Polyphenol and nutrient release from skin of almonds during simulated human digestion

The bioaccessibility of nutrients and phytochemicals from almond skin has not been previously evaluated. We quantified the release of lipid, protein and polyphenols during simulated human digestion from natural (NS) and blanched (BS) skins, the latter being a by-product of the almond industry. Higher percentages of polyphenols were released from NS compared to BS during in vitro digestion. Most of the limited release of lipid and protein occurred during gastric digestion, with no significant differences between NS and BS. The total dietary fibre content was 45% for NS and 46% for BS, glucose and galacturonic acid being the major sugars present. No changes in dietary fibre composition and distribution of autofluorescent phenolics were observed in the cell walls of almond skin after simulated digestion. In the GI tract, the cell walls may therefore function as a useful source of fermentable fibre with beneficial implications for gut health.     

Pathogenic potential of Salmonella Typhimurium DT104 following sequential passage through soil, packaged fresh-cut lettuce and a model gastrointestinal tract

From a quantitative microbial risk assessment perspective it is important to know whether certain food environments influence the pathogenic potential of pathogens and to what extent. The purpose of the present study was to examine the pathogenic potential of S. Typhimurium DT104, measured as the capability to survive a simulated gastrointestinal tract system and the capability of adhering to and invading differentiated Caco-2 cells, after sequential incubation (without intermediate culturing) into soil, lettuce and cut lettuce stored under modified atmosphere (MAP) conditions. Two S. Typhimurium DT104 strains were used, one isolated from a pig carcass and one isolated from lettuce. The most important result of the present study is that the sequential incubation of S. Typhimurium in soil and lettuce slightly increased the capability of surviving the simulated gastric fluid, increased the capability to grow in the simulated intestinal fluid but decreased the capability of epithelial attachment and invasion and decreased the overall survival probability of the gastrointestinal tract system. Some variation in responses between the strains was observed, with the lettuce strain maintaining higher epithelial attachment capability and the carcass strains maintaining higher epithelial invasion capability. This study provided quantitative data on the effect of environmental and food matrices on the pathogenic potential of S. Typhimurium DT104 using a realistic system of sequential incubations in environmental and food matrices, followed by simulated gastrointestinal tract passage without intermediate culturing. These results could aid the development of more realistic quantitative microbial risk assessments.     

Release of folic acid from sodium alginate-pectin-poly(ethylene oxide) electrospun fibers under in vitro conditions

The present study evaluated the release behavior of folic acid from ultrafine sodium alginate-pectin-poly(ethylene oxide) electrospun fibers under in vitro conditions. In aqueous solution, the release of folic acid at pH 1.2 (64%) was significantly higher than at pH 3 (21%). At pH 7.8, the majority of folic acid was released (97%) due to extensive swelling and partial dissolution of the fibers. In simulated gastric juice, the folic acid release profile was similar to that of aqueous solution at pH 1.2. By contrast, using the simulated pH 7.8 intestinal fluid, a lower amount (40%) of folic acid was released as compared with the aqueous alkaline solution. These results showed that the release of folic acid from the alginate fibers is affected by the constituents present in the simulated intestinal fluid, in addition to the pH effect. The in vitro release study showed that the composite alginate electrospun fibers have good potential as a carrier that retains folic acid in acidic food products (pH 3), but selectively releases the micronutrient in the small intestine.     

Advances in the in vitro digestion and fermentation of polysaccharides

In vitro digestion models are widely used to study the structural changes, digestion and release of food components under simulated gastrointestinal conditions. As compared to the in vivo digestion tests, the in vitro digestion reflects the digestion and utilisation of food after ingestion and has the advantages of being time consuming, inexpensive, reproducible and free from moral and ethical restrictions. This study reviewed the current research studies on the in vitro simulated digestion of polysaccharides conducted in the last 5 years and focused on the oral, gastric and intestinal digestion models, with the aim of providing a basis for the further testing of changes in the content, structure and active ingredients of polysaccharides before and after digestion.     

