Dietary fibre and physicochemical properties of edible Spanish seaweeds

 Total dietary fibre content of five edible marine Spanish seaweeds: Fucus vesiculosus, Laminaria digitata (Kombu), Undaria pinnatifida (Wakame), Chondrus crispus (Irish moss), and Porphyra tenera (Nori) ranged from 33.6 to 50% of which 19.6 to 64.9% was soluble. For brown algae, the soluble fibre obtained by the AOAC method followed by dialysis, contained uronic acids from alginates and neutral sugars from sulphated fucoidan and laminarin. For red seaweeds, the main neutral sugars corresponded to sulphated galactans: carrageenan (Chondrus) or agar (Nori), respectively. Insoluble fibres (12–40%) were essentially made of cellulose, plus residual fucose-containing polysaccharides, except for the red seaweed Nori, which contained an insoluble mannan and xylan. Protein content in powdered algae was higher in red (20.9–29.8%) than in brown seaweeds (6.9–16%), although protein digestibility was apparently low as inferred from preliminary in vitro results with Fucus and Laminaria. Ashes (21–39.8%) and sulphate content (2.8–10.5%) were high in all seaweeds. Minor components were lipids (0.2–2.5%) and extractable polyphenols (0.4%). Regarding the physicochemical properties, oil retention was low, while swelling, water retention, and cation exchange capacity were higher in brown algae, related to their higher uronic acid plus sulphate content. Received: 2 May 2000 / Revised version: 13 June 2000     

食用海藻膳食纤维的分离与表征研究进展

膳食纤维被誉为"第七营养素"。合理摄入膳食纤维可以调节人体生理机能,改善健康和预防疾病。我国海藻资源丰富,食用经济海藻产量长期居于世界首位。研究表明可食性海藻富含不可被人体消化吸收的膳食纤维类成分;海藻膳食纤维主要由多糖类物质组成,并具有独特的理化性质以及显著的生理功效。因此,从大型可食性海藻中提取膳食纤维并用于健康食品加工具有高度的发展潜力。本文重点对可食性红藻、褐藻及绿藻中的典型可溶性与不溶性膳食纤维成分的分离纯化与理化性质研究相关报道进行了梳理总结,以期为我国健康食品及经济海藻精深加工领域研究开发提供参考。     

可食性褐藻纤维素的分离纯化与结构分析

以我国主要可食性褐藻海带和裙带菜为对象,对其中的纤维素成分进行分离纯化,并分析纤维素的结构属性。海带的纤维素含量明显高于裙带菜,二者纤维素的提取率分别达原料干质量的5.59%及2.61%。通过酸水解-高效液相色谱分析及傅里叶变换红外光谱分析,提取的纤维素的纯度分别达99.86%及98.91%。海带纤维素的平均聚合度为813,高于裙带菜纤维素的315。粉末X射线衍射分析揭示了2种褐藻纤维素均具有天然高度结晶性结构,结晶度指数分别达72.06%和71.48%,与市售高等植物来源微晶纤维素的水平相当。对X射线衍射图谱的进一步解析表明:褐藻纤维素的结晶性区域以单链三斜晶系(Iα)为主,显著区别于高等植物纤维素的双链单斜晶系(Iβ)为主的结构。研究结果以期为优质膳食纤维资源的开发提供参考。     

Bioavailability of nutrients in rats fed on edible seaweeds,Nori (Porphyra tenera) and Wakame (Undaria pinnatifida), as a source of dietary fibre

A comparative study of the influence of two edible seaweeds, Nori (Porphyra tenera) and Wakame (Undaria pinnatifida), on dietary nutritive utilization was performed. Male adult Wistar rats were fed, for 2 weeks, diets containing Nori, Wakame or cellulose as source of dietary fibre. All diets contained similar amounts of dietary fibre (5%), protein (14%) and ash (5%). Intake, body weight gain, food efficiency (weight gain/food intake), apparent digestibility and retention coefficients for protein, fat, and minerals (calcium, iron, magnesium, zinc, sodium, and potassium) were evaluated. The addition of Wakame or Nori did not affect the gain in body weight of rats or food efficiency. Fresh and dry stool weights were higher in rats fed seaweeds than in the control group. Seaweed-fed animals showed significantly lower apparent digestibilities of protein and fat but absorbed nitrogen was more effectively used by animals. Apparent digestibility and retention coefficients for calcium, magnesium, zinc, iron, sodium and potassium were lower for seaweed-fed rats, and showed lower values for Wakame than Nori. The seaweeds could be a good source of dietary fibre in diet but they may modify digestibility of dietary protein and minerals.     

