Maataloustieteellinen Aikakauskirja Vol. 56: 39—48, 1984 Dietary fibre and available carbohydrates in Finnish cereal products PERTTI VARO, RAILI LAINE, KIRSTI VEIJALAINEN, KRISTIINA PERO and PEKKA KOIVISTOINEN Department of Food Chemistry and Technology, University of Helsinki, SF-00710 HELSINKI, Finland Abstract. The contents of dietary fibre and available carbohydrates in Finnish cereal products were analysed using the Englyst total carbohydrate method. The tabulation gives the carbohydrate compositions of 44 cereal foods. The cereal-based estimated daily intakes were: total soluble sugars 14.8 g, starch 103 g and dietary fibre 11.6 g (energy level 10 MJ). Introduction Cereal products are the major source of most carbohydrates. They are the most im- portant source of starch, and usually of di- etary fibre. Certain bakery products contain considerable amounts of sugars, added as sucrose or syrups or as lactose from pow- dered milk. The functions of carbohydrates in foods and nutrition are various. Although chem- ically related, the carbohydrates are difficult to analyse simultaneously. Southgate (1969), Southgate et al. (1978), Englyst (1981), and Theander & Äman (1982) have developed methods that allow available car- bohydrates and dietary fibre to be deter- mined within a single analytical procedure. The method chosen in this study was the analytical scheme of Englyst (1981). The present study is part of a research pro- ject determining the carbohydrate composi- tion of Finnish foods. The project, in turn, is part of a larger attempt to gather new and dependable data on Finnish foods and diet, of which the studies on mineral composition have been completed (Koivistoinen 1980, Varo 1981). The need for such data has be- come increasingly evident along with the sop- histication of our daily lives: the information is required by nutritionists, dietitians and food inspectors, in the industry, and for medical research, to mention but a few. Material and methods The samples used in this study were col- lected for a previous study on the mineral element composition of Finnish foods (Koi- Index words: food composition, dietary intake, sugars, starch, dietary fibre 39 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=L6uFGPEPHYoaCwn7.oqh0q5bCr4OXhWeaW9F8Pg.jj4sHZCKB-iUTS8AQkdJ9Ds1xtTD58XMUAXlVyiLJ9YrcAWRGzzsgG6kFU2fAh2YODagaLuWtmWLiYkXxPCqo-FaApBPT94dzCQZgMO2XbRsvEsZDxga3z96_T0qhpbvhZCb_wS4ZAy8SPM34_TCZsacf3RYh_zesRIkwmjr_nZDcuLA26vAz-bZpunKYMxPTlsyVQGpSol-NSVyJsA9HLWu2aynt0DuDLhmEaa3PwwB48OnULyHIFdzg65Pgtb-vQ visioinen 1980). The original study com- prised an average of 4—6 samples per food item, representing large amounts of the product. In the present study, only one sample, pooled from two samples chosen at random, was analysed per item. This is a re- flection of the complexity of the analytical procedure, which allowed only a very limited number of samples to be analysed within the context of the present study. For the prin- ciples of sampling and the details of sampl- ing procedures, refer to the reports of the mineral study (Koivistoinen 1980). The analytical scheme used was that de- veloped by Englyst (1981) and slightly mo- dified by Laine et ai. (1981). The method measures the total carbohydrate composition as the following fractions: soluble sugars, starch, and dietary fibre as cellulose, water- soluble and water-insoluble non-cellulosic polysaccharides (w.s. and w.i.s. NCP, re- spectively), and lignin. The detailed sugar compositions of soluble sugars, w.s. NCP and w.i.s. NCP are determined by gas chro- matography (GLC). The dry sample (200 mg) is incubated in an acetate buffer (pH 6, 48°C), first on its own for 5 h (aliquot 1)and then with amylogluco- sidase (16 h), after which it is separated by centrifugation into aliquot 2 and residue. The supernatants are analysed for free su- gars, starch and w.s. NCP. Free sugars (ali- quot 1), and free sugars and glucose from starch together (aliquot 2) are freeze-dried, formed into aldonitrilo acetates (Morrison 1975) and analysed by GLC. W.s. NCP are precipitated with 4 volumes of ethanol from aliquot 2, hydrolysed with 1 M H2S0 4 and analysed for neutral sugars as aldonitrilo acetates by GLC and for uronic acids colori- metrically after the carbazole reaction (Bit- ter & Muir 1962). The residue is sequen- tially hydrolysed with 1 M H2SG 4 and 72 % H2S0 4, and analysed by GLC and colori- metry for w.i.s. NCP constituents, by colori- metry for cellulose (Roe 1955), and gravi- metrically for lignin. The chromatography of the sugars was performed using an equimolar mixture of different sugars as an external standard, and inositol as an internal standard. The overall analytical feasibility of the method was tested in two interlaboratory comparisons made during the present study (Theander 1981, Varo et ai. 1983). Whole meal wheat flour, which was used as a stand- ard, was analysed several times during the study. As seen in Table 1, the variation in some fractions may be considerable. This may be due at least partly to the initial small sample size (200 mg). All samples were anal- ysed as six replicates, and the fractions with over 10 % variation were re-analysed. The analysis of starch tended to be especially problematic, and so it was also analysed on a macroscale from all samples using enzy- matic hydrolysis and colorimetry. Free su- gars and, less often, lignin also entailed re- checks. Table 1. Carbohydrate composition of wheat flour (standard), g/100 g dry matter. Sample no. 1 2 3 4 5 X 1 s V% Free sugars 3.1 2.4 3.1 2.5 3.2 2.9 0.4 14 Starch 58.3 61.8 62.4 61.9 63.2 61.5 1.9 3 Dietary fibre 13.3 11.3 11.9 12.8 12.5 12.4 0.8 7 w.s. NCP 1.7 1.2 1.2 1.8 1.4 1.5 0.3 20 w.i.s. NCP 8.0 7.0 7.5 7.7 8.1 7.7 0.4 5 cellulose 2.3 1.9 2.0 2.2 2.0 2.1 0.2 10 lignin 1.4 1.3 1.2 1.1 1.0 1.2 0.2 17 1 X = mean, s = standard deviation, V% = coefficient of variation. 40 Table 2. Carbohydrate composition of Finnish cereal-based foods. Content in 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 100 g of food Wheat Wheat Wheat Wheat Wheat Wheat Rye Rye Barley Rolled (edible portion) flour, flour, flour, flour, bran germ flour, flour, flour, oats whole- c. 1.3 % c. 0.7 % c. 0.5 % whole- c. 0.5 % whole- meal ash ash ash meal ash meal Water g 14 14 14 14 14 13 14 14 14 12 Available carbo- g 54.5 59.4 63.5 63.6 15.4 31.0 52.0 66.3 58.9 57.0 hydrates Free sugars g 0.7 0.5 0.5 0.4 1.3 16.4 2.4 0.5 0.9 1.3 fructose g 0.1 0.1 0.2 0.2 0.2 0.6 0.3 0.1 0.2 0.2 glucose g 0.1 0.1 0.1 0.1 0.2 0.6 0.2 0.2 0.2 0.2 sucrose g 0.5 0.3 0.2 0.1 0.9 15.2 1.0 0.2 0.5 