Effect of gastric pH and bile acids on the survival of Listeria monocytogenes and Salmonella Typhimurium during simulated gastrointestinal digestion

The human gastrointestinal tract (GIT) harbors numerous defensive mechanisms to impede pathogen colonization, including gastric acidity and bile acids in the small intestine. This study aims to elucidate the survival of Salmonella Typhimurium and Listeria monocytogenes under different levels of gastric pH (2.0–3.5) and bile acid concentrations (2.5 mM – 10.0 mM), during an in vitro digestion process following the ingestion of a contaminated food model system. The results showed that S. Typhimurium  was more susceptible to gastric acidity than L. monocytogenes, yet more bile acid tolerant. Interestingly, the bile acids bactericidal effect towards L. monocytogenes was higher if the previous exposure to the gastric acidity was harsher. Our findings suggest that, despite the different microbial behavior of the two species in the simulated GIT, the effects of gastric acidity and bile acids alone could not prevent their survival in the intestine.Industrial relevanceS. Τyphimurium and L. monocytogenes represent biological threats that are of major concern for the food industry due to their ubiquitous nature and their ability to trigger foodborne illnesses. Their ability to survive the gastrointestinal passage is crucial for their subsequent intestinal colonization that can lead to host infection. Therefore, obtaining a deeper insight into the factors affecting pathogen survival in the gut is vital for the establishment of more efficient strategies to prevent foodborne diseases. Given the limitations and ethical constraints of conducting studies like this in vivo, the applied in vitro digestion model system along with the mathematical modelling can provide a valuable alternative that can be readily utilized in the food and pharmaceutical industry as a platform for similar digestion studies.     

From pre- to postweaning: Transformation of the young calf's gastrointestinal tract

The ruminant gastrointestinal tract (GIT) faces the challenge of protecting the host from luminal contents and pathogens, while supporting the absorption and metabolism of nutrients for growth and maintenance. The GIT of the calf in early life undergoes some of the most rapid microbial and structural changes documented in nature, and these adaptations in GIT function make the young calf susceptible to GIT diseases and disorders. Despite these challenges, the calf's GIT has a certain degree of plasticity and can sense nutrient supply and respond to bioactive ingredients. Calf GIT research has historically focused on the transition during weaning and characterizing ruminal papillae development using microscopy and digesta metabolite responses. Through the use of new molecular-based approaches, we have recently shown that delaying the age of weaning and providing a step-down weaning protocol is associated with a more gradual shift in ruminal microbiota to a postweaned state. In addition to ruminal adaptations during weaning, nutrient flow to the lower gut changes dramatically during weaning, coinciding with a wide array of structural and microbiological changes. Structural and gene expression changes suggest that the lower gut of the dairy calf undergoes alterations that may reduce barrier function when solid feeds are consumed. More recently, in vivo data revealed that the weaning transition increases total gut permeability of the calf. Interestingly, the lower gut may be able to communicate with the forestomach, meaning that a nutrient can be sensed in the lower gut and cause subsequent adaptations in the forestomach. An improved understanding of how diet, microbiota, and functional ingredients interact to affect growth and barrier function of the intestinal tract would greatly benefit the dairy calf industry. A mechanistic understanding of such adaptations would also aid in the formulation of specific management regimens and provision of functional ingredients required to characterize and enhance gut function in young calves.     

Survival of Lactobacillus rhamnosus strains inoculated in cheese matrix during simulated human digestion

Survival of probiotic bacteria during transit through the gastrointestinal (GI) tract is influenced by a number of environmental variables including stomach acidity, bile salts, digestive enzymes and food matrix. This study assessed survival of seven selected Lactobacillus rhamnosus strains delivered within a model cheese system to the human upper GI tract using a dynamic gastric model (DGM). Good survival rates for all tested strains were recorded during both simulated gastric and duodenal digestion. Strains H12, H25 and N24 demonstrated higher survival capacities during gastric digestion than L. rhamnosus GG strain used as control, with H12 and N24 continuing to grow during duodenal digestion. Strains L. rhamnosus F17, N24 and R61 showed adhesion properties to both HT-29 and Caco-2 cells. The ability to attach to the cheese matrix during digestion was confirmed by scanning electron microscopy, also indicating production of extracellular polysaccharides as a response to acid stress.     