Influence of different types and proportions of added edible seaweeds on characteristics of low-salt gel/emulsion meat systems

The effects of three different types of edible seaweeds, Sea Spaghetti (Himanthalia elongata), Wakame (Undaria pinnatifida), and Nori (Porphyra umbilicalis) added at two concentrations (2.5% and 5% dry matter) on the physicochemical and morphological characteristics of gel/emulsion systems were evaluated. The addition of seaweeds improved (P<0.05) water- and fat-binding properties except in the case of Nori added at 2.5%. Hardness and chewiness of the cooked products with added seaweed were higher (P<0.05), and springiness and cohesiveness were lower (P<0.05) than in control samples. Colour changes in meat systems were affected by the type of seaweed. The morphology of sample differed depending on the type of seaweed added, and this is the result of differences in physical and chemical characteristic of the seaweed powder used. In general, products formulated with the brown seaweeds (Sea Spaghetti and Wakame) exhibited similar behaviour, different from that of products made with the red seaweed Nori.     

Bio-accessibility of bioactive compounds (ACE inhibitors and antioxidants) from extruded maize products added with a red seaweed Porphyra columbina

An expanded maize product added with red seaweeds Porphyra columbina (3.5 g 100 g⁻¹) was developed and bio-accessibility of minerals and bioactive compounds such as ACE inhibitors and antioxidants provide by algae were evaluated using a pepsin/pancreatin digestion and equilibrium dialysis method. Extruded maize added with red seaweed showed higher dialyzability of ACE inhibitor compounds (41.0% ACE inhibition), total phenolic content (0.83 mg gallic acid/g dialysate) and antioxidant capacity (36.6% DPPH inhibition, 2.4 mM TEAC, power reduction and 99.4% copper-chelating activity) than extruded maize. Results about bio-accessibility of bioactive compounds provided by red edible seaweeds may help food technologists to tailor new bio-functional foods, such as functional snacks.     

Mineral content of edible marine seaweeds

Mineral content was determined in several brown (Fucus vesiculosus, Laminaria digitata, Undaria pinnatifida) and red (Chondrus crispus, Porphyra tenera) edible marine sea vegetables. Seaweeds contained high proportions of ash (21.1–39.3%) and sulphate (1.3–5.9%). In brown algae, ash content (30.1–39.3%) was higher than in red algae (20.6–21.1%). Atomic absorption spectrophotometry of the ashes indicated that marine seaweeds contained higher amounts of both macrominerals (8.083–17,875 mg/100g; Na, K, Ca, Mg) and trace elements (5.1–15.2 mg/100 g; Fe, Zn, Mn, Cu), than those reported for edible land plants. Edible brown and red seaweeds could be used as a food supplement to help meet the recommended daily intake of some essential minerals and trace elements.     

Antioxidant compounds in edible brown seaweeds

Seaweeds are an excellent source of compounds with biological activity. Among the bioactive substances identified, antioxidants have received particular interest due to their beneficial effects on health. In the present study, the total phenolic content and the pigment contents in edible seaweeds were evaluated. The total phenolic content was determined by Folin-Ciocalteu’s method for four species of brown algae included Himanthalia elongata, Laminaria sp., Laminaria saccharina and Undaria pinnatifida. The total polyphenol content varied between 1.3 and 10.0 g phloroglucinol/kg wet weight of sample. The components responsible of the colour (carotenoids and chlorophylls) of the seaweeds were evaluated by using a spectrophotometric method. In addition, pigments were separated and identified by on line HPLC coupled with UV–Vis and fluorescence detectors and confirmed by liquid chromatography coupled to mass spectrometry (LC–MS APCI). Fucoxanthin, β-carotene, chlorophyll a and phaeophytin a were identified in the samples analysed.     

