Impact of industrial cream heat treatments on the protein composition of the milk fat globule membrane.

The impact of cream processing on milk fat globule membrane (MFGM) was assessed in an industrial setting for the first time. Three creams and their derived MFGM fractions from different stages of the pasteurization procedure at a butter dairy were investigated and compared to a native control as well as a commercial MFGM fraction. The extent of cross-linking of serum proteins to MFGM proteins increased progressively with each consecutive pasteurization step. Unresolved high molecular weight aggregates were found to consist of both indigenous MFGM proteins and ß-lactoglobulin as well as αs1- and ß-casein. With regards to fat globule stability and in terms of resistance towards coalescence and flocculation after cream washing, single-pasteurized cream exhibited reduced sensitivity to cream washing compared to non- and double-pasteurized creams. Inactivation of the agglutination mechanism and the increased presence of non-MFGM proteins may determine this balance between stable and non-stable fat globules.

Short communication: Inhibition of angiotensin 1-converting enzyme by peptides derived from variants of bovine ß-casein upon apical exposure to a Caco-2 cell monolayer.

This study investigated the consequence of genetically contingent amino acid substitutions in bovine ß-casein (CN) genetic variants A1, A2, B, and I on the structure and bioactive potential of peptides following in vitro digestion. The ß-CN variants were digested in vitro using pepsin and pancreatin, and a peptide profile was obtained by liquid chromatography tandem mass spectrometry, revealing among others, the ß-casomorphin precursor peptides VYPFPGPIHN and VYPFPGPIPN, derived from variant A1/B and from A2/I, respectively. These 2 peptides were synthesized and assessed for angiotensin 1-converting enzyme (ACE) inhibitory capacity before and after incubation with a monolayer of Caco-2 intestinal cells. The VYPFPGPIHN was a stronger ACE inhibitor than VYPFPGPIPN, with the concentration needed to reach half-maximal inhibition (IC50) of 123 ± 14.2 µM versus 656 ± 7.6 µM. Exposure to a Caco-2 intestinal cell monolayer did not affect ACE inhibition by VYPFPGPIHN, but resulted in an almost 2-fold increase in inhibition by VYPFPGPIPN after incubation. Subsequent tandem mass spectrometric analysis identified the truncated peptide VYPFPGPIP, suggesting hydrolysis by a cell membrane associated peptidase. Thus, genetic variation in bovine ß-CN results in the generation of peptides that differ in bioactivity, and are differently affected by intestinal brush border peptidases.

Textural and Consumer-Aided Characterisation and Acceptability of a Hybrid Meat and Plant-Based Burger Patty.

The hamburger has been targeted for substitution by numerous plant-based alternatives. However, many consumers find the taste of these alternatives lacking, and thus we proposed a hybrid meat and plant-based burger as a more acceptable alternative for these consumers. The burger was made from 50% meat (beef and pork, 4:1) and 50% plant-based ingredients, including texturised legume protein. Texture and sensory properties were evaluated instrumentally and through a consumer survey (n = 381) using the check-all-that-apply (CATA) method. Expressible moisture measurements indicated a significantly juicier eating experience for the hybrid compared to a beef burger (33.5% vs. 22.3%), which was supported by the CATA survey where "juicy" was used more to describe the hybrid than the beef burger (53% vs. 12%). Texture profile analysis showed the hybrid burger was significantly softer (Young's modulus: 332 ± 34 vs. 679 ± 80 kPa) and less cohesive than a beef burger (Ratio 0.48 ± 0.02 vs. 0.58 ± 0.01). Despite having different textural and CATA profiles, overall liking of the hybrid burger and a beef burger were not significantly different. Penalty analysis indicated that "meat flavour", "juiciness", "spiciness" and "saltiness" were the most important attributes for a burger. In conclusion, the hybrid burger had different attributes and was described with different CATA terms than a beef burger but had the same overall acceptability.

In vitro effects of rebaudioside A, stevioside and steviol on porcine cytochrome p450 expression and activity.

The physiological effects of the Stevia-derived compounds, rebaudioside A, stevioside and steviol have been the focus of several studies due to their use as sweeteners in food. Despite that, little is known about their potential food-drug interactions. In the present study, IPEC-J2 cells and primary hepatocytes were used to investigate the effect of rebaudioside A, stevioside and steviol on cytochrome p450 (CYP) mRNA expression. Moreover, hepatic microsomes were used to investigate direct interactions between the compounds and specific CYP activity. In IPEC-J2 no changes in mRNA expression of CYP1A1 or CYP3A29 were observed with the Stevia-derived compounds. In primary hepatocytes all three tested compounds induced a significant increase in CYP3A29 expression. The tested compounds had no direct effect on specific CYP activity. In conclusion, rebaudioside A, stevioside and steviol induce only minor or no changes to the CYP expression and activity, and are not likely to cause food-drug interactions.

Constitutive expression and activity of cytochrome P450 in conventional pigs.

Pigs have often been suggested to be a useful model for humans, when investigating CYP dependent events, like drug metabolism. However, comprehensive knowledge about the constitutive expression of the major CYP and corresponding transcription factors is limited. We compared the constitutive mRNA expression of aryl hydrocarbon receptor, constitutive androstane receptor and pregnane X receptor and CYP1A1, CYP1A2, CYP2A, CYP2E1 and CYP3A in liver, adipose tissue, muscle and small intestine in pigs, as well as the expression along the length of the small intestine and colon. Tissue samples were taken from female pigs, and analyzed for gene expression, as well as CYP dependent activity using qPCR and specific probe substrates, respectively. For all investigated transcription factors and CYPs the mRNA expression and activity was highest in the liver. CYP1A1 and CYP3A mRNA expression and activity was shown in all investigated tissues. Along the small intestine and colon the mRNA expression and activity of CYP1A1 and CYP3A was gradually decreased. The results demonstrated, similarity to that reported for humans, and hence adds to the use of pigs as a model for humans.

Whole Milk Increases Intestinal ANGPTL4 Expression and Excretion of Fatty Acids through Feces and Urine.

The angiopoietin-like 4 (ANGPLT4) protein is involved in lipid metabolism and is known to inhibit lipoprotein lipase in the bloodstream. We investigated the effect of milk on intestinal ANGPTL4 and the metabolic profile of growing pigs and the effect of free fatty acids (FFAs) on ANGPTL4 in ex vivo and in vitro assays. Feeding pigs whole milk increased intestinal ANGPTL4 mRNA and increased fecal excretion of long-chain FFA compared to the control group fed soybean oil (n = 9). Furthermore, FFAs (C4-C8) induced ANGPTL4 gene expression in porcine intestinal tissue mounted in Ussing chambers and ANGPTL4 protein secretion to both the apical and basolateral sides of intestinal Caco-2 cells on permeable membranes. Altogether, these results support an ANGPTL4-induced secretion of fecal FFAs. Urinary levels of FFAs (C4-C12), 3-hydroxyadipic acid, and suberic acid were also increased by milk consumption, indicating higher energy expenditure compared to the control group.