J. Home Econ. Jpn. Vol. 49 No. 8 865 `871 (1998) Effects of Adding Mushrooms to Dough on Gas Production during Bread Making Tokumitsu OKAMURA,*, ** Yumi NISHIKAWA,** Nobuko OKUDA* * and Masahiro OHSUGI* * Institute of Bioscience, Mukogawa Women's University, Nishinomiya 663-8137, Japan School of Human Environmental Science, Mukogawa Women's University, Nishinomiya 663-8137, Japan The effects of adding mushrooms to wheat flour on gas production during bread making are reported. The loaf volume and specific loaf volume of bread containing 5% maitake, bunashimeji, kikurage or nameko mushrooms were markedly decreased. In contrast, the values of the bread containing shiitake or enokitake were similar to those of standard bread. The addition of such mushrooms as maitake, bunashimeji, kikurage and nameko to bread dough supplied carbohydrate to baker's yeast and promoted fermentation under anaerobic conditions, this leading to increased gas production and resulting in a sharp fall of the dough. In a liquid culture medium, shiitake inhibited the growth of yeast and this led to no gas being produced. However, the yeast-inhibitory effect by shiitake may have been decreased in the dough because the yeast did not come into contact with the shiitake. Therefore, dough containing shiitake mushrooms did not break down, because this mushroom inhibited the growth of baker's yeast resulting in no excessive gas being produced by alcohol fermentation. (Received December 1, 1997; Accepted in revised form June 2, 1998) Keywords: mushroom, bread, loaf volume, gas production, baker's yeast, fermentation. INTRODUCTION Many attempts have been made to popularize bakery products, because they represent an easy, convenient and inexpensive means of taking in a hygienically prepared, ready-to-eat form of nutrition (Niihara and Harigai 1991; Takasaki and Karasawa 1993; Nakano and Oba 1995; Oba and Nakano 1996; Tsuda et al. 1996). Dietary fiber has been reported to be a significant factor in human nutrition, and several diseases such as appendicitis and cancer of the colon are believed to be associated with the consumption of refined carbohydrate-rich foods (Michell and Eastwood 1976). Increased cereal fiber intake is desirable, and this can be easily achieved by eating bread. Shiitake (Lentinus edodes), enokitake (Flammulina velutipes), maitake (Grifola frondosa), bunashimeji (Hypsizygus marmoreus), kikurage (Auricularia auricula) and nameko (Pholiota nameko) are all edible mushrooms, and their commercial cultivation has been begun in many countries (Eicker 1992; Flegg 1992; Bech 1992; Okamura et al. 1996). Mushrooms are rich in fiber, protein and vitamins, and could thus be used for fiber-rich bread making. We report here various kinds of mushroom bread in which the mushrooms were added to wheat flour, and compare the characteristics of mushroom bread with those of standard white bread. As the addition of mushrooms has an effect on loaf volume, the mechanism in mushroom bread making concerned with gas production is also described. MATERIALS AND METHODS Materials The wheat flour used was a commercial product with protein, lipid, carbohydrate and water contents of 12, 1.8, 69 and 14.5 %, respectively. "Camellia" wheat flour and "Super Camellia" dry yeast were obtained from Nisshin Flour Milling Co. (Tokyo, Japan). Raw shiitake (L. edodes), enokitake (F. velutipes), maitake (G. frondosa), bunashimeji (H. marmoreus), kikurage (A. auricula) and nameko (P. nameko) mushrooms with a water content of 91.1, 89.7, 91.0, 92.5, 87.2 and 96.0%, respectively, were purchased at a local market in Nishinomiya Japan. Measurement methods An SD-BT 7 Bread Bakery appliance (National Co.), an automatic bread baker designed to sense the (865) 7