食用红藻鸡冠菜的营养成分分析及评价

对鸡冠菜的主要营养成分、不溶性膳食纤维、氨基酸及矿质元素进行测定,并进行营养分析。结果显示,碳水化合物、蛋白质和灰分是鸡冠菜的主要成分。其中不溶性膳食纤维和蛋白质含量较高,分别占藻体干重的31.5%和19.2%,氨基酸种类齐全,含有丰富的呈味氨基酸。脂肪含量低,具有人体必需脂肪酸--γ-亚麻酸。矿物质元素含量丰富,尤其是铁含量高。因此鸡冠菜是一种高蛋白、低脂肪、高纤维,且富含矿物质的可食用海藻,具有良好的应用前景。     

Benthic marine and blue–green algal species as a source of choline

Species of red, brown and green seaweeds and blue-green algae were evaluated as sources of choline. A third of the seaweeds and all the blue-green algae gave very low values. Of the remainder, the brown seaweeds yielded contents between 0.1 to 6, the red 1 to 6 and the green 3 to 8 mg choline/g of dry alga. The seasonal variation was investigated in three brown algae. Commercial seaweed meals from Ascophyllum nodosum showed nearly constant levels of choline. The chromatographic behaviour of the choline-reineckate complex was also studied.     

Infrared analysis of Macedonian mushroom dietary fibre

The existing confusion in the terminology and composition of the mushroom dietary fibre literature data induced us to analyze simultaneously the chemical constitution of various dietary fibre isolates obtained from numerous mushroom samples. For that purpose, in 53 kinds of edible Macedonian mushrooms total dietary fibre was isolated by two parallel methods intended for material of plant and animal origin. With the aid of infrared spectroscopy the chemical constitution of the both isolated components was also investigated. The infrared spectra of the total dietary fibre isolates, obtained according to both applied methods, were similar and close to chitin. In all spectra cellulose is missing.     

Enhancement of the phytochemical and fibre content of beef patties with Himanthalia elongata seaweed

The effect of adding Himanthalia elongata seaweed (10–40% w/w) as a source of antioxidants and dietary fibre on physical, chemical, microbial and sensory traits of cooked beef patties was studied throughout chilled storage. Patties with seaweed showed reduced cooking losses and were nearly 50% more tender as compared to patties without seaweed. Microbiological counts and lipid oxidation were significantly lower in patties containing seaweed (P < 0.05), and by day 30 of storage, there was no bacterial growth in samples with ≥20% seaweed and lipid oxidation levels were low (0.61 mg malondialdehyde kg^?1 of sample). Seaweed incorporation significantly increased the dietary fibre (1.64 g per 100 g fw in 40% seaweed patties), total phenolic content (up to 28.11 mg GAE per 100 g fw) and DPPH radical scavenging activity (up to 52.32%) of patties compared to the control. Sensory analysis indicated that the seaweed patties were accepted by consumers in terms of aroma, appearance, texture and taste. Patties containing 40% seaweed were rated highest in terms of overall acceptability, most likely due to improvement in texture and mouthfeel. Addition of seaweed in the formulation of beef patties leads to the enhancement of the nutritional and technological quality together with an acceptable sensory quality.     

Edible Japanese seaweed,wakame (Undaria pinnatifida) as an ingredient in pasta: Chemical,functional and structural evaluation

Wakame (Undaria pinnatifida) is edible seaweed rich in fucoxanthin; whilst, pasta is an important dish from nutritional and gastronomic point of view. Pasta was prepared with wakame as an ingredient at different levels. In vitro antioxidant properties, total phenolic content, fatty acid composition, fucoxanthin and fucosterol contents formed the major bio-functional characteristics analysed. Pasta with 10% wakame was acceptable sensorially. The total phenolic content varied between 0.10 and 0.94 mg gallic acid equivalents (GAE)/g, whilst total antioxidant activity varied from 0.16 to 2.14 mg ascorbic acid equivalents (AAE)/g, amongst different samples. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging activities of sensorily acceptable pasta were 7.71% and 4.56%, respectively. The sensorily acceptable pasta had a mild seaweed flavour with taste similar to control pasta, as assessed by panelists. The ratio of n-3 to n-6 fatty acid in seaweed incorporated pasta was 1:3.4 as compared to 1:15.2 in the control. Heat process involved in pasta preparation and cooking did not destroy fucoxanthin. Microstructure studies revealed the enhanced interaction between starch granules and protein matrix in pasta containing seaweeds up to 20%.     

