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Effect of wood ash on tannin content of oak (Quercus incana) leaves
Bioresource Technology 41 (1992) 85-86
Short Communication Effect of Wood Ash on Tannin Content of Oak ( Quercus incana ) Leaves
The objective of the present study was to investigate the possibility of detannification of oak leaves using wood ashes.
Abstract
METHODS
A 10% solution of oak (Quercus incana) and pine (Pinus roxburghii) wood ash was used for detannification of Q. incana leaves. The decrease in the contents of total phenols and condensed tannins and protein precipitation capacity was 66, 80 and 75%, respectively, using oak wood ash, whereas these values were 69, 85 and 80% for pine wood ash. The use of this cheap source of alkali can be adopted at farm level for detannification of oak lea yes for livestock feeding.
The woods of oak (Q. incana) and pine (Pinus roxburghii) were made into a fire. The ashes were collected for the study. Ash (80 g) was added to 800 ml water, stirred for about 20 min at room temperature (-25°C) and the residue allowed to settle. The supernatant was passed through cotton to remove large particles. This supernatant was termed a 10% solution of the ash. Dilutions of this stock solution were made with water. Mature oak leaves of Q. incana were dried at 60°C and ground to pass a 2 mm screen. To 10 g of these leaves in a 250 ml conical flask was added 100 ml of the ash solution. The flasks were shaken for 20 min at room temperature. The leaves were separated by filtration, washed with 50 ml distilled water and dried at 60°C. The extracts were prepared in 50% aqueous methanol using 60 mg leaf powder as described by Martin and Martin (1982). Total phenolic content (TP), condensed tannins (CT) and protein precipitation capacity (PPC) were determined as described earlier (Makkar et al., 1988).
Key words: Tannins, polyphenolics, phenols, condensed tannins, wood ash.
INTRODUCTION Oak leaves are widely available in the Himalayan region spread over India, Nepal and Bhutan. The most common species in the North Western Himalayan region is Quercus incana (Makkar et al., 1986). In these regions there is an acute shortage of fodder for livestock in winter; however, oak leaves are available during this period of scarcity. Feeding of the leaves to livestock has been shown to cause adverse effects and even death of animals (Negi et al., 1979), attributed to the presence of high levels of tannins in the leaves (Lohan et al., 1983; Negi et al., 1979; Makkar et aL, 1988). This vast resource of greens could be exploited for feeding to livestock if a simple and economically viable process for removal or inactivation of tannins were developed. Alkalis have been shown to be very effective for detannification of various feedstuffs (Kumar & Singh, 1984; Reddy et al., 1985; Virk & Menke, 1986). A cheap source of alkalis is wood ash. It is easily available in the countries where the problem of feeding oak leaves exists. Moreover, ash is non-corrosive and farmers handle it regularly.
RESULTS AND DISCUSSION Treatment using ash of both oak and pine woods decreased the content of TP and CT. The removal of TP and CT increased with increase in the level of the soluble portion of the ash in the extracting system. The behaviour was similar for protein precipitation capacity (PPC) (Table 1) which is considered as a measure of biological activity of tannin-rich feeds and foods (gee Makkar, 1989). At 10% level of the oak wood ash, the decreases in the content of TP, CT and PPC were 66, 80 and 75% respectively, whereas these values for pine wood ash were 69, 85 and 80%. The pine wood ash was more effective, and this could be attributed to a higher level of alkalis in the pine wood
85 Bioresource Technology 0960-8524/92/S05.00 © 1992 Elsevier Science Publishers Ltd, England. Printed in Great Britain
86
H. P. S. Makkar, B. Singh
Table 1. Reduction in the contents of total phenols (TP), condensed tannins (CT) and protein precipitation capacity (PPC) in oak leaves using oak and pine wood ashes Ash
Reduction (%) in:
(,r,,)
TP
CT
PPC
ACKNOWLEDGEMENT T h e authors thank the D i r e c t o r of the Institute for facilities.
REFERENCES
Oakwood 1 2 3 5 10 Pinewood 1 2 3 5 10
39.7±4.1 50.9±4.4 51.7±2.8 58.6±3.7 65.5±4.6
49.2±3.6 57.5±4.7 67.1±3.9 69.2±4.3 80.0±5.6
43.8±5.0 55.1±6.4 65.3±5.2 66.9±6.1 75.3±5.8
44.6±2-3 52,7±3.6 56.4±4.1 63-6±5"3 69"0±5"3
57.4±3.5 63.9±4.2 68"9±3.9 78.7±5.3 85"3±6"1
54"5±4.2 60"1±4.1 64"8±5.0 75.3±6.5 80"3±6'2
Treatment conditions: 20 rain with shaking at room temperature. Values are mean + SD (n = 4).
ash ( p H values of 10% ash solutions of pine and oak w o o d s were 11.3 and 10.5, respectively). Price et al. (1979) have also r e p o r t e d 8 5 % tannin inactivation in sorghum grain using a water extract of h a r d w o o d ash. Magadi soda, a n o t h e r unrefined material containing alkalis (sodium sesquicarbonate, Na2CO3 N a H C O 3 . H 2 0 ) has also b e e n shown to r e d u c e assayable tannins in sorghum grain by 4 0 - 5 7 % (Muindi et al., 1981). W o o d ash solutions have also b e e n traditionally used in U g a n d a and R w a n d a for treatment of high-tannin containing sorghums and millets for h u m a n consumption (Doggett, 1977). T h e present study and that of Price et al. (1979) p r o v i d e a scientific explanation for this tradition. O a k and pine w o o d s are generally used as fuel in rural areas of the H i m a l a y a n region in India and adjoining countries. W o o d ash is also used for cleaning utensils and is spread in the fields, as farmers believe that it is g o o d for crops. So ash is easily available to the farmers of the H i m a l a y a n region w h e r e o a k is abundant. M o r e o v e r , the use of this cheap source of alkali should also be exploited since the insoluble p o r t i o n of the ash could still b e used b y the farmers for traditional functions.
