Effect of milk protein composition and amount of ß-casein on growth performance, gut hormones, and inflammatory cytokines in an in vivo piglet model.

The objective of this work was to better understand the effect of differences in milk protein composition, and specifically, a change in ß-casein to total casein in a milk-based matrix, on growth performance and metabolic and inflammatory responses using a piglet model. Three formulas were optimized for piglets, with similar metabolizable energy, total protein content, and other essential nutrients. Only the protein type and ratio varied between the treatments: the protein fraction of the control diet contained only whey proteins, whereas 2 other matrices contained a whey protein to casein ratio of 60:40, and differed in the amount of ß-casein (12.5 and 17.1% of total protein). Piglets fed formula containing whey proteins and caseins, regardless of the concentration of ß-casein, showed a significantly higher average daily gain, average daily feed intake, and feed efficiency compared with piglets consuming the formula with only whey protein. Consumption of the formula containing only whey protein showed higher levels of plasma glucagon-like peptide-1 and ghrelin compared with the consumption of formula containing casein and whey protein. A positive correlation was observed between postprandial time and glucagon-like peptide-1 response. The intestinal pro-inflammatory cytokine tumor necrosis factor α increased significantly in piglets fed the whey protein/casein diet compared with those fed whey protein formula. All formula-fed piglets showed a lower level of IL-6 cytokine compared with the ad libitum sow-fed piglets, regardless of composition. No significant differences in the anti-inflammatory IL-10 concentration were observed between treatment groups. Milk protein composition contributed to the regulation of piglets' metabolic and physiological responses, with whey protein/casein formula promoting growth performance and a different immune regulatory balance compared with a formula containing only whey protein. Results indicated no differences between treatments containing different levels of ß-casein.

Effect of fermented milk from Lactococcus lactis ssp. cremoris strain JFR1 on Salmonella invasion of intestinal epithelial cells.

The process of fermentation contributes to the organoleptic properties, preservation, and nutritional benefits of food. Fermented food may interfere with pathogen infections through a variety of mechanisms, including competitive exclusion or improving intestinal barrier integrity. In this study, the effect of milk fermented with Lactococcus lactis ssp. cremoris JFR1 on Salmonella invasion of intestinal epithelial cell cultures was investigated. Epithelial cells (HT29-MTX, Caco-2, and cocultures of the 2) were treated for 1 h with Lactococcus lactis ssp. cremoris JFR1 fermented milk before infection with Salmonella enterica ssp. enterica Typhimurium. Treatment with fermented milk resulted in increased transepithelial electrical resistance, which remained constant for the duration of infection (up to 3 h), illustrating a protective effect. After gentamicin treatment to remove adhered bacterial cells, enumeration revealed a reduction in numbers of intracellular Salmonella. Quantitative reverse-transcription PCR data indicated a downregulation of Salmonella virulence genes hilA, invA, and sopD after treatment with fermented milk. Fermented milk treatment of epithelial cells also exhibited an immunomodulatory effect reducing the production of proinflammatory IL-8. In contrast, chemically acidified milk (glucono delta-lactone) failed to show the same effect on monolayer integrity, Salmonella Typhimurium invasion, and gene expression as well as immune modulation. Furthermore, an oppA knockout mutant of Salmonella Typhimurium infecting treated epithelial cells did not show suppressed virulence gene expression. Collectively, these results suggest that milk fermented with Lactococcus lactis ssp. cremoris JFR1 is effective in vitro in the reduction of Salmonella invasion into intestinal epithelial cells. A functional OppA permease in Salmonella is required to obtain the antivirulence effect of fermented milk.

Effect of partial whey protein depletion during membrane filtration on thermal stability of milk concentrates.