J. Home Econ. Jpn. Vol. 49 No. 8 (1998) Table 1. White bread and mushroom bread ingredients Fig. 1. Automatic baking process with the Bread Bakery appliance temperature and automatically control the heating system during the entire process of baking, was used. All the steps from mixing to baking were automatic, the baking process being shown in Fig. 1. Table 1 shows the ingredients of the basic white bread and mushroom bread. Mushrooms, which had been homogenized into particles of about 0.1 to 1 mm in size, were added at a 5% weight ratio (mushroom/ wheat flour) to white bread dough, mixed, and then baked. The loaf volume was measured by rapeseed replacement method. The sensory characteristics of each bread were evaluated by a panel of twelve students and teachers from Mukogawa Women's University, and a factor analysis was conducted by using the results of the sensory evaluation. A semantic differential (SD) method (Akusawa et al. 1991), using the 8 parameters of texture (textural perception was evaluated directly through the tactile (touch) and kinaesthetic (movement) senses, and indirectly through the senses of vision and hearing), color, gloss, hardness, flavor, crispness, taste and total effect, was employed. Liquid culture experiments on gas production Dry baker's yeast (Saccharomyces cerevisiae) and mushrooms were cultured in bottles with 1 ml of a previously autoclaved basal medium containing 2% malt extract (2% malt extract medium, ph 5.6). Gas production was measured as the accumulation of carbon dioxide. The number of baker's yeast cells in the medium was determined by directly counting with a Thoma hemacytometer under an Olympus BHS-323 phasecontrast microscope (Olympus Co., Japan). Solid culture experiments on dough expansion Portions of 10 g of dough with the ingredients of the basic white bread and mushroom bread (Table 1) containing dry baker's yeast were placed in flatbottomed tubes. The expansion of the dough in the flat-bottomed tubes was measured by determining the height of the dough attained during dough development (fermentation) at 30 Žfor 0 to 5 h. Growth inhibition of baker's yeast by mushrooms The growth inhibition of baker's yeast by the shiitake and other mushrooms was examined by the cup assay method. Ten milliliters of a 2% malt extract agar medium containing baker's yeast (1 ~ 107 cells/ml) was poured into a Petri dish, and a penicillin cup (8 mm dia.) containing homogenized mushrooms was placed on each dish. After a 24-h incubation at 30 Ž, the growth of the baker's yeast was checked. RESULTS AND DISCUSSION Making mushroom bread The characteristics of mushroom bread such as the loaf volume differed markedly from those of standard white bread. As shown in Figs. 2 and 3, the loaf volume and specific loaf volume (specific loaf volume is expressed as the loaf volume per gram of dough [loaf volume (ml)/weight (g)]) of the bread containing 5% homogenized maitake, bunashimeji, kikurage or nameko were markedly decreased. The values for the bread containing shiitake or enokitake were similar to those of standard white bread, shiitake bread being 8 (866)
Effects of Adding Mushrooms to Dough on Gas Production during Bread Making Fig. 2. Photographs of the 7 kinds of bread (A) (B) Fig. 3. Effects of mushrooms on the loaf volume (A) and specific loaf volume (B) slightly higher and enokitake bread being slightly lower. The addition of maitake, bunashimeji, kikurage or nameko to white bread caused the dough to lose its strength and to become plastic and sticky to the touch. Sensory evaluation The sensory attributes and palatability of 6 kinds of mushroom bread were compared with those of standard white bread. Figure 4 shows the average grade of each sensory attribute for the 6 kinds of mushroom bread and standard white bread. Unsatisfactory baking results were obtained with several types of mushroom bread. Standard white bread without mushrooms was preferred by the evaluating panel in respect of gloss. The texture of shiitake bread was most preferred, while enokitake bread was most preferred for its color, hardness flavor, crispness, taste and total evaluation. However, the other types of mushroom bread containing maitake, bunashimeji, kikurage or nameko were not preferred in any of the aspects evaluated. These latter 4 kinds of mushroom bread also had low loaf volume and specific loaf volume relative to the standard white bread (Figs. 2 and 3). Therefore, it is thought that the loaf volume of mushroom bread may be related to the (867) 9