0.9 maltose g 0.9 tr—- lactose g Starch g 53.8 58.9 63.0 63.2 14.1 14.6 49.6 65.8 58.0 55.7 Dietary fibre g 9.9 5.5 3.6 3.5 37.5 14.0 13.6 4.5 7.6 5.7 W.s. NCP g 1.0 1.0 1.0 0.9 1.2 1.3 2.2 1.5 1.0 1.1 W.i.s. NCP g 6.5 3.2 1.7 1.7 24.2 8.9 6.9 1.9 4.0 3.1 Cellulose g 1.5 0.6 0.5 0.4 7.5 2.3 1.9 0.9 1.3 0.7 Lignin g 0.9 0.7 0.4 0.5 4.6 1.5 2.6 0.2 1.3 0.8 41 Content in 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 100 g of food Rice, Rice, Rye Wheat Wheat Oat Brown Crisp Crisp Whole- (edible portion) polished par- bread, bread bread, bread bread, bread bread, wheat boiled sour dark sweetened wholerye rusk Water g 14 12 38 33 36 36 35 8 5 4 Available carbo- g 75.5 70.9 36.9 41.3 40.0 41.2 40.0 56.1 57.8 63.9 hydrates Free sugars g 0.3 0.7 3.5 3.2 2.6 3.5 7.8 1.6 2.4 2.1 fructose g tr tr 0.8 0.3 0.2 0.8 2.8 0.3 1.2 0.3 glucose g tr 0.1 0.8 0.2 0.2 0.5 2.4 0.2 1.0 0.3 sucrose g 0.3 0.6 tr 0.1 tr 0.1 tr tr—- maltose g 1.9 2.5 2.1 2.2 2.5 1.1 0.2 1.5 lactose g 0.2 Starch g 75.2 70.2 33.4 38.1 37.4 37.7 32.2 55.5 55.4 61.8 Dietary fibre g 2.3 4.8 9.9 3.5 5.0 6.4 4.7 12.9 14.9 8.5 W.s. NCP g 0.2 0.6 1.7 0.8 1.0 1.2 1.1 2.9 2.7 1.4 W.i.s. NCP g 1.6 3.1 6.1 1.7 2.7 3.9 2.5 6.6 8.0 4.9 Cellulose g 0.2 0.7 0.9 0.6 0.7 0.8 0.8 1.9 2.2 1.3 Lignin g 0.3 0.4 1.2 0.4 0.6 0.6 0.3 1.5 2.0 0.9 42 43 Content in 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 100 g of food Sweet Sweet Doughnut Swiss Biscuit Cream »Mämmi» Macaroni Corn Rice, (edible portion) wheat wheat roll cracker Easter flakes puffed bread, bread, dessert 5 % fat 10 % fat Water g 20 16 22 25 2 5 59 12 4 3 Available carbo- g 49.7 43.2 44.4 40.9 69.9 57.4 27.6 66.4 80.2 78.6 hydrates Free sugars g 10.5 8.6 13.3 25.3 19.6 1.6 13.2 0.5 6.1 5.2 fructose g 3.8 3.0 1.6 1.0 2.4 0.3 6.4 0.1 0.9 0.4 glucose g 3.0 2.2 1.9 1.9 2.1 0.3 4.5 0.2 1.5 0.4 sucrose g 0.7 0.4 8.3 22.1 14.4 2.2 0.2 3.6 4.4 maltose g 2.3 2.2 1.5 tr 0.7 1.0 lactose g 0.7 0.8 0.3 Starch g 39.2 35.6 31.1 15.6 50.3 55.8 14.4 65.9 74.1 73.6 Dietary fibre g 3.6 2.8 2.5 1.5 2.0 4.3 4.9 3.1 5.4 5.0 W.s. NCP g 0.8 0.9 0.7 0.8 0.4 1.3 1.2 1.0 0.4 0.5 W.i.s. NCP g 2.1 1.5 1.2 0.4 0.8 2.3 1.9 1.6 3.1 3.4 Cellulose g 0.5 0.3 0.3 0.1 0.4 0.4 0.7 0.3 0.7 0.3 Lignin g 0.2 0.1 0.3 0.2 0.4 0.3 1.1 0.1 1.2 0.8 Content in 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 100 g of food Oats, Roasted Buckwheat Millet, Spring Rye, Barley, Oats, Rice Maize, (edible portion) puffed oatmeal, whole whole wheat, whole whole whole whole whole »Talk- grain grain whole grain grain grain grain grain kuna» grain Water g 3 14 14 14 14 14 14 14 13 13 Available carbo- g 70.6 57.6 60.4 55.3 52.9 52.9 48.2 47.3 65.4 63.6 hydrates Free sugars g 9.8 0.7 0.4 0.6 2.6 2.4 1.3 0.3 0.8 1.0 fructose g 0.3 tr tr 0.2 0.2 0.4 0.2 0.1 tr 0.1 glucose g 0.3 0.1 0.2 0.3 0.3 0.6 0.3 0.2 0.3 0.5 sucrose g 9.2 0.6 0.2 0.1 0.8 1.0 0.6 tr 0.5 0.4 maltose g 1.3 0.4 0.2 lactose g Starch g 60.8 56.9 60.0 54.7 50.3 50.5 46.9 47.0 64.6 62.6 Dietary fibre g 4.9 9.9 5.8 3.2 10.8 12.7 16.5 18.5 7.4 9.2 W.s. NCP g 0.7 1.6 0.8 0.6 1.3 2.4 2.2 1.8 1.1 0.8 W.i.s. NCP g 3.4 3.6 2.8 1.6 6.6 6.8 8.0 7.1 3.6 5.9 Cellulose g 0.4 2.4 1.5 0.4 1.8 2.2 3.7 6.2 1.7 2.0 Lignin g 0.4 2.3 0.7 0.6 1.1 1.3 2.6 3.4 1.0 0.5 44 Results and discussion The available carbohydrates and fibre constituents of