Digestion Kinetics Research Articles

Sous-vide cooking improves the quality and in-vitro digestibility of Semitendinosus from culled dairy cows.

Effect of sous-vide processing was evaluated on in-vitro simulated protein digestion, myofibrillar protein profile, lipid oxidation and physicochemical properties of cold-boned beef Semitendinosus. Sous-vide processed [T1, 60 °C (4.5 h); T2, 60 °C (10 h)] samples along with control beef (cooked at 80 °C until a core temperature of 75 °C was attained) were subjected to in-vitro simulated gastrointestinal protein digestion. Samples collected at 0, 30 and 60 min of gastric digestion and 120 and 180 min of intestinal digestion were analysed for protein profile (SDS-PAGE), protein digestibility (%), soluble protein (%), free amino acid analysis and mineral profile. A significant (P < 0.05) decrease was observed in shear force (N) and cooking loss (%) of sous-vide processed samples in comparison to control whereas a significant (P < 0.05) increase was observed in colour (L*, a*, b*). A significant (P < 0.05) increase was also observed in protein digestibility (%), soluble protein (%) and release of free amino acids and minerals from sous-vide processed samples during in-vitro digestion. By modifying the protein profile of the meat, sous-vide processing had a positive influence on in-vitro digestion kinetics that led to a greater and faster digestion of proteins during simulated digestion.

Dietary nitrate metabolism and enteric methane mitigation in sheep consuming a protein-deficient diet

It was hypothesised that the inclusion of nitrate (NO3–) or cysteamine hydrochloride (CSH) in a protein deficient diet (4.8% crude protein; CP) would improve the productivity of sheep while reducing enteric methane (CH4) emissions. A complete randomised designed experiment was conducted with yearling Merino sheep (n = 24) consuming a protein-deficient wheaten chaff control diet (CON) alone or supplemented with 1.8% nitrate (NO3–; DM basis), 0.098% urea (Ur, DM basis) or 80 mg cysteamine hydrochloride/kg liveweight (CSH). Feed intake, CH4 emissions, volatile fatty acids (VFA), digesta kinetics and NO3–, nitrite (NO2–) and urea concentrations in plasma, saliva and urine samples were measured. There was no dietary effect on animal performance or digesta kinetics (P &amp;gt; 0.05), but adding NO3– to the CON diet reduced methane yield (MY) by 26% (P = 0.01). Nitrate supplementation increased blood MetHb, plasma NO3– and NO2– concentrations (P &amp;lt; 0.05), but there was no indication of NO2– toxicity. Overall, salivary NO3– concentration was greater than plasma NO3– (P &amp;lt; 0.05), indicating that NO3– was concentrated into saliva. Our results confirm the role of NO3– as an effective additive to reduce CH4 emissions, even in a highly protein-deficient diet and as a source of additional nitrogen (N) for microbial protein synthesis via N-recycling into saliva and the gut. The role of CSH as an additive in low quality diets for improving animal performance and reducing CH4 emissions is still unclear.

The effect of dietary nitrate and canola oil alone or in combination on fermentation, digesta kinetics and methane emissions from cattle

