Effect of glycation on sodium caseinate-stabilized emulsions obtained by ultrasound

This work explores the potential of high-intensity ultrasound to produce fine-dispersion, long-time-stable, oil-in-water emulsions prepared with native and glycated bovine sodium caseinate (SC). Regardless the ultrasound amplitude and time assayed, the sonicated emulsions of native SC at 0.5 mg/mL had much higher emulsifying activity indexes compared with those emulsions formed by Ultra-Turrax (IKA Werke GmbH & Co., Staufen, Germany) homogenization. Nevertheless, the native SC emulsions were very unstable despite the optimization of parameters such as protein concentration, amplitude of ultrasound wave, and sonication time by using a Box-Behnken design. Early glycation of SC with either galactose, lactose, or 10 kDa dextran substantially improved both emulsifying activity and the stability, whereas at advanced stages of glycation, SC emulsions showed notably reduced emulsifying properties, likely because extensive glycation of SC promoted its polymerization mainly through covalent cross-linking, as was demonstrated by particle size measurements. The increase in particle diameter of glycoconjugates likely affected the diffusion of SC from bulk to the oil-water interface and slowed the reorientation process of the protein at the interface. These findings show that the combined effect of early-stage glycation of SC and high-intensity ultrasound as an emergent technique to form emulsions has the potential to provide improved emulsions that could be used in several food applications.     

Effects of simulated gastric and intestinal digestion on chitooligosaccharides in two in vitro models

Chitooligosaccharides (COS) with different degree of polymerisation (DP) have different physiological activities such as anti-tumour and anti-hyperlipidemia activities. However, the digestive process might lead to the change of DP of COS as well as cause the change of physiological activities in vivo. In this study, two in vitro digestion models (static and dynamic) were used to investigate digestion behaviours of COS and the influencing factors during digestion with or without food matrix. The results showed that COS with DP 2–5 were indigestible and COS with DP 6–10 degraded with time during gastric and intestinal digestion. Pepsin, pancreatin and lipase were the main factors leading to degradation. Food matrix could protect COS with DP 6–10 from degradation during gastric digestion. However, the degradation of COS with DP 6–10 accelerated and the degradation of COS with DP 5 occurred during intestinal digestion with food matrix due to pancreatin, lipase and bile salt.     

Influence of forage type on ruminal bacterial populations and subsequent in vitro fiber digestion

Adaptation of the rumen fibrolytic bacteria to legume, C3 grass, and C4 grass forages was examined in a 3 X 3 Latin square. Fistulated steers were fed alfalfa, smooth bromegrass, and switchgrass hays for 6 wk at 1.8% of body weight. Rumen samples were collected weekly after an overnight fast. Bacterial counts were conducted on rumen samples and all rumen samples were used in an in vitro fiber digestion study with three stages of maturity each for alfalfa, smooth bromegrass, and switchgrass as the substrates. Consumption of alfalfa hay resulted in the highest total viable counts of rumen bacteria but a lower proportion of fibrolytic counts than seen on the grass diets. Use of filter paper as the isolation substrate gave higher fibrolytic counts than seen with NDF of the forage fed as the isolation substrate. Fifty percent or more of the fibrolytic bacteria were Bacteriodes succinogenes, and the switchgrass diet resulted in higher proportions of this organism in the fibrolytic population than seen for alfalfa and smooth bromegrass hays. The rumen inoculum from animals fed alfalfa degraded the fiber fractions of all substrate forages best. Improved in vitro digestibility of a forage was not observed due to feeding the same forage to the donor animals. Volatile fatty acid concentrations and proportions in the in vitro fermentations were related more to forage substrate than diet source. The results indicate that adaptation of the rumen population to diet forage composition occurred, but in vitro digestibility was unrelated to fibrolytic bacterial numbers or proportions.     

Influence of lipid type on gastrointestinal fate of oil-in-water emulsions: In vitro digestion study

The potential gastrointestinal fate of oil-in-water emulsions containing lipid phases from different sources was examined: vegetable oils (corn, olive, sunflower, and canola oil); marine oils (fish and krill oil); flavor oils (orange and lemon oil); and, medium chain triglycerides (MCT). The lowest rates and extents of lipid digestion were observed for emulsified flavor oil, followed by emulsified krill oil. There was no appreciable difference between the final amounts of free fatty acids released for emulsified digestible oils. Differences in the digestibility of emulsions prepared using different oils were attributed to differences in their compositions, e.g., fatty acid chain length and unsaturation. The particle size distribution, particle charge, microstructure, and macroscopic appearance of the emulsions during passage through the simulated GIT depended on oil type. The results of this study may facilitate the design of functional foods that control the digestion and absorption of triglycerides, as well as the bioaccessibility of hydrophobic bioactives.     

