Simulated Gastrointestinal Model Research Articles

Factors impacting lipid digestion and nutraceutical bioaccessibility assessed by standardized gastrointestinal model (INFOGEST): Emulsifier type

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.

Thermo-tolerant Saccharomyces cerevisiae var. boulardii coated cornflakes as a potential probiotic vehicle

Functional probiotic breakfast products are being sought because of strong consumer demand. Cornflakes, a popular breakfast cereal is usually consumed with hot milk in Asian countries. Coating the probiotics on cornflakes would potentially be a way to deliver a probiotic; however, the survivability of the probiotics is a major concern. Thus, this study aimed to develop a heat-stable probiotic cornflakes using hydrocolloids as a coating agent. Hydrocolloids were blended with Saccharomyces boulardii, coated on the cornflakes, and then assayed for the viability of S. boulardii after exposure to pre-heated milk. Probiotic-coated cornflakes with acacia gum (6%) showed maximum protection of S. boulardii (7.3 ± 0.1 log CFU/g) over the control (2.3 ± 0.1 log CFU/g) when treated with pre-heated milk at 80±2 °C. The water absorption index, water absorption capacity, milk absorption capacity, and surface area were significantly reduced in the probiotic-coated cornflakes. Brunauer-Emmett-Teller modeling of the surface area using nitrogen, and scanning electron microscopy analysis showed the efficient binding of hydrocolloids to cornflakes. The simulated gastrointestinal model suggested a noticeable resistance of S. boulardii to acid, pepsin, and moderate resistance to pancreatic juice. Probiotic-coated cornflakes showed an 88.3% survival rate of S. boulardii when stored at 30±2 °C for 90 days. In conclusion, acacia gum might protect probiotic microorganisms in hot served food products.

Encapsulation of lycopene within oil-in-water nanoemulsions using lactoferrin: Impact of carrier oils on physicochemical stability and bioaccessibility

The influence of physicochemical properties of carrier oils on nanoemulsion stability and the bioaccessibility of lycopene were studied. Lycopene-loaded nanoemulsions were prepared by using sesame oil, linseed oil or walnut oil as the oil phase and lactoferrin as the emulsifier. The stability was investigated by particle size, zeta potential, pH sensitivity, thermal stability and lycopene retention. Results showed that the stability was positively correlated with oil density but negatively related to oil viscosity and unsaturation degree; the lycopene nanoemulsion prepared by sesame oil exhibited greater stability and a slower degradation rate of lycopene compared to the other nanoemulsions. In addition, the lycopene retention in sesame oil-nanoemulsions was significantly higher during the first three weeks of storage. The bioaccessibility of lycopene, as measured by a simulated gastrointestinal model, was greatly improved in the nanoemulsion system. The lycopene bioaccessibility was around 25% in sesame oil- and linseed oil-nanoemulsions, and 18% in walnut oil-nanoemulsions, showing a similar trend with their stability. This information may facilitate the design of more efficacious lycopene-fortified delivery systems.

Probiotic Supplementation is Associated with Increased Antioxidant Capacity and Copper Chelation in C. difficile-Infected Fecal Water.

Probiotic supplementation plays a key role in maintaining intestinal homeostasis due to its ability to modulate gut microbiota. Although their potential as potent antioxidants have previously been explored, their ability to affect the redox status in the gut lumen of healthy subjects or those with gastrointestinal (GI) disorders remains unclear. In our study, we assessed the ability of single strain and multispecies probiotic supplementation to cause a change in the redox status of normal fecal water and in Clostridium (C.) difficile-infected fecal water using a simulated gastrointestinal model. Changes in redox status were assessed by ferric-reducing antioxidant power (FRAP), 2’,2’-diphenyl-1-picrylhydrazyl (DPPH), and iron and copper chelation assays. The findings from our study showed that in normal fecal water, probiotic supplements, apart from Lactobacillus (L.) rhamnosus R0011, showed a significant increase in iron chelation (p < 0.05), which was associated with lower FRAP and copper chelation. In C. difficile-infected fecal water, all probiotic supplements showed a significant increase in FRAP (p < 0.05) and were associated with increased copper chelation. The DPPH assay showed no treatment effect in either fecal water. These findings suggest that C. difficile mediates dysregulation of redox status, which is counteracted by probiotics through ferric-reducing ability and copper chelation.