Membrane filtration technologies are widespread unit operations in the dairy industry, often employed to obtain ingredients with tailored processing functionalities. The objective of this work was to better understand the effect of partial removal of whey proteins by microfiltration (MF) on the heat stability of the fresh concentrates. The micellar casein concentrates were compared with control concentrates obtained using ultrafiltration (UF). Pasteurized milk was microfiltered (80 kDa polysulfone membrane) or ultrafiltered (30 kDa cellulose membrane) without diafiltration (i.e., no addition of water) to 2× and 4× concentration, based on volume reduction. The final concentrates showed no differences in pH, casein micelle size, or mineral concentration in the serum phase. The micellar casein retentates (obtained by MF) showed a 20 and 40% decrease in whey protein concentration compared with the corresponding UF milk protein concentrates for 2× and 4× concentration, respectively. The heat coagulation time decreased with increasing protein concentration, regardless of the treatment; however, MF retentates showed a higher thermal stability than the corresponding UF controls. The average diameter for casein micelles increased after heating in UF but not MF concentrates. The turbidity (measured by light scattering) increased after heating, but to a higher extent for UF retentates than for MF retentates at the same protein concentration. It was concluded that the reduced amount of whey protein in the MF retentates caused a significant increase in the heat stability compared with the corresponding UF retentates. This difference was not due to ionic composition differences or pH, but to the type and amount of complexes formed in the serum phase.

Effect of milk protein composition of a model infant formula on the physicochemical properties of in vivo gastric digestates.

We investigated the effect of protein composition and, in particular, the presence of whey proteins or ß-casein on the digestion behavior of a model infant formula using an in vivo piglet model. Three isocaloric diets optimized for piglets were prepared with the same concentrations of protein. For protein source, 1 diet contained only whey proteins and 2 contained a casein:whey protein ratio of 40:60 but differed in the amount of ß-casein. To obtain the desired protein compositions, skim milk was microfiltered at 7 or 22°C, and retentates and permeates were combined with whey protein isolate. The diets were optimized to the nutritional needs of the piglets and fed to 24 newborn piglets for 18 d. Eight piglets were also fed ad libitum with sow milk and considered only as reference (not included in the statistical analysis). The study was carried out in 2 blocks, killing the animals 60 and 120 min after the last meal. All gastric contents, regardless of diet, showed a wide range of pH. Postprandial time did not affect the pH or physical properties of the gastric digesta. The digesta from whey protein-casein formulas showed significantly higher viscosity, a higher storage modulus, and a denser microstructure than digesta obtained from piglets fed whey protein formula. The ß-casein:total casein ratio at the level used in this study did not significantly affect the physical and chemical properties of the stomach digestate. Although caseins showed extensive gastric hydrolysis, whey proteins remained largely intact at both postprandial times. The results indicate that the presence of different concentrations of milk proteins can be critical to the digestion properties of the food matrix and may affect the nutritional properties of the components.

Invited review: Milk phospholipid vesicles, their colloidal properties, and potential as delivery vehicles for bioactive molecules.

The milk fat globule membrane (MFGM) is a unique colloidal assembly of phospholipids and proteins, with numerous potential applications as functional ingredient. The phospholipid components of the MFGM are gaining interest as they are a useful matrix for use as a constituent of delivery systems such as liposomes. Liposomes formulated with milk phospholipids are becoming an alternative to other sources of phospholipids such as soybean or egg yolk. However, incorporation of phospholipids fractionated from the milk fat globule membrane in dairy products requires an in-depth understanding of the functional properties of phospholipids. In particular, it is critical to understand which factors play a role in their stability and bioefficacy as delivery systems. Moreover, chemical and physical modifications of phospholipid liposomes occurring during digestion and the fate of the encapsulated compounds are very important to understand. This review discusses recent findings on the structure and functionality of MFGM, the bioactivity of the phospholipids fraction, their utilization as delivery systems, and their stability through gastrointestinal transit.

Prediction of milk fatty acid content with mid-infrared spectroscopy in Canadian dairy cattle using differently distributed model development sets.