蚕蛹蛋白和蚕蛹短肽的模拟胃肠道消化特性研究

研究了蚕蛹蛋白和蚕蛹短肽的氨基酸组成,并分析了其在模拟胃肠道消化过程中的消化特性和氮释放量,探究蚕蛹蛋白和短肽在人类营养支持方面的应用。使用自动氨基酸分析仪测定蚕蛹蛋白和蚕蛹短肽的氨基酸含量,并计算氨基酸评分(AAS)、化学评分(CS)和必需氨基酸指数(EAAI)。蚕蛹蛋白和蚕蛹短肽的消化特性和氮释放量通过体外模拟胃肠道消化实验和凯氏定氮法进行评价的计算。结果表明,蚕蛹蛋白和蚕蛹短肽含有人体所需的18种氨基酸,而且必需氨基酸的组成合理。蚕蛹蛋白和蚕蛹短肽在体外模拟胃肠道消化实验中有良好高效的消化率和较高的氮释放量(约90%)。因此在今后将蚕蛹蛋白和蚕蛹短肽作为优质且经济的蛋白质原料,在动物饲料和人类肠内营养支持制剂方面有巨大的应用潜力。      

Effect of processing conditions on physicochemical properties of sodium caseinate-stabilized astaxanthin nanodispersions

The aim of the present study was to investigate the preparation of sodium caseinate-stabilized astaxanthin nanodispersions as potential active ingredients for food formulations in order to optimize processing conditions. Nanodispersions containing astaxanthin were prepared by an emulsification-evaporation processing technique. The influence of the processing conditions, namely, the pressure of the high-pressure homogenizer (20-90 MPa), the number of passes through the homogenizer (0-4) and the evaporation temperature (16-66 °C) on the physicochemical properties of the prepared astaxanthin nanodispersions were evaluated using a three-factor central composite design. Average particle size, polydispersity index (PDI) and astaxanthin loss in the prepared nanodispersions were considered as response variables. The multiple-response optimization predicted that using three passes through the high-pressure homogenizer at 30 MPa for the preparation of the astaxanthin nanoemulsion and then removing the organic phase (solvent) from the system by evaporation at 25 °C provided astaxanthin nanodispersions with optimum physicochemical properties.     

Influence of dietary fiber on in-vitro lipid digestion of emulsions prepared with high-intensity ultrasound

In terms of disease prevention, nutrition is becoming an increasingly important aspect. Therefore, emulsions as an innovative food product containing health-promoting plant fiber and canola oil prepared with high-intensity ultrasound were investigated. They were analysed regarding their physicochemical properties and their influence on in-vitro digestion. Ultrasound led to a reduction in oil droplet size and a modification of plant fiber, which influenced their techno-functional properties and improved emulsion stability due to higher viscosities. It turned out that fibers with high amounts of soluble dietary fiber were able to stabilize the emulsions during in-vitro digestion until they entered the intestinal phase, forming a micelle-like network. The digestibility could be increased by about 5%. The usage of plant fibers in emulsions can help to increase the daily uptake of dietary fiber and at the same time counteract absorption deficiencies due to better fat digestibility.     

Influence of xanthan gum on the formation and stability of sodium caseinate oil-in-water emulsions

Studies have been made of the changes in droplet sizes, surface coverage and creaming stability of emulsions formed with 30% (w/w) soya oil, and aqueous solution containing 1 or 3% (w/w) sodium caseinate and varying concentrations of xanthan gum. Addition of xanthan prior to homogenization had no significant effect on average emulsion droplet size and surface protein concentration in all emulsions studied. However, addition of low levels of xanthan (≤0.2 wt%) caused flocculation of droplets that resulted in a large decrease in creaming stability and visual phase separation. At higher xanthan concentrations, the creaming stability improved, apparently due to the formation of network of flocculated droplets. It was found that emulsions formed with 3% sodium caseinate in the absence of xanthan showed extensive flocculation that resulted in very low creaming stability. The presence of xanthan in these emulsions increased the creaming stability, although the emulsion droplets were still flocculated. It appears that creaming stability of emulsions made with mixtures of sodium caseinate and xanthan was more closely related to the structure and rheology of the emulsion itself rather than to the rheology of the aqueous phase.     