Finnish cereal products are given in Table 2. The results are largely con- sistent with those reported previously for ce- real foods (Paul & Southgate 1978, Souci et al. 1981, Salo & Kotilainen 1970, Fro- lich & Asp 1981). Free sugars. Cereal grains and flours are low in sugars, sucrose being the main one. Maltose was usually found only in trace amounts. Sugars other than those tabulated were sometimes detected (e.g. 4 % raffinose in wheat germ). Bakery products with added sucrose and leavened with yeast contained only little sucrose, but more fructose and glucose. Breads commonly contained 1 2 °?o maltose. Lactose was detected in breads with added milk or powdered milk. Starch. The starch content of cereal prod- ucts was generally in the expected range. The starch content was highest in polished rice and lowest in nuts. Dietary fibre (DF). The fibre content of cereal products follows closely the extraction of flour used as a raw material. The bulk of the fibre constituents are in the bran frac- tion. Whole meal wheat flour containedabout 10 % DF, whereas white flour contained 3.5 % and wheat bran c. 40 °Io. The fibre concentration of many bakery products was slightly higher than might be expected of their raw materials. This may indicate that bread making causes an increase in the amount of fibre especially while the crust is forming. However, not only lignin but other fibre fractions, too, were slightly increased. Similar increments have been found in heat- treated potato (Varo et al. 1983, Varo et al. 1984). W.i.s. NCP was generally the main DF fraction in cereal products. The present method shows that the concentrations of eel- Content in 1.41 1.42 1.43 1.44 100 g of food Dis- Pea, Hazel- Almond (edible portion) tiller's dried nut spent grain Water g 12 15 5 5 Available carbo- g 1.1 48.5 3.4 6.6 hydrates Free sugars g 0.0 2.1 3.4 6.6 fructose g 0.1 0.5 0.5 glucose g 0.2 0.4 0.3 sucrose g 1.8 2.5 5.8 maltose g lactose g Starch g 1.1 46.4 0.0 0.0 Dietary fibre g 21.0 10.7 6.0 7.2 W.s. NCP g 4.7 0.7 0.3 0.3 W.i.s. NCP g 8.4 4.1 2.5 3.7 Cellulose g 3.1 5.7 1.4 1.5 Lignin g 4.8 0.2 1.8 1.7 45 46 lulose and lignin were approximately the same in cereal foods. The concentration of w.s. NCP was fairly constant. As an exam- ple, whole meal wheat flour and white wheat flour contained equal amounts of this frac- tion. Table 3 gives the relative neutral sugar and uronic acid compositions of w.s. NCP and w.i.s. NCP of some flour and bread samples. The most variable is that of glucose, especial- ly in the w.i.s. NCP fraction, suggesting that traces of starch may have been left in some of the w.i.s. NCP fractions. The relative amounts of other constituents remain fairly constant with increasing extraction. Since the number of samples was limited to one per item, no information was obtain- ed in the variation within a single food com- modity. The main purpose of the study, to obtain average carbohydrate values for as many of the principal cereal foods as possi- ble, was probably covered reasonably well considering the sampling procedure, which was planned to produce samples representing high volumes of production. The analytical procedure chosen for the present study is too laborious for routine fibre determinations. The actual rate was only 2—4 samples/week/2 