Nitrate and lipids have been recognized as effective dietary additives to reduce enteric methane (CH4) production. The objective of this experiment was to evaluate the effects of nitrate (NO3¯) and canola oil, alone or in combination, on enteric CH4, volatile fatty acid (VFA) concentrations, digesta kinetics and outflow of DM and microbial non-ammonia nitrogen (MicNAN) from the rumen of cattle. Four rumen-cannulated steers were used in the experiment which was designed as 4 × 4 Latin Square with four 21-d periods and four treatments. Dietary treatments consisted of a control diet (CON: 400 g/kg lucerne chaff and 600 g/kg barley grain), NO3¯ (CON + 20 g NO3¯/kg), O (CON + 50 g canola oil/kg), and NO3¯+O (CON + 20 g NO3¯/kg + 50 g canola oil/kg) with all inclusions expressed as g/kg as-fed. Exogenous markers (Co-EDTA, Yb-acetate and 15NH4Cl) were continuously infused into the rumen over 4 d to estimate digesta flow and rumen N outflow while whole tract digestibility (DMD) was determined using chromic oxide. Compared with the CON diet, feeding the NO3¯+O diet reduced (P < 0.01) methane yield (MY, g CH4/kg DMI) by 25%, daily methane production (DMP, g CH4/d) by 26% (P < 0.01) and the rumen mean retention time (MRT; P < 0.05). Nitrate containing diets reduced DMD (P < 0.01). Total VFA did not differ between treatments (P > 0.05) but NO3¯-containing diets increased acetate proportion (P < 0.01) whereas feeding the O diet increased propionate proportion (P < 0.01). Oil-containing diets reduced rumen volume (P < 0.01). The rumen protozoa concentration was reduced by including NO3¯ and canola oil alone or in combination in the diet of cattle (P < 0.05). This experiment demonstrates that feeding NO3¯+O has a synergistic effect on reducing methanogenesis from beef cattle which is consistent with NO3¯ and canola oil having complementary mechanisms for suppressing enteric CH4 production. Reducing methanogenesis by feeding NO3¯+O in this experiment did not improve the flow of MicNAN from the rumen (g MicNAN/d), microbial growth efficiency (g MicNAN/digestible organic matter intake, DOMI) or the proportion of microbial N derived from rumen NH3.

Spray dried smectite clay particles as a novel treatment against obesity

To explore the feasibility of spray dried smectite clay particles fabricated from montmorillonite or laponite materials for adsorbing dietary lipids and reducing rodent weight gain in vivo. Spray dried montmorillonite (SD-MMT) and spray dried laponite (SD-LAP) particles were prepared via spray drying. Particle morphology, surface area and redispersion/aggregation properties in aqueous media were characterized. The ability of SD-MMT and SD-LAP particles to inhibit lipid digestion kinetics and adsorb lipid species from solution was assessed during in vitro lipolysis using proton nuclear magnetic resonance analysis. SD-MMT and SD-LAP particles were dosed to rodents fed a high-fat diet and their effect on body weight gain was evaluated. Both SD-MMT and SD-LAP particles adsorbed significant quantities of medium chain triglycerides and lipolytic products from solution during in vitro lipolysis. At a concentration of 50% w/w relative to lipid content, SD-MMT and SD-LAP particles adsorbed 42% and 94% of all lipid species, respectively. SD-MMT and SD-LAP particles also reduced the extent of rodent weight gain relative to the negative control treatment group and performed similarly to orlistat via an alternate mechanism of action. Spray dried smectite clay particles (SD-MMT and SD-LAP) with significant adsorptive capacities for dietary lipids and digestion products were successfully fabricated. These particles may be developed as novel anti-obesity treatments with fewer adverse effects than currently marketed treatment options.

Basal and Postprandial Myofibrillar Protein Synthesis Rates Do Not Differ between Lean and Obese Middle-Aged Men

