WO2011012933A1

WO2011012933A1 - Process for obtaining mushroom dietary fiber and respective fiber

Info

Publication number: WO2011012933A1
Application number: PCT/IB2009/055552
Authority: WO
Inventors: Fernando Hermínio FERREIRA MILHEIRO NUNES; Ana Isabel Ramos Novo Amorim De Barros; Sara Margarida Moreira Meneses Fraga
Original assignee: Universidade De Trás-Os-Montes E Alto Douro
Priority date: 2009-07-28
Filing date: 2009-12-07
Publication date: 2011-02-03
Also published as: PT104691A; PT104691B

Abstract

The present invention finds application in food industry and refers to a process for obtaining mushroom dietary fiber obtained from mushroom residues and surpluses from mushroom production. This process includes the treatment and optimization of mushroom residues and surpluses from mushroom production, creating a product with appropriate characteristics to be used as food ingredient, specifically as a dietary fiber. The process consists of milling and separating the components without dietary fiber effect of the mushroom residues and whole mushrooms with an alkaline solution containing hydrogen peroxide, having an enrichment in dietary fiber, the final product presenting a low caloric content and a polysaccharide composition different from the fibers obtained from vegetable sources and cereal usually used for the production of this food ingredient.

Description

Title of Invention: PROCESS FOR OBTAINING MUSHROOM

DIETARY FIBER AND RESPECTIVE FIBER

Technical domain of the invention

[1] The present invention refers to a process for obtaining mushroom dietary fibers

obtained from mushroom residues and surpluses of mushroom production, resulting in a food ingredient with an improved chemical composition in terms of food fiber, once it is different from those already existing from vegetable origin.

Summary of the invention

[2] The invention consists of a process that uses residues from mushroom production

(mycelium, feet and defective mushrooms) and surplus mushrooms, which are manually or mechanically mixed with an alkaline solution containing hydrogen peroxide, thus originating a product with appropriate physiochemical characteristics to be used as food ingredient in the form of dietary fiber with an unique chemical composition.

Background of the Invention

[3] The dietary fiber is usually defined as food components which do not undergo

digestion by the enzymes of the human gastrointestinal system, either fermented in the colon or not. According to the CODEX ALIMENT ARIUS, the dietary fiber means carbohydrate polymers with a polymerization degree not inferior to 3, which do not undergo digestion nor are absorbed in the small intestine (FAO/WΗO, 1997; Champ et al, 2003).

[4] The benefits for health resulting from dietary fiber consumption are well

documented, presenting a beneficial action in terms of the time of intestinal traffic, constipation prevention and treatment, colorectal cancer, coronary disease and diabetes (Eastwood, 1987; Mendeloff, 1987; Harig, 1989; Tinker, 1991; Anderson, 1994;

Cassidy and Bingham, 1994), promotion of colon's health by the use thereof in the production of short chain fat acids by their fermentation in the colon, thus stimulating the beneficial intestinal microflora growth, therefore acting as a prebiotic (Roediger, 1980; Cummings, 1981; Fleming et al, 1983; Cummings, 1984; MCBurney et al.

1985; Whitehead et al, 1986; McBurney et al, 1987; Mendeloff, 1987; Mortensen et al, 1988; Schweizer. et al, 1991; Demigne et al, 1995).

[5] The contribution of the dietary fiber in the viscosity development within the intestine seems to be related with the metabolism control of the glucose and lipids (Kritchvsky et al, 1974; Barbaro et al, 1981; Smith - Anderson et al, 1984; Demigne et al, 1986; Jacobs 1986; Howe, et al, 1992; Callaher et al, 1992; Glore et al, 1994; Salminen et al., 1998).

[6] The dietary fiber also presents technological properties that might be used in product formulation, resulting in foods with modified texture and/or an increase in the stability thereof during production and storage phases.

[7] These properties, namely the nutritional properties, have recently led to the

production of food enriched in dietary fiber, for instance, bread, cookies, breakfast cereals, yogurts, sauces, beverage, meat products, etc., due to consumer awareness of the benefits in one's health provided by its consumption.

[8] Nowadays, there is a variety of raw materials from which dietary fibers can be

obtained from vegetable sources, as for instance, cereals (wheat, corn, oats, rye), fruit (citrines and apple), vegetables (pea and beet), and powder cellulose.

[9] The main characteristics of the available products are a total dietary fiber content over 50%, humidity content inferior to 9%, low lipid content, low caloric value (inferior to 8.36 kJ/g), and neutral flavor and odor (Thebaudin et al., 1997).