Development of a simple model device for in vitro gastric digestion investigation

There have been some reports in the literature of model gastric digestion systems to mimic the dynamic physiological processes within the gastrointestinal tract. However, such devices often require the specification of many control parameters making routine digestion tests unfeasible. This paper introduces a simple in vitro digestion device, comprising of a water-jacketed glass vessel into which a spherical Teflon probe of variable diameter can be inserted. The probe is controlled by a texture analyser to simulate the kinetics of a food digestion process. Using this device under well controlled hydrodynamic flow and biochemical conditions key digestion parameters such as pH, food particle size, protein release, lipid release, cloudiness, etc, can be determined. Feasibility tests of the model device have been conducted using roasted and non-roasted peanuts particles. The status of peanut digestion was examined by the changes in particle size distribution and the mean particle size. Significant differences of surface microstructure have also been observed for peanut particles after the digestion. The influence of parameters such as food to gastric juice ratio, the probe speed and pepsin concentration have been examined in this work. Initial results confirm that all these factors influence the kinetic process of gastric digestion considerably and should be well regulated in any in vitro digestion investigations. We propose that the model device has the advantages of easy control and operation and furthermore could be an ideal tool for routine in vitro gastric digestion studies.     

Food protein glycation: A review focusing on stability and in vitro digestive characteristics of oil/water emulsions

Recently, increasing studies have shown that the functional properties of proteins, including emulsifying properties, antioxidant properties, solubility, and thermal stability, can be improved through glycation reaction under controlled reaction conditions. The use of glycated proteins to stabilize hydrophobic active substances and to explore the gastrointestinal fate of the stabilized hydrophobic substances has also become the hot spot. Therefore, in this review, the effects of glycation on the structure and function of food proteins and the physical stability and oxidative stability of protein-stabilized oil/water emulsions were comprehensively summarized and discussed. Also, this review sheds lights on the in vitro digestion characteristics and edible safety of emulsion stabilized by glycated protein. It can further serve as a research basis for understanding the role of structural features in the emulsification and stabilization of glycated proteins, as well as their utilization as emulsifiers in the food industry.     

Interactions between pig gastric mucin and sodium caseinate in solutions and in emulsions

The interactions between pig gastric mucin (PGM) and sodium caseinate (Cas) were studied in solutions and in Cas-stabilized emulsions with respect to the ratio of the two components and the pH (1–7) with an emphasis on pH cycling, using absorbance, zeta potential, light scattering, creaming and microscopy measurements. In solutions, pH-reversible interactions were observed at pH 3 or lower, down to pH 1. Zeta potential measurements suggest that interactions are electrostatic in nature at pH 3, while the negligible charge of PGM allows for some attractive interactions with positively charged Cas at pH 1. Caseinate-stabilized oil-in-water emulsions are stable toward coalescence at pH 1 and pH 7; some coalescence is observed at pH 3. Addition of PGM results in flocculation, either due to depletion (pH 7), or due to bridging flocculation and Cas–PGM interactions similar to those observed in solution (pH 1 and pH 3). The flocculation is reversible, as is shown in pH cycling at pH 1 to pH 7, then to pH 1. Overall, the above can be of interest as an examination of the fate of emulsions in pH transitions and cycling in the human gastrointestinal tract.     

The effect of alginates on in vitro gastric digestion of particulated whey protein

The aim of the study was to investigate how microparticulated and nanoparticulated whey proteins mixed with alginate respond to simulated in vitro gastric digestion conditions at pH 3.0. Initially, particle size distributions and zeta potential were measured in all mixtures at pH 3.0. Particle size distributions as well as SDS‐PAGE were used to investigate the rate of protein degradation by pepsin during simulated in vitro gastric digestion. The complexation of nanoparticulated and microparticulated whey protein with alginates causes formation of insoluble and soluble complexes, which can resist pepsin degradation to a different degree. These results highlight the potential of developing new food products, which can enhance satiety.     