J. Home Econ. Jpn. Vol. 49 No. 8 (1998) Table 2. Effects of adding mushrooms on gas production by baker's yeast Table 3. Ratio of carbohydrate in mushrooms Fig. 4. Sensory evaluation of each mushroom bread sensory evaluation. Effects of adding mushrooms on gas production As shown in Figs. 2 and 3, the loaf volume, specific loaf volume and sensory evaluation of the maitake, bunashimeji, kikurage and nameko types of bread were markedly less than those of the standard white bread. It is thought, however, that mushroom bread would be preferred for its healthy attributes if the baking process could be improved to achieve a loaf volume similar to that of the standard white bread. Therefore, the production of gas during dough development (fermentation) for mushroom bread making was investigated by using these mushrooms with a basic liquid culture medium. To evaluate the effect of adding the homogenized mushrooms to white bread on the gas produced by fermentation, each type of homogenized mushroom was added to the basic liquid culture medium (2% malt extract) at a 0 to 50% concentration with dry baker's yeast, and the mixture incubated anaerobically at 30 Ž. Table 2 shows the effect of adding each mushroom on gas produced in the 2% malt extract medium after 3 h of anaerobic incubation at 30 Ž. In the medium containing maitake, bunashimeji or nameko, gas production increased with increasing concentration of the mushrooms added (0 to 50%). On the other hand, the medium containing 5, 10 or 50% shiitake or 50% kikurage produced no gas. In the medium containing 50% enokitake, gas production was less than that in the medium containing only 10% enokitake. The addition of mushrooms, therefore, affected the gas produced by the baker's yeast. However, there was no response in the medium containing mushrooms without baker's yeast. All of the 6 kinds of mushroom examined contain carbohydrate as shown in Table 3. The addition of maitake, bunashimeji or nameko to white bread seems to have supplied additional carbohydrate to baker's yeast and to have promoted alcohol fermentation under anaerobic conditions, thus increasing gas production. Therefore, it may be that excessive gas production by adding these mushroom to bread dough resulted in breakdown of the dough. Effects on dough development of adding mushrooms To confirm the results of the experiment using the 2% malt extract medium, dough development was examined for dough containing 5% homogenized mushrooms. As shown in Table 4, the standard dough 10 (868)
Effects of Adding Mushrooms to Dough on Gas Production during Bread Making Table 4. Time-course for the development of dough containing mushrooms Table 5. Effect of adding mushrooms on the growth of baker's yeast was expanded by incubating at 30 Žfor 0 to 5 h. However, the dough containing maitake, bunashimeji, Table 6. Growth inhibition of baker's yeast by mushrooms kikurage or nameko expended for the first 2 h of incubation, and then the loaf volume (height in the cm) decreased. The shiitake dough showed better expansion than the standard dough without mushrooms, and in the case of enokitake, the loaf volume was equivalent to that of standard white bread and was retained for 3 to 5 h of incubation. Furthermore, many small holes were formed during the first 2 h of incubation, some of these developing into large holes on the top of the dough containing maitake, bunashimeji, kikurage or nameko after 4 h of incubation. On the other hand, there were few holes on the top of the standard bread dough or on that containing shiitake or enokitake. It is concluded that the excessive gas production formed the holes, the gas then escaped went out from the dough, and as a result, the dough produced a small loaf volume. Effects of adding mushrooms on the growth of baker's yeast Dough containing shiitake or enokitake formed loaves with almost the same volume as that of standard white bread (Fig. 3), especially in the case of shiitake, despite the lack of gas produced with 10% shiitake in the 2% malt extract medium (Table 2). Therefore, the growth of baker's yeast after 21 h of incubation in a 2% malt extract medium containing each type of mushroom was investigated. As shown in Table 5, in the case of the dough containing 1-50% maitake, bunashimeji, kikurage or nameko, the total number of baker's yeast cells in the 2% malt extract medium after 21 h of incubation was about 20-40 ~ 107 cells/ml. In the medium containing 50% enokitake, the total yeast cell number was 8 ~ 107 cells/ml, whereas, in that containing shiitake, it was 6 5 cells/ml, thus showing less growth than with any other type of mushroom. Shiitake thus inhibited the growth of baker's yeast, so we examined the anti-yeast