Determination of Hemicellulose, Cellulose and Lignin Contents of Dietary Fibre and Crude Fibre of Several Seed Hulls. Data Comparison

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  • Z Lebensm Unters Forsch (1983) 177:200 202 Zeitschrift fLir

    Lebensmittel- Untersuchung

    und-Forschung @ J. F. Bergmann Verlag 1983

    Determination of Hemieellulose, Cellulose and Lignin Contents of Dietary Fibre and Crude Fibre of Several Seed Hulls. Data Comparison

    Fulgencio Saura-Calixto, Jaime Cafiellas, Juan Garcia-Raso

    Department of Organic Chemistry, University of Palma de Mallorca, Palma de Mallorca, Spain

    Bestimmung des HemiceUulose-, Cellulose- und Lignin-Gehaltes der Rohfaser versehiedener Sehalen. Datenvergleich

    Zusammenfassung. Der Gehalt an Hemicellulose, Cel- lulose und Lignin von ErdnuB-, Haselnul3-, Sonnen- blumensamen-, Kastanie-, Kiirbissamen-, Eichel-, und KokosnuBschalen wurde untersucht. Die Zusammen- setzung der Paare Sonnenblumensamen und Eichel, ErdnuB und Kiirbissamen und Haselnul3 und Kastanie sind ~ihnlich. Daraus kann man folgern, dab sie fihnli- che Zel lwandzusammensetzungen haben. Grol3e Men- gen von Hemicellulose und niedrige von Cellulose und Lignin wurden bei der Bestimmung der Rohfaser auf- gel6st.

    Summary. The contents of hemicellulose, cellulose and lignin in neutral-detergent fibre, and acid-detergent fibre in hulls of hazelnuts, peanuts, coconuts, sun- flower seeds, pumpkin seeds, acorns and chestnuts were determined. Similar cell-wall characteristics for sunflower-acorn, peanut-pumpkin and hazelnut-chest- nut pairs can be deduced from their similar composi- tion. High amounts of hemicellulose and lower ones of cellulose and lignin are dissolved in the process of de- termining crude fibre. The results are discussed.

    Introduction

    Fibre has long been considered a food fraction of very little nutrition- al interest. There is current evidence, however, that its components have a direct effect upon some biochemical and physiological pro- cesses. An adequate intake in the diet is now considered necessary. Studies of relationships of a lowered dietary fibre intake with several diseases such as diabetes, cancer of the colon, obesity, disorders in cholesterol metabolism and on its effects in mineral and micronutri- ent balance, protein digestibility, etc. have been the subject of many papers. Compilations of these are available in the literature [1, 2].

    As is known, the use of crude fibre (CF) is not convenient in food analysis because some non-digestible constituents are dissolved and some digestible components remain in the residue during determina- tion. More significant is dietary fibre, where the neutral-detergent fibre (NDF) residue, obtained by treating the vegetable matter with neutral detergent, remains the principal component of the cell walls. Van Soest methods [3, 4] are widely used for its determination, and other modifications have been proposed [5-8]. The FAO has re-

    commended the substitution of CF values for dietary fibre values in tables of food composition.

    On the other hand, the knowledge of the hemicellulose and cel- lulose contents of vegetables may be important for industrial appli- cations such as production of furfural, active carbons and other sub- stances to increase the microbial growth in soils [9, 10] and for use in mixtures for animal feeding.

    Experimental

    Hulls of hazelnuts (Corylus avellana), peanuts (Arachis hypogaea), coconuts (Cocos nucifera), sunflower seeds (Helianthus annuus), pumpkin seed (Cucurbita pepo), chestnuts (castanea sativa), and acorns (Quercus ilex) were studied.

    Samples were homogenized and ground to particles of < 0.5 ram. Moisture was determined by heating at 105 C to constant weight. Treatments with 0.255 N-H2SO 4 and 0.13 N-NaOH were per- formed to determine CF, following AOAC methods [11].

    NDF values were obtained by refluxing the samples with sodium lauryl sulfate (pH 7.0) solution during 1 h. Hemicellulose contents were determined as in loss-weight of the NDF residue when treated with acid detergent, following treatment with 72% HzSO4 and cal- cination at 550 C to obtain cellulose and lignin contents. Prepara- tion of reagents and assay conditions were performed following Van Soest procedures [3, 4]. The same method was used to obtain acid de- tergent fibre (ADF).

    CF were also treated with acid detergent, 72% H2SO4, and cal- cination in a similar fashion as for NDF in order to determine its con- tents of hemicellulose (H), cellulose (C) and lignin (L).

    Data obtained were the mean of at least four different determi- nations.

    Results and Discussion

    Dietary Fibre

    The contents of moisture, NDF, ADF, H, C and L for the samples studied are listed in Table 1. As can be ob- served, all samples have a high NDF content and for this reason may be considered a potential source di- etary fibre. H contents of the sunflower (24.0%), hazel- nuts (24.9%) and coconut (31.9%) are of the same or- der as the primary matter to obtain furfural. The con- tents of L (19.3 to 29.6) are higher than corresponding products used in animal feeding (e. g. wheat straw, 12%; alfalfa, 9%) and its use is only possible as part of nutrit ional mixtures. Percentages of H, C and L in NDF are included in Table 2. Values of the same order for peanut hulls appear in the literature [12, 13]. We have not found data concerning other products stud- ied.