The fatty acid profile of milk is a prevailing issue due to the potential negative or positive effects of different fatty acids to human health and nutrition. Mid-infrared spectroscopy can be used to obtain predictions of otherwise costly fatty acid phenotypes in a widespread and rapid manner. The objective of this study was to evaluate the prediction of fatty acid content for the Canadian dairy cattle population from mid-infrared spectral data and to compare the results produced by altering the partial least squares (PLS) model development set used. The PLS model development sets used to develop the predictions were reference fatty acids expressed as (1) grams per 100 g of fatty acid, (2) grams per 100 g of milk, (3) the natural logarithmic transform of grams per 100 g of milk, and (4) subsets of samples randomly selected by removing excess records around the mean to present a more uniform distribution, repeated 10 times. Gas chromatography measured fatty acid concentration and spectral data for 2,023 milk samples of 373 cows from 4 breeds and 44 herds were used in the model development. The coefficient of determination of cross-validation (Rcv2) increased when fatty acids were expressed on a per 100 g of milk basis compared with on a per 100 g of fat basis for all examined fatty acids. The logarithmic transformation used to create a more Gaussian distribution in the development set had little effect on the prediction accuracy. The individual fatty acids C12:0, C14:0, C16:0, C18:0, C18:1n-9 cis, and saturated, monounsaturated, unsaturated, short-chain, medium-chain, and long-chain fatty acid groups had (Rcv2) greater than 0.70. When model development was performed with subsets of the original samples, slight increases in (Rcv2) values were observed for the majority of fatty acids. The difference in (Rcv2) between the top- and bottom-performing prediction equation across the different subsets for a single predicted fatty acid was on average 0.055 depending on which samples were randomly selected to be used in the PLS model development set. Predictions for fatty acids with high accuracies can be used to monitor fatty acid contents for cows in milk recording programs and possibly for genetic evaluation.

Addition of glycerol to lactating cow diets stimulates dry matter intake and milk protein yield to a greater extent than addition of corn grain.

The objective of this study was to determine if the addition of glycerol to the diet of dairy cows would stimulate milk protein yield in the same manner as the addition of corn grain. Twelve multiparous lactating dairy cows at 81 ± 5 d in milk were subjected to 3 dietary treatments in a replicated 3 × 3 Latin square design for 28-d periods. The diets were a 70% forage diet considered the basal diet, the basal diet with 19% ground and high-moisture corn replacing forages, and the basal diet with 15% refined glycerol and 4% added protein supplements to be isocaloric and isonitrogenous with the corn diet. Cows were milked twice a day and samples were collected on the last 7 d of each period for compositional analysis. Within each period, blood samples were collected on d 26 and 27, and mammary tissue was collected by biopsy on d 28 for Western blot analysis. Dry matter intake increased from 23.7 kg/d on the basal diet to 25.8 kg/d on the corn diet and 27.2 kg/d on the glycerol diet. Dry matter intake tended to be higher with glycerol than corn. Milk production increased from 39.2 kg/d on the basal diet to 43.8 kg/d on the corn diet and 44.2 kg/d on the glycerol diet. However, milk yield did not differ between corn and glycerol diets. Milk lactose yields were higher on the corn and glycerol diets than the basal diet. Milk fat yield significantly decreased on the glycerol diet compared with the basal diet and tended to decrease in comparison with the corn diet. Mean milk fat globule size was reduced by glycerol feeding. Milk protein yield increased 197 g/d with addition of corn to the basal diet and 263 g/d with addition of glycerol, and the glycerol effect was larger than the corn effect. The dietary treatments had no effects on plasma glucose concentration, but plasma acetate levels decreased 27% on the glycerol diet. Amino acid concentrations were not affected by dietary treatments, except for branched-chain amino acids, which decreased 22% on the glycerol diet compared with the corn diet. The decreases in plasma acetate and branched-chain amino acid concentrations with glycerol and the larger effects of glycerol than corn on milk protein and fat yields suggest that glycerol is more glucogenic for cows than corn grain.

Variation in fat globule size in bovine milk and its prediction using mid-infrared spectroscopy.

