Model Stomach System Research Articles

Effect of Antacid Concentration on Acetaminophen-Alginate Sphere Diffusion in a Model Gastric System

This paper presents a growing awareness for socio-cultural and socio-economic factors in medical and pharmaceutical treatments through a review of the current literature, and a concurrent need to produce a cheap and vegetarian alternative to current capsules. It was hypothesized that increasing the concentration of antacid would increase the rate of diffusion of the contents of an acetaminophen-alginate sphere due to the neutralization of pH between stomach acid and the antacid. The methodology employed prepared these spheres with reverse spherification, tested them via spectrophotometry in a model stomach system, and analyzed the data using the Beer-Lambert Law. Finally, it was found that increasing antacid concentration has a direct, yet exponentially decreasing relationship with the rate of diffusion, therefore the hypothesis was only partially correct.

Effects of the gastric juice injection pattern and contraction frequency on the digestibility of casein powder suspensions in an in vitro dynamic rat stomach made with a 3D printed model

Previously, we have prepared a version of the dynamic in vitro rat stomach system (DIVRS-II or Biomimic Rat II). It was constructed and tested by showing similar digestive behaviors with those occurred in vivo. In the present work, a 3D-printed plastic mold was employed to create highly repeatable silicone rat stomach model. It has been seen to have shortened the time to handcraft a model like that used in DIVRS-II. The maximum mechanical force of the current stomach model generated by rolling extrusion is found to be more stable probably due to the more uniform wall thickness of the new model. Then the effects of the simulated gastric secretion patterns and contraction frequency of the system on the in vitro digestibility of casein powder suspensions were investigated. The results have shown that the location of the gastric secretion injection has an impact on experimental digestibility. The position of rolling-extrusion area, established at the central part of glandular portion (stomach B), displayed the highest digestibility compared to that at the other locations. Furthermore, the extent of digestion was positively correlated with the contraction frequency of the model stomach system, with the maximum frequency of 12cpm giving the highest digestibility. This highest digestibility is almost the same as the average value found in vivo. The better digestive performance produced by optimizing the gastric secretion pattern and contraction frequency may be both resulted from the improved mixing efficiency of the food matrix with digestive juice. This study shows that it is possible to achieve what in vivo in a simulated digestion device, which may be used for future food and nutrition studies in vitro.

Comparison between the digestive behaviors of a new in vitro rat soft stomach model with that of the in vivo experimentation on living rats – Motility and morphological influences

A ‘near-real’in vitro stomach model should not only resemble of the biochemical and physiological conditions found in the real stomachs, but also possess their geometrical and morphological details. In this work, quantitative evidences regarding the physiological relevant morphology including wrinkles on the inner-surface of a new rat model stomach, which assisted the compression and digestion behavior of the dynamics in vitro rat stomach (DIVRS), have been presented. A good repeatability in the tests on the DIVRS is shown, compared with the in vivo experiments of the living rats. However the digestion efficiency and the buffering capacity in the DIVRS were lower than the in vivo systems, most likely due to the limited motility mechanism of the movement of the model stomach system. Further improvements are needed to make the DIVRS more attractive for practical applications.

Effect of boiling, roasting and frying on disintegration of peanuts in simulated gastric environment

The objective of this study was to investigate the influence of boiling, roasting and frying on the digestion of peanuts in simulated gastric environment. Raw and processed peanuts were tested for disintegration in a model stomach system. The differences in disintegration rate were explained with respect to the changes in moisture absorption and texture. The absorption of moisture and the swelling of peanuts during gastric digestion were studied using Magnetic Resonance Imaging (MRI). The results show that processing improved the gastric disintegration of peanuts, and the disintegration rate was in an order of fried > roasted > boiled > raw peanuts. The changes in total weight, moisture and the dry solid loss in the samples were described by Linear–exponential equation, Peleg's equation and the Weibull equation, respectively. Absorption of gastric juice played a critical role in softening the texture contributing to the breakdown of peanuts. Static soaking test indicated that the disintegration rate, as indicated by half time, has a good exponential relationship with the textural parameters of soaked samples. MRI shows potential as being used to analyze the mass transfer phenomenon in solid foods under digestion.