In vitro assessment of the upper gastrointestinal tolerance of potential probiotic dairy propionibacteria

This study aimed to assess the transit tolerance of potential probiotic dairy propionibacteria strains in human upper gastrointestinal tract in vitro, and to evaluate the effect of food addition on viability of these strains in simulated pH 2.0 gastric juices. The transit tolerance of 13 dairy propionibacteria strains was determined at 37 degrees C by exposing washed cell suspensions to simulated gastric juices at pH values at 2.0, 3.0, and 4.0, and simulated small intestinal juices (pH 8.0) with or without 0.3% bile salts. The viability of dairy propionibacteria in pH 2.0 simulated gastric juice with So-Good original soymilk or Up & Go liquid breakfast was also determined. The simulated gastric transit tolerance of dairy propionibacteria was strain-dependent and pH-dependent. All tested strains were tolerant to simulated small intestinal transit. The addition of So-Good original soymilk or Up & Go liquid breakfast greatly enhanced the survival of dairy propionibacteria strains in pH 2.0 simulated gastric juices. Dairy propionibacteria strains demonstrate high tolerance to simulated human upper gastrointestinal tract conditions and offer a relatively overlooked, yet alternative source for novel probiotics besides Lactobacillus and Bifidobacterium.     

Roles for dietary fibre in the upper GI tract: The importance of viscosity

Dietary fibre has long been recognised as healthy because of its prebiotic quality and a number of dietary fibres, especially beta glucan have been shown to lower levels of circulating LDL cholesterol. However, although EFSA allow health claims to be made for this, there is no fundamental understanding of the detailed mechanism involved. More recently dietary fibre has been shown to have a range of functionality in the upper GI tract. The presence of fibre can alter gastric emptying thus affecting fullness and satiety. These alterations are a result of differences in viscosity, nutrient release and nutrient sensing in the duodenum. The current proposed mechanisms for the cholesterol lowering effects involve disruption of the normal recycling of bile possibly by sequestering bile salts and fatty acids or by significantly decreasing the rate of absorption as a result of entanglement with intestinal mucus.The use of quantitative confocal microscopy methods such as fluorescence recovery after photobleaching (FRAP) and multiple particle tracking has provided evidence that dietary fibre can combine with intestinal mucus and produce a layer that significantly delays the transport of lipid digestion products. We have also used similar methods in conjunction with more conventional rheology to show that DNA from the gut epithelium can contribute significantly to the barrier properties of the intestinal mucus layer.The delay in the transport of nutrients to the gut epithelium has implications for the control of gastric emptying and through secretion of GI hormones such as CCK and thus for the satiating ability of foods. It may also have implications for the reabsorption of bile.     

Effect of different matrices on probiotic resistance to in vitro simulated gastrointestinal conditions

In this study, we evaluated the effect of different matrices (MRS, milk and milk with inulin) on the tolerance of probiotic strains (Lactobacillus acidophilus La‐5 and Bifidobacterium animalis subsp. lactis BB‐12) to simulated conditions similar to those found in the gastrointestinal tract. Both probiotic strains demonstrated a significantly lower viability after exposure to in vitro gastric and intestinal conditions, and B. animalis subsp. lactis BB‐12 showed higher survival during the test compared to L. acidophilus La‐5 in all tested matrices. Milk and inulin protected probiotics from in vitro gastrointestinal stress. These results suggest that it is critical to formulate the food matrix to be used as probiotic carrier.     

Survival of Lactobacillus rhamnosus strains in the upper gastrointestinal tract

In the present study six probiotic Lactobacillus rhamnosus strains were investigated for their ability to survive in the human upper gastrointestinal tract through a dynamic gastric model of digestion. MRS broth was used as delivery vehicle and survival was investigated during in vitro gastric and gastric plus duodenal digestion. Results highlighted that all tested strains showed good survival rate during both gastric and duodenal digestion. In particular, three strains exhibited a great survival showing a recovery percentage in the range between 117 and 276%. In agreement with survival data, high lactic acid production was detected for all strains, confirming their metabolic activity during digestion.     

Specific surface modification of liposomes for gut targeting of food bioactive agents

Liposomes have become a research hotspot in recent years as food delivery systems with attractive properties, including the bilayer structure assembled like the cell membrane, reducing the side-effect and improving environmental stability of cargos, controlling release, extending duration of functional ingredients, and high biodegradable and biocompatible abilities in the body. However, the conventional liposomes lack stability during storage and are weak in targeted absorption in the gastrointestinal track. At present, surface modification has been approved to be an effective platform to shield these barricades and help liposomes deliver the agents safely and effectively to the ideal site. In this review, the gastrointestinal stability of conventional liposomes, cargo release models from liposomes, and the biological fate of the core materials after release were emphasized. Then, the strategies in both physical and chemical perspectives to improve the stability and utilization of liposomes in the gastrointestinal tract, and the emerging approaches for improving gut targeting by specifically modified liposomes and the intestinal receptors relative to liposomes/cargos absorption were highlighted. Last but not the least, the safety, challenges, and opportunities for the improvement of liposomal bioavailability were also discussed to inspire new applications of liposomes as oral carriers.     