technicians. The need for rechecks of results was also unde- sirably high despite careful standardization of the procedures. One major problem was the difficulty of obtaining exactly repro- ducible fractionation of the small quantity of starting material. For instance, the gravimet- ric determination of a few milligrams of lig- nin necessarily caused high variation, which was greatly enhanced by small differences in fractionation. In 1981 the consumption of cereals in Fin- land was 209 g/d/person, of which 128 g was wheat, 57 g rye and the rest equal amounts of barley, oats and rice (Agric. Econ. Res. Inst. 1983). Nearly all the rye is consumed as whole grain products, whereas about 80 °/o of the wheat is used as refined flour (Salo- vaara 1979). About 70 % of all industrial bakery products are unsweetened rye and Table 3. Sugar and uremic acid composition of w.s. NCP and w.i.s. NCP in somecereal products. w.s. NCP w.i.s. NCP % of total /lAr , % of total /ln _g/100g g/100 g rha man glu gal ara xyl uro total 8 rha man glu gal ara xyl uro total" Whole meal wheat flour tr 7 11 14 25 40 4 1.2 1 1 10 3 25 53 6 7.6 Wheat flour, 1.3 °/o ash 4 7 20 21 16 32 tr 1.2 tr 2 13 3 29 43 9 3.7 Wheat flour, 0.7 % ash tr 4 12 15 25 44 tr 1.2 0 2 41 4 17 28 5 2.0 Wheat bran tr 4 17 8 24 42 5 1.4 0 19 2 29 53 6 28.1 Wheat bread, white tr tr 10 10 24 53 2 1.2 0 5 50 4 15 26 1 2.5 Whole rye flour 0 5 10 4 28 49 4 2.6 0 2 21 4 24 42 7 8.0 Rye crisp bread 2 3 7 4 29 50 5 2.8 0 4 19 6 25 43 4 8.4 Rolled oats 5 4 46 8 12 12 13 1.3 2 3 19 9 25 35 7 3.5 " In dry product Abbreviations: rha = rhamnose, man = mannose,glu = glucose, gal = galactose, ara = arabinose, xyl = xylose, uro = uronic acids, tr = traces w.s. = water soluble, w.i.s. = water insoluble, NCP = non-cellulosic polysaccharides wheat bread, the remainder being sweetened products. Home baking, however, increases the share of sweetened products to at least 40 % of total bread consumption. It is es- timated that homebaked products account for about 13 % of total sugar consumption (Prättälä 1983). These findings, together with data on the detailed distribution of the production of bakery products (Salovaara 1979), and the present analytical data en- abled us to estimate roughly the average in- take of carbohydrates from cereal products (Table 4). Acknowledgement. This study has been supportedby the Academy of Finland and the Finnish Sugar Com- pany Ltd. Table 4. Cereal products as sources of sugars, starch and dietary fibre in 1981 (energy level 10 MJ). g/d Sugars 14.8 sucrose 5.5 glucose 2.5 fructose 2.9 maltose 3.5 lactose 0.4 Starch 103 Dietary fibre 11.6 w.s. NCP 2.3 w.i.s. NCP 5.8 cellulose 1,7 lignin 1.8 References Agricultural Economics Research Institute, 1983. Food balance sheet 1981. Helsinki. Bitter, T. & Muir, M.H. 1962. A modified uronic acid carbazole reaction. Anal. Biochem. 4: 330—334. Englyst, H. 1981. Determination of carbohydrate and its composition in plant materials. In: The Analysis of Dietary Fiber in Food (Eds. W.P.T. James & O. The- ander), p. 71 —93. Marcel Dekker, N.Y. Frolich. W. & Asp, N.-G. 1981. Dietary fiber content in cereals in Norway. Cereal Chem. 58: 524—527. Koivistoinen, P. (ed.) 1980. Mineral element composi- tion of Finnish foods. Acta Agric. Scand. Suppl. 