Solid Loss of Carrots During Simulated Gastric Digestion

The knowledge of solid loss kinetics of foods during digestion is crucial for understanding the factors that constrain the release of nutrients from the food matrix and their fate of digestion. The objective of this study was to investigate the solid loss of carrots during simulated gastric digestion as affected by pH, temperature, viscosity of gastric fluids, mechanical force present in stomach, and cooking. Cylindrical carrot samples were tested by static soaking method and using a model stomach system. The weight retention, moisture, and loss of dry mass were determined. The results indicated that acid hydrolysis is critical for an efficient mass transfer and carrot digestion. Internal resistance rather than external resistance is dominant in the transfer of soluble solids from carrot to gastric fluid. Increase in viscosity of gastric fluid by adding 0.5% gum (w/w) significantly increased the external resistance and decreased mass transfer rate of carrots in static soaking. When mechanical force was not present, 61% of the solids in the raw carrot samples were released into gastric fluid after 4 h of static soaking in simulated gastric juice. Mechanical force significantly increased solid loss by causing surface erosion. Boiling increased the disintegration of carrot during digestion that may favor the loss of solids meanwhile reducing the amount of solids available for loss in gastric juice. Weibull function was successfully used to describe the solid loss of carrot during simulated digestion. The effective diffusion coefficients of solids were calculated using the Fick’s second law of diffusion for an infinite cylinder, which are between 0.75 × 10−11 and 8.72 × 10−11 m2/s, depending on the pH of the gastric fluid.

Inactivation of alternative sigma factor 54 (RpoN) leads to increased acid resistance, and alters locus of enterocyte effacement (LEE) expression in Escherichia coli O157 : H7

Alternative sigma factor 54 (RpoN) is an important regulator of stress resistance and virulence genes in many bacterial species. In this study, we report on the gene expression alterations that follow rpoN inactivation in Escherichia coli O157 : H7 strain Sakai (Sakai rpoN : : kan), and the influence of RpoN on the acid resistance phenotype. Microarray gene expression profiling revealed the differential expression of 103 genes in SakairpoN : : kan relative to Sakai. This included the growth-phase-dependent upregulation of genes required for glutamate-dependent acid resistance (GDAR) ( gadA, gadB, gadC and gadE), and the downregulation of locus of enterocyte effacement (LEE) genes, which encode a type III secretion system. Upregulation of gad genes in SakairpoN : : kan during exponential growth correlated with increased GDAR and survival in a model stomach system. Complementation of SakairpoN : : kan with a cloned version of rpoN restored acid susceptibility. Genes involved in GDAR regulation, including rpoS (sigma factor 38) and gadE (acid-responsive regulator), were shown to be required for the survival of SakairpoN : : kan by the GDAR mechanism. This study describes the contribution of rpoN to acid resistance and GDAR gene regulation, and reveals RpoN to be an important regulator of stress resistance and virulence genes in E. coli O157 : H7.

Digestion of Raw and Roasted Almonds in Simulated Gastric Environment

Knowledge of digestion kinetics of solid foods in human stomach, as affected by food processing methods, is critical in establishing processing conditions at the manufacturing stage to achieve desirable release of nutrients in the gastrointestinal tract. The objective of this study was to investigate how roasting affected disintegration and solid release properties of almond in simulated gastric environment. In vitro trials were performed for raw and roasted almonds by using static soaking method and a model stomach system. The changes in sample weight, dry mass, and moisture during the trials were determined. Both compression and penetration tests were used to investigate the texture of almonds with a focus on the influence of absorption of gastric juice. Light microscopy and transmission electronic microscopy were used to study the change in microstructure of the raw and roasted almonds after simulated digestion. The results suggested that the slow disintegration rate and the high amount of swelling of the almonds in the stomach may contribute to their high satiety property. Roasting significantly improved the disintegration rates of almonds and increased loss of solids during simulated digestion, which is well correlated with the decrease in the rigidity of almond samples after absorbing gastric juice. Microstructure of digested almonds showed breakage and breach of cell walls due to acid hydrolysis. Intercellular and intracellular channels formed in almonds during roasting are important for penetration of gastric juice that may facilitate an effective digestion.

Modes of Disintegration of Solid Foods in Simulated Gastric Environment

A model stomach system was used to investigate disintegration of various foods in simulated gastric environment. Food disintegration modes and typical disintegration profiles are summarized in this paper. Mechanisms contributing to the disintegration kinetics of different foods were investigated as related to acidity, temperature, and enzymatic effect on the texture and changes in microstructure. Food disintegration was dominated by either fragmentation or erosion, depending on the physical forces acting on food and the cohesive force within the food matrix. The internal cohesive forces changed during digestion as a result of water penetration and acidic and enzymatic hydrolysis. When erosion was dominant, the disintegration data (weight retention vs. disintegration time) may be expressed with exponential, sigmoidal, and delayed-sigmoidal profiles. The different profiles are the result of competition among the rates of water absorption, texture softening, and erosion. A linear-exponential equation was used to describe the different disintegration curves with good fit. Acidity and temperature of gastric juice showed a synergistic effect on carrot softening, while pepsin was the key factor in disintegrating high-protein foods. A study of the change of carrot microstructure during digestion indicated that degradation of the pectin and cell wall was responsible for texture softening that contributed to the sigmoidal profile of carrot disintegration.

