Ham processing: effects of tumbling, cooking and high pressure on proteins

International audienceMeat is recognized as an important source of protein and amino acids. Before consumption, meat products are transformed, and processing modifies the protein characteristics and impacts their digestibility. The present study aims to evaluate the impact of physicochemical modifications (solubility, oxidation, and denaturation) on the degree of in vitro digestibility and the digestion rate of high-pressure-treated cooked ham during the different process steps (curing, cooking and high-pressure treatment). Samples were homogenized and digested by pepsin and then by trypsin. The curing step increased the degree of proteolysis and the digestion rate compared with those of raw meat. Brining and tumbling caused partial denaturation of the proteins, which provided digestive enzymes better access to their specific cleavage sites. Otherwise, the substantial denaturation and protein oxidation induced by the cooking step decreased the degree of digestibility and significantly increased the digestion rate of cooked ham. Finally, the high-pressure treatment decreased the digestibility of cooked ham and simultaneously increased its digestion rate. The denaturation and oxidation phenomena leading to protein aggregation thus masked the cleavage sites necessary for the digestive enzymes. Therefore, each step of the processing of high-pressure cooked ham had an impact on the protein digestion parameters: the curing step promoted the digestibility and proteolysis rate of pork protein, while cooking and high-pressure treatment reduced the digestibility and proteolysis rate of pork protein

Digestibility of high-pressure processed cooked ham

International audienc

Interactions of β-Lactoglobulin Variants A and B with Vitamin A. Competitive Binding of Retinoids and Carotenoids

International audiencebeta-Lactoglobulin (beta-Lg) is the major whey protein -of bovine milk present at a concentration of 2-3 g L-1. Its biological role is still not well-known. However, many studies have suggested that beta-Lg may play either nutritional or specific transporter role. The high affinity of beta-Lg for retinol and other retinoids was reported. The results of interaction studies of beta-Lg with carotenoids, that is, beta-carotene, beta-cryptoxanthin, and alpha-carotene, which display similar structures are reported in this study. The affinities of beta-Lg for binding of retinoids and carotenoids were compared, providing more information about the binding site(s) of these molecules by beta-Lg. Interactions were followed by the measurements of quenching of beta-Lg tryptophan fluorescence and retinol fluorescence. The obtained results indicate that carotenoids are bound by beta-Lg with high affinity of the order of 10(-8) M. Measurement of retinol competition with carotenoids for binding by beta-Lg suggests that the binding of these two ligands occurs at two different sites of beta-Lg

Role of the bolus degree of structure on the protein digestibility during in vitro digestion of a pea protein fortified sponge-cake chewed by elderly

International audienceThis study investigated the digestibility of proteins in a pea protein fortified sponge-cake, as well as the impact of the degree of structure of the bolus produced by elderly subjects on the digestibility of proteins by combining ex vivo and in vitro approaches via the standardized protocol INFOGEST. The sponge-cakes were consumed by a group of 20 elderly subjects with contrasting physiology, their boli were recovered just before swallowing, and their apparent viscosity was measured to delineate the bolus degree of structure. According to this criterion, two pools were formed with boli from subjects selected at the extremes: low viscosity (LV) and high viscosity (HV), with apparent viscosity values (at 120s(-1) ) of 124 +/- 18 Pas and 208 +/- 19 Pas, respectively. The sponge-cakes and the two pools underwent in vitro digestion. Protein hydrolysis kinetics was followed by measuring the released primary amino groups (NH2 ) and by SDS-PAGE at different time points. For all samples, the representative bands of pea proteins disappear gradually during digestion, accompanied by the appearance of bands indicating the presence of proteins with MW < 15kDa. In addition, the NH2 concentrations increase over time and do not differ between sponge-cake and pea protein isolate. Moreover, the degree of structure of the food bolus has no significant effect on the concentration of NH2 released. These results showed that pea proteins in a fortified sponge-cake are bioaccessible under standardized conditions, and that the degree of structure of the bolus did not influence protein digestibility for these foods

Release kinetics of [lidocainium][ibuprofenate] as Active Pharmaceutical Ingredient-Ionic Liquid from a plasticized zein matrix in simulated digestion

