Simulated Small Intestinal Digestion Research Articles

Phenolic Release during In Vitro Digestion of Cold and Hot Extruded Noodles Supplemented with Starch and Phenolic Extracts

Dietary phenolic compounds must be released from the food matrix in the gastrointestinal tract to play a bioactive role, the release of which is interfered with by food structure. The release of phenolics (unbound and bound) of cold and hot extruded noodles enriched with phenolics (2.0%) during simulated in vitro gastrointestinal digestion was investigated. Bound phenolic content and X-ray diffraction (XRD) analysis were utilized to characterize the intensity and manner of starch-phenolic complexation during the preparation of extruded noodles. Hot extrusion induced the formation of more complexes, especially the V-type inclusion complexes, with a higher proportion of bound phenolics than cold extrusion, contributing to a more controlled release of phenolics along with slower starch digestion. For instance, during simulated small intestinal digestion, less unbound phenolics (59.4%) were released from hot extruded phenolic-enhanced noodles than from the corresponding cold extruded noodles (68.2%). This is similar to the release behavior of bound phenolics, that cold extruded noodles released more bound phenolics (56.5%) than hot extruded noodles (41.9%). For noodles extruded with rutin, the release of unbound rutin from hot extruded noodles and cold extruded noodles was 63.6% and 79.0%, respectively, in the small intestine phase, and bound rutin was released at a much lower amount from the hot extruded noodles (55.8%) than from the cold extruded noodles (89.7%). Hot extrusion may allow more potential bioaccessible phenolics (such as rutin), further improving the development of starchy foods enriched with controlled phenolics.

Bilosomes: A controlled delivery system for the sustained release of torularhodin during digestion in the small intestine both in vitro and in vivo

Torularhodin is a carotenoid with various biological activities, but its poor chemical stability and low bioavailability are obstacles to its usage. In this study, different small intestinal controlled delivery systems of torularhodin; including liquid-lip, liposomes, niosomes, and bilosomes; were prepared and characterized. Then, in vitro simulated gastrointestinal digestion model and in vivo mouse model were used to evaluate their sustained-release properties. Finally, mathematical models such as release kinetics revealed the release mechanisms of different systems. The results of particle size distribution and release rate of torularhodin indicated that both the liquid-lip and liposomes systems were almost completely digested after 2 h of simulated small intestinal digestion. However, the bilosomes system remained intact after simulated gastric digestion and were slowly cleaved during simulated small intestinal digestion with a sustained release effect of torularhodin. The fitting results of six kinetic models demonstrated that the kinetic mechanism of torularhodin release from bilosomes was a non-fickian mechanism. The main mechanism may be that bilosomes enhance the permeability of enterocyte biofilms by opening tight junctions between intestinal epithelial cells, thereby prolonging the release of torularhodin in the small intestine. Pharmacokinetic results in mice showed that the area under the concentration time curve in the bilosomes system was 2.73 times that of the liquid-lip system, and the t 1/2 was as long as 22.5 h, demonstrating that bilosomes system was an efficient delivery system for enhancing both the stability and bioavailability of torularhodin in the small intestine. These findings can be used to help future potential applications of bilosomes delivery systems for improving the bioavailability of carotenoids in food.

Release characteristics and bioaccessibility of lutein from calcium alginate hydrogels during simulated digestion in vitro

SummaryIn this study, the release of lutein from calcium alginate hydrogels during simulated digestion in vitro was investigated. The results showed that the cross‐linked hydrogel with Ca2+ concentration >7.5 mM had a large amount of lutein retained on the surface, and digestive enzymes caused rapid degradation of the hydrogel structure, resulting in a high initial release rate. The particle size of the digestate was the largest in the simulated small intestinal digestion stage, with the gradual degradation of the outer wall proteins of lutein nanoparticles, showing a decreasing trend in the colonic digestion stage. The hydrogel cross‐linked with high concentration of Ca2+ mainly released lutein nanoparticles with small particle size. In the later stage, the probability of agglomeration between lutein nanoparticles increased. The cumulative release rate of lutein in the hydrogel with Ca2+ concentration <7.5 mM was higher after digestion, but lutein retention was <80%. The formation of lutein mixed micelles was hindered by the hydrogel with a Ca2+ content more than 7.5 mM, and lutein bioaccessibility was reduced. As a result, appropriate concentration of Ca2+ cross‐linked hydrogel carrier improved lutein bioavailability while also extending the residence period.

