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BACKGROUND: The artichoke (Cynara scolymus L.) accumulates about 50–70 g kg−1 of its fresh weight as inulin-type fructan. Inulin fermentation increases gas production and thereby provokes intestinal discomfort in some people. The present research focuses on the changes in carbohydrate composition occurring in artichoke heads during storage under different conditions (18 °C, 4 °C and 4 °C under polypropylene film packing). RESULTS: Carbohydrate content and composition were determined by anion-exchange high-performance liquid chromatography with pulsed amperometric detection. Storage time caused a decrease in inulin content and an average degree of polymerization, accompanied by an increase of free fructose and sucrose due to depolymerization of inulin. CONCLUSION: Higher-temperature storage and storage without packing induce strong carbohydrate changes. Thereby, eating stored artichoke leads to consumption of an inulin quantity that does not provoke unwanted symptoms related to gas production but sufficient to have a prebiotic effect. Copyright © 2010 Society of Chemical Industry

The in vitro degradation of dietary fibre from three brown seaweeds (Himanthalia elongata, Laminaria digitata and Undaria pinnatiJda) was studied, using human faecal flora. Two sets of fibre were tested: (1) total algal fibres extracted from the whole algae, mainly composed of alginates, and (2) purified fibres (sulphated fucans, Na-alginates and laminarans) representative of those contained in the whole brown algae. Mannuronate, one algal component, was also investigated. Substrate disappearance and short- chain fatty acid (SCFA) production were monitored after 6, 12 and 24 h fermentation. Gas production was followed hourly during the first 9 h and then at 12 and 24 h. Sugarbeet fibre was used as a fermentation reference substrate. According to the fermentative indices used, most of each of the total algal fibres disappeared after 24 h (range 60–76 %) hut, unlike the reference substrate, they were not completely metabolized to SCFA (range 47–62 %). Among the purified algal fibres, disappearance of laminarans was approximately 90% and metabolism to SCFA was approximately 85% in close agreement with the fermentation pattern of reference fibres. Sulphated fucans were not degraded. Na- alginates exhibited a fermentation pattern quite similar to those of the whole algal fibres with a more pronounced discrepancy between disappearance and production of SCFA: disappearance was approximately 83 % but metabolism was only approximately 57 YO. Mannuronate was slowly fermented hut its metabolism corresponded to its disappearance from the fermentative medium. Thus, the characteristic fermentation pattern of the total fibres from the three brown algae investigated was attributed to the peculiar fermentation of alginates, and mannuronate was shown not to be directly involved.

The in vitro degradation of dietary fibre from three brown seaweeds (Himanthalia elongata, Laminaria digitata and Undaria pinnatifida) was studied, using human faecal flora. Two sets of fibre were tested: (1) total algal fibres extracted from the whole algae, mainly composed of alginates, and (2) purified fibres (sulphated fucans, Na-alginates and laminarans) representative of those contained in the whole brown algae. Mannuronate, one algal component, was also investigated. Substrate disappearance and short-chain fatty acid (SCFA) production were monitored after 6, 12 and 24 h fermentation. Gas production was followed hourly during the first 9 h and then at 12 and 24 h. Sugarbeet fibre was used as a fermentation reference substrate. According to the fermentative indices used, most of each of the total algal fibres disappeared after 24 h (range 60-76%) but, unlike the reference substrate, they were not completely metabolized to SCFA (range 47-62%). Among the purified algal fibres, disappearance of laminarans was approximately 90% and metabolism to SCFA was approximately 85% in close agreement with the fermentation pattern of reference fibres. Sulphated fucans were not degraded. Na-alginates exhibited a fermentation pattern quite similar to those of the whole algal fibres with a more pronounced discrepancy between disappearance and production of SCFA: disappearance was approximately 83% but metabolism was only approximately 57%. Mannuronate was slowly fermented but its metabolism corresponded to its disappearance from the fermentative medium. Thus, the characteristic fermentation pattern of the total fibres from the three brown algae investigated was attributed to the peculiar fermentation of alginates, and mannuronate was shown not to be directly involved.

