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     

Effect of micronisation on dietary fibre content and hydration properties of lotus node powder fractions

Fibre‐rich fractions were obtained from nodes of lotus root and micronised by nine different ball‐milling treatments. The optimum milling conditions were screened out by comparing its effects on physicochemical and hydration properties of micro‐sized particles of lotus node powder fraction (LNPF). The micronisation by ball‐milling treatments was carried out at different speeds (200–400 r min^?1) and time (4–12 h). Ball‐milling treatments could effectively (P < 0.05) pulverise the LNPF particles to different micro‐sizes. As particle size decreased, a redistribution of fibre components from insoluble to soluble fractions was observed. Furthermore, micronisation treatments, especially 12 h at 300 r min^?1, could significantly (P < 0.05) increase the hydration characteristics, as well as impart lightness in colour to different extents. Our findings suggested that micronisation can improve physicochemical and hydration characteristics of the fibre components, which provide an opportunity to improve the utilisation and application of lotus node dietary fibre.     

Effect of raw and cooked onion dietary fibre on the antioxidant activity of ascorbic acid and quercetin

The effect of cell walls (dietary fibre) from raw and cooked onions (Allium cepa L. red skinned variety) on two dietary antioxidants, l-ascorbic acid (AA) and quercetin, was investigated. Cell walls isolated from onion parenchyma tissues were incubated with AA or quercetin in HEPES buffer at pH 6.5 and 37 °C for 2 h. The resulting supernatants were analysed by the ferric reducing antioxidant power (FRAP) assay and cyclic voltammetry (CV). Results show that onion cell walls effectively reduced AA degradation, but provided no protective effect against quercetin degradation, and may increase the degradation. This suggests some type of favourable interaction of the cell wall components with AA but not with quercetin. Cooking facilitates the extraction of cell wall polysaccharides and hence influences the extent of interaction of cell wall components and antioxidants. The redox behaviour of the antioxidants, the polysaccharide components of cell walls, and their relative extractabilities all appear to have important influences on the interactions.     

Date flesh: Chemical composition and characteristics of the dietary fibre

The date by-products of two date palm (Phoenix dactylifera L.) cultivars, Deglet-Nour and Allig, from the Degach region (Tunisia), were analysed for their main chemical composition. Studies were also conducted on the physicochemical properties (colour, water and oil-holding capacity and rheological behaviour) of dietary fibre (DF) extracted from date flesh. The following values (on a dry matter basis: DM) were obtained for fleshes of Deglet-Nour and Allig cultivars, respectively: sucrose 52.7% and 13.9%, glucose 13.7% and 29.9%, fructose 12.6% and 29.0%, total dietary fibre 14.4% and 18.4%, protein 2.1% and 3%, ash 2.5% and 2.52%. Insoluble DF, the major fraction of total DF, constituted 9.19–11.7% DM for Deglet-Nour and Allig, respectively. The elaboration of DF concentrates from date fleshes was characterised by an extraction yield of 67%. The chemical composition of these DF concentrates showed high total DF contents (between 88% and 92.4% DM) and low protein and ash contents (8.98–9.12% and 2.0–2.1% DM, respectively). The DF concentrates showed a high water-holding capacity (∼15.5 g water/g sample) and oil-holding capacity (∼9.7 g oil/g sample) and pseudoplasticity behaviour of their suspensions. Thus, date DF concentrates may not only be an excellent source of DF but an ingredient for the food industry.     

Liver paté enriched with dietary fibre extracted from potato fibre as fat substitutes

This experiment included studies of the functionality of three new enzymatically extracted fibres as ingredients in pig liver paté prepared using reduced amounts of pig fat with dry potato pulp and a commercial potato fibre (Potex) as references. The measured quality characteristics included colour, flavour, and texture profile analysis. Dry potato pulp, Potex and two of the new enzymically extracted fibre 1 and 2 with high contents of cellulose and lignin resulted in very hard patties with a high level of deformation energy, gumminess, and modulus that had a detrimental effect on paté texture and flavour. The enzymatically extracted fibre 3 with a low content of cellulose and lignin and a high content of soluble non-starch polysaccharides (SNSP) resulted in patties with a very delicious texture and flavour and values of the measured texture characteristics determined by texture profile analysis. The colour of the patties processed using the enzymatically extracted fibre 3 were darker, more red and less yellow compared to patties processed using Potex, dry potato pulp and new fibre 1 and 2. Baking loss that varied from 9.2 to 11.3 g/100 g was the lowest for patties processed using the new extracted fibre 3. The content of total dietary plant fibre in liver patties varied from 4.0 to 6.2 g/100 g paté.     