A Model Stomach System to Investigate Disintegration Kinetics of Solid Foods during Gastric Digestion

Knowledge of the disintegration kinetics of food particulates in the human stomach is essential for assessing the bioaccessibility of nutrients in solid foods and understanding stomach emptying. The objective of this study was to develop a model stomach system and to investigate the kinetics of food disintegration. Our system consisted mainly of a turntable and a jacketed glass chamber containing simulated gastric juice in which plastic beads were added to simulate food particulates as well as provide a suitable mechanical destructive force on food samples. The mechanical force on the samples was simultaneously measured using the load cell of a TA-XT2 texture analyzer. Cylindrical carrots and ham samples were used as representative foods. The system is capable of simulating the in vivo stomach in terms of providing a wide range of continuous and periodic forces comparable to those measured in vivo. The modified power exponential function of the form y(t)= 1 - (1 -e(-kt))(beta), where y(t) is the mass retention ratio at time t, provided a reasonable description for the disintegration performance of tested foods. The mass retention curve can be either a sigmoidal decay with an initial delay or an exponential decay, which are decided largely by the hardness of the foods during digestion and the extent of physical force acting on the foods. A good match was observed between the kinetics of food disintegration and in vivo stomach emptying.

The antimicrobial effect of wine on Listeria innocua in a model stomach system

A model stomach, containing a food matrix and a synthetic gastric fluid, was used to study the bactericidal effect of ingested wine on Listeria innocua. Volumes of wine equivalent to the ingestion of one glass and half a bottle, led, over a period of less than 2 h, to a reduction of 3 and 4 logarithmic cycles of the initial population respectively. The influence of ethanol and organic acids, wine constituents with known antimicrobial properties, was investigated. Ethanol exhibited a higher bactericidal effect than the mixture of the main wine organic acids. When testing the organic acids separately, malic and lactic acids were found to have the strongest effect. The combination of ethanol with the organic acids acted synergistically but to a lesser extent than wine itself. The results suggest that the ingestion of wine during a meal may diminish the quantity of Listeria persisting further in the alimentary tract.

Variation in acid resistance among enterohaemorrhagic Escherichia coli in a simulated gastric environment

To compare survival of enterohaemorrhagic Escherichia coli (EHEC) strains of two clonal groups in a simulated gastric environment and to quantify the effect of storage in an acidic food, apple juice, on subsequent survival of EHEC in the simulated gastric environment. To characterize acid resistance of EHEC under conditions simulating the gastric environment, survival was measured in a model stomach system (MSS) for two clonal groups of EHEC: 14 EHEC 1 strains of serotype O157:H7 and 12 EHEC 2 strains of serotypes O26:H11 and O111:H8. There were significant differences between the two EHEC groups, with the average survival rate of O157 strains in the MSS twice as great as the O26/O111 strains. Strains of the two groups also differed in the quantity of injured cells in MSS and in the transcript levels of the glutamate decarboxylase genes (measured by quantitative PCR) in stationary phase before cultures entered the MSS. The results indicate that E. coli O157:H7 strains have superior ability to survive simulated gastric acidity compared with the non-O157 EHEC. E. coli O157:H7 becomes acid resistant rapidly upon entry into stationary phase, which may underlie the low infectious dose of this pathogen.

Antimicrobial Effects of Wine on Escherichia coli O157:H7 and Salmonella typhimurium in a Model Stomach System

ABSTRACT: Survival of Escherichia coli O157:H7 and Salmonella spp. was evaluated in grape juice and wine. Bacteria were inactivated in wine within 60 min but survived up to 16 d in juice. A model stomach system containing food and synthetic gastric fluid (SGF) was designed to investigate the antibacterial effect of wine when consumed with a meal. In this system, wine had little effect on E. coli O157:H7 survival whereas Salmonella was undetectable after 120 min. A nonvolatile wine fraction (containing acids) was more effective in killing Salmonella than a volatile wine fraction (containing alcohol), suggesting that antibacterial activity of wine is primarily acid dependent.