The objectives of this study were to investigate the sources of variation in milk fat globule (MFG) size in bovine milk and its prediction using mid-infrared (MIR) spectroscopy. Mean MFG size was measured in 2,076 milk samples from 399 Ayrshire, Brown Swiss, Holstein, and Jersey cows, and expressed as volume moment mean (D[4,3]) and surface moment mean (D[3,2]). The mid-infrared spectra of the samples and milk performance data were also recorded during routine milk recording and testing. The effects of breed, herd nested within breed, days in milk, season, milking period, age at calving, parity, and individual animal on the variation observed in MFG size were investigated. Breed, herd nested within breed, days in milk, season, and milking period significantly affected mean MFG size. Milk fat globule size was the largest at the beginning of lactation and subsequently decreased. Milk samples with the smallest MFG on average came from Holstein cows, and those with the largest were from Jersey and Brown Swiss cows. Partial least squares regression was used to predict MFG size from MIR spectra of samples with a calibration data set containing 2,034 and 2,032 samples for D[4,3] and D[3,2], respectively. Coefficients of determination of cross validation for D[4,3] and D[3,2] prediction models were 0.51 and 0.54, respectively. The associated ratio of performance deviation values were 1.43 and 1.48 for D[4,3] and D[3,2], respectively. With these models, individual mean MFG size could not be accurately predicted, but results may be sufficient to screen samples for having either small or large MFG on average. Significant but low correlations of D[4,3] and D[3,2] with milk fat yield were estimated (0.16 and 0.21, respectively). Significant and moderate Pearson correlation coefficients for fat percent with D[4,3] and D[3,2] were assessed (0.34 and 0.36, respectively). This correlation was greater between milk fat percentage and predicted MFG size than with measured MFG size with coefficients of 0.47 and 0.49 for D[4,3] and D[3,2], respectively. The MIR prediction equations are potentially overusing the correlation between fat and MFG size and exploiting the strong relationship between the MIR spectra and total milk fat. However, the predictions of MFG size are able to determine variation in mean globule size beyond what would be achieved just by looking at the correlation with fat production.

Heritabilities of measured and mid-infrared predicted milk fat globule size, milk fat and protein percentages, and their genetic correlations.

The objective of this study was to estimate the heritability of milk fat globule (MFG) size and mid-infrared (MIR) predicted MFG size in Holstein cattle. The genetic correlations between measured and predicted MFG size with milk fat and protein percentage were also investigated. Average MFG size was measured in 1,583 milk samples taken from 254 Holstein cows from 29 herds across Canada. Size was expressed as volume moment mean (D[4,3]) and surface moment mean (D[3,2]). Analyzed milk samples also had average MFG size predicted from their MIR spectral records. Fat and protein percentages were obtained for all test-day milk samples in the cow's lactation. Univariate and bivariate repeatability animal models were used to estimate heritability and genetic correlations. Moderate heritabilities of 0.364 and 0.466 were found for D[4,3] and D[3,2], respectively, and a strong genetic correlation was found between the 2 traits (0.98). The heritabilities for the MIR-predicted MFG size were lower than those estimated for the measured MFG size at 0.300 for predicted D[4,3] and 0.239 for predicted D[3,2]. The genetic correlation between measured and predicted D[4,3] was 0.685; the correlation was slightly higher between measured and predicted D[3,2] at 0.764, likely due to the better prediction accuracy of D[3,2]. Milk fat percentage had moderate genetic correlations with both D[4,3] and D[3,2] (0.538 and 0.681, respectively). The genetic correlation between predicted MFG size and fat percentage was much stronger (greater than 0.97 for both predicted D[4,3] and D[3,2]). The stronger correlation suggests a limitation for the use of the predicted values of MFG size as indicator traits for true average MFG size in milk in selection programs. Larger samples sizes are required to provide better evidence of the estimated genetic parameters. A genetic component appears to exist for the average MFG size in bovine milk, and the variation could be exploited in selection programs.

Influence of sodium chloride on the colloidal and rennet coagulation properties of concentrated casein micelle suspensions.

The research investigated the influence of NaCl on the colloidal and rennet coagulation properties of concentrated milk. Milk was concentrated to 1×, 3×, and 5× using ultrafiltration. Rennet gelation was followed by rheology and diffusing wave spectroscopy. Soluble protein, total and diffusible calcium and phosphate, size, and zeta potential were also measured as a function of concentration history. In the presence of 300mM NaCl, colloidal calcium phosphate solubilized and pH and the negative charge on the surface of casein micelles decreased. Increasing the volume fraction caused the formation of stiffer gels for both samples with or without NaCl. The addition of NaCl caused a significant increase in the bulk viscosity of the milk concentrated 5× and a decrease in turbidity. The concentration had no effect on the gelation time of control samples, nor on the kinetics of caseinomacropeptide release. On the other hand, rennet gelation was retarded by the addition of NaCl, and the gels showed lower elastic moduli compared with those obtained with control milk.

