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Whey proteins are widely used food ingredients due to their nutritional and functional properties (gelling, emulsifying, foaming). Owning to their structure (free thiol group, lysine residues, hydrophobic pocket), they can also be used as carriers for bioactives. In this study, conjugates between beta-lactoglobulin (beta-lg), and a bioactive metabolite from Brassicaceae vegetables, allyl isothiocyanate (AITC) were formed. Heat aggregation behavior (85 degrees C, 15 min), foaming and emulsifying properties of conjugates, at pH 4.0 and 7.1, were evaluated.
Conjugates were formed by incubating beta-lg (0.5 mM) with AITC (0.05-20 mM) in water at pH 8.5 and room temperature. AITC primarily reacted with beta-lg's free thiol group (K-D = 0.2 +/- 0.1 mM) and thereafter with its amino groups (K-D 10.8 +/- 3.4 mM). AITC binding destabilized secondary and tertiary structure of beta-lg at pH 7.1, whereas induced molten globule conformation at pH 4.0. Conjugation reduced the heat aggregation of beta-lg at pH 7.1, while promoting it at pH 4.0. Conjugates adsorbed faster to air/water and oil/water interfaces at pH 4.0 than at pH 7.1. After 30 min, air/water surface tension was lower at pH 4.0 (47 mN m(-1)) than at pH 7.1 (57 mN m(-1)), while the surface tension of the oil/water interface was 8 mN m(-1) at both pHs. Foams produced with beta-lg-AITC conjugates at pH 4.0 exhibited higher volume and liquid stabilities compared to foams obtained at pH 7.1. Emulsions formed with conjugates at both pHs were destabilized by creaming due to flocculation, but coalescence was prevented. This study revealed that whey protein could potentially be used for the delivery of isothiocyanates in the form of foam or emulsion-based products.
The effect of tannins on mediterranean ruminant ingestive behavior the role of the oral cavity
(2011)
Sheep, cattle and goat are domestic ruminants of significant economic interest in the Mediterranean region. Although sharing the same pasture ranges, they ingest different plants and plant parts and, consequently different levels of tannins. This suggests an ability to detect and adapt ingestion according to animal physiological limits of tolerance for plant secondary metabolites. This review will detail the effects of dietary tannins on feeding behavior, and the role of the oral cavity in this process, with focus on such ruminant species. The role of salivary protein profile in tannin perception in the oral cavity, and as a defense mechanism, will be discussed.
Fusarium spp. infection of cereal grain is a common problem, which leads to a dramatic loss of grain quality. The aim of the present study was to investigate the effect of Fusarium infection on the wheat storage protein gluten and its fractions, the gliadins and glutenins, in an in vitro model system. Gluten proteins were digested by F. graminearum proteases for 2, 4, 8 and 24 h, separated by Osborne fractionation and characterised by chromatographic (RP-HPLC) and electrophoretic analysis (SDS-Page). Gluten digestion by F. graminearum proteases showed in comparison with gliadins a preference for the glutenins whereas the HMW subfraction was at most affected. In comparison with a untreated control, the HMW subfraction was degraded of about 97% after 4 h incubation with Fusarium proteases. Separate digestion of gliadin and glutenin underlined the preference for HMW-GS. Analogue to the observed change in the gluten composition, the yield of the proteins extracted changed. A higher amount of glutenin fragments was found in the gliadin extraction solution after digestion and could mask a gliadin destruction at the same time. This observation can contribute to explain the frequently reported reduced glutenin amount parallel to an increase in gliadin quantity after Fusarium infection in grains.
Fusarium spp. infection of cereal grain is a common problem, which leads to a dramatic loss of grain quality. The aim of the present study was to investigate the effect of Fusarium infection on the wheat storage protein gluten and its fractions, the gliadins and glutenins, in an in vitro model system. Gluten proteins were digested by F. graminearum proteases for 2, 4, 8 and 24 h, separated by Osborne fractionation and characterised by chromatographic (RP-HPLC) and electrophoretic analysis (SDS-Page). Gluten digestion by F. graminearum proteases showed in comparison with gliadins a preference for the glutenins whereas the HMW subfraction was at most affected. In comparison with a untreated control, the HMW subfraction was degraded of about 97% after 4 h incubation with Fusarium proteases. Separate digestion of gliadin and glutenin underlined the preference for HMW-GS. Analogue to the observed change in the gluten composition, the yield of the proteins extracted changed. A higher amount of glutenin fragments was found in the gliadin extraction solution after digestion and could mask a gliadin destruction at the same time. This observation can contribute to explain the frequently reported reduced glutenin amount parallel to an increase in gliadin quantity after Fusarium infection in grains.