[10] The dietary fiber might exclusively contain soluble fractions - soluble dietary fiber, exclusively insoluble fractions - insoluble dietary fiber, or more frequently a mixture thereof in several ratios.

[11] There are several technological methods for the preparation of fiber-rich food ingredients, these being able to be separated in enzymatic and chemical methods.

[12] Among the enzymatic methods, the protease and amilase treatment (with both or just one of the enzymes), so as to simulate the digestion process, followed by precipitation of the soluble fiber with ethanol, has been applied in several products.

[13] The enzymatic treatment was also used for the purpose of obtaining vegetable fibers with high solubility and improved texture (Caprez et al., 1987). Another used method is soy residue fermentation with Aspergillus oryzae so as to obtain a product with a dietary fiber content superior to 50% (Matsuo, 1989).

[14] A diversity of chemical methods includes:

1. washing with water for the removal of the soluble components as simple sugars, at temperatures ranging 38 ⁰C to 60 ⁰C (US Patent 4,795,653);

2. after obtaining of the corn starch by wet process (US 4,994,115);

3. delignification treatment of the straw fiber with an alkaline solution of

hydrogen peroxide (US 4, 774 098);

4. acid hydrolysis of lignocellulose plant fiber, at temperatures ranging 150⁰C to 300⁰C and at 0.6 MPa to 8.7 MPa (US 4,997,665);

5. treatment of oat husk with a sodium hydroxide solution (4.5-50%) in a 100 ⁰C to 200⁰C autoclave and at 0.1 MPa to 1.0 MPa for the removal of most existing silica and lignin (US 5,023,103).

General description of the invention [15] Nowadays, the greater concerns of agro-industry Corporations are focused on the development of improvements in productivity and competitiveness. The valorization of their production residues and resulting wastes, through the creation of products with increased value, has been an additional competitiveness factor.

[16] In this sense, the present invention provides a solution to the agro-industrial sector, namely in mushroom production are, since it provides a technological solution for the valorization of the sub-products and production surpluses in this sector, resulting in the development of a valuable product as food ingredient.

[17] The present invention differs from any methodology so far presented, not only due to the substrate used (non- vegetable), but also due to the extraction method in which an alkaline solution containing hydrogen peroxide is used, a product with appropriate physiochemical characteristics being obtained which is adequate as food ingredient as dietary fiber, comprising an unique chemical composition.

[18] So far, dietary fibers are mainly available from vegetable origin, mushrooms and their residues are however also rich materials in dietary fiber stemming from their cell walls. The cell walls of fungi, among which mushrooms are included, are unique in structure and significantly differ from the cell walls of cellulose-based plants. The fungi cell walls contain glycoprotein and polysaccharides, mainly beta-glucanes and chitin (Pamela, 2000; Vetter, 2007). The present glycoprotein in cell walls is widely glicosylated containing carbohydrates both N -, as O-linked and in many situations contain Glycosylphosphatidylinositol-anchoring.

[19] The glucane component it is predominantly composed of a main chain of glucose residues in beta connection (1→3). Some glucanes may contain glucose branches in beta connection (1→6). Chitin is composed of straight chains of beta-linked N- Acetyl- glucosamine residues (1→4).

[20] These polysaccharides present all the nutritional characteristics of a dietary fiber, that is, they are not digestible by the superior gastrointestinal enzymes (Cheung, 1996). It should be noted that polysaccharides isolated from the mushroom cellular walls has drawn attention in recent years due to their imunomodulatory and antitumor properties (Czop et al., 1985; Ishibashi et al., 2001; Mizuno et al., 2001; Wasser, 2002; Brown et al., 2003; Borchers et al., 2004; Hong et al., 2004).

[21] The chemical composition of mushrooms is variable among species and within the same species, depending on several factors such as maturity, relative humidity and temperature during its growth and post-harvest conditions, among others.

[22] The Table 1 describes the centesimal composition of the most common mushrooms grown worldwide (world production: Agaricus -31.8%; Lentinula -25.4%; Pleurotus- 14.2%). The major component is water ranging among 82 to 95% of the fresh weight of the mushrooms. The protein content varies between 11 to 35% and the ash content varies among 6 to 13%. The fat content is also variable ranging between 2 to 9%, being mainly composed of polyunsaturated, oleic and linoleic acids (> 70%).

[23] The carbohydrates, calculated by gradient, are the main components in the dry matter of the mushrooms.