ABSTRACTBackgroundExcess lipid availability has been associated with the development of anabolic resistance. As such, obesity may be accompanied by impairments in muscle protein metabolism.ObjectiveWe hypothesized that basal and postprandial muscle protein synthesis rates are lower in obese than in lean men.MethodsTwelve obese men [mean ± SEM age: 48 ± 2 y; BMI (in kg/m2): 37.0 ± 1.5; body fat: 32 ± 2%] and 12 age-matched lean controls (age: 43 ± 3 y; BMI: 23.4 ± 0.4; body fat: 21 ± 1%) received primed continuous L-[ring-2H5]-phenylalanine and L-[ring-3,5-2H2]-tyrosine infusions and ingested 25 g intrinsically L-[1-13C]-phenylalanine labeled whey protein. Repeated blood and muscle samples were obtained to assess protein digestion and amino acid absorption kinetics, and basal and postprandial myofibrillar protein synthesis rates.ResultsExogenous phenylalanine appearance rates increased after protein ingestion in both groups (P < 0.001), with a total of 53 ± 1% and 53 ± 2% of dietary protein–derived phenylalanine appearing in the circulation over the 5-h postprandial period in lean and obese men, respectively (P = 0.82). After protein ingestion, whole-body protein synthesis and oxidation rates increased to a greater extent in lean men than in the obese (P-interaction < 0.05), resulting in a higher whole-body protein net balance in the lean than in the obese (7.1 ± 0.2 and 4.6 ± 0.4 µmol phenylalanine · h−1 · kg−1, respectively; P-interaction < 0.001). Myofibrillar protein synthesis rates increased from 0.030 ± 0.002 and 0.028 ± 0.003%/h in the postabsorptive period to 0.034 ± 0.002 and 0.035 ± 0.003%.h−1 in the 5-h postprandial period (P = 0.03) in lean and obese men, respectively, with no differences between groups (P-interaction = 0.58).ConclusionsBasal, postabsorptive myofibrillar protein synthesis rates do not differ between lean and obese middle-aged men. Postprandial protein handling, including protein digestion and amino acid absorption, and the postprandial muscle protein synthetic response after the ingestion of 25 g whey protein are not impaired in obese men. This trial was registered at www.trialregister.nl as NTR4060.

A more general approach to fitting digestion kinetics of starch in food

Two models for the digestion of starch in foods are considered: sequential, where two or more reactions follow one another, and parallel, where they occur simultaneously. Each reaction is assumed to be first-order, and to be characterized by a rate coefficient and a digestible fraction. For parallel kinetics, a new fitting method is developed; methods for sequential reactions are already available, based on the “logarithm of slopes” technique. Least-squares fitting methods for each are set out, which identify the uncertainties associated with each rate parameter, so that one can see if one has assumed too many or too few processes. The methods gave robust results with synthetic data, and were applied to real in vitro digestion data for wheat starches with up to 93% amylose. The combination of parallel and sequential models provides a general approach to investigating the kinetics of starch digestion in food.

Biodegradable biopolymer network structures to create delayed burst digestive release of encapsulated lipids

This study sought to investigate whether encapsulation of lipids in core-shell hydrogel structures of tailored shell porosity could create a delayed burst release of encapsulated lipids, and examined the underpinning mechanisms. We demonstrated that gastrointestinal digestion of core-shell structures resulted in a delay in the onset of lipid digestion, without affecting lipid digestion kinetics. Systematic increase in hydrogel protein content above 65 g/L lead to an exponential increase in digestive delay (250 min). Whilst an increase in xanthan content between 5 and 9 g/L lead to a modest decrease in digestive delay (40 min). Rheological investigations revealed a linear relationship between hydrogel storage modulus G′ and digestive breakdown delay (T1/2). Given that G’ is directly related to hydrogel mesh size, this result suggests that the main factor controlling the timing of digestive release is the average mesh size of the outer protein hydrogel. A kinetic model was created to describe the delayed burst release behaviour of encapsulated lipids and successfully predicted the influence of shell thickness, shell protein density on the timing of gastro-intestinal release (in vitro). By combining microstructural/rheological experiments with in vitro digestive studies we have understood the main factors controlling the digestive breakdown of hierarchical biopolymer hydrogels. We could successfully miniaturise these core-shell structures so they would easily empty from the stomach whilst maintaining programmable delayed burst release. We have created a novel family of core-shell hydrogel oral dosage forms for the delivery of poorly soluble drugs and the programmed delivery of lipids within the gut.

