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Ligand-binding properties of β-lactoglobulin (β-lg) are well documented, but the subsequent biological functions are still unclear. Focusing on fatty acids/β-lg complexes, the structure-function relationships are reviewed in the light of the structural state of the protein (native versus non-native aggregated proteins). After a brief description of β-lg native structure, the review takes an interest in the binding properties of native β-lg (localization of binding sites, stoichiometry, and affinity) and the way the interaction affects the biological properties of the protein and the ligand. The binding properties of non-native aggregated forms of β-lg that are classically generated during industrial processing are also related. Structural changes modify the stoichiometry and the affinity of β-lg for fatty acids and consequently the biological functions of the complex. Finally, the fatty acid-binding properties of other whey proteins (α-lactalbumin, bovine serum albumin) and some biological properties of the complexes are also addressed. These proteins affect β-lg/fatty acids complex in whey given their competition with β-lg for fatty acids.

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Tributyrin, a short-chain triglyceride oil used as a food additive, has been reported to be a potential preventive agent against colon cancer. The purpose of this study was to develop tributyrin delivery systems based on food-grade oil-in-water emulsions that could potentially be incorporated into foods. Emulsions containing only tributyrin as the lipid phase were highly unstable to droplet growth due to Ostwald ripening (OR) because of the relatively high water solubility of this low molecular weight triacylglycerol. The stability of the emulsions to OR could be greatly improved by incorporating >or=15-25% corn oil (a food-grade oil with a low water solubility) into the lipid phase. In addition, the tendency for droplet sedimentation to occur was reduced because the density contrast between the lipid and water phases was reduced in the mixed tributyrin/corn oil systems. The potential anticarcinogenic ability of the tributyrin emulsions was demonstrated using a cell culture model. Treatments with emulsions containing tributyrin significantly inhibited the viability of HT29 colon carcinoma cells. These results have important implications for the development and testing of nutraceuticals encapsulated in food-grade delivery systems as anticancer agents.

The dairy protein β-lactoglobulin (βlg) is known to bind hydrophobic ligands such as fatty acids. In the present work, we investigated the biological activity in vitro of linoleate once complexed to bovine βlg. Binding of linoleate (C18:2) to bovine βlg was achieved by heating at 60 °C for 30 min at pH 7.4, resulting in a linoleate/βlg molar binding stoichiometry of 1.1, 2.1, and 3.4. Two types of binding sites were determined by ITC titrations. Binding of linoleate induced the formation of covalent dimers and trimers of βlg. The LD50 on Caco-2 cells after 24 h was 58 μM linoleate. However, cell viability was unaffected when 200 μM linoleate was presented to the Caco-2 cells as part of the βlg complex. The Caco-2 cells did not increase mRNA transcript levels of long chain fatty acid transport genes, FATP4 and FABPpm, or increase levels of the cAMP signal, in response to the presence of 50 μM linoleate alone or as part of the βlg complex. Therefore, it is proposed that βlg can act as a molecular carrier and alter the bioaccessibility of linoleate/linoleic acid.

Bovine α-lactalbumin (α-La) contains numerous dipeptidyl peptidase IV (DPP-IV) inhibitory peptides sequences within its primary structure. In silico analysis indicated that the targeted hydrolysis of α-La with elastase should release DPP-IV inhibitory peptide sequences. An α-La isolate was hydrolysed with elastase under different conditions using an experimental design approach incorporating 3 factors (temperature, pH and enzyme to substrate ratio (E:S) ratio) at 2 levels. The hydrolyzate generated at pH 8.5, 50C, E:S 2.0% (w/w) (H9) displayed the lowest half maximal DPP-IV inhibitory concentration (IC50 = 1.20 ± 0.12 mg mL -1). Five α-La-derived DPP-IV inhibitory peptides (GY, GL, GI, NY and WL) predicted to be released in silico were identified by liquid-chromatography tandem mass spectrometry (LC-MS/MS) within H9 and its simulated gastrointestinal digestion (SGID) sample. This proof of concept study demonstrated the benefit of using a targeted approach combined with an experimental design in the generation of dietary protein hydrolyzates with DPP-IV inhibitory properties. IntroductionDipeptidyl peptidase IV (DPP-IV) is an ubiquitous enzyme which is responsible for the cleavage and inactivation of the incretin hormones, glucose dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) 1 . In the context of type 2 diabetes management, DPP-IV inhibition may be used as a means to improve the regulation of serum glucose in humans. Various DPP-IV inhibitory drugs (gliptins), have been developed to maintain the insulinotropic activity of the incretins in the post-prandial phase 2 .Dietary components, including food protein-derived peptides, have been shown to play a role in the inhibition of DPP-IV in vitro and in certain instances in vivo, for reviews, see: 3,4,5 . In silico studies have shown that selected DPP-IV inhibitory peptide sequences may be found within a wide range of dietary proteins 6,7 . To date, milk proteins appear to be the most frequently studied substrate for the generation of DPP-IV inhibitory peptides. Depending on the enzymatic strategy employed, different milk proteins may appear to be more suitable substrates for the production of DPP-IV inhibitory peptides. For instance, it was recently predicted by Tulipano et al.8 using in silico digestion with gastrointestinal proteinases that -lactoglobulin (-Lg) should yield a higher number of previously identified DPP-IV inhibitory peptides than -La. This was further confirmed following in vitro digestion of -Lg and -La with gastrointestinal enzymes, yielding hydrolyzates with IC 50 values of 0.74 and 1.70 mg mL -1, respectively 8 . Other in silico analysis of the major milk proteins indicated that -lactalbumin (-La) displayed the highest level of sequence coverage (43.9%) for previously identified DPP-IV inhibitory peptides as well as the highest DPP-IV inhibitory potency index (i.e., 17.9 10 -6 µM -1 g -1 ) 7 . It has been suggested that discrepancies between studies to determine the most adequate substrate for the genera...

Short peptides in food protein hydrolysates are of significant interest as they may be highly bioactive whilst also being bioavailable. A dipeptidyl peptidase IV (DPP-IV) inhibitory whey protein hydrolysate (WPH) was fractionated using nanofiltration (