[24] Among the carbohydrates, the dietary fiber is the main component of the mushrooms, ranging between 18 to 50% of its dry weight, turning the mushrooms into a rich source in dietary fiber. The mushroom dietary fiber is predominantly rich in insoluble dietary fiber (-90%), being mainly composed of glucanes and chitin.

[25] Table 1 - Centesimal analysis and other components of mushrooms (Manzi et ah, 2001; Cheung, 2008).

[Table 1]

[Table ]

a %Nx4.35;^b calculated by gradient (% Dry matter -% Protein -%ashes -%Fat); ^c SDF - Soluble Dietary fiber; ^d in relation to the dietary fiber; ^e IDF - Insoluble Dietary fiber.

[26] In terms of yield and global composition, except for the case of cereal crumbs (42%) and peas (5.3%), the dietary fiber percentage in mushrooms represents an equivalent amount, and many times superior, to that of fibers from fruit (0.5-3%) and vegetables (1.4%).

[27] In technological terms, and among functional properties, the color and odor of the fiber are the main factors in its selection, the fiber having to be scentless, in order not to introduce unpleasant aromas in the food to which it is added, and having to be of white color, in order not to cause an alteration of the color of the product. The water and oil retention capacities are, at an industrial level, two parameters of equal high importance, because they are the responsible for the change in the texture of the food to which the fiber is added (Thebaudin, et ah, 1997).

[28] The hydration properties of the dietary fibers determine their optimal use in the food since, these should present a desirable texture. In a simplified way, the water can be held by the insoluble dietary fibers in two ways: water linked by superficial tension of the matrix pores; water linked by hydrogen bridges, ionic and/or hydrophobic interactions. The distribution of the water among these two states depends on the chemical structure of the components, on the association between the molecules, on the particle size, on the fiber porosity, on the effect of the solvents and on the temperature.

[29] In technological terms, the water retention capacity leads to the food weight increase by water incorporation. At a nutritional level it might be verified that the increase on the water retention is related to the increase on the intestinal traffic time (Staniforth et al., 1991).

[30] The oil retention capacity is explored in food such as cooked meat products for an increase on its fat retention, since fat is usually lost when cooked. This property can also be important for the retention of aromas and for an increase on the product's weight.

[31] Mushrooms and mushroom residues are highly perishable products having a useful life of just a few days at room temperature. These are live materials proceeding with their active metabolism after the crop, and entering in a senescence process. This process leads to a deterioration of their cells with the loss of water and to the development of a brownish color, a significant change occurring during this period on the color, texture, odor and flavor (Beelman,1988; Soler-Rivas et al., 1999).

[32] The brownish enzymatic color is due to the presence of a high activity of the tyrosine enzyme (EC 1.14.18.1), also designated polyphenol oxidase. This enzyme catalyzes the monophenol hydroxylation (monophenolase activity) and the ortho-diphenol oxidation to the respective quinones. The quinones are highly reactive substances that can either react with proteins or polymerize, forming melanins which are responsible for the development of the dark brown color. Most os these enzymes is inactive in mushrooms and mushroom residues in their latent form, being however activated in the senescence process, by acid or basic treatments, mechanical stress, etc.

[33] The contact between the enzyme and its natural substrata happens when mushrooms are damaged or cut, thus leading to melanin production. The function of the melanins is to protect fungi against the environmental stress (Bell et al., 1986). In general terms, the fungi melanins are classified in four types: DOPA (β - (3,4-dihydroxyphenil)alanine)-melanin, derived from tyrosine; GDBH ( g - glutaminyl-3,4-dihydroxybenzene)-melanin, derived from g - glutaminyl-4- dihydrox- ybenzene (GHB); catechol-melanins derived from catechol and dihydroxynaftalene; and pentacid- melanin derived from 1,8-dihydroxynaftalene. In all cases, the phenol compositions are oxidized to quinones, which polymerize in a non- enzymatic way, so as to form brown pigments. In the case of Agaricus bisporus the brownish color is mainly due to the formation of DOPA and GDHB-melanins, the tyrosine having an essential role in the synthesis thereof.

[34] Another alteration occurring during the senescence process is the mushroom aroma change. One can verify that the storage during just one day causes an undesirable alteration in the aroma of the mushrooms, an increase occurring in l-octen-3-ol levels, also known as mushroom alcohol, and l-octen-3-one levels, the increase on the level of the later being undesirable. This compound presents a metal odor, being considered as an off-flavor in milk products (Maga, 1981).

[35] The oxidation of unsaturated fat acids, predominant in mushroom fat (oleic and

linoleic) also causes undesirable odors (Frankel, 1983; Donnelly et al., 1995).