Protein‐loaded sodium alginate and carboxymethyl cellulose beads for controlled release under simulated gastrointestinal conditions

Network characteristics of sodium alginate and carboxymethyl cellulose, in relation to the controlled release of bovine serum albumin under simulated gastrointestinal conditions, have been examined. Small‐deformation dynamic oscillation in‐shear, compression testing and optical microscopy were employed to monitor the structural characteristics of polysaccharide beads as excipients for protein entrapment. Work focused on gastrointestinal functionality and controlled release utilising variable acidity and counterion addition in preparations. Beads were found to shrink in gastric and swell in intestinal conditions, thus emphasising the disparate effect of experimental conditions. Changes in mechanical properties reflected alterations in gel microstructure, with beads becoming relatively strong in the gastric environment. In contrast, networks were weakened in the intestinal environment resulting in bead disintegration towards the end of digestion time. This type of structural behaviour allows the controlled delivery of the protein, as a model bioactive, in a particular part of the gastrointestinal tract.     

Antiacetylcholinesterase and antioxidant activities of Plectranthus barbatus tea,after in vitro gastrointestinal metabolism

This study describes the in vitro metabolism, by the gastrointestinal tract, together with the biological activity of the herbal tea obtained from Plectranthus barbatus leaves. The results showed that there was no appreciable degradation and that the activity was kept constant after gastric juice digestion. In the presence of pancreatic juice, degradations varied from negligible, in the case of flavonoid glucuronides, to almost complete, in the case of the abietane diterpenoid. The digested decoction contained only 50% of its initial biological activity, after pancreatic digestion. The action of Caco-2 cells on the extract revealed that neither rosmarinic acid, the main compound of the extract, nor the other components present in minute quantities were metabolised by the intact cells. Rosmarinic acid could be found inside Caco-2 cells although in trace amount. Glucoronidase from Escherichia coli, a gut bacterium, was able to hydrolyse the flavonoid derivatives, thus the aglycones were formed and permeate the Caco-2 cells.     

In vitro digestion of whole chia seeds (Salvia hispanica L.): Nutrient bioaccessibility,structural and functional changes

Dietary chia seed (Salvia hispanica L.) has significant health-related benefits due to its high nutrient contents. However, few studies reported the fate of whole seeds in the gastrointestinal tract. Herein, we explored the digestive characteristics in terms of hydrolysis of nutrients, structural and functional properties with a static in vitro digestion method. After gastrointestinal digestion, the digestibility of lipid and protein was 0.46% and 11.38%, respectively. The release rates of tryptophan, tyrosine and lysine were greater than 20%, whereas the glutamic acid and aspartic acid were less than 5%. The microscopic results (optical microscopy (OM), laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM)) demonstrated that the seeds remained intact, and the mucilage adhered tightly to the seed coat during digestion. The water holding capacity and oil holding capacity of seeds accounted for 6.37 and 3.28 g/g after intestinal digestion, which were significantly lower than gastric digestion endpoints (P < 0.05). And there were no significant differences in Fourier transform infrared spectroscopy of G-Mucilage and I-Mucilage. In general, preprocessing before being consumed is necessary for chia seeds to take full advantage of rich polyunsaturated fatty acids and proteins.     

Kiwifruit remnants from digestion in vitro have functional attributes of potential importance to health

The physicochemical properties of plant cell walls in the gut are important in modulating processes that influence health. We investigated the physicochemical properties of kiwifruit cell walls digested under gastric and gastroileal conditions in vitro. Soluble and insoluble undigested polymer fractions were measured, the hydration properties of the digested pulp, and the capacity to retard diffusion and mixing in a simulated small intestinal segment. Undigested polymer (dietary fibre) fractions differed little between “Hayward’ (‘Hayward’) and ‘Hort16A’ (gold) kiwifruit cultivars in their relative proportions, although total dietary fibre was greater in ‘Hayward’ than in the ‘Hort16A’. The polysaccharide composition of seed-free digestion-resistant polymer was similar in both cultivars and not affected by in vitro digestion. Indigestible remnants from kiwifruit had strong water retention and swelling capacities, also little affected by digesting, and retarded both glucose diffusion and mixing significantly, especially in the presence of low background viscosity. We conclude that the particulate cell wall remnants of digested kiwifruit retain substantial potential to influence the properties of gut contents.     