Effect of heat-moisture treatment to raw paddy rice (Oryza sativa L.) on cooked rice properties

Heat moisture treatment is safe and non-chemical use method for modifying physicochemical properties and digestibility of starch. Slow starch digestion in rice product would provide numerous health benefits for the consumers. This study investigated the heat-moisture treatment to the raw paddy rice at 60 and 80 °C for 4 and 24 h, and their effects on the attributes of cooked rice. The firmness, adhesiveness, starch hydrolysis and morphological changes during in vitro digestion were examined. Results showed that heat-moisture treatment to raw paddy rice for 24 h significantly reduced the moisture content and could increase the total starch content of the rice grain. The apparent amylose content ranged from 23.83% to 25.65% at the variation in the values between treated and untreated rice. Enhancement in the firmness and reduction in the starch hydrolysis was found in rice treated by longer heating time of 24 h. Meanwhile, the adhesiveness of cooked rice was decreased when increasing the heating temperature. The morphological observation showed that the treated rice exhibited a honey-comb-like structure during simulated gastric digestion, while the untreated rice displayed a non-uniform structure. Noteworthy, the porous structure observed in all digested rice grains during simulated small intestinal digestion could favor the starch hydrolysis. This study showed that the heat-moisture treatment to the raw paddy rice at certain conditions obviously influenced the attributes of cooked rice, especially on the starch hydrolysis, which would provide a fundamental knowledge to enable development and improvement of slow digestion rice products.

A novel apparatus for time-lapse optical microscopy of gelatinisation and digestion of starch inside plant cells

A new instrument was developed for time-lapse optical microscopy of a cohort of individual food particles, which we denote as ParCS (Particle Cohort Study). The cohort can be observed through each stage of simulated hydrothermal processing, followed by in vitro gastrointestinal digestion. Instrument capabilities include the quantification of cooking and digestion dynamics of starch trapped inside isolated cotyledon cells from navy beans. The cells, contained within a flow-through chamber, were cooked at 90°C and subsequently subjected to simulated gastric digestion and simulated small-intestinal digestion. Little or no cell expansion was observed, and the cells remained intact, i.e., the cell walls showed no signs of rupture throughout the entire process. In contrast, intracellular starch granules partially swelled and gelatinised with a maximum relative granule area of approximately 2.4 at the end of cooking. During the small intestinal digestion, cellular contents were observed to visually “shrink” radially inwards towards the centre of the cells, implying that starch hydrolysis by pancreatic α-amylase had occurred inside the cells. Kinetic modelling of this shrinking process showed that the cells underwent amylolysis of cellular contents at different rates. This latter finding demonstrates that our new technique allows quantitative characterisation of starch gelatinisation and digestion inside cotyledon cells at the single-particle scale and may be used to test mechanistic hypotheses.

Comparison between microwave‐cooking and steam‐cooking on starch properties and in vitro starch digestibility of cooked pigmented rice

AbstractThe influence of two types of cooking method, that is, steam‐cooking and microwave‐cooking, on the morphological structure, starch fractions, and starch digestibility of cooked Thai pigmented rice (three cultivars) was examined. The relationship between starch hydrolysis and change in X‐ray diffraction (XRD) pattern, including the change of crystallinity degree during in vitro digestion, was also investigated. The results indicated that the cooked rice morphological structure and starch hydrolysis rate during in vitro digestion was varied by the cooking method. All non‐waxy rice cultivars exhibited Vh‐type crystallinity, whereas, no crystalline peak was detected in the waxy rice cultivar. However, the XRD pattern and crystallinity degree of steam‐cooked rice were dramatically changed after simulated small intestinal digestion for 360 and 480 min when compared with microwave‐cooked rice. Moreover, steam‐cooked rice showed a significantly lower percentage of equilibrium starch hydrolysis than that of the microwave‐cooked rice.Practical applicationsRice attributes and change of crystallinity in XRD pattern during in vitro digestion have found to correlate with rice starch digestibility, which varied depending on rice cooking methods. Steam‐cooking could enhance the degree of crystallinity during in vitro digestion, which would affect to retard rice starch digestion. This finding is interesting for the consumer on the selection of the optimized cooking process that promotes a healthier effect.

Droplet coalescence as a potential marker for physicochemical fate of nanoemulsions during in-vitro small intestine digestion

Intestinal droplet coalescence is central to the lipid digestibility of oil-in-water nanoemulsions. In the present study, a methodology has been proposed to investigate the rheological transformations of nanoemulsions in response to the simulated conditions of small intestinal mechanical forces. The relationship between rheological changes and droplet coalescence phenomenon was probed. Elastic moduli of nanoemulsions attained a maximum at a specific point of digestion time, which was found to be characteristic of the emulsifier used. The onset of droplet coalescence showed evident dependence on the elastic modulus. The above correlation was quantified with an improved empirical model for droplet coalescence frequency. However, droplet coalescence was beyond the scope of rheology and depended on changes in the zeta potential of droplets, which eventually determined the release of free fatty acids. The critical time point was mapped at which the balance of rheological and electrostatic forces on droplet coalescence was altered as the lipolysis proceeds during the simulated small intestinal digestion of nanoemulsions.