activity of shiitake and the other mushrooms. As shown in Table 6, shiitake inhibited the growth of baker's yeast, possibly due to the release of lentinamycin. None of the other types of mushroom inhibited the growth of yeast. Dough containing shiitake did not break down, unlike that containing maitake, nameko, kikurage or bunashimeji, presumably because shiitake inhibited the growth of baker's yeast which resulted in no excessive gas production by fermentation as shown in Table 4. In the case of enokitake, as well, no excessive gas production occurred. Thus, enokitake may also have a yeastinhibitory effect similarly to that of shiitake. In the liquid culture medium, shiitake inhibited the growth of yeast and this led to no gas being produced. However, the yeast-inhibitory effect by shiitake may (869) 11
J. Home Econ. Jpn. Vol. 49 No. 8 (1998) have been less in the dough because there was no contact between the yeast and shiitake; thus, shiitake would not strongly inhibit the growth of yeast, this would result in no excessive gas being produced by fermentation, and the loaf volume of the bread containing shiitake and enokitake would be similar to that of standard white bread. The results of these experiments indicate that mushrooms can be classified into at least 2 types for their bread-making properties. One type is maitake, bunashimeji and nameko, the addition of which to dough resulted in breakdown of the bread due to excessive gas production. The other type is shiitake, the addition of which to dough resulted in the formation of bread with a good loaf volume. Enokitake may belong to the shiitake type, and kikurage may belong to same type as maitake, bunashimeji and nameko. However, it is not clear why the liquid culture medium containing 50% kikurage did not produce gas, despite the lack of anti-yeast activity. Many papers have been published on the significance of dietary fiber for human nutrition. An increased cereal fiber intake is desirable and this can best be achieved by means of bread. We studied the making of bread in which mushrooms were added to the wheat flour. A fiber content of 6.44 g/100 g was calculated in baked bread containing 5% of mushrooms such as shiitake, enokitake or maitake (Table 3). The standard white bread had a fiber content of 5.54 g/100 g (baked bread). Mushrooms are thus a good food additive to provide dietary fiber. We are currently examining the relationship between fermentable sugars from mushrooms and gas production by baker's yeast in mushroom bread making. REFERENCES Akusawa, S., Sawayama, S., and Kawabata, A. (1991) Sensory Attributes and Palatability of Different Varieties of Cooked Rice (in Japanese), Nihon Kasei Gakkaishi (J. Home Econ. Jpn.), 42, 441-450 Bech, K. (1992) Mushroom Production and Research in Denmark, Mushroom J., 513, 17-18 Eicker, A. (1992) The South African Mushroom Industry, Mushroom J., 513, 19-21 Flegg, P. (1992) Professor Chang Visits Indian Research Centre, Mushroom J., 513, 16-17 Michell, W. D., and Eastwood, M. A. (1976) Fiber in Human Nutrition (ed. by Spiier, A. G. and Amen, J. R.), Plenum Press, New York, 185 Nakano, A., and Oba, K. (1995) The Effect of Green-Yellow Vegetables on Physical Properties and Sensory Attributes of White Bread (in Japanese), Nihon Kasei Gakkaishi (J. Home Econ. Jpn.), 46, 321-329 Niihara, R., and Harigai, Y. (1991) Effect of Flour Protein and Lipid Quantities on Bread and Noodle Qualities (in Japanese), Nihon Kasei Gakkaishi (J. Home Econ. Jpn.), 42, 983-987 Oba, K., and Nakano, A. (1996) Making Quality, Crumbing Properties and Sensory Attributes of Bread Containing Soybean Flour (in Japanese), Nihon Kasei Gakkaishi (J. Home Econ. Jpn.), 47, 21-27 Okamura, T., Noda, H., Hoshino, Y., Sohgawa E., Uesugi, S., Mohri, A., and Ohsugi, M. (1996) Utilization of Sake Lees for the Cultivation of Pleurotus ostreatus, Nihon Shokuhin Kagaku Kogaku Kaishi, 43, 333-335 Takasaki, S., and Karasawa, K. (1993) Effects of Whole Wheat Flour on the Rheological Properties of Dough, Gassing Power and Breadmaking Properties (in Japanese), J. Cookery Sci. Jpn., 26, 327-334 Tsuda, T., Hasumi, T., and Watanabe, T. (1996) Utilization of Bean-Curd Refuse (Okara) in Fiber-Bread Processing, J. Cookery Sci. Jpn., 29, 25-31
Effects of Adding Mushrooms to Dough on Gas Production during Bread Making