[36] The present invention discloses an effective method for the production of a new

dietary fiber-based food ingredient, capable to avoid the darkening and unpleasant odor, resulting in a product with appropriate technological characteristics for application as food ingredient, based on dietary fiber, and with an unique chemical composition in terms of polysaccharides such as chitin and β-glucanes, when compared with the composition of the dietary fibers obtained from the traditional vegetable sources, which present predominantly cellulose, xylanes, pectines, arabinoxylanes and arabinogalactanes as polysaccharides components.

[37] The mushroom dietary fiber is predominantly rich in insoluble dietary fiber (-90%), being mainly composed of glucanes and chitin.

Drawbacks of the previous technology

[38] The attempt on obtaining dietary fiber from mushrooms and mushroom residues by conventional methods applicable to vegetables and cereals (for instance: boiling water, 80% ethanol, enzymatic treatments) resulted in products with strong brown color, presenting an intense mushroom odor, especially in those from mushroom residues, and a high energy content due to the high protein content, turning these products into inapplicable as food ingredients. These changes, in the case of darkening, are related to the presence of the tyrosine enzyme and to the presence of phenol compositions in the mushrooms, which lead to the formation of melanins. The intense and unpleasant odor obtained is due to the presence high l-octen-3-ol and l-octen-3-one contents and lipid oxidation, and which were not removed during the preparation process of fiber following the above-mentioned methods.

[39] The application of conventional techniques on dietary fiber preparation, such as boiling water, 80% ethanol and enzymatic treatments, results in products with strong brown color, presenting an intense mushroom odor, especially in those derived from mushroom residues, turning these products into inapplicable as food ingredients. These changes, in the case of darkening, are related to the presence of the tyrosine enzyme and to the presence of phenol compositions in the mushrooms, which lead to the formation of melanins. The intense and unpleasant odor obtained is due to the presence high l-octen-3-ol and l-octen-3-one contents and lipid oxidation. The process for the production of mushroom and mushroom residues dietary fiber described in this invention allows obviating the problems caused by the enzymatic darkening and elimination of the odor, resulting in a product with high fiber content and low protein and fat content.

Description of the Drawings

[40] Figure 1 - Schematic view of the process for obtaining mushroom dietary fiber.

[41] Figure 2 - Spectrum of X-ray diffraction of the dietary fiber obtained from

mushrooms and mushroom residues.

[42] Figure 3 - Infrared Spectrum of the dietary fiber obtained from mushrooms and

mushroom residues.

Detailed description of the invention

[43] The process of the present invention can be applied to any type of mushroom

production, namely and not limited to, Agaricus bisporus (white and brown mushrooms), Pleurotus ostreatus, Lentinun edodes, etc., products being obtained presenting a fiber with a chemical composition different from those of vegetable origin.

[44] To present invention consists in promoting component extraction without fiber

effect, from the by-products from mushroom production (mycelium, feet, damaged mushrooms), and from whole mushrooms, resulting in a fiber-based product of white color and inodorous with the appropriate physiochemical characteristics (dietary fiber content, low fats and protein content, low caloric content, good water and oil retention capacity), for the use thereof as food ingredient.

[45] The product resulting from the present invention presents a chemical composition in terms of β-glucanes- and chitin-based polysaccharides, which is significantly different from the composition of other fiber-based products and obtained from vegetable and cereal residues, which present predominantly cellulose, xylanes, pectines, arabi- noxylanes and arabinogalactanes as polysaccharide constituents.

[46] Due to its technological properties such as color, smell, water and oil absorption capacity and energy value, the product obtained from the process of the present invention can be incorporate in a variety of food products such as: bread, bread- making and pastry products, meat-derived such as sausages, ham and hamburgers, and an entire range of dietary products with solid presentation.

[47] The attempt to prepare dietary fiber from mushrooms and mushroom residues by conventional methods which are applied to vegetate and cereals (for instance: boiling water, 80% ethanol, enzymatic treatments), resulted in products with strong brown color, presenting an intense mushroom odor, especially in those from mushroom residues, as well as a high energy content (>3 kcal/g, for instance using the hot ethanol treatment)due to the high protein content(40%, for instance using the hot ethanol treatment), turning these products into inapplicable as food ingredients.

[48] To solve this problem an oxidative method for dietary fiber preparation was used, by means of hydrogen peroxide, from the mushrooms and mushroom residues. Basic conditions were used, resulting in a product with white color and exempt from detectable odor, with appropriate quality for its use as food ingredient.