Impact of Food Emulsions on the Bioaccessibility of Hydrophobic Pesticide Residues in Co-Ingested Natural Products: Influence of Emulsifier and Dietary Fiber Type.

In the typical Western diet, fruits and vegetables are often consumed with food products that exist as oil-in-water emulsions, such as creams, dressings, and sauces. Studies have shown that coingestion of fruits and vegetables with emulsions can increase the bioavailability of beneficial lipophilic bioactive agents, such as nutraceuticals or vitamins. Agricultural produce, however, may also be contaminated with low levels of detrimental lipophilic agents, such as hydrophobic pesticides. We therefore examined the impact of coingesting a common agricultural product (tomatoes) with model food emulsions on the bioaccessibility of a hydrophobic pesticide (chlorpyrifos). The impact of emulsifier types (phospholipids, whey protein, Tween 80) and dietary fiber types (xanthan, chitosan, β-glucan) on the bioaccessibility of the pesticide was measured using a simulated gastrointestinal model. Chlorpyrifos bioaccessibility depended on the type of emulsifier used to formulate the emulsions: phospholipids > Tween 80 > whey protein. Dietary fiber type also influenced pesticide bioaccessibility by an amount that depended on the nature of the emulsifier used. Overall, our results suggest that the bioaccessibility of undesirable pesticides on fruits and vegetables will depend on the nature of the emulsions they are consumed with.

Comparision of heteroaggregation, layer-by-layer and directly mixing techniques on the physical properties and in vitro digestion of emulsions

This paper systematically compared the effects of heteroaggregation, layer-by-layer and directly mixing techniques on the physical properties of emulsions through mechanical rheology, microrheology, LUMisizer stability analyzer, Cryo-scanning electron microscopy (Cryo-SEM) and in vitro simulated gastrointestinal model. The shear rheology results showed that the viscosity of emulsions stabilized with whey protein isolate (WPI) and flaxseed gum (FG) by different techniques was in the order of heteroaggregated emulsion > layer-by-layer emulsion > directly mixing emulsion. Furthermore, it confirmed that the heteroaggregated emulsion had a best stability and the interface moving speed was the slowest compared with those of layer-by-layer and directly mixing emulsions. Cryo-SEM microstructure results showed that the three dimensional network structure of heteroaggregate was the main reason for maintaining high stability and shear rheological properties. Microrheological properties results indicated that heteroaggregated emulsion was sensitive to the shearing force due to the liquid behavior. While, the structures of WPI-FG emulsions prepared by layer-by-layer and directly mixing were not destroyed after shearing due to their high elasticity and solid behaviors. It was found that the order of released FFA content at the beginning of 30 min was directly mixing emulsion > layer-by-layer emulsion > heteroaggregated emulsion, but the released free fatty acid of heteroaggregated emulsion was the most in the end, which indicated that heteroaggregated emulsion had a certain controlled release effect. The study could be helpful for choosing proper technique to gain good emulsion delivery system.

Applications of simulated gastro-intestinal model in foodborne pathogens: tolerance and pathogenesis

We evaluated the tolerance and pathogenesis of foodborne pathogens with a simulated gastro-intestinal tract model that simulates the chemical, physical and biological effects of human digestion process under laboratory conditions. This could be used to study the tolerance, pathogenesis, gut microbiota interaction and vaccine development of foodborne pathogens, so as to contribute to control and treatment of foodborne pathogens. This review introduces the applications of simulated gastro-intestinal tract model tp evaluate foodborne pathogens, which includes in-vitro static gastro-intestinal model, in-vitro dynamic gastro-intestinal model, conventional animal model and humanized animal model. And the concepts and characteristics of all models are described in detail. Also, the shortcomings of existing models are analyzed, and improvements of artificial gastro-intestinal tract model are prospected. In conclusion, this review could provide comprehensive data for promoting the progress of studying tolerance and pathogenesis of foodborne pathogens.

Stability and digestibility of one- or bi-layered medium-chain triglyceride emulsions with gum Arabic and whey protein isolates by pancreatic lipase in vitro.