The importance of an oral digestion step in evaluating simulated in vitro digestibility of starch from cooked rice grain

To examine the effect of oral digestion step in a simulated in vitro starch digestion model, the digestibility of intact, homogenized and actual chewed cooked rice grains was investigated and analyzed. The kinetics of starch digestibility were calculated from changes in the hydrolysis percent of starch that were achieved during simulated small intestinal digestion stage. Morphological and histological microscopic tissue structures were also examined. Compared with the trend of starch hydrolysis changes of the actual chewed grain, 1.3U/ml of salivary α-amylase concentration treated for 60min was regarded as a mimicked condition to the simulate in vitro oral digestion step in this study. The results showed that the equilibrium percent of starch hydrolysis for all of the samples ranged from 84.2% to 95.9% with no significant differences observed regardless of whether the oral digestion step was included (p>0.05). In contrast, the kinetic constant, which is one of the measure of starch digestion rate during small intestinal stage, significantly increased with the degree of grain homogenization increased: 120s>actual chewed ≥1s>intact, for both the gastrointestinal and oral plus gastrointestinal processes. These results indicated that the kinetic constant was influenced by the change of cooked rice grain structure in oral digestion step that would be related to increase in enzyme accessibility to rice starch. Thus, rice grain digestibility was affected by grain-scale structural changes, including grain tissue damages which were normally observed during the oral digestion step.

Simulated intestinal hydrolysis of native tapioca starch: Understanding the effect of soluble fibre

Abstract Soluble fibre has been shown to have a reducing effect on plasma glucose levels, which is of particular importance due to the rapidly increasing rates in type 2 diabetes. Researchers speculate that an increase in digesta viscosity is responsible for lowering glucose in the blood; however, the exact mechanism remains to be elucidated. In the present study we examined the effect that adding viscous soluble fibres would have on starch digestibility during simulated intestinal digestion. Tapioca starch was formulated with skim milk powder to act as a control. The treatments consisted of xanthan gum, guar gum, soluble flaxseed gum and soy soluble polysaccharide (SSPS) at constant viscosity. Subsequently, all solutions were exposed to a 3-stage in vitro digestion, mimicking the salivary, gastric, and small intestinal steps. Light scattering results showed that the particle size of starch granules decreased as digestion proceeded. Microscopy showed evidence of substantial degradation along the surface of the granules extracted from the control, flax and SSPS solutions upon completion of simulated small intestinal digestion. The progression of these changes was attenuated for granules that were extracted from the guar gum and xanthan gum solutions, which we believe is linked to their rheological behaviour as both solutions had greater viscosities inside the digesta in comparison to the other treatments. The results of this study suggest that the glucose-lowering ability of viscous fibres may be related to their ability to reduce the rate at which starch granules are hydrolysed inside the lumen.

Impact of structural characteristics on starch digestibility of cooked rice

To examine the impact of structural characteristics of cooked rice grains on their starch digestibility, a simulated in vitro gastro-small intestinal digestion technique was applied to intact and homogenised cooked rice samples. The starch hydrolysis percentage increased during simulated small intestinal digestion, in which approximately 65% and 24% of the starch was hydrolysed within the first 5min, for homogenised and intact cooked rice, respectively. The kinetic constant of homogenised cooked rice, which was regarded as an estimated digestion rate, was ∼8 times higher than the intact cooked rice. The homogenised and intact samples were also examined for any microstructural changes occurring during the in vitro digestion process using fluorescent and scanning electron microscopy. In the intact samples, the aleurone layers of the endosperm remained as thin-film like layers during in vitro digestion and thus may be regarded as less digestible materials that influence cooked rice digestibility.