Flavonoids from a grape seed extract interact with digestive secretions and intestinal cells as assessed in an in vitro digestion/Caco-2 cell culture model

Although the bioactivity of flavonoids is related to their bioavailability, little is known about pre-absorption events in the gastrointestinal tract and their possible interactions with digestive constituents and intestinal cells. Using an in vitro digestion/Caco-2 cell culture model, we investigated the effect of digestive secretions on the stability of (+)-catechin (CAT), (−)-epicatechin (EC) and B2 and B3 dimers from a procyanidin-rich grape seed extract (GSE). The availability of phenolic compounds was not affected by salivary and gastric incubations but decreased during intestinal digestion in the absence of Caco-2 cells due to interactions with pancreatic proteins, unmasked by acetonitrile extraction. Then, in the presence of cells, about 43.9% of CAT, 85.3% of EC and all dimers disappeared at the end of 2 h of intestinal incubation. The stability of all compounds at intestinal pH was demonstrated as well as interactions with proteins, associated with a decrease of some cells enzyme activities, e.g., alkaline phosphatase (−79.8%), sucrase-isomaltase (−60.9%) and aminopeptidase N (−60.7%). Moreover, no compounds were detected in the basal compartment of transwells or in cell monolayers.     

Influence of hydrocolloid type on structural breakdown of vegetable purees during in vitro digestion

The aim of this study was to evaluate the effects of the addition of hydrocolloids on the reformulation of pureed zucchini to obtain a healthy food. Changes in the rheological properties after in vitro digestion and in the sensory acceptability of purees were studied. After saliva addition, the carrageenan puree was the sample that kept its structure more stable with similar G′ and G″ values, whereas the guar gum and HPMC purees exhibited a very small decrease in the viscoelastic functions after mixing with saliva and the starch puree was completely degraded due to the effect of amylase. Regarding sensory properties, the scores of the carrageenan puree were the ones that were closest to the starch puree, so carrageenan puree is a good option for preparing a healthy food without any significant modification in its structure after digestion and in the sensory acceptability properties of a traditional puree.     

Influence of sodium dodecyl sulfate on the thermal stability of bovine serum albumin stabilized oil-in-water emulsions

The influence of an anionic surfactant (sodium dodecyl sulfate, SDS) on the thermal stability of emulsions stabilized by a globular protein (bovine serum albumin, BSA) was examined. 1 wt% n-hexadecane oil-in-water emulsions (0.5 wt% BSA, 100 mM NaCl, 20 mM imidizole, pH 7.0) were held isothermally at temperatures from 30 to 90 °C for 30 min. Extensive droplet flocculation was only observed in emulsions held at 90 °C, which lead to rapid creaming instability. The thermal stability of emulsions heated at 90 °C could be greatly improved by adding SDS at surfactant-to-protein molar ratios (R) greater than 5 (∼0.01 wt% SDS). On the other hand, adding surfactant (0<R<600) to the emulsions after heating could not prevent extensive droplet aggregation. Adding SDS to emulsions prior to heating may have improved their thermal stability by increasing the electrostatic repulsion between the lipid droplets or by increasing the denaturation temperature of the adsorbed proteins. These results may have important applications in the development of heat-stable emulsions.     

Proteolysis of milk fat globule membrane proteins during in vitro gastric digestion of milk

The influence of gastric proteolysis on the physicochemical characteristics of milk fat globules and the proteins of the milk fat globule membrane (MFGM) in raw milk and cream was examined in vitro in simulated gastric fluid (SGF) containing various pepsin concentrations at pH 1.6 for up to 2 h. Apparent flocculation of the milk fat globules occurred in raw milk samples incubated in SGF containing pepsin, but no coalescence was observed in either raw milk samples or cream samples. The changes in the particle size of the fat globules as a result of the flocculation were dependent on the pepsin concentration. Correspondingly, the physical characteristics of the fat globules and the composition of the MFGM proteins in raw milk changed during incubation in SGF containing pepsin. The major MFGM proteins were hydrolyzed at different rates by the pepsin in the SGF; butyrophilin was more resistant than xanthine oxidase, PAS 6, or PAS 7. Peptides with various molecular weights, which altered with the time of incubation and the pepsin concentration, were present at the surfaces of the fat globules.     

Influence of dairy practices on the capacity of probiotic bacteria to overcome simulated gastric digestion

The aim of this study was to evaluate the influence of microbiological and technological factors on the viability and functionality of probiotic Lactobacillus strains. In particular, the influence of harvesting time, food matrix, refrigerated storage, time of inoculation and refrigerated storage in fermented milk on the resistance to simulated gastric digestion (RSGD) was evaluated. Moreover, strain resistance to simulated gastric digestion was compared to human gastric fluid. Results showed that the variables studied affected, in a different way and in a strain‐dependent manner, the RSGD. No direct relation was observed between cell viability and RSGD.