Interfacial engineering approaches have been used to design functional foods so as to control lipase-induced digestion of emulsified lipids and release of bioactive lipophilic components in the gastrointestinal tract. In this study, emulsion droplets with the interface stabilized with gum Arabic (GA) and whey protein isolate (WPI) were prepared by mixing or sequential adsorption. WPI/GA intramolecular soluble complexes (ISCs) have superior emulsifying properties in stabilizing oil-in-water emulsions. The impact of the interfaces for WPI/GA ISC-layered (one-layered) and double-layered emulsions formed by sequential deposition of WPI or GA on the lipolysis of emulsions was investigated using an in vitro simulated gastrointestinal model. Transglutaminase and dithiothreitol were introduced to crosslink the interfacial proteins and improve the interfacial stability. The ISC-layered emulsion was less stable to aggregation than the double-layered ones in simulated gastric fluid due to dissociation of ISCs caused by the electrostatic screening of ions and proteolysis of interfacial proteins driven by pepsin. The ISC-layered emulsion conferred a significant slower rate and extent of lipid digestion compared to the double-layered emulsions post gastric proteolysis (P < 0.05). It is presumed for the ISC-layered emulsion that the destabilization to aggregation and coalescence within the simulated gastrointestinal fluids and the steric hindrance of the robust and thick interfacial layer might contribute to delaying free fatty acids release. It suggests that both the initial interfacial properties and the stability of the emulsified lipid droplets within the simulated gastrointestinal fluids play an important role in determining the rate and extent of lipid digestion. It is predicted that direct destabilization of emulsified lipids using interfacial engineering approaches has the potential of modifying lipid digestibility or bioactive release at specific sites within the gastrointestinal tract.

Effects of Environmental Stresses and in Vitro Digestion on the Release of Tocotrienols Encapsulated Within Chitosan-Alginate Microcapsules.

Considering the health benefits of tocotrienols, continuous works have been done on the encapsulation and delivery of these compounds. In this study, we encapsulated tocotrienols in chitosan-alginate microcapsules and evaluated their release profile. Generally, these tocotrienols microcapsules (TM) displayed high thermal stability. When subjected to pH adjustments (pH 1-9), we observed that the release of tocotrienols was the highest (33.78 ± 0.18%) under basic conditions. The TM were also unstable against the effect of ionic strength, with a high release (70.73 ± 0.04%) of tocotrienols even at a low sodium chloride concentration (50 mM). As for the individual isomers, δ-tocotrienol was the most sensitive to pH and ionic strength. In contrast, β-/γ-tocotrienols were the most ionic-stable isomers but more responsive toward thermal treatment. Simulated gastrointestinal model showed that the chitosan-alginate-based TM could be used to retain tocotrienols in the gastric and subsequently release them in the intestines for possible absorption.

Study on the digestion of milk with prebiotic carbohydrates in a simulated gastrointestinal model

The behaviour of oligosaccharides from lactulose (OsLu) included with milk was examined during in vitro gastrointestinal digestion using the Infogest protocol as well as some small intestine rat extract. The digestion was compared with commercial prebiotics GOS and Duphalac®. Electrophoretic analysis demonstrated that the prebiotic carbohydrates did not modify the gastric digestion of dairy proteins. Similarly, no significant effect of gastrointestinal digestion was shown on the prebiotic studied. In contrast, under the intestinal conditions using a rat extract, the oligosaccharides present in OsLu samples were less digested (<15%) than in GOS (35%). Moreover, lactulose was more prone to digestion than their corresponding trisaccharides. These results demonstrate the limited digestion of OsLu and their availability to reach the large intestine as prebiotic.

Spray drying probiotics along with maoluang juice plus Tiliacora triandra gum for exposure to the in vitro gastrointestinal environments

Application of potential probiotic bacteria in dehydrated fruit juices could be an optional diversity for the consumers who are aware of functional beverages. This study purposed to investigate the impact of Tiliacora triandra gum on the survival of Lactobacillus casei 01 and Lactobacillus acidophilus LA5 along with maoluang juice after spray drying and their activities under simulated gut models, as compared to inulin addition. The results showed that probiotic-maoluang juice powders as immobilized by Tiliacora triandra gum and inulin similarly showed protective ability on probiotic bacteria against adverse conditions of simulated gastrointestinal (SGI) model. After 6 h incubation in SGI, the survival rates of spray dried L. casei 01 and L. acidophilus LA5 with maoluang juice and Tiliacora triandra gum or inulin were higher than the free cells, by increasing around 15–20% and 20–21%, respectively. According to the in vitro colon experiments, Tiliacora triandra gum and inulin apparently enhanced the accumulation of lactic acid, short-chain fatty acids (SCFA) and beneficial colon bacteria (i.e. lactobacilli and bifidobaccteria), whilst the levels of toxic ammonia and the populations of harmful bacteria (i.e. clostridia and fecal coliforms) were diminished. Therefore, this indicates that Tiliacora triandra gum displayed prebiotic impacts on the human colon microbiome.