Identification of selected seaweed polysaccharides (phycocolloids) by vibrational spectroscopy (FTIR-ATR and FT-Raman)

The wide industrial application of phycocolloids (e.g. alginates, agar and carrageenans) is based on their particular properties to form gels in aqueous solution. These seaweed polysaccharides present a chemical structure related with the taxonomic position of the algae: carrageenans are produced by carrageenophytes (red algae belonging mainly to the genera Kappaphycus, Eucheuma, Chondrus, Gigartina and Chondracanthus). Recently, new spectroscopic techniques have provided more accurate identification of the natural composition of the polysaccharides produced by these seaweeds. With the combination of two spectroscopic techniques (FTIR-ATR and FT-Raman) it is possible to identify the principal seaweed colloids in ground seaweed samples as in extracted material. Since the seaweed samples receive the minimum of handling and treatment (e.g. they are simply dried and ground), the composition determined represents, as accurately as possible, the native composition of the phycocolloids.     

Enrichment of nutritional compounds in seaweeds via abiotic stressors in integrated aquaculture

Seaweeds may contain significant amounts of essential proteins, carbohydrates, and minerals, offering an alternative, sustainable, healthy food source from the sea. However, there are yet challenges impending their full exploitation. Our study presents an innovative, two-step aquaculture approach integrating seaweeds and finfish, dedicated to enrich seaweeds with nutritional compounds. The approach involves diverting fish effluents rich in nutrients into a series of seaweed cultivation tanks. Then, the seaweeds were exposed to short-term abiotic stressors (namely, high irradiance, nutrient starvation, and high salinity) to stimulate synthesis of desired ingredients in their tissues. Our methodology enabled high growth rates of up to 25% seaweed biomass increase per day, with significant enhancements in the amount of protein, starch, and minerals within days. Moreover, the seaweeds presented elevated bioremediation capabilities assimilating the ammonia nitrogen, NO₃ and PO₄ with high uptake rates, and with 50–75% removal efficiencies.Industrial relevanceThe rising public awareness to quality of healthier food products has stimulated growing demand for seaweed supply. Our new approach suggests a promising direction toward the transition from seaweed production of raw, commodity seaweed biomass, to a tailored production of functional seaweeds, enriched with valued compounds that can be utilized in the emerging food and health industries.     

基于红藻多糖的生物转化研究进展

与陆地生物质相比,海洋生物质因具有光合作用效率高、生长速度快、碳水化合物含量高、不含木质素等优点,受到了越来越多的关注,被称为第3代生物质资源。红藻是典型的大型海藻,其细胞壁富含多糖。本文首先介绍了红藻的分布与组成,之后围绕红藻多糖的生物转化,分别综述了其在酶解制备琼胶寡糖和3,6-内醚-L-半乳糖以及发酵生产乙醇和有机酸方面的研究进展,并对未来红藻生物质的利用方向进行了展望。     

Dietary Fibre Content and Composition of Some Edible Fungi Determined by Two Methods of Analysis

Six common edible fungi from four orders of Basidiomycetes, namely Agaricus bisporus (Agaricales), Auricularia auricula and Auricularia polytricha (Auriculariales), Tremella fuciformis (Tremellates), Ganoderma lucidum and Poria cocos (Aphyllophorales), were analysed for their total dietary fibre (TDF) content using the Association of Official Analytical Chemists (AOAC) method and for dietary fibre content and composition using the Uppsala method. The non-protein nitrogen contributed from fungal chitin was corrected in the fibre residue obtained by the AOAC method. The TDF content measured by the AOAC method was always greater than that of the Uppsala method. The TDF content determined by the AOAC and Uppsala methods ranged from 182 and 132 g kg^-1 (dry matter) in A bisporus to 735 and 711 g kg^-1 (dry matter) in P cocos, respectively. Neutral and amino sugars were the dominant sugars in all the fungi. Sugar composition of the TDF reflected that the major cell wall polysaccharides in most fungi were hemicelluloses, such as β-glucan and glucuronoxylomannan, pectic substances and chitin. Judging from their high fibre content and unique fibre composition, edible fungi have considerable value as sources of dietary fibre in human nutrition. © 1997 SCI.     