Proteins have been extracted from the edible seaweeds Ulva rigida Agardh and Ulva rotundata Bliding using classical or enzymatic procedures. The protocols using NaOH under reductive conditions or a two-phase system (PEG/K2CO3) produced the best protein yields. The cleavage or the limitation of the linkages between proteins and polysaccharides caused by these experimental conditions probably explains the efficiency of these protocols. In SDS PAGE, the protein fraction obtained after NaOH extraction from U. rotundata is characterised by the presence of three major bands with apparent molecular weights of 45 600, 31 800 and 18 600. The protein fraction from U. rigida presents two specific bands with apparent molecular weights of about 27 000 and 12 000. These fractions are mainly rich in aspartic and glutamic acids, alanine, glycine and contain few hydroxyproline residues (0.91–2.44% total amino acid content). The use of cellulase does not significantly improve the extraction of algal proteins in comparison with the blank procedure (without enzymes). The weak accessibility of the substrates in the intact cell wall could explain these experimental data. The improvement of protein yield after the use of the polysaccharidase mixture (β-glucanase, hemicellulase, cellulase) partially confirms this hypothesis.

The effect of polysaccharidases (κ-carrageenase, β-agarase, xylanase, cellulase) on the protein extraction from three rhodophytes has been studied. The kinetic parameters (apparent V m, apparent K m) and the optimum activity conditions (pH, temperature) of each enzyme were determined by using pure substrates. All the tested enzymes possess Michaelis Menten mechanism with estimated substrate saturating concentrations of 8 000 mg l−1(carrageenan) for κ-carrageenase, 8 000 mg l−1 (agar) for β-agarase, 5000 mg l−1 (xylane) for β-xylanase and 6 000 mg l−1 (carboxymethylcellulose) for cellulase. The optimum activity conditions are pH 6.5–6.8 at 45°C for carrageenase, pH 6–6.5 at 55°C for agarase, pH 5 at 55°C for xylanase and pH 3.8 at 50°C for cellulose. Different alga/enzymes couples (κ-carrageenase/Chondrus crispus, β-agarase/Gracilaria verrucosa, β-xylanase/Palmaria palmata) were tested under the optimum activity conditions. Alga/cellulase + specific enzyme (e.g. Chondrus crispus/carrageenase + cellulase) systems were also studied at the optimum activity conditions of a specific enzyme (e.g. carageenase). The use of the only cellulose was also tested on each alga. Except for Palmaria palmata, the highest protein yields were observed with the procedures using cellulase coupled with carrageenase or agarase for an incubation period limited to 2 h. The Chondrus crispus/carrageenase + cellulose and Gracilaria verrucosa/agarase + cellulase systems gave ten-fold and three-fold improvements, respectively, in protein extraction yield as compared to the enzyme-free blank procedure. The combined action of xylanase and cellulose on protein extraction from Palmaria palmata does not significantly improve protein yield. The best overall protein yield for P. palmata is for P. palmata/xylanase with a 14-h incubation time. This study shows the interest in the use of a polysaccharidase mixture for improving protein extractibility from certain rhodophytes. This biotechnology approach, adapted from procedures for protoplast production or enzymatic liquefaction of higher plants, could be tested as an alternative method to obtain proteins from seaweeds of nutritional interest.

Four species of red marine algae (Rhodophyceae), five species of brown marine algae (Pheophyceae) and two species of green marine algae (Chlorophyceae) were examined for the fatty acid composition of the three lipid groups separated by silica gel column chromatography (neutral lipids, glycolipids, phospholipids). The four red algae had high contents of 16:0 and C20-polyunsaturated fatty acids (PUFA), 20:5n-3 ranging from 18 to 49% of the total fatty acid content and 20:4n-6 from 1.4 to 22.5%, these fatty acids were evenly distributed in all lipid groups. The five brown algae had high contents of 18:1n-9, 18:2n-6 and 18:3n-3 but low content of 20:5n-3. No precise trend was detected for the distribution of these fatty acids in the three lipid groups. The two green algae had high contents of 16:0, 18:1n-7 and 18:3n-3 and a very low content of PUFA. They contained also large amounts of 16:4n-3 together with 16:2n-6 and 16:3n-3. While 16:2n-6 was mainly found in phospholipids, 16:4n-3 was mainly distributed in neutral lipids and glycolipids.Porphyra umbilicalis represents the richest source of 20:5n-3 whileUndaria pinnatifida can be selected when a balanced mixture of (n-6) and (n-3) PUFA is required.