Effect of encapsulated carvacrol on the incidence of necrotic enteritis in broiler chickens

ABSTRACTThere is an urgent need to control necrotic enteritis (NE) caused by Clostridium perfringens in chickens when antibiotics are withdrawn from feed. Carvacrol has strong antimicrobial activity and its delivery to the animal intestine can be significantly enhanced after encapsulation. The present study has investigated the potential of encapsulated carvacrol in controlling NE. In general, micro-encapsulation of carvacrol in an alginate-whey protein matrix showed no adverse effect on its antimicrobial activity towards C. perfringens in either Brain Heart Infusion (BHI) broth or a simulated gastrointestinal model. The minimum inhibitory concentrations of both encapsulated and un-encapsulated carvacrol were approximately 200 μl/l against C. perfringens in BHI. In a broiler infection model with C. perfringens, the diets supplemented with encapsulated carvacrol at the dose of either 250 or 650 μg/g significantly reduced NE in the chicken intestine, which was close to the degree of lesions observed in bacitracin/salinomycin treated birds. Supplementation with either bacitracin/salinomycin or encapsulated carvacrol showed no significant impact on intestinal burden of Lactobacillus. However, the treatment with bacitracin/salinomycin or the low dose of encapsulated carvacrol reduced the level of C. perfringens in the ileum of birds at 35 days of age. These results suggest that our encapsulated carvacrol can be used to combat NE disease in chickens.

Designing self-nanoemulsifying delivery systems to enhance bioaccessibility of hydrophobic bioactives (nobiletin): Influence of hydroxypropyl methylcellulose and thermal processing

Emulsion-based delivery systems are widely utilized for encapsulation of hydrophobic bioactive compounds. However, they must be carefully designed to retain and stabilize the encapsulated components during storage, and to release them after ingestion. In the present work, the influence of hydroxypropyl methylcellulose (HPMC) addition and heat treatment on the retention and release of a model hydrophobic nutraceutical (nobiletin) in nanoemulsions prepared by self-emulsification was investigated. Physical stability was assessed by measuring nobiletin retention, crystal morphology, and droplet size during storage. Further, the bioaccessibility of nobiletin was evaluated using a simulated gastrointestinal model. The results indicated that the presence of HPMC in the aqueous phase improved the retention of nobiletin in the nanoemulsions, without promoting any physical instability. The saturation concentration of nobiletin in the nanoemulsions increased from 4.5 to 6.0 mg/mL in the presence of HPMC. Heating the nanoemulsions promoted rapid droplet coalescence above a critical temperature. The combination of HPMC addition and heat treatment increased the retention time of nobiletin in nanoemulsions. Neither HPMC addition nor heat treatment affected the bioaccessibility (around 85%) of nobiletin when it was fully dissolved in the nanoemulsions. However, when nobiletin was not fully dissolved in the nanoemulsions, HPMC addition (from 52 to 59% without heat treatment) and heat treatment (from 52% to 82% without HPMC and from 59% to 84% with HPMC) increased the bioaccessibility. These findings are useful for the rational design and fabrication of nanoemulsion-based delivery systems with high loading efficiency and good release characteristics.