22, pp. 171. Laine, R., Varo, P. & Koivistoinen, P. 1981. Observa- tions on the analysis of dietary fiber. In: The Analysis of Dietary Fiber in Food (Eds. W.P.T. James & O. Theander), p. 21—27. Marcel Dekker, N.Y. Morrison, I.M. 1975. Determination of the degree of polymerisation of oligo- and polysaccharides by gas-liquid chromatography. J. Chromatogr. 108: 361—364. Paul, A.A. & Southgate, D.A.T. 1979. McCance and Widdowson’s The Composition of Foods, 4th ed. HMSO, London. Prättälä, R. 1983. Suomalaiset sokerinsyöjinä. Lisen- siaattitutkimus, Helsingin yliopisto, ravitsemustieteen laitos. Roe, J.H. 1955. The determination of sugar in blood and spinal fluid with anthrone reagent. J. Biol. Chem. 212: 335—343. Salo, M.-L. & Kotilainen, K. 1970. On the carbo- hydrate composition and nutritive value of some ce- reals. J. Scient. Agric. Soc. Finl. 42: 21—29. Salovaara, H. 1979. Viljan tiet kulutukseen. Leipätoi- mikunta, Helsinki. Souci, S. W., Fachmann, W. & Kraut, H. 1981. Food Composition and Nutrition Tables 1981/82. Wis- senschaftliche Verlagsgesellschaft, Stuttgart. Southgate, D.A.T. 1969. Determination of carbohyd- rates in foods. 11. Unavailable carbohydrates. J. Sci. Food. Agric. 20: 331—335. Southgate, D.A.T., Hudson, G.J. & Enolyst, H. 1978. The analysis of dietary fibre the choices for the analyst. J. Sci. Food Agric. 29; 979—988. Theander, O. 1981. Review of the different analytical methods and remaining problems. In; The Analysis of Dietary Fiber in Food (Eds. W.P.T. James & O. The- ander), p. 263—276, Marcel Dekker, N.Y. Theander, O. & Äman, P, 1982. Studies on dietary fibre. A method for the analysis and chemical charac- terisation of total dietary fibre. J. Sci. Food Agric. 33: 340—344. Varo, P. 1981. Kivennäisainetaulukko, 2. p. Otava, Helsinki. Varo, P., Laine, R. & Koivistoinen, P. 1983. Effect of heat treatment on dietary fiber: Interlaboratory study. J. AOAC 66: 933—938. Varo, P. Veijalainen, K. & Koivistoinen, P. 1984. The effect of heat treatment on the dietary fibre contents of potato and tomato. J. Food Tech, (in press). Ms received January 30, 1984 47 SELOSTUS Suomalaisten elintarvikkeiden hiilihydraatti- tutkimus viljavalmisteiden ravintokuitu-, tärkkelys- ja sokeripitoisuudet Pertti Varo, Raili Laine, Kirsti Veijalainen, Kristiina Pero ja Pekka Koivistoinen Elintarvikekemian ja -teknologian laitos, Helsingin yliopisto, 00710 Helsinki Suomalaisten viljavalmisteiden hiilihydraattikoostu- mus määritettiin tässä tutkimuksessa ns. Englystin ko- konaishiilihydraattimenetelmällä. Se antaa yksityiskoh- taisen kuvan sekä hyväksikäytettävien hiilihydraattien että ravintokuidun määrästä ja laadusta. Tutkimus on osa poikkileikkaustutkimusta, jonka kohteena oli tär- keimpien suomalaisten elintarvikkeiden hiilihydraatti- koostumus. Menetelmän työläydestä johtui, että vain yksi kokoomanäyte kutakin nimikettä voitiin analysoi- da. Tutkimuksen vaikeutena olivat monimutkainen fraktiointikaavio ja pieni näytemäärä (200 mg), ja tar- kistusanalyysien määrä kasvoikin ajoittain epätoivotta- van suureksi. Saatujen tulosten jakulutustietojen perusteella arvioi- tiin hiilihydraattien keskimääräinen päiväsaanti viljaval- misteista. Liukoisia sokereita arvioitiin saatavan yhteen- sä 14.8 g/d, tärkkelystä 103 g/d ja ravintokuitua 11.6 g/d (energiataso 10 MJ). 48