Factors limiting the biodegradation of Ulva sp cell-wall polysaccharides

The dietary fibres of the seaweed Ulva sp (sea-lettuce) consist of water-soluble ulvan, alkali-soluble β(1,4)-D -glucuronan and β(1,4)-D -glucoxylan, and an insoluble α-cellulose containing xylose residues. They are poorly degraded by human colonic bacteria particularly when associated within the intact plant cell wall. In order to better understand this resistance to microbial attack, their organisation in the cell-wall has been investigated by light and electron microscopy after sequential chemical extractions. Their susceptibility to enzymatic degradation and their accessibility to bacteria and enzyme were also studied. Microscopic localisation in native and sequentially extracted Ulva sp demonstrated that ulvan is in all the cell-walls of the algae and particularly between the two cell layers constituting the thallus. Glucuronan is close to the cytoplasmic membrane facing the outside of the seaweed and between adjacent cells. The xylose and glucose containing polysaccharides form packed layers surrounding the cells. A model of the spatial distribution of the different polysaccharides within the algae is proposed. Ulvan and glucuronan did not limit the xyloglucan and α-cellulose degradation by an endo-xylanase in the whole seaweed and its insoluble dietary fibre but the α-cellulose was not affected by a cellulase. The cell-wall of Ulva sp was accessible to enzymes but poorly to bacteria as assessed from porosity measurements. These results established that the poor fermentation of sea-lettuce by human colonic flora is primarily due to the ubiquitous presence of the degradation-resistant ulvan in the cell wall of Ulva sp. ©1997 SCI     

高效液相色谱氢化物发生原子荧光光谱联用检测海藻中砷形态

目的测定14种海藻样品中总砷和无机砷的含量,同时分析样品中6种砷形态。方法将海藻样品经过微波消解的前处理方法,通过电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,ICP-MS)测定总砷含量;根据国标方法中无机砷检测的前处理方法,通过原子荧光光谱(atomic fluorescence spectrometry,AFS)测定无机砷含量;最后通过酸提的前处理方法,利用高效液相色谱-氢化物发生-原子荧光光谱法(high performance liquid chromatography-ultraviolet photo-oxidation-hydride generation-atomic fluorescence spectrometry,HPLC-(UV)-HG-AFS)测定海藻样品中6种形态砷含量并与国标无机砷方法比较。结果 14种海藻样品中总砷含量为0.038~46.2 mg/kg;无机砷含量为0.006~19.3 mg/kg;对HPLC-(UV)-HG-AFS仪器的优化和方法的摸索后,从海藻样品中主要测得的砷形态为As(III)、As(V)和DMA,MMA含量较少,没有测出As B和As C。结论在砷形态较为复杂的海藻样品检测中,通过HPLC-(UV)-HG-AFS检测方法可以有效避免无机砷前处理中可能出现的有机砷向无机砷转变的现象,降低干扰,增加测试的准确性,更为具体地表现海藻样品中主要的砷形态含量。     

8种海藻和3类海带的色素抗氧化活性的研究

实验选取褐藻、绿藻、红藻及微藻中的8种代表性海藻,采取酶辅助有机溶剂法提取色素,测其含量及抗氧化活性,筛选出一种高抗氧化活性的海藻,研究其不同加工方式对色素的抗氧化活性产生的影响,并对色素含量与抗氧化活性进行了相关性分析。结果表明,8种海藻色素粗提物都具有一定的体外抗氧化活性,海带、裙带菜、石莼的色素粗提物体外抗氧化活性较好,尤以海带为佳。在海带色素粗提液终浓度0.8 mg/mL下,DPPH自由基的清除率为52.58%,羟自由基清除率为68.14%,超氧阴离子自由基清除率为60.79%。3种海带色素的含量和抗氧化活性的大小均为:新鲜海带 > 盐渍海带 > 晒干海带。相关性和线性回归分析表明,三种自由基清除率与叶绿素含量和类胡萝卜素含量的相关性都达到了0.75以上,且显著性都呈极显著,叶绿素含量与类胡萝卜素含量对三种自由基的清除率的影响是具有共同作用的,但类胡萝卜素含量与三种自由基的清除率的相关性更高。