Effect of dietary fibre enrichment on selected properties of gluten-free bread

The enrichment of gluten-free baked products with dietary fibre seems to be necessary since it has been reported that coeliac patients have generally a low intake of fibre due to their gluten-free diet. In the present study different cereal fibres (wheat, maize, oat and barley) were added at 3, 6 and 9 g/100 g level into a gluten-free bread formulation based on corn starch, rice flour and hydroxypropyl methyl cellulose (HPMC). Doughs were evaluated based on consistency, viscosity and thermal properties. Results showed that maize and oat fibre can be added to gluten-free bread with positive impact on bread nutritional and sensory properties. All breads with 9 g/100 g fibre increased the fibre content of control by 218%, but they were rated lower than those with 3 and 6 g/100 g fibre due to their powdery taste. The formulation containing barley fibre produced loaves that had more intense color and volume comparable to the control. During storage of breads a reduction in crumb moisture content and an increase in firmness were observed. The micrographs of the crumb showed the continuous matrix between starch and maize and/or oat fibre obtaining a more aerated structure.     

Modification of insoluble dietary fibres in soya bean okara and their physicochemical properties

The changes in physicochemical and physiological properties of modified soluble dietary fibre (mSDF) in the okara using enzymatic [cellulase/substrates ratio of 2.0–6.0% (w/w) at 50 °C for 90–150 min], chemical [water bath of 1–3 h, water bath temperature of 50–90 °C, Na₂HPO₄ concentration of 0.1–0.9% and sample/reagent radio (S/R) of 1:40–1:60 (w/v)] and physical (homogenised once or twice under the optimal cellulase treatment condition) treatments were evaluated. The mSDF yield with chemical treatment (57.16%) was significantly (P < 0.05) higher than that of physical treatment [homogenisation once (16.54%) or twice (42.02%)] in combination with cellulase treatment. All treatments improved swelling capacity of mSDF and promoted bile acid‐ and cholesterol‐absorption capacity, but enzymatic and chemical treatments decreased the total reducing power of mSDF, except homogenisation‐cellulase treatment (141.74 μm  TE g^?1). Therefore, homogenisation‐cellulase treatment may be the appropriate method to improve the SDF proportion and ameliorate the functionality of okara.     

Extrusion improved the physical and chemical properties of dietary fibre from bamboo shoot by-products

Bamboo shoot by-products are regarded as waste and environmental pollutant. This study aimed to improve the functional properties of dietary fibre from bamboo shoot by-products. After CO₂ extrusion, the particle size of CO₂-extruded bamboo fibre was 17.6% lower than that of the control, and its specific surface area was 2.85 times that of the control. The soluble dietary fibre content was significantly increased from 5.64 g/100 g to 11.05 g/100 g (P < 0.05), and the capacities for water holding, swelling and oil holding were remarkably improved. The cholesterol adsorption of CO₂-extruded bamboo fibre was increased from 96.54 μg g⁻¹ to 174.65 μg g⁻¹ (pH 7.0), and its nitrite ion adsorption capacity was increased from 503.33 μg g⁻¹ to 657.27 μg g⁻¹ (pH 2.0). In summary, the structural changes of bamboo fibre such as internal porosity, surface roughening and low crystallinity indicated that its functional properties were improved after CO₂ extrusion.     

Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products

Dehydration promoted important modifications affecting both the physico-chemical properties of dietary fibre (DF) and the antioxidant capacity of orange by-products (peel and pulp remaining after juice extraction). The significance of such changes was largely dependent on the air-drying temperature used (from 30 °C to 90 °C). The major modifications on the DF components were observed when either extended drying periods, i.e. at lower temperatures, or elevated drying temperatures were applied. Dehydration around 50–60 °C apparently promoted the minor disruption of cell wall polymers, in particular of pectic substances. Pulp samples exhibited higher values of swelling (SW) and fat adsorption capacity (FAC) than those derived from orange peel. Although, significant decreases in water retention capacity (WRC), FAC and solubility values were detected for both by-products as the air-drying temperature increased. The antioxidant capacity associated to dehydrated citrus by-products was significantly higher for orange peel than for pulp samples. In general, the by-products studied proved to be quite resistant to the different heat treatments applied within the range of 40–70 °C. In overall, the study shows that, in order to preserve either the DF quality and/or the antioxidant capacity, air-drying temperature should be controlled since both types of compounds, DF components and antioxidants, might be degraded or modified either when extended drying periods and/or high drying temperatures are applied.     

Production of high quality gels from sea bass: Effect of MTGase and dietary fibre

The effects of MTGase (5 g/kg, w/w) and dietary fibre (inner pea fibre, 40 g/kg, w/w, carrageenan, 10 g/kg, w/w, carrageenan + konjac flour, 10 + 10 g/kg, w/w) on heat-induced gels from sea bass (Dicentrarchus labrax) trimmings were studied. MTGase incorporation had a positive effect on texture: gel strength and force at rupture increased. MTGase reduced protein solubility, meaning greater protein aggregation, according to electropherograms. Pea fibre had no positive effects: texture was quite similar to that of the control products and WHC was reduced. Carrageenan addition had no deleterious effect upon the texture of the gels and made them harder and springier. Force at rupture (even without MTGase) and WHC were greatly improved. Combination of carrageenan and konjac further enhanced these effects. For those gels without MTGase, protein solubility in urea and urea + DTT was reduced by both fibres, suggesting a reduction of hydrogen bonding between proteins.     

Effect of extraction method on chemical composition and functional characteristics of high dietary fibre powders obtained from asparagus by-products

Asparagus (Asparagus officinalis L.) by-products, which represent around 50% of the processed vegetable, are a potential source of dietary fibre. The way that these by-products are treated affects the composition and functional properties of fibre-rich powders. Factors such as treatment intensity, solvent, and drying system were studied. Only the more soluble components (soluble sugars, uronic acids and proteins) showed significant differences. All the fibre-rich powders had high concentrations of TDF (62–77%). The IF/SF proportion decreased with the severity of treatment, in this way increasing the physiological quality of the fibre. Functional properties, namely water-holding capacity (WHC), oil-holding capacity (OHC), solubility (SOL), and glucose dialysis retardation index (GDRI), varied according to the preparation procedure. WHC and GDRI were higher in intensely extracted fibres; due to the effect of thermal processing. WHC showed values (11–20 ml water/g powder) similar to those described for other agricultural by-products, but OHC and GDRI were much higher (5–8 ml oil/g powder and 25–45%, respectively). These properties make fibre-rich powders from asparagus by-products a valuable source of dietary fibre to be included in the formulation of fibre-enriched foods.     

Non-waste technology through the enzymatic hydrolysis of agro-industrial by-products

BackgroundOne of the major challenges facing the world at present is the utilisation of by-products. European food industries generate millions of tonnes of by-products annually. Fruit and grain processing industries do not fully utilise potentially valuable raw materials (peels, husks, seeds, stones, bran) that contain a significant amount of dietary fibre and antioxidants. According to recent research, due to the complexity in structure of agro-industrial by-products, both lipophilic and hydrophilic compounds integrated into the matrix and furthermore they are linked with various macromolecules. These interactions have a great influence on bioavailability and hence antioxidant ability of biologically active compounds present in by-products. At present, one major concern is the development of efficient and green technology for the degradation of starch and non-starch polysaccharides presented in by-products, thus contributing to their reduction, as well as long-term improvements in environmental quality and enhancement of extractability of antioxidant compounds.Scope and ApproachThis review summarizes the research progress on the enzymatic hydrolysis of by-products, gives a brief insight into the current state of the amount of the by-products, and describes one possible method of waste recycling.Key findings and conclusionsProcessing of by-products, using enzymatic hydrolysis is promising technique for prebiotic substrates development. Moreover, enzymatic hydrolysis is able to increase the extractability of polyphenols including non-extractable proanthocyanidins from food matrix with no utilisation of organic solvents, nor any other toxic chemicals.     