  • F. Saura-Calixto et al.: Hemicelluose, Cellulose and Lignin Contents of Dietary Fibre

    Table 1. NDF, ADF, Hemicellulose, Lignin and Lignin contents (% dry matter a)

    201

    Hull Moisture NDF Hemicellulose Lignin Cellulose ADF % % % % % %

    Sunflower seed 9.4 _+ 0.8 89.9 1.0 24.0_+ 0.7 23.2 1.0 42.7 _+ 2.7 70.0 _+ 1.3 Peanut 10.5 -+ 0.2 82.7 _+ 0.9 16.3 -+ 0.6 27.6 _+ 1.1 38.8 -+ 2.4 75.1 -+ 1.1 Acorn 16.6 _+ 0.4 77.8 1.5 20.5 _+ 0.9 21.4 _+ 1.0 35.9 _+ 2.6 67.8 _+ 2.0 Chestnut 22.4_+ 0.5 70.3 1.4 19.9 _+ 1.0 21.9 _+ 1.3 28.5 _+ 3.7 65.9 + 1.6 Pumpkin seed 12.0_+ 0.3 85.9 _+ 1.3 17.5 1.0 28.5 -+ 1.2 39.9 _+ 3.5 77.3 _+ 1.2 Coconut 6.40.8 89.9 1.3 31.9_+0.9 19.3 +0.8 38.7_+ 3.0 66.2_+ 1.0 Hazelnut 11.0-+0.2 92.0_+ 1.0 24.9_+0.8 29.6 _+ 1.0 37.5 _+2.8 74.6_+0.9

    a Average value-+standard deviation

    Table 2. Percentages of hemicellulose, lignin and cellulose in neutral detergent fibre (NDF)

    Hull Hemi- Lignin Cellulose cellulose % % %

    Sunflower seed 26.7 25.8 47.5 Peanut 19.7 33.3 47.0 Acorn 26.3 27.5 46.2 Chestnut 28.3 31.1 40.6 Pumpkin seed 20.4 33.2 46.4 Coconut 35.5 21.5 43.0 Hazelnut 27.1 32.2 40.7

    Table 3. Components of crude fibre (CF)

    Hull % Respect dry matter a

    Crude fibre Hemicellulose Lignin

    % Respect crude fibre

    Cellulose H2SO4 b Hemi- Ligniia residue cellulose

    Cellulose

    Sunflower seed 64.0_+0.5 6.9__0.5 20.4-+0.1 Peanut 62.2 _+ 1.5 4.5 -+ 0.3 25.2 _+ 1.2 Acorn 43.7-+ 1.0 5.0_+0.5 13.2_+0.9 Chestnut 31.8 _+ 1.0 3.7_+0.3 9.8 _+0.9 Pumpkin seed 68.0 1.1 8.9_+0.8 28.0_+ 1.4 Coconut 47.6 _+0.9 9.5 _ 0.7 13.5 1.0 Hazelnut 66.1 _+ 1.4 8.7 0.6 26.4 _+ 1.1

    36.7_+0.9 80.0_+0.8 10.8 31.9 57.3 32.5_+3.0 82.5_+0.9 7.2 40.5 52.3 25.5_+2.4 78.9_+0.7 11.4 30.2 58.4 18.3-+2.2 77.9-+1.0 11.6 30.8 57.6 31.1-+3.2 86.0_+0.9 13.1 41.2 45.7 24.6_+2.6 81.7_+0.9 19.9 28.4 51.7 31.0_+3.1 89.6_+1.0 13.2 39.9 46.9

    a Average value _+ standard deviation 0.255 N-H2SO4 (CF treatment)

    From the similar percentage of components, it can be considered that the pairs sunflower-acorn, peanut- pumpkin, hazelnut-chestnut have similar cell-wall characteristics. The cotents of C are more uniform (44.5+3.0), while greater differences appear for L (29.2_+4.5) and H (23.3__5.3), The high H content gives a greater hardness to these samples, especially in coconuts, as in the case of wood [14].

    It must be noticed that the difference between NDF and ADF does not coincides with the hemicellulose content, which is due to the presence in ADF of other components cited in the literature, such as tannins and

    pectins [15, 16]. Small ammounts of tannins, in partic- ular, are also sometimes detected in NDF. As these amounts are not significant in NDF comparing with H, C or L contents and are also indigestible, their determi- nat ion was omitted.

    Comparison of Dietary and Crude Fibre

    Table 3 shows the contents of H, C and L in the CF. Values in CF are always markedly lower than in NDF. Comparing the data in tables 2 and 3, it can be seen that H is the fraction most prone to loss in the process

  • 202 F. Saura-Calixto et al.: Hemicellulose, Cellulose and Lignin Contents of Dietary Fibre

    of determining CF, dissolving in amounts of 69.2 + 10.2%. Although lower, appreciable amounts of C (21.3_+10.6%) and L (22.4_+19.3%) are also dis- solved. Pearson coefficients were 14 for H, 49.7 for C and 86 for L, indicating that the variation in the amounts dissolved increase in the order H, C and L. During treatment to obtain CF variable amounts (from 20% for pumpkin, to 50% for coconut) of NDF were dissolved. By treating the samples with 0.255 N-H2SO4 in a similar way for obtaining CF (but omitting the NaOH treatment), residues of higher weights than those corresponding to ADF were obtained in all cases. Considering the CF contents of the products studied against the contents of H, C and L in its NDF, the fol- lowing equation was obtained:

    CF=0.18 H+2.14 C+2.00 L - 26.52, with a high correlation coefficient (r = 0.988) and low standard deviation (s= 0.94). This expression is in ac- cord with the above statistical considerations.

    References

    1. F.A.O. (1980) Los carbohidratos en la nutrici6n humana. Infor- me conjunto FAO/OMS. Organizaci6n de las Naciones Unidas para ta Agricultura y la Alimentaci6n. Roma, pp. 71-79

    2. Symposium on Dietary Fiber, Houston, USA, 1980. J Agric Food Chem (1981) 29.'448-471

    3. Van Soest PJ, Wine RH (1976) J Assoc Off Agric Chem 50:50 4. Van Soest PJ, Robertson JB (1979