Lipid emulsion enhances fish allergen parvalbumin’s resistance to in vitro digestion and IgG/IgE binding capacity

This study was performed to determine Parvalbumin (PV), a well-known fish allergenic protein, digestion kinetics and immunoreactivity of digestion products with Immunoglobulin G/Immunoglobulin E recognition to understand its allergic potential with or without lipid emulsion process. PV was subjected to simulated gastrointestinal digestion in emulsified condition. Digestion kinetics of the protein was analysed by electrophoresis, IgG/IgE binding ability by immunoblotting and indirect ELISA. Lipid emulsion significantly (p < 0.01) reduced the degree of PV hydrolysis by 52.10% for gastric digestion. Immune fragments of gastric digestion were detectable for 90–120 min longer in emulsified condition showing resistance. Consequently, lipid emulsion decreased the digestive ability of PV in stomach, increasing resistance to gastrointestinal digestion by pepsin proteases. It also altered IgG/IgE binding ability of digestion products, thereby indicating that PV with lipid emulsion was resistant to digestion and possessed increased IgE binding ability resulting in higher risk of allergy among sensitized individuals.

Effect of starch properties and zein content of commercial maize hybrids on kinetics of starch digestibility in an in vitro poultry model.

The kinetics of starch digestion is a key determinant of poultry performance. Research so far has shown that starch digestibility kinetics depends on the molecular structure of starch but also on the properties of the complex matrix in which starch granules are embedded in most feedstuffs. However, the manner in which genotype differences in the same plant affect starch digestibility kinetics has not yet been addressed. The present study explored the extent to which the starch digestibility rate in commercial high-yielding maize hybrids depended on amylose / amylopectin content, starch granule size and shape, and zein in total starch (TS) content. Hybrids differed in all the traits examined, giving the following ranges: amylose content, 165-207 g kg-1 DM; zein in TS content, 70-89 g kg-1 DM; starch granule equivalent diameter, 11.5-12.3 μm, and in vitro starch digestion rate, 1.22-1.44 h-1 . The starch digestion rate correlated negatively with zein in TS content (r = -0.36) and positively with equivalent diameter (r = 0.45). The negative correlation between starch digestion rate and zein in TS suggests that some zein remained after grinding and pepsin incubation and acted as a barrier to amylolytic enzymes. When starch granules are embedded in a complex protein matrix, zein limits their accessibility to enzymes and affects the starch digestibility rate. Surprisingly, our results suggest that when enzymes reach starch granules, they digest a greater proportion of the starch when the granules are larger. © 2019 Society of Chemical Industry.

In vivo digestion characteristics of protein sources fed to broilers

The rate and extent of protein digestion are relevant to broiler performance and health, but information is lacking on the rate of digestion and the characteristics of the undigested fraction for common protein feed ingredients. Therefore, this study evaluated the digestion kinetics and the distal ileum (DI) digesta protein characteristics of protein meals fed to broiler chickens. Using a completely randomized design, 360 male broilers at 14 D of age were assigned to 60 battery cages and fed semi-purified diets composed of wheat starch (N-free) or wheat starch with either corn distillers dried grains with solubles (CDDGS), corn gluten meal, meat and bone meal, soybean meal, fish meal (FM), porcine meal (PCM), canola meal, blood meal (BM), or feather meal. At day 21, the protein digestion kinetics and total and soluble protein of the DI content were determined. Differences were considered significant when P ≤ 0.05. Protein source affected the extent of amino acid (AA) and CP digestibility at the DI. The results demonstrated differences in digesta mean retention time (MRT) and the rate of digestion of AA and CP among protein sources. FM had the shortest MRT of 46min, whereas CDDGS had the longest at 142min. Both FM and PCM had the highest digestion rates for most of the AA evaluated among the protein sources, whereas CDDGS had the lowest. In turn, the total and soluble CP in the distal ileal contents ranged from 54 to 1466 mg and 6 to 347mg, respectively. In conclusion, dietary protein source influences the amount and solubility of the undigested protein in the DI and the digestion kinetics of AA and CP along the small intestine of broilers. These parameters may contribute to the effects of protein source on muscle deposition and could influence the impact protein sources may have on gut health through protein fermentation.