Effects of Chitosan Addition on In Vitro Digestibility of Protein-Coated Lipid Droplets

In this study, we characterized the protein-coated lipid droplets with/without cationic polysaccharide under in vitro oral, gastric, and small intestinal conditions. The effects of chitosan (CHI) addition on the mean particle diameter, zeta-potential, micro-structure, rheological properties, microstructure and lipid digestion of emulsions containing whey protein isolate (WPI) at pH 6.5 or 3.0 were investigated. At pH 6.5, the protein charge was negative, strong electrostatic attraction between the oppositely charged CHI and WPI led to the increase in emulsion viscosity and size, while at pH 3.0, both CHI and WPI were positively charged, CHI molecules could not be attracted onto the surface of positively charged protein-coated droplets, and it has weaker effect on the interfacial properties of emulsions. The results showed that WPI–CHI electrostatic interactions played an important role on the physical property, microstructure and lipid digestion of protein-coated lipid droplets. In the simulated gastrointestinal model, the structures were more stable and the lipid digestion rates decreased significantly in WPI–CHI stabilized emulsions compared to WPI-stabilized emulsions. These results suggest that mixed emulsions can be used to design delivery systems for controlling the physicochemical properties of bioactive lipophilic compounds in the food and pharmaceutical industries.

Artificial cell microcapsule for oral delivery of thalidomide: design, preparation, and in-vitro characterization for Crohn’s disease application

Crohn's disease is a chronic inflammatory disorder of the gut and is classified as a type of inflammatory bowel disease. The anti-inflammatory drug thalidomide has shown to be very effective against Crohn’s disease, but presents several limitations such as drowsiness, skin rash and hypertension. Therefore, development of novel delivery system is urgent and necessary. The aim of this paper is to present the formulation of Alginate- Poly-L-Lysine-Alginate (APA) microcapsules for the delivery of thalidomide to desired locations of the gastrointestinal tract. APA microcapsules were designed, prepared and characterized in-vitro for thalidomide release. Mechanical stability of capsules and the drug release profile were monitored in a simulated gastrointestinal model. Data suggest that APA microcapsules enable a slow release of thalidomide in a pH and time-dependent manner. Indeed, the characteristics of APA microcapsules make it a suitable carrier for the targeted delivery of thalidomide to specific areas of the gastrointestinal tract.

The effect of submicron fat droplets in a drink on satiety, food intake, and cholecystokinin in healthy volunteers

Small fat droplets infused into the gut reduce food intake and hunger more than bigger ones, at levels as low as 6 g, and these effects are hypothesized to occur via satiety hormones such as cholecystokinin. It is, however, unknown whether the effect of droplet size would persist after oral consumption. It is also unknown whether an even smaller droplet size can affect hunger and food intake and at what minimum amount of fat. Therefore, the aim of the study was to test the effect of very fine fat droplets on satiety and food intake in two different quantities. In a balanced-order 4-way crossover design, 24 volunteers consumed a fat-free meal replacement drink with either 5 or 9 g oil (rapeseed) and either 3 or 0.1 μm droplet size. Appetite scores and plasma cholecystokinin levels (in n = 12 subset) were measured for 180 min, when food intake was assessed during an ad libitum meal. Data were analyzed by ANCOVA, followed by Dunnett's test and paired t test. The behavior of the emulsions was also characterized in a simulated gastrointestinal model. Despite faster in vitro lipolysis of the smallest droplets, neither droplet size nor fat amount affected satiety or food intake. From t = 45-150 min, cholecystokinin response was 50% higher (P < 0.05) after the 0.1 versus 3 μm, but only with 9 g fat. When this particular fat at these amounts is delivered in a meal replacement drink, droplet size does not influence appetite or food intake. This effect is independent of the amount of fat or plasma cholecystokinin changes.

Characterization and bioaccessibility of tangeretin‐loaded zein colloidal system

Tangeretin, a citrus flavonoid has been shown to possess many beneficial bioactivities. However, bioaccessibility of tangeretin is relatively low due to its high hydrophobicity, which limits its absorption in gastrointestinal tract. The aim of this study was to design a delivery system to improve bioaccessibility of tangeretin. Tangeretin‐loaded zein colloidal system with an average particle size of 400 nm was produced by mixing aqueous phase containing β‐lactoglobulin and organic phase containing zein and tangeretin. After removal of organic solvent, particle size was decreased to about 300 nm. The influence of temperature, pH, ionic strength on the stability of the system was examined. Apparent particle aggregation occurred at high temperature (70 °C), low ionic strength and around isoelectic point of β‐lactoglobulin. Powder form of the above delivery system was successfully produced by lyophilization. After reconstitution into an aqueous solution, the delivery system maintained similar responses to the environment stress as freshly prepared one, suggesting an excellent applicability of the system as a convenient powder ingredient. Using a simulated gastrointestinal model, we demonstrated the colloidal system significantly enhanced tangeretin bioaccessibility. In conclusion, we successfully developed a stable colloidal system that can potentially improve bioaccessibility of tangeretin.Grant Funding Source: EPA‐USDA‐NSF grant

