that the physical and chemical stability of curcumin-loaded emulsions is influenced by emulsifier type and level. This information may be useful for formulating emulsion-based delivery systems for curcumin with improved physicochemical and functional properties.