188 Comparison of two software methods of fitting one- and two-compartment age-dependent digesta kinetics models

Abstract Ruminant nutritionists fit digesta kinetics models to better understand processes in the gastrointestinal tract. Several software packages are available to fit one- and two-compartment, age-dependent digesta kinetics models to fecal marker concentration over time after giving a marker dose. We characterized repeatability and agreement for two programs (R and SAS) used to fit these models. We constructed 8100 datasets using a Monte-Carlo approach where errors were added to true marker concentrations for samples from 81 synthetic profiles representing different animal and diet combinations (100 datasets per profile). Datasets contained concentrations at 15 nominal times (from 0 to 120 hours after dosing). The two error sources were sampling time (uniform between -3 and 1 hours) and concentration measurement (normal with mean 0 and SD = 5 + 0.08CT, where CT is true concentration). The resulting datasets were fit to G2 and G2G1 models using both software and model parameters (K0, λ or λ1, K2, and τ) were used to calculate digesta kinetics parameters (particle passage rate, gastrointestinal DM fill, fecal DM output, gastrointestinal mean retention time, and rumen retention time). When fitting G2 models, all converged, but when fitting G2G1 model, 60 did not converge. The parameters were more repeatable from R than from SAS, but the ratios of repeatability to the mean was generally less than 10%. Bias and SD of differences between software packages were also small. The G2G1 models produced smaller bias and SD of differences than the G2 models. Bias and SD for digestion parameters between software were also small, however, G2G1 models had smaller biases and SD of differences than G2 models. Repeatability was better with R than with SAS, but mean differences were small; the G2G1 model was more repeatable than the G2 model, but differences between software were small for G2G1 models.

Replacing alfalfa hay with triticale hay has minimal effects on lactation performance and nitrogen utilization of dairy cows in a semi-arid region of Mexico

In the semi-arid highlands of central Mexico, triticale (× Triticosecale L.) is emerging as an alternative, less water-demanding forage crop than alfalfa for dairy cattle. Studies reported here were aimed at evaluating triticale hay (TH) relative to alfalfa hay (AH) for lactating cow performance, apparent digestibility, N partition, and ruminal degradation kinetics of dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF). Study 1 was conducted on a privately owned farm. Four barns were used to conduct 4 replicated 3 × 3 Latin squares (1 barn = 1 square), where each barn included 3 pens (experimental units) receiving 1 of 3 dietary treatments. Each pen had 62 Holstein dairy cows. All diets included a forage-to-concentrate ratio of 42:58 (DM basis), which is typical for intensive dairy farms of the region. Dietary treatments were formulated to replace AH with TH on a CP basis, and included (DM basis) 15.1% AH and 0% TH, 9.0% AH and 7.4% TH, and 0% AH and 16.4% TH. Diets were iso-energetic (1.64 Mcal of net energy for lactation/kg of DM) and iso-nitrogenous (17.9% CP). Pen-level DM intake and milk production were from all cows in the pen, but pen-level milk composition, apparent digestibility, and N partitioning were from 8 cows (observational units) randomly selected in each pen. Orthogonal contrasts were used to determine linear and quadratic effects of increasing TH from 0 to 7.4, and 16.4% of dietary DM. Although DM intake was not affected, there was a tendency for CP intake to decline linearly and for NDF intake to increased linearly as TH replaced AH in the diet. Milk production declined linearly by 0.077 kg/d for each additional percentage unit of TH in the diet, which amounted to a 3.5% decline when TH replaced AH entirely. However, no effect was observed on energy-corrected milk production because of a compensatory linear effect of increasing milk fat concentration with the incorporation of TH in the diet. Total-tract NDF digestibility tended to increase linearly by 18.5%, but no differences were detected for urinary urea-N excretion and for N utilization estimated as milk N/(fecal N + urinary N + milk N). Study 2 was an in situ trial conducted to determine the degradation kinetics of AH and TH used in study 1. In spite of differences in degradation kinetics parameters for DM, CP, and NDF, only NDF effective ruminal degradation tended to be greater for TH than AH. Replacing AH with TH at the level typically found in intensive dairy farms of the semi-arid regions of Mexico had minimal effects on milk production and N utilization.