Short communication: Variation of total immunoglobulin G and ß-lactoglobulin concentrations in colostrum and milk from Canadian Holsteins classified as high, average, or low immune responders.

The objective of this study was to evaluate IgG and ß-lactoglobulin (ß-LG) concentrations in colostrum and milk of Canadian Holsteins (n=108) classified as high (H), average (A), or low (L) for antibody-mediated (AMIR) or cell-mediated immune responses (CMIR) based on estimated breeding values. It was hypothesized that H-AMIR and H-CMIR cows produce colostrum (first milking) and milk (d 5 postcalving) with higher concentrations of IgG and ß-LG. Data for IgG and ß-LG in colostrum and milk were analyzed independently using mixed linear models. Least squares means were compared using Tukey's test. Cows classified as H-AMIR had higher IgG and ß-LG concentrations in colostrum compared with A- and L-AMIR cows; 84% of H-AMIR, 69% of A-AMIR, and 68% of L-AMIR cows had over 5,000 mg/dL IgG in colostrum. No differences in IgG and ß-LG concentrations in colostrum were noted among cows ranked on CMIR or in milk of cows ranked on AMIR. ß-Lactoglobulin and IgG concentrations were positively correlated in colostrum. Breeding cows for H-AMIR status may reduce failure of passive transfer of IgG in their calves; ß-LG may play a role in bovine immune defenses. Colostrum from H-AMIR cows may serve as a more economical feedstock source for manufacturing natural health products.

Rennet-induced gelation of concentrated milk in the presence of sodium caseinate: differences between milk concentration using ultrafiltration and osmotic stressing.

Concentrating milk is a common unit operation in the dairy industry. With the reduction of water, the particles interact more frequently with each other and the functionality of the casein micelles may depend on the interactions occurring during concentration. The objective of this research was to investigate the effect of concentration on the renneting properties of the casein micelles by comparing 2 concentration methods: ultrafiltration and osmotic stressing. Both methods selectively concentrate the protein fraction of milk, while the composition of the soluble phase is unaltered. To evaluate possible differences in the rearrangements of the casein micelles during concentration, renneting properties were evaluated with or without the addition of soluble caseins, added either before or after concentration. The results indicate that casein micelles undergo rearrangements during concentration and that shear during membrane filtration may play a role in affecting the final properties of the milk.

Partial calcium depletion during membrane filtration affects gelation of reconstituted milk protein concentrates.

Milk protein concentrate powders (MPC) with improved rehydration properties are often manufactured using processing steps, such as acidification and high-pressure processing, and with addition of other ingredients, such as sodium chloride, during their production. These steps are known to increase the amount of serum caseins or modify the mineral equilibrium, hence improving solubility of the retentates. The processing functionality of the micelles may be affected. The aim of this study was to investigate the effects of partial acidification by adding glucono-δ-lactone (GDL) to skim milk during membrane filtration on the structural changes of the casein micelles by observing their chymosin-induced coagulation behavior, as such coagulation is affected by both the supramolecular structure of the caseins and calcium equilibrium. Milk protein concentrates were prepared by preacidification with GDL to pH 6 using ultrafiltration (UF) and diafiltration (DF) followed by spray-drying. Reconstituted UF and DF samples (3.2% protein) treated with GDL showed significantly increased amounts of soluble calcium and nonsedimentable caseins compared with their respective controls, as measured by ion chromatography and sodium dodecyl sulfate-PAGE electrophoresis, respectively. The primary phase of chymosin-induced gelation was not significantly different between treatments as measured by the amount of caseino-macropeptide released. The rheological properties of the reconstituted MPC powders were determined immediately after addition of chymosin, both before and after dialysis against skim milk, to ensure similar serum composition for all samples. Reconstituted samples before dialysis showed no gelation (defined as tan δ=1), and after re-equilibration only control UF and DF samples showed gelation. The gelation properties of reconstituted MPC powders were negatively affected by the presence of soluble casein, and positively affected by the amount of both soluble and insoluble calcium present after reconstitution. This work, testing the chymosin-induced gelation behavior of various reconstituted MPC samples, clearly demonstrated that a decrease in pH to 6.0 during membrane filtration affects the integrity of the casein micelles supramolecular structure with important consequences to their processing functionality.