International audienceAn in vitro approach is proposed to study the release of an Active Pharmaceutical Ingredient-Ionic Liquid (API-IL) from a natural biopolymer matrix based on zein, a maize storage protein. Zein can be processed in the molten state with 20 w% [Lidocainium][Ibuprofenate] added as API-IL also acting as plasticizer and potentially coplasticized by glycerol. The thermal stability of the matrix is checked, as well as the in vivo biological activity of the API-IL confirming anesthetic and anti-inflammatory activities. Model tablets are thermomolded at 130 • C (∅20 mm, 0.2 mm thick) and submitted to simulated digestion based on the INFOGEST static protocol of gastrointestinal food digestion at 37 • C (2 h under gastric conditions followed by 2 h under intestinal ones). The release of the API-IL is evaluated by HPLC-UV to dissociate lidocainium, that shows a progressive release (35 % after 2 h and 60 % after 4 h digestion), from ibuprofenate, that is mainly released under intestinal conditions due to low solubility in acidic conditions. The monitoring of the tablets reveals release mechanisms based on diffusion without noticeable erosion of the matrix. These results demonstrate the interest of this thermoplastic material to provide a relevant drug delivery system

In vitro digestion of food grade TiO 2 (E171) and TiO 2 nanoparticles: physicochemical characterization and impact on the activity of digestive enzymes

International audienceTitanium dioxide is a food additive that has raised some concerns for humans due to the presence of nanoparticles. We were interested in knowing the fate of TiO2 particles in the gastro-intestinal tract and their potential effect on digestive enzymes. For this purpose, we analysed the behaviour of two different food grade TiO2 samples (E171) and one nano-sized TiO2 sample (P25) through a standardized static in vitro digestion protocol simulating the oral, gastric and intestinal phases with appropriate juices including enzymes. Both E171 and P25 TiO2 particles remained intact in the digestive fluids but formed large agglomerates, and especially in the intestinal fluid where up to 500 mu m sized particles have been identified. The formation of these agglomerates is mediated by the adsorption of mainly alpha-amylase and divalent cations. Pepsin was also identified to adsorb onto TiO2 particles but only in the case of silica-covered E171. In the salivary conditions, TiO2 exerted an inhibitory action on the enzymatic activity of alpha-amylase. The activity was reduced by a factor dependent on enzyme concentrations (up to 34% at 1 mg mL(-1)) but this inhibitory effect was reduced to hardly 10% in the intestinal fluid. In the gastric phase, pepsin was not affected by any form of TiO2. Our results hint that food grade TiO2 has a limited impact on the global digestion of carbohydrates and proteins. However, the reduced activity specifically observed in the oral phase deserves deeper investigation to prevent any adverse health effects related to the slowdown of carbohydrate metabolism

Antifungal properties of synthetic fragments and entire durancins isolated from Enterococcus durans A5-11

National audienc

Antifungal properties of synthetic fragments and entire durancins isolated from Enterococcus durans A5-11

National audienc

Characterization of antifungal organic acids produced by Lactobacillus harbinensis K.V9.3.1Np immobilized in gellan-xanthan beads during batch fermentation

International audienceAntifungal activity of lactic acid bacteria (LAB) has been observed in many food fermentation processes. Organic acids produced during the growth of these microorganisms play a major role in antagonism towards molds. The present study characterizes antifungal compounds produced during growth of Lactobacillus harbinensis K.V9.3.1Np that was previously isolated from raw cow milk and found to possess strong antifungal activities. A pH-controlled batch fermentation in enriched milk protein medium with immobilized cells of this bacterium was carried out in the presence of disrupted cells of Debaryomyces hansenii UBOCC-A-211003 and Kluyveromyces lactis UBOCC-A-212021. After seven days of fermentation, cell-free culture supernatants with robust antifungal activities against D. hansenii, Penicillium expansum and Penicillium roqueforti were obtained. These cell-free supernatants contained high amounts of organic acids such as lactic and acetic acids as well as hexanoic acid (9 mM), which the latter revealed to be the most efficient antifungal compound. The antifungal activity of hexanoic acid was influenced by the environmental conditions including the nature of the matrix and the pH. Under the conditions tested, even if organic acids were key antifungal agents, they were only part of a complex mixture of various molecules that acted in a synergistic manner. (C) 2013 Elsevier Ltd. All rights reserved