A simplified model to simulate bioaugmented anaerobic digestion of lignocellulosic biomass: Biogas production efficiency related to microbiological data

Mathematical model applications for the bioaugmented anaerobic digestion (BAD) process seem to be lacking in the scientific literature, even more so when related to microbiological data. The present study suggests a simplified mathematical model to investigate and simulate the process kinetics of bioaugmented anaerobic digestion (BAD) aimed at improving biogas production from wheat straw (WS). Bioaugmented conditions were obtained through a mixed inoculum of anaerobic ruminal fungi (ARF) and hydrogen-producing fermenting bacteria (F210) added to a methanogenic inoculum. The investigation focused on two process configurations characterized by a mono (I-BAD) and two-stage (II-BAD) process and a conventional anaerobic digestion (AD) control test. Each configuration was used on two operating scales (i.e., 120 ml and 12,000 ml reactor volume) to provide different data sets for the calibration and validation of the mathematical model proposed. The model calibration step was used to determine the optimal values of selected parameters displaying higher significance for experimental result predictability. The model calibration results highlighted a similar behavior for both BAD tests, which was further strengthened by a statistical analysis supporting the observed correlation regardless of the BAD configuration involved. The BAD configuration always enhanced the CH4 production (>70%) with a faster kinetic in the II-BAD test. The microbiological results support the superior performance of the II-BAD test, displaying higher Archaea fractions (up to 14.5% on day 23) with values more than double compared to I-BAD and triple compared to the AD test. Furthermore, the presence of Methanosarcina inside the Archaea guild (6.4% and 4.5% at days 11 and 61, respectively) ensures a greater diversification of the metabolic pathways and supports the strength of the process performance. Cell density values are strongly in line with these results.

Effect of process-induced common bean hardness on structural properties of in vivo generated boluses and consequences for in vitro starch digestion kinetics

In the present study, we evaluated the effect of process-induced common bean hardness on structural properties of in vivo generated boluses and the consequences for in vitro starch digestion. Initially, the impact of human mastication on the particle size distribution (PSD) of oral boluses from common beans with different process-induced hardness levels was investigated through a mastication study. Then the effect of structural properties of selected boluses on in vitro starch digestion kinetics was assessed. For a particular process-induced hardness level, oral boluses had similar PSD despite differences in masticatory parameters between participants of the mastication study. At different hardness levels, a clear effect of processing (P<0·0001) was observed. However, the effect of mastication behaviour (P=0·1141) was not significant. Two distinctive fractions were present in all boluses. The first one was a cotyledon-rich fraction consisting of majorly small particles (40-125 µm), which could be described as individual cells based on microscopic observations. This fraction increased with a decrease in process-induced hardness. The second fraction (>2000 µm) mostly contained seed coat material and did not change based on hardness levels. The in vitro starch digestion kinetics of common bean boluses was only affected by process-induced hardness. After kinetic modelling, significant differences were observed between the reaction rate constant of boluses generated from the hardest beans and those obtained from softer ones. Overall this work demonstrated that the in vitro nutritional functionality of common beans is affected to a greater extent by structural properties induced by processing than by mechanical degradation in the mouth.

Different duck products protein on rat physiology and gut microbiota

We report the effects of protein from different duck products on the intestinal flora and physiology of rats. After 30 days of feeding, rats fed water–boiled salted duck protein had the lowest gut microbial diversity and richness. Allobaculum, Lactobacillus, Coprococcus and Eubacterium increased in rats fed wine-cured duck protein, while rats fed water–boiled salted and wine-cured duck protein showed increased serum urea (UREA) concentrations and serum cholesterol (CHOL) to HDL-cholesterol (HDLC) ratios, but decreased retroperitoneal white adipose tissue (rWAT) and perirenal white adipose tissue (pWAT) to body weight ratios. The changes in gut bacteria were mainly associated with the fat-mass index (weight of rWAT or pWAT to body weight ratio), accompanied by the opposite correlation with UREA content. SignificanceIt showed that protein from different duck products impacted the intestinal flora and caused physiological changes in rats. Different sources of processed protein vary in their digestibility and digestive kinetics, all of which can affect the intestinal microbiota and physiology. We report the effects is an effort to map the complex interactions of “host physiology-nutrition-microbiota” in order to provide some insights into that food processing can be improved to promote beneficial gut microbes and enhance human health.