In vitro digestibility of starch in cooked potatoes as affected by guar gum: Microstructural and rheological characteristics

► In vitro digestion of starch in cooked potatoes was performed. ► Guar gum delays starch hydrolysis in cooked potatoes. ► Microstructural and rheological characteristics of cooked potatoes were studied. Potatoes from different New Zealand cultivars (Nadine, Moonlight, Red Rascal, Agria) were analysed for starch digestibility in vitro (under simulated gastric and small intestinal conditions). The extent of starch hydrolysis (%) for all the potato cultivars ranged between 85% and 95% at the end of in vitro digestion. Nadine potatoes, which were waxy in texture, showed higher starch hydrolysis (%) whereas these levels did not differ significantly among the other three cultivars. Confocal laser scanning microscopy and scanning electron microscopy were performed on the digests in order to study the microstructural changes occurring during digestion in cooked potatoes. The micrographs clearly showed that starch was quickly hydrolysed by the enzymes present in simulated intestinal fluid (SIF) whereas the cell walls remained intact during simulated digestion process. Addition of guar gum (0.5%) to cooked potatoes reduced their starch hydrolysis (%) by ∼15% during the in vitro digestion. Online viscosity measurements were also performed on the cooked potatoes during simulated small intestinal digestion using a dynamic rheometer. Cooked potato viscosity dropped considerably upon the action of enzymes from SIF on starch as the digestion progressed. The presence of 0.5% guar gum facilitated the cooked potato matrix to maintain viscosity similar to undigested cooked potato sample throughout the in vitro digestion, which might have resulted in lower starch hydrolysis (%).

Impact of Style of Processing on Retention and Bioaccessibility of β-Carotene in Cassava (Manihot esculanta, Crantz)

We previously demonstrated that the quantity of beta-carotene (BC) partitioning in mixed micelles during simulated small intestinal digestion, i.e., the bioaccessibility, of boiled cassava is highly correlated with the BC content of different cultivars. However, cassava is also traditionally prepared by fermentation and roasting. These different methods of preparation have the potential to affect both the retention and bioaccessibility of BC. Here, we first compared retention of BC in boiled cassava, gari (fermentation followed by roasting), and fufu (fermentation followed by sieving and cooking into a paste) prepared from roots of three cultivars. BC content in unprocessed cultivars ranged from 6-8 microg/g wet weight, with cis isomers accounting for approximately one-third of total BC. Apparent retention of BC was approximately 90% for boiled cassava and fufu. In contrast, roasting fermented cassava at 195 degrees C for 20 min to prepare gari decreased BC content by 90%. Retention was increased to 63% when temperature was decreased to 165 degrees C and roasting was limited to 10 min. Processing was also associated with a decline in all-trans-BC and concomitant increase in 13-cis-BC. The efficiency of micellarization of all-trans and cis isomers of BC during simulated digestion was 25-30% for boiled cassava and gari and independent of cultivar. However, micellarization of BC isomers during digestion of fufu was only 12-15% (P < 0.05). These differences in retention and bioaccessibility of BC from cassava products prepared according to traditional processing methods suggest that gari and fufu may provide less retinol activity equivalents than isocaloric intake of boiled cassava.

Bioaccessibility of Pro-Vitamin A Carotenoids Is Minimally Affected by Non Pro-Vitamin A Xanthophylls in Maize (Zea mays sp.)

The absorption of some carotenoids has been reported to be decreased by coingestion of relatively high concentrations of other carotenoids. It is unclear if such interactions occur among carotenoids during the digestion of plant foods. Current varieties of maize contain limited amounts of the pro-vitamin A (pro-VA) carotenoids beta-carotene (BC) and beta-cryptoxanthin (BCX) and relatively higher levels of their oxygenated metabolites lutein (LUT) and zeaxanthin (ZEA). Here, we examined if LUT and ZEA attenuate the bioaccessibility of pro-VA carotenoids at amounts and ratios present in maize. BC incorporation into bile salt mixed micelles during chemical preparation and during simulated small intestinal digestion of carotenoid-enriched oil was slightly increased when the concentration of LUT was sixfold or more greater than BC. Likewise, the efficiency of BC micellarization was slightly increased during simulated small intestinal digestion of white maize porridge supplemented with oil containing ninefold molar excess of LUT to BC. Mean efficiencies of micellarization of BC, BCX, LUT, and ZEA were 16.7, 27.7, 30.3, and 27.9%, respectively, and independent of the ratio of LUT plus ZEA to pro-VA carotenoids during simulated digestion of maize porridge prepared from flours containing 0.4-11.3 microg/g endogenous pro-VA carotenoids. LUT attenuated uptake of BC by differentiated cultures of Caco-2 human cells from medium-containing micelles in a dose-dependent manner with inhibition reaching 35% when the molar ratio of LUT to BC was 13. Taken together, these results suggest that the bioaccessibility of pro-VA carotenoids in maize is likely to be minimally affected by the relative levels of xanthophylls lacking pro-VA activity present in cultivars of maize.