Characterisation of onion (Allium cepa L.) by-products as food ingredients with antioxidant and antibrowning properties

Processing and stabilising onion wastes (residues and surpluses of onion) could solve the environmental problem derived from a great onion wastes disposal. Moreover, obtaining stabilised onion by-products as natural antioxidant food ingredients could be advantageous to food industry, not only to improve the use of onion wastes but also to obtain new natural and functional ingredients. The aim of this study was to characterise onion by-products – juice, paste and bagasse – from two Spanish onion cultivars – ‘Figueres’ and ‘Recas’ – that have been stabilised by thermal treatments – freezing, pasteurisation and sterilisation – in order to evaluate the effect of the processing and stabilisation treatment on the bioactive composition, antioxidant activity and polyphenol oxidase (PPO) enzyme inhibition capacity. The results obtained triggered to choose one onion by-product offering better characteristics for its potential development as a food ingredient: source of antioxidant and antibrowning bioactive compounds. In this study it was shown that processing of ‘Recas’ onion wastes to obtain a paste (mixture content) and applying a mild pasteurisation were the best alternatives to obtain an interesting stabilised onion by-product with good antioxidant properties that made useful its use as functional food ingredient.     

Avocado by-products: Nutritional and functional properties

BackgroundAvocado (Persea americana Mill.) is a tropical and subtropical fruit that is native to Mexico and Central America; avocado is gaining increasing worldwide acceptance and has received extensive marketing and a wide distribution due to its relevant nutritional benefits for human health. Mexico harvests more than 30% of avocados worldwide, representing the main producer and exporter of avocado, which has become a crop of high interest and has great economic impact on Mexico.Scope and approachIn this paper, we describe relevant information on the production, composition and application of avocado, with an emphasis on its by-products, focusing on the proper use of waste and the possibility of monetizing waste for nutritional and environmental purposes. The entire avocado is rich in biocompounds (pulp, seed and peel) and has many health benefits, such as antimicrobial, antioxidant and anticancer activities, as well as dermatological uses and others. In this paper, we demonstrate the current panorama of production, exportation and uses of avocado in Mexico.Key findings and conclusionsSeveral food grade ingredients can be obtained from avocado wastes, particularly premium-grade fats or extracts with a high functional power. Studies should continue to identify the profiles and phytochemicals available to the business sector, which can also be implemented to valorize the nutritional and functional potential of avocado seeds and peels.     

Technological properties of date paste obtained from date by-products and its effect on the quality of a cooked meat product

Fresh date processing (picking, storage or conditioning) may lead to date losses. Such by-products from fresh dates (Medjoul variety) can be processed to prepare date paste. Chemical composition, physicochemical and technological properties of this date paste were determined regarding its potential application as an ingredient in the elaboration of meat products. The date paste had a high content of sugars (53.00 g/100 g) especially reducing sugars (fructose and glucose), total and insoluble dietary fiber (7.00 g/100 g and 4.04 g/100 g, respectively) and natural antioxidants (polyphenol content; 225 mg GAE/100 g). Its emulsion capacity was 57.00 mL/100 mL and it showed also a high emulsion stability (98.59 mL/100 mL). The addition of up to 15% date paste in the formulation of bologna-type products leads to the enhancement of the nutritional (lower fat content and higher fiber content than control) and technological quality (redder-colored and less hard, chewy and cohesive product than the control) together with a satisfactory sensory quality.     