Structurally Different Dry Bean Matrices Modulate in Vitro Lipid Digestion (FS14-08-19)

ObjectivesEpidemiological evidence suggests that common beans are hypolipidemic agents and therefore able to alleviate obesity and cardiovascular disease. The observed positive effect of bean consumption on blood lipid levels is mainly attributed to their high content of dietary fiber (DF) and it is linked to the ability of DF to interfere with lipid digestion in different ways. Some proposed mechanisms are related to the physicochemical properties of DF and involve binding of bile acids (BA) which could decrease the rate of lipid digestion and absorption in the duodenum. This study aimed to investigate the effect of bean matrices varying in structure, content and distribution of DF fractions on lipid digestion kinetics in vitro. MethodsStructurally different bean matrices obtained by several processing techniques (i.e., hydrothermal, high pressure and mechanical treatments) as well isolated DF fractions were investigated. b-glucan was used as comparison. The viscosity, particle size and water and oil-binding ability of bean matrices were determined. We used dialysis, under duodenal conditions and HPLC analysis to determine BA-binding capacity. A standardized multistage static in vitro digestion protocol was used to assess the effect of bean matrices on the lipolysis rate of extrinsic lipids. ResultsBeans matrices reduced the extent and rate of digestion of corn oil compared to blank, with the water-soluble DF showing the largest reduction. Hydrothermal-treated beans and bean matrices with larger particle size showed the lowest capacity to retain BA and consequently were less effective at reducing the extent of lipolysis. The lower lipolysis rate observed in specific samples was related to their higher BA-binding. ConclusionsDifferent processing variables generated bean microstructures with different potential to modulate lipid digestion. Overall, processing decreased the ability of bean matrices to delay lipolysis. Isolated bean DF has the potential to control lipolysis depending on DF distribution and BA-binding ability. However, none of the bean matrices reached the levels observed with b-glucan. Funding SourcesUS Dry Bean Council and Hatch Program (NIFA), USDA.

Leucine coingestion augments the muscle protein synthetic response to the ingestion of 15 g of protein following resistance exercise in older men.

Older adults have shown an attenuated postexercise increase in muscle protein synthesis rates following ingestion of smaller amounts of protein compared with younger adults. Consequently, it has been suggested that older adults require the ingestion of more protein to increase postexercise muscle protein synthesis rates compared with younger adults. We investigated whether coingestion of 1.5 g of free leucine with a single 15-g bolus of protein further augments the postprandial muscle protein synthetic response during recovery from resistance-type exercise in older men. Twenty-four healthy older men (67 ± 1 yr) were randomly assigned to ingest 15 g of milk protein concentrate (MPC80) with (15G+LEU; n = 12) or without (15G; n = 12) 1.5 g of free leucine after performing a single bout of resistance-type exercise. Postprandial protein digestion and amino acid absorption kinetics, whole body protein metabolism, and postprandial myofibrillar protein synthesis rates were assessed using primed, continuous infusions with l-[ring-2H5]phenylalanine, l-[ring-2H2]tyrosine, and l-[1-13C]leucine combined with ingestion of intrinsically l-[1-13C]phenylalanine-labeled milk protein. A total of 70 ± 1% (10.5 ±0.2 g) and 75 ± 2% (11.2 ± 0.3 g) of the protein-derived amino acids were released in the circulation during the 6-h postexercise recovery phase in 15G+LEU and 15G, respectively (P < 0.05). Postexercise myofibrillar protein synthesis rates were 16% (0.058 ± 0.003 vs. 0.049 ± 0.002%/h, P < 0.05; based on l-[ring-2H5]phenylalanine) and 19% (0.071 ± 0.003 vs. 0.060 ± 0.003%/h, P < 0.05; based on l-[1-13C]leucine) greater in 15G+LEU compared with 15G. Leucine coingestion further augments the postexercise muscle protein synthetic response to the ingestion of a single 15-g bolus of protein in older men.