Vitamin E bioaccessibility: Influence of carrier oil type on digestion and release of emulsified α-tocopherol acetate

Vitamin E is an essential micronutrient for humans and animals due to its antioxidant and non-antioxidant biological activities. The α-tocopherol acetate form is often used in foods and other products due to its high biological activity and chemical stability. In this study, we examined the influence of carrier oil type on the bioaccessibility and molecular form of emulsified vitamin E using a simulated gastrointestinal model. Oil-in-water emulsions containing α-tocopherol acetate were prepared using quillaja saponin as a natural surfactant, and either long chain triacylglycerols (LCT) or medium chain triacylglycerols (MCT) as carrier oils. The rate and extent of lipid digestion was higher for MCT- than LCT-emulsions, which was attributed to differences in the water dispersibility of the free fatty acids formed during lipolysis. Conversely, the total bioaccessibility of vitamin E after digestion was higher for LCT- than MCT-emulsions, which was attributed to the greater solubilisation capacity of mixed micelles formed from long chain fatty acids. The conversion of α-tocopherol acetate to α-tocopherol after in vitro digestion was also considerably higher for LCT- than MCT-emulsions, which may impact the subsequent absorption of vitamin E. Overall, this research has important implications for the design and fabrication of effective emulsion-based delivery systems for increasing the bioavailability of vitamin E.

Novel strategies for fabricating reduced fat foods: Heteroaggregation of lipid droplets with polysaccharides

This study describes the formation of emulsion-based materials with novel textural characteristics by controlled heteroaggregation of food-grade colloidal particles and polymers. Heteroaggregation was induced by mixing a suspension of colloidal particles (β-lactoglobulin-coated lipid droplets) with a solution of polymer molecules (pectin) under conditions where the particles and polymers had similar charges (pH 7) or opposite charges (pH 4). The mean particle size, microstructure, flow behavior, and shear modulus of the mixtures formed depended on particle-to-polymer ratio and solution pH. At pH 4, negatively charged pectin molecules were attracted to the surfaces of positively charged protein-coated droplets leading to particle aggregation, increased viscosity, and gel formation, which were attributed to bridging flocculation. At pH 7, pectin molecules were not attracted to the droplet surfaces, but there was still an increase in emulsion viscosity and gel strength above a critical pectin concentration due to depletion flocculation. Bridging flocculation (pH 4) led to more extensive particle aggregation, higher viscosities, and stronger gels than depletion flocculation (pH 7). The presence of pectin in the emulsions had little impact on their microstructure or lipid digestion rate in a simulated gastrointestinal model. This study has important implications for the creation of reduced fat foods, and the development of foods, cosmetics, personal care, and other products with novel properties.

Calcium alginate‐resistant starch mixed gel improved the survival of Bifidobacterium animalis subsp. lactis Bb12 and Lactobacillus rhamnosus LBRE‐LSAS in yogurt and simulated gastrointestinal conditions

SummaryThe aim of this study was to investigate the protective effect of microencapsulation in calcium alginate‐resistant starch mixed gel of a new human isolated strain of Lactobacillus rhamnosus LBRE‐LSAS compared with the probiotic strain of Bifidobacterium animalis subsp. lactis Bb12. Influence of microencapsulation was tested under deleterious digestive environment, when challenged to salivary α‐amylase, to simulated gastric fluid and to simulated intestinal fluid. Bacterial survival, post‐acidifying activity and exopolysaccharides (EPS) content in stored mix yogurt were assessed. Integrity of the beads was acceptable under α‐amylase levels largely higher than those found in human saliva. Under simulated gastrointestinal model, viable cell counts of encapsulated cells were significantly higher than those observed with free cells and remained at the recommended levels. Additionally, microencapsulation allowed an improved viability of bacteria and generated higher EPS amounts in mix yogurt stored at 4 °C. Our results indicate that calcium alginate‐resistant starch beads extend survival under digestive conditions and in yogurt and could be used as an efficient delivery system for probiotics.