A new nanofibrillated and hydrophobic grafted dietary fibre derived from bamboo leaves: enhanced physicochemical properties and real adsorption capacity of oil

Dietary fibre (DF) has been used for enhancing health benefits for centuries. In this study, an innovative nanofibrillated cellulose (NFC) was obtained by the combined application of high‐density steam flash‐explosion and enzymatic hydrolysis of bamboo leaves. The NFC prepared in this study was characterised by long, well‐defined and distinct NFC fibres, exhibiting excellent functional properties (water retention capacity: 20 g water g^?1, swelling capacity: 97 mL g^?1, oil‐holding capacity: 13 g oil g^?1, and higher adsorption of bile acids and cholesterol). Octenyl succinic anhydride (OSA) was further successfully grafted onto the NFC to improve its hydrophobicity. Thus, the oil‐holding capacity of the NFC reached 18.5 g oil g^?1 and the adsorption of bile acids and cholesterol increased twofold. A gastrointestinal digestion experiment further showed that the nanofibrillated and hydrophobic grafted dietary fibre represented a high‐quality dietary supplement providing enhanced health benefits, highlighted by the strong ability to absorb oil. These results indicate that the OSA‐NFC has a great potential for use as a functional ingredient in food products.     

Effect of wheat fibre in frozen stored fish muscular gels

The technological effect of wheat fibre, as a healthy ingredient in which consumers are interested, was studied in surimi gel products. Three and six per cent wheat fibre with different particle sizes was added. Functional properties of wheat fibre, such as water retention capacity (WRC), swelling (SW) and fat adsorption capacity (FAC), were determined. Elastic modulus (G′) of surimi with 6% wheat fibre was lower throughout thermal gelling. Under scanning electronic microscopy (SEM), gel samples with added fibre presented uneven distribution of fibre. This induced the formation of a non-homogeneous protein net associated with lower gel strength, cohesiveness and water binding capacity (WBC). The sensory panel found no differences in appearance but differences in texture among samples containing different proportions and types of fibre. Fibre with large particle sizes protected surimi from loss of gel strength and hardness during freezing. There were very few variations during frozen storage of different samples.     

Effect of autoclaving on dietary fibre content of beetroot (Beta vulgaris). Evaluation by different methods

Modifications of dietary fibre in beetroot during autoclaving have been evaluated by different methods: acid detergent (raw=1.45%; processed=1.17%) and neutral detergent (raw=2.30%; processed=2.00%), the enzymatic-gravimetric method of Asp (raw=3.35%; processed=3.34%), HPLC (raw=1.42%; processed=1.60%) and 3,5-dimethylphenol (raw=0.36; processed=0.28%). The correlation between different methodologies was studied. Autoclaving was carried out at 121°C under pressure for 15 min. Variance analysis indicated that quantitative variations originating in the thermic treatment were not statistically significant (P>0.05).     

Certain physicochemical and functional properties of fibre fractions from pulses

The physicochemical and functional properties of the fibre fractions from peas (Pisum sativum), lentils (Lens culinaris), chickpeas (Cicer arietinum L.) and navy beans (Phaseolus vulgaris) were evaluated, and the relationships amongst those properties were determined. Fibre fractions from several varieties of each species were prepared using a laboratory wet milling procedure. The fibre fractions contained 663.2 to 808.5 g/kg DM of total dietary fibre, 45.4 to 171.1 g/kg DM of crude protein, 102.7 to 195.6 g/kg DM of starch and 1.9 to 10.5 g/kg DM of crude fat. Fibre fractions from pea and kabuli chickpea displayed significant higher fat absorption (FA) than those from lentil, navy bean and desi chickpea. Lentil and navy bean fibre fractions exhibited larger mean particle size than did pea and chickpea fibre fractions. Pulse fibre fractions exhibited significantly higher water hydration, swelling and water retention capacities in comparison to commercial pea fibre products. A significant reverse relationship (r = − 0.956, p < 0.001) between mean particle size and specific surface area (SpSA) of pulse fibre fractions was observed. FA of fibre fractions was positively correlated with SpSA (r = 0.820, p < 0.001).