应用体外全仿生模型初步分析2种富硒产品中硒形态及生物可给性

建立微波消解-高分辨-连续光源石墨炉原子吸收光谱(high resolution-continuum source graphite furnace atomic absorption spectrophotometry,HR-CS GFAAS)法测定富硒蛹虫草和富硒酵母胃、肠全仿生提取液中各形态硒的方法,研究胃、肠消化对富硒产品中硒形态和生物可给性的影响。采用体外全仿生消化技术对富硒蛹虫草和富硒酵母进行预处理,得到胃、肠全仿生提取液;通过0.45μm微孔滤膜实现可溶态和悬浮态的分离;选择D101大孔树脂分离可溶态中有机态和无机态;分别利用丙酮和无水乙醇沉淀可溶态中蛋白和多糖,得到蛋白结合态和多糖结合态;分别以正辛醇和单层脂质体为细胞膜,模拟富硒产品中硒在人体胃、肠中的分配行为。通过单因素试验,确定最佳测定条件:分析谱线为196.026 7 nm,基体改进剂为1 g/L Pd(NO_3)_2和0.5 g/L Mg(NO_3)_2混合溶液,添加体积为5μL,灰化温度为1 100℃,原子化温度为2 200℃。在此条件下,测定富硒蛹虫草和富硒酵母中硒含量分别为2.129μg/g和27.75μg/g,肠全仿生提取液中除悬浮态其他各形态硒的含量都高于胃全仿生提取液,在肠消化过程中产生的正辛醇醇溶态硒和单层脂质体结合态硒的含量都高于各自水溶态硒。     

Characteristic of microencapsulated 1,3-dioleoyl-2-palmitoylglycerol and its application in infant formula powder

1,3-Dioleoyl-2-palmitoylglycerol (OPO) is used widely as a food additive. However, the structured lipid is sensitive to oxygen and light in the production process. This results in the loss of its original nutrition and production of harmful substances. In this study, the OPO was microencapsulated using whey protein isolate and maltodextrin as the wall material and monostearin as an emulsifier by spray-drying technology added to the infant formula milk, in order to improve its oxidative stability. The OPO microcapsules were released in vitro through the simulated gastrointestinal tract; sensory evaluation of microencapsulated OPO in infant formula powder and nutrition absorption of microencapsulated OPO in infant formula power by animal experiments were investigated. The results showed that OPO microcapsules have a slow-release effect; after 2 h of simulated gastric fluid digestion, only 16.1 ± 3.2% of the oil was released from microencapsulated OPO, and after another 2 h of simulated intestinal fluid digestion, there was 92.3 ± 2.8% of oil released from the microencapsulated OPO. The infant formula with microencapsulated OPO has a uniform colour and no odour. The quality of infant formula with microencapsulated OPO was obviously better than infant formula with OPO by storage test. Everted mice gut sac experiments confirmed that microencapsulation did not affect absorption of mice to OPO in infant formula and prevented the loss of calcium. The study confirmed that addition of microencapsulated OPO makes infant formula more efficient for product quality and nutrition absorption.     

Influence of functional food components on gut health

Intestinal epithelial cells (IECs) lining the gastrointestinal tract establish a barrier between external environments and the internal milieu. An intact intestinal barrier maintains gut health and overall good health of the body by preventing from tissue injury, pathogen infection and disease development. When the intestinal barrier function is compromised, bacterial translocation can occur. Our gut microbiota also plays a fundamentally important role in health, for example, by maintaining intestinal barrier integrity, metabolism and modulating the immune system, etc. Any disruption of gut microbiota composition (also termed dysbiosis) can lead to various pathological conditions. In short, intestinal barrier and gut microbiota are two crucial factors affecting gut health. The gastrointestinal tract is a complex environment exposed to many dietary components and commensal bacteria. Dietary components are increasingly recognized to play various beneficial roles beyond basic nutrition, resulting in the development of the functional food concepts. Various dietary modifiers, including the consumption of live bacteria (probiotics) and ingestible food constituents such as prebiotics, as well as polyphenols or synbiotics (combinations of probiotics and prebiotics) are the most well characterized dietary bioactive compounds and have been demonstrated to beneficially impact the gut health and the overall well-being of the host. In this review we depict the roles of intestinal epithelium and gut microbiota in mucosal defence responses and the influence of certain functional food components on the modulation of gut health, with a particular focus on probiotics, prebiotics and polyphenols.