Pulsed electric field processing preserves the antiproliferative activity of the milk fat globule membrane on colon carcinoma cells.

The present work evaluated the effect of processing on the antiproliferative activities of milk fat globule membrane (MFGM) extracts. The antiproliferative activity on human adenocarcinoma HT-29 cells of untreated MFGM extracts were compared with those extracted from pasteurized cream, thermally treated cream, or cream subjected to pulsed electrical field (PEF) processing. The PEF with a 37 kV/cm field strength applied for 1,705µs at 50 and 65°C was applied to untreated cream collected from a local dairy. Heating at 50 or 65°C for 3min (the passage time in the PEF chamber) was also tested to evaluate the heating effect during PEF treatments. The MFGM extracted from pasteurized cream did not show an antiproliferative activity. On the other hand, isolates from PEF-treated cream showed activity similar to that of untreated samples. It was also shown that PEF induced interactions between ß-lactoglobulin and MFGM proteins at 65°C, whereas the phospholipid composition remained unaltered. This work demonstrates the potential of PEF not only a means to produce a microbiologically safe product, but also as a process preserving the biofunctionality of the MFGM.

Calcium release from milk concentrated by ultrafiltration and diafiltration.

The present work studied the solubilization of Ca during acidification in milk concentrated by ultrafiltration (UF) and diafiltration (DF). The effect of heating milk at 80°C for 15min was also evaluated. In addition to measuring buffering capacity, the amount of Ca released as a function of pH was determined. The area of the maximum peak in buffering capacity observed at pH ~5.1, related to the presence of colloidal Ca phosphate, was significantly affected by casein volume fraction but did not increase proportionally with casein concentration. In addition, a lower buffering capacity and less solubilized Ca were measured in 2× DF milk compared with 2× UF milk. Heat treatment did not change the buffering capacity or Ca release in 1× and 2× concentrated milk. On the other hand, at a higher volume fraction (4×), more Ca was present in the soluble phase in heated 4× UF and DF milk compared with unheated milk. This is the first comprehensive study on the effect of concentration, distinguishing the effect of UF from that of DF, before and after heating, on Ca solubilization.

Changes in the physical properties, solubility, and heat stability of milk protein concentrates prepared from partially acidified milk.

A limiting factor in using milk protein concentrates (MPC) as a high-quality protein source for different food applications is their poor reconstitutability. Solubilization of colloidal calcium phosphate (CCP) from casein micelles during membrane filtration (e.g., through acidification) may affect the structural organization of these protein particles and consequently the rehydration and functional properties of the resulting MPC powder. The main objective of this study was to investigate the effects of acidification of milk by glucono-δ-lactone (GDL) before ultrafiltration (UF) on the composition, physical properties, solubility, and thermal stability (after reconstitution) of MPC powders. The MPC samples were manufactured in duplicate, either by UF (65% protein, MPC65) or by UF followed by diafiltration (80% protein, MPC80), using pasteurized skim milk, at either the native milk pH (~pH 6.6) or at pH 6.0 after addition of GDL, followed by spray drying. Samples of different treatments were reconstituted at 5% (wt/wt) protein to compare their solubility and thermal stability. Powders were tested in duplicate for basic composition, calcium content, reconstitutability, particle size, particle density, and microstructure. Acidification of milk did not have any significant effect on the proximate composition, particle size, particle density, or surface morphology of the MPC powders; however, the total calcium content of MPC80 decreased significantly with acidification (from 1.84 ± 0.03 to 1.59 ± 0.03 g/100 g of powder). Calcium-depleted MPC80 powders were also more soluble than the control powders. Diafiltered dispersions were significantly less heat stable (at 120°C) than UF samples when dissolved at 5% solids. The present work contributes to a better understanding of the differences in MPC commonly observed during processing.

Antiproliferative activity of tea catechins associated with casein micelles, using HT29 colon cancer cells.