[49] From an implementation of the present invention point of view, it is summarily

described in the outline in Figure 1.

[50] In this process, the mycelium mushrooms and mushroom residues, feet, damaged mushrooms, after removing of strange bodies (dusts and stones), are mixed with an appropriate volume of alkaline reagent and oxidizing agent in a ratio of approximately 40% (w/v), and they are mechanically disintegrated. The oxidizing agent is hydrogen peroxide with a concentration that can range from 0.2% to 30% (v/v). The alkaline reagent can be sodium hydroxide, potassium hydroxide or sodium carbonate, typically in concentrations ranging 2% to 30%.

[51] The process might occur with or without pH adjustment during the reaction/extraction. The process can elapse among Ih up to 24 h, and can be carried out at temperatures ranging 4⁰C to 80 ⁰C, depending on the characteristics intended for the final product. After this period of time, the solution is neutralized with sulfuric acid, or another, for a pH ranging 3 to 7, and the residual oxidizing reagent is destroyed by conventional methods, adding sodium bisulphite.

[52] The solid residue thus obtained is physically separated from the liquid, for example, by filtration or centrifugation, and the humidity content of the obtained solid is reduced the a value among 5% to 10%, for instance by freeze-drying, fluidized bed, heat tunnel or greenhouse effect. The dry product can be milled after drying or it can undergo a selection process of the particle size, for instance, by screening, followed by storage and/or packing.

[53] The composition, yield and functional properties of the obtained product can be differentiated, using different species of mushrooms, different concentrations of oxidizing and base agent, and different times for extraction. After the process of the present invention, the obtained products from mushrooms and mushroom residues present, among other and by means of example, the detailed physiochemical characteristics in Tables 2, 3 and 4.

[54] Figures 2 and 3 show by means of example the spectrum of ray -X diffraction and the infrared spectrum of a dietary fiber from mushrooms or mushroom residue. Figure 2 shows the presence of chitin in its crystalline form α, which is the typical aspect of the cell walls in mushrooms containing it. The presence of chitin is also observed in the infrared spectrum (Figure 3) wherein Amide I, Amide II and Amide II characteristic bands are identified, in relation to N- acetylglucosamine which is chitin's structural unit. The band at 896 cm- 1 is further observed, which is a β-linked polysaccharides characteristic, which is a chitin and β-glucanes characteristic. The fat absence can also be further identified by the absence of its characteristic bands in the 1750-1700 cm-1 region, in relation to the presence of ester groups.

[55] Table 2 - Examples of Composition (g / 100 g) of Mushroom Fibers obtained by the Method of the Present Invention.

[Table 2]

[Table ]

a in relation to the dry mass of mushrooms and residues

b calculations by gradient on the total nitrogen percentage with the nitrogen percentage from glucosamine x 4.35

c as non-starch polysaccharides (Englyst et al., 1994)

d in kcal = 4x(g protein+g carbohydrates)+9x(g lipids) or in kJ = 17x(g protein + g carbohydrates)+ 37x(g lipids).

[56] Table 3 - Examples of Functional Characteristics of the Mushroom Fibers obtained by the Method of the Present Invention. [Table 3]

[Table ]

E Mushroom species Agaricus bisporus Agaricus bisporus Pleurotus ostreatus

Preparation (White) 12 h/T. amb (Brown) lh/35°C lh/35°C

conditions

Water retention 12.9 g/g 3.8 g/g 3.9 g/g

capacity

Oil retention 6.8 g/g 3.0 g/g 4.7 g/g

capacity

Color White White /soft Beige White

Odor Inodorous Inodorous Inodorous

[57] Table 4 - Examples of Sugar Composition of the Dietary Fibers Obtained by the

Method of the Present Invention.

[Table 4]

[Table ]

[58] Summarizing, the valorization of the mushroom residues and surpluses from mushroom production allows obtaining a value-added food ingredient, being a suitable alternative to its simple use as fertilizer, or to its mere disposal in waste dumps.

Application examples

[59] Some non-limiting examples shall be hereinafter presented for the treatment and valorization process of mushrooms and mushroom residues.

[60] Example 1: - Treatment and valorization process of mushrooms and mushroom

residues, in order to obtain a product with lower energy content, comprising the following steps:

• Roughly mixing the mushrooms and/or mushroom by-products (mycelium, feet, damaged mushrooms), if necessary with the aid of a mechanical stirrer, with a 5% sodium hydroxide solution, in a solid/liquid ratio of 4Og: 100 mL. 30% w/w hydrogen peroxide is added until the mixture comprises 5% hydrogen peroxide. Leave under stirring for 12 h at 25 ⁰C.