Seaweeds, which have traditionally been used by the Western food industry for their polysaccharide extractives — alginate, carrageenan and agar — also contain compounds with potential nutritional benefits. Seaweeds have recently been approved in France for human consumption (as vegetables and condiments), thus opening new opportunities for the food industry. These seaweed ingredients must meet industrial and technical specifications and consumer safety regulations. This paper is a short review of biochemical and nutritional aspects associated with the use of seaweeds in food products.

Samples of two edible seaweeds, Palmaria palmata and Ulva rigida, were stored at 4 °C after harvesting, and their microbial flora were measured over a period of two weeks, using food control methods. The results showed a low level of mesophilic aerobes, fungi and yeasts throughout the storage period, whether the seaweeds were unwashed, or washed with seawater, and there was a satisfactory retention of physical characteristics. Seaweeds washed with tap water degraded in less than one week.

Cell walls were isolated from the brown algae Pelvetia canaliculata, Fucus vesiculosus, Sargassum muticum (Fucales) and Laminaria digitata (Laminariales) and then submitted to sequential chemical extraction. Various fucans were isolated, i.e. free fucans released upon cell wall isolation, and fucans extracted with Triton X-100, acid and alkali. The fucans were present in a continuous spectrum of compounds, from high-uronic-, low-sulphate- and fucose-containing polymers to highly sulphated homofucans. Their composition was, however, related to their position of isolation in sequential extraction procedure. The free fucans were similar in composition to homofucans in P. canaliculata, F. vesiculosus and L. digitata and to glucuronofucogalactans in S. muticum ; the fucans released by Triton and those extracted by acid from the isolated cell walls were xylofucoglucuronan-like; and the fucans released upon alginate extraction were again very similar in composition to typical fucoidans. The possible distribution of the various fucans throughout the cell wall is discussed.

Sulphated fucans were fractionated from different brown algae using quaternary ammonium detergents. Purified fractions from different species had the same general chemical composition, that of a typical sulphated homofucans, or fucoidan. The interaction of univalent and divalent counter-ions with fucoidan was investigated by viscometry and polarimetry, and by measuring the counter-ion activites and conductance coefficients in salt-free solutions. The activity and conductance coefficients were found to be independent of the polyanion concentration and approximately the same within each family of counter-ions. This indicates that cation binding in salt-free solutions of fucoidan is purely electrostatic. The conductivity results were in good agreement with the Manning's condensation polyelectrolyte model. The density charge parameter was 2.08 and the mean length of the monomeric unit was 4.5 A. Both the reduced viscosity and the optical rotation were dependent on the valency of the counter-ions used. Coupled with the data obtained from light-scattering measurements. ( M W = 1.7 10 6 and R g = 1760 A ), our results suggest that fucoidan in aqueous solution is an extended, flexible coil.

Mabeau, S. and Kloareg, B. 1987. Isolation and analysis of the cell walls of brown algae: Fucus spiralis, F. ceranoides, F. vesiculosus, F. serratus, Bifurcaria bifurcata and Laminaria digitata.—i. exp. Bot. 38: 1573-1580. Cell walls were isolated from six marine brown algae, Fucus spiralis, F. ceranoides, F. vesiculosus, F. serratus, Bifurcaria bifurcata (Fucales, Phaeophyta) and Laminaria digitata (Laminariales, Phaeo phyta). Yields of isolated cell walls ranged from 35-45% of thallus dry weight. Walls were composed mainly of alginates and sulphated fucans, the proportions of which correlated with species zonation in the intertidal region. This result is consistent with the hypothesis that the sulphated fucans are associated with the adaptation ofmacroalgae to the intertidal environment. Comparing the chemical composition of isolated cell walls with that of whole plants, we conclude that alginic acid is mainly part of the fibrillar wall while a significant proportion of the sulphated fucans probably belongs to the intercellular space matrix. Since ascophyllan-like polysaccharides were more abundant in the fucan extracts from the isolated cell walls than from the whole plants, it is suggested that differences in the structure of fucans might be related to differences in their localization throughout the tissue. Key words—Ce 11 walls, Phaeophyta, sulphated fucans. Correspondence to: Centre d'Etudes Oceanologiques et de Biologie Marine, CNRS, LP 4601, Place