Numerous studies have shown that green tea polyphenols display anticancer activities in many organ sites by using different experimental models in rodents and in cultured cell lines in vitro. The present study tested the ability of casein micelles to deliver biologically active concentrations of polyphenols to HT-29 colon cancer cells. Epigallocatechin gallate (EGCG), the major catechin found in green tea, was used as the model molecule, as it has been shown to have antiproliferative activity on colon cancer cells. In the present work, we hypothesized that due to the binding of caseins with EGCG, casein micelles may be an ideal platform for the delivery of this bioactive molecule and that the binding would not affect the bioaccessibility of EGCG. The cytotoxicity and proliferation behavior of HT-29 colon cancer cells when exposed to free EGCG was compared with that of nanoencapsulated EGCG in casein micelles of skim milk. Epigallocatechin gallate-casein complexes were able to decrease the proliferation of HT-29 cancer cells, demonstrating that bioavailability may not be reduced by the nanoencapsulation. As casein micelles may act as protective carriers for EGCG in foods, it was concluded that nanoencapsulation of tea catechins in casein micelles may not diminish their antiproliferative activity on colon cancer cells compared with free tea catechins.

Modulation of immune function by milk fat globule membrane isolates.

The nutritional value and characterization of minor milk components on mammalian immune function are not fully understood. The aim of this research was to test the ability of a milk fat globule membrane (MFGM) isolate to modulate murine immune function in vitro, by studying its effects on splenocyte proliferation, apoptosis, and cytokine production. Proliferation of spleen cells was not affected by the MFGM isolate; however, in the presence of polyclonal activators, the MFGM isolate suppressed cell proliferation. Results obtained by flow cytometry did not support programmed cell death as the cause of the MFGM immune-modulating capacity. A mode of suppression on the splenocyte activation process was suggested from a marked decrease in the production of IFN-γ and tumor necrosis factor-α cytokines, typical indicators of immune cell activation. The effect of MFGM on IL-4 secretion was significantly less than that for the other 2 cytokines. The activity exerted by the MFGM over concanavalin A-stimulated cells differed from that observed in cells treated with lipopolysaccharide, suggesting a different mode of action depending on the activator used. These results indicate the potential of MFGM extracts as functional ingredients with bioactive modulating capacity.

In vitro gastric digestion of polysaccharides in mixed dispersions: Evaluating the contribution of human salivary α-amylase on starch molecular breakdown.

The aim of this work was to investigate the impact of the addition of salivary α-amylase on starch hydrolysis in protein-containing dispersions during an in vitro digestion process. In vitro digestion provides useful insights on the fate of nutrients during gastro-intestinal transit in complex food matrices, an important aspect to consider when developing highly nutritious foods. Many foods contain polysaccharides, and as their disruption in the gastric stage is limited, salivary α-amylase is often neglected in in vitro studies. A reference study on the effect of salivary α-amylase using one of the most advanced and complex in vitro digestion models (INFOGEST) is, however, not available. Hence, this work reports the gastrointestinal breakdown of three mixed dispersions containing whey protein isolate with different polysaccharides: potato starch, pectin from citrus peel and maize starch. The latter was also studied after heating. No polysaccharide or salivary α-amylase-dependent effect on protein digestion was found, based on the free NH2 and SDS-PAGE. However, in the heat-treated samples, the addition of salivary α-amylase showed a significantly higher starch hydrolysis compared to the sample without α-amylase, due to the gelatinization of the starch granules, which improved the accessibility of the starch molecules to the enzyme. This work demonstrated that the presence of different types of polysaccharides does not affect protein digestion, but also it emphasizes the importance of considering the influence of processing on food structure and its digestibility, even in the simplest model systems.

Variation of in vitro digestibility of pea protein powder dispersions from commercially available sources.

With raising consumer demand for plant-derived proteins, there has been an increased interest in the utilization of pea ingredients in food formulations. It was hypothesized that differences in processing history and composition affect their colloidal properties and their breakdown during in vitro simulated gastrointestinal digestion. The gastrointestinal fate of three different commercial pea protein ingredients, two protein isolates and one less refined concentrate was compared. The concentrate dispersion showed greater solubility, different protein composition and smaller particle size than the reconstituted pea protein isolates. When heat-treated, the release of free amino groups decreased for the isolates, but increased for the concentrate dispersions. LC-TQMS of free amino acids in the intestinal digestates indicated a significantly higher release of methionine (limiting amino acid in pea protein) in the concentrates than in the isolates. This work highlights the influence of processing and composition on techno-functional and digestion properties of pea ingredients.