• Adjusting pH at 5-7 by adding an appropriate amount of concentrated sulfuric acid.

• Adding sodium bisulphite to a 5% concentration. Stirring for 15 min.

• Separating the solid by filtration or alternatively by centrifugation.

• Drying the resulting product, the mushroom fiber, in forced-air greenhouse at 45 ⁰C, until a humidity content no superior to 9% is obtained. After this period of time, the product comes as a white solid, with a yield superior to 20% in relation to the mushroom dry mass, and inodorous, with a fiber content superior to 60% and an energy content of < 1.2 kcal/g.

• Milling the product with a particle size ranging 1.0 mm and 0.25 mm, and proceed with its packaging and storage.

[61] Example 2: - Treatment and valorization process of the mushrooms and mushroom residues, so as to obtain a larger product yield, comprising the following steps:

• Roughly mixing the mushrooms and/or mushroom by-products (mycelium, feet, damaged mushrooms), if necessary with the aid of a mechanical stirrer, with a 5% sodium hydroxide solution, in a solid/liquid ratio of 4Og: 100 mL. 30% w/w hydrogen peroxide is added until the mixture comprises 5% hydrogen peroxide. Leave under stirring for Ih at 35 ⁰C.

• Adding sodium bisulphite to a 5% concentration. Stirring for 15 min.

• Separating the solid by filtration or alternatively by centrifugation.

• Drying the resulting product, the mushroom fiber, in forced-air greenhouse at 45 ⁰C, until humidity content no superior to 9% is obtained. After this period of time, the product comes as a white solid and inodorous, with a yield ranging 30% to 63% in relation to the dry mass of base material, with a fiber content superior to 13% -20% and an energy content of < 2.9 kcal/g.

Milling the product with a particle size ranging 1.0 mm and 0.25 mm, and proceed with its packaging and storage.

Claims

[Claim 1] Process for obtaining mushroom dietary fiber and residues characterized in that a mixture of mushroom residues and mushrooms takes place, manually or mechanically, by means of an oxidative method under basic conditions.

[Claim 2] Process according to claim 1 characterized in that the mushroom residues consist of mycelium, feet and defective mushrooms.

[Claim 3] Process according to claims 1 and 2, characterized in that an amount of alkaline reagent is used in a ratio ranging from 2% to 40% (Wt/v), and an agent oxidizer volume in a ratio ranging from 0.2% to 30% (v/v).

[Claim 4] Process according to the previous claim characterized in that the alkaline reagent can be sodium hydroxide, potassium hydroxide or sodium carbonate, and in that the oxidizer agent can be hydrogen peroxide.

[Claim 5] Process according to the previous claims, characterized in that components are removed without fiber effect.

[Claim 6] Process according to the previous claims, characterized in that a pH adjustment might be carried out during reaction/extraction stages.

[Claim 7] Process according to the previous claims, characterized in that it takes place between 1 h up to 24 hrs, at a temperature ranging among 4 ⁰C up to 80⁰C, depending on the characteristics intended for the final product.

[Claim 8] Process according to the previous claims, characterized in that the mixture is neutralized with sulfuric acid, or another, for a pH between 3 and 7, and in that the residual oxidizer reagent is destroyed in a conventional method, such as the addition of sodium bisulphite.

[Claim 9] Process according to claim 1 characterized in that the solid

residue obtained is physically separated from the liquid, for instance, by filtration or centrifugation, the moist content of the solid obtained being reduced to a value among 5% to 10%, for instance, by freeze-drying, fluidized bed, heat tunnel or greenhouse effect, wherein the dry product can be milled after drying or it can be submitted to a selection process of the particle size, for instance, by screening, followed by storage and/or packing.

[Claim 10] Fiber obtained by the process according to claims 1 to 9, characterized in that there is no vegetable component involved.

[Claim 11] Fiber according to the previous claim, characterized in that it presents a white to beige color and in that it has no detectable odor.

[Claim 12] Fiber according to the previous claim, comprising polysaccharides isolated from the cell walls, such as chitin, β

(l→3)-glucanes, β(l→6)-glucanes, β (l→3)(l→6)glucanes.

[Claim 13] Fiber according to the previous claims, characterized in that it contains a low fat and protein content, low caloric content and a good water and oil retention ability.

[Claim 14] Use of the fiber characterized in that it is applicable in human food industry and animal industry in general.