Kinetics of starch digestion in native and modified sweetpotato starches from an orange fleshed cultivar

Starch from orange-fleshed sweet potato cultivar was modified using dual autoclave retrogradation, annealing and lintnering modification treatment and their digestibility properties studied. The rate and extent of digestion were suitably predicted with a first-order kinetic model derived in the course of the study. The starches clearly displayed monophasic digestograms while modified starches were observed to have lower glycemic load and glycemic index when compared to the unmodified starch. This study clearly demonstrates the effect of various starch modification treatments on the digestibility of sweet potato starches and also predicted it digestion kinetics parameters.

Screening a Resource of Recombinant Protein Fragments for Targeted Proteomics.

The availability of proteomics resources hosting protein and peptide standards, as well as the data describing their analytical performances, will continue to enhance our current capabilities to develop targeted proteomics methods for quantitative biology. This study describes the analysis of a resource of 26,840 individually purified recombinant protein fragments corresponding to more than 16,000 human protein-coding genes. The resource was screened to identify proteotypic peptides suitable for targeted proteomics efforts, and we report LC-MS/MS assay coordinates for more than 25,000 proteotypic peptides, corresponding to more than 10,000 unique proteins. Additionally, peptide formation and digestion kinetics were, for a subset of the standards, monitored using a time-course protocol involving parallel digestion of isotope-labeled recombinant protein standards and endogenous human plasma proteins. We show that the strategy by adding isotope-labeled recombinant proteins before trypsin digestion enables short digestion protocols (≤60 min) with robust quantitative precision. In a proof-of-concept study, we quantified 23 proteins in human plasma using assay parameters defined in our study and used the standards to describe distinct clusters of individuals linked to different levels of LPA, APOE, SERPINA5, and TFRC. In summary, we describe the use and utility of a resource of recombinant proteins to identify proteotypic peptides useful for targeted proteomics assay development.

Physico-chemical properties of purified starch affect their in vitro fermentation characteristics and are linked to in vivo fermentation characteristics in pigs

Fermentation characteristics and short-chain fatty acid (SCFA) production of purified starch sources differing in physico-chemical properties and in vitro digestion kinetics were investigated using an in vitro porcine model. Four starch sources (rapidly digestible, RD; moderately rapid digestible, MRD; moderately slow digestible, MSD; and slowly digestible, SD) were used. These starch sources were previously fed to growing pigs to determine their net portal appearance (NPA) of SCFA and glucagon-like peptide-1 (GLP-1) and fecal SCFA. Samples were incubated in a buffered mineral solution inoculated with pig feces. Gas production was measured for 72 h and fermentation kinetics were modeled. The fermented solution was analyzed for SCFA at the end of the fermentation. The SD had the greatest (P < 0.05) lag time (2.7 h) while RD to MSD did not differ (mean 2.3 h). Total gas production was greatest (P < 0.05) for MSD (239 ml/g sample) followed by RD, MRD, and SD (236, 226 and 219 ml/g sample, respectively). The fractional rate of degradation was greatest (P < 0.05) for RD (0.19/h), intermediate for MRD and MSD (0.17/h) and lowest for SD (0.11/h). Starch types did not differ (P = 0.749) in total SCFA production (5.8–6.0 mmol/g sample). Amylose content and crystallinity of starches was correlated to in vitro fermentation kinetics, total gas production, and SCFA profile. For example, fractional rate of degradation was negatively correlated with amylose content (r = −0.90, P < 0.001). Butyrate content from starch fermentation was associated with increased in vitro fractional rate of degradation and total gas production and in vivo fermentation metabolites and NPA of SCFA and GLP-1. In conclusion, physico-chemical properties and in vitro digestion kinetics of starch affect in vitro fermentation characteristics and SCFA production and are associated with NPA of SCFA and GLP-1 in pigs. Thus, the in vitro fermentation model can serve to screen starch sources to determine their fermentation characteristics in pigs.