Doggett, H. (1977). Quality improvement in sorghums and millets. In Proceedings of the Symposium on Sorghum and Millets for Human Food. Tropical Products Institute, London, pp. 7-9. Kumar, R. & Singh, M. (1984). Tannins: their adverse role in ruminant nutrition. J. Agric. Food Chem., 32,447-53. Lohan, O. P., Laii, D., Vaid, J. & Negi, S. S. (1983). Utilization of oak tree (Quercus incana) fodder in cattle rations and fate of oak-leaf tannins in the ruminant system. Indian J. Anim. Sci., 53, 1057-63. Makkar, H. P. S. (1989). Protein precipitation methods for quantitation of tannins: a review. J. Agric. Food Chem., 37, 1197-202. Makkar, H. P. S., Dawra, R. K. & Singh, B. (1986). Can oak leaves be fed to animals? Farmers and Parliament, 24, 17-18. Makkar, H. P. S., Dawra, R. K. & Singh, B. (1988). Changes in tannin content, polymerisation and protein precipitation capacity in oak (Quercus incana)leaves with maturity. J. Sci. Food Agric., 44, 301-7. Martin, J. S. & Martin, M. M. (1982). Tannin assays in ecological studies: lack of correlations between phenolics, proanthocyanidins and protein-precipitation constituents, in mature foliage of six oak species. Oecologia, 54, 205-11. Muindi, P. J., Thomke, S. & Ekman, R. (1981). Effect of magadi soda treatment on the tannin content and in-vitro nutritive value of grain sorghums. J. Sci. Food Agric., 32, 25-34. Negi, S. S., Pal, R. N. & Ehrich, C. (1979). Tree Fodders in Himachal Pradish. Germany Agency for Technical Cooperation, Eschborn, FRG, p. 41. Price, M. L., Butler, L. G., Rogler, J. C. & Featherston, W. R. (1979). Overcoming the nutritionally harmful effects of tannin in sorghum grain by treatment with inexpensive chemicals. J. Agric. Food Chem., 27, 441-5. Reddy, N. R., Pierson, M. D., Sathe, S. K. & Salunkhe, D. K. (1985). Dry bean tannins: a review of nutritional implications. JAOCS, 62, 541-9. Virk, A. S. & Menke, K.-H. (1986). Occurrence and nutritional significance of tannins present in unconventional feeds in India. Anim. Res. Dev., 24, 7-22.
H. P. S. Makkar & B. Singh Indian Veterinary Research Institute, Regional Station, Palampur, Kangra Valley, HP 176 061, India (Received 28 January 1991; revised version received 8 June 1991; accepted 12 June 1991)
Short Communication Effect of Wood Ash on Tannin Content of Oak ( Quercus incana ) Leaves
The objective of the present study was to investigate the possibility of detannification of oak leaves using wood ashes.
Abstract
METHODS
A 10% solution of oak (Quercus incana) and pine (Pinus roxburghii) wood ash was used for detannification of Q. incana leaves. The decrease in the contents of total phenols and condensed tannins and protein precipitation capacity was 66, 80 and 75%, respectively, using oak wood ash, whereas these values were 69, 85 and 80% for pine wood ash. The use of this cheap source of alkali can be adopted at farm level for detannification of oak lea yes for livestock feeding.
The woods of oak (Q. incana) and pine (Pinus roxburghii) were made into a fire. The ashes were collected for the study. Ash (80 g) was added to 800 ml water, stirred for about 20 min at room temperature (-25°C) and the residue allowed to settle. The supernatant was passed through cotton to remove large particles. This supernatant was termed a 10% solution of the ash. Dilutions of this stock solution were made with water. Mature oak leaves of Q. incana were dried at 60°C and ground to pass a 2 mm screen. To 10 g of these leaves in a 250 ml conical flask was added 100 ml of the ash solution. The flasks were shaken for 20 min at room temperature. The leaves were separated by filtration, washed with 50 ml distilled water and dried at 60°C. The extracts were prepared in 50% aqueous methanol using 60 mg leaf powder as described by Martin and Martin (1982). Total phenolic content (TP), condensed tannins (CT) and protein precipitation capacity (PPC) were determined as described earlier (Makkar et al., 1988).
Key words: Tannins, polyphenolics, phenols, condensed tannins, wood ash.
INTRODUCTION Oak leaves are widely available in the Himalayan region spread over India, Nepal and Bhutan. The most common species in the North Western Himalayan region is Quercus incana (Makkar et al., 1986). In these regions there is an acute shortage of fodder for livestock in winter; however, oak leaves are available during this period of scarcity. Feeding of the leaves to livestock has been shown to cause adverse effects and even death of animals (Negi et al., 1979), attributed to the presence of high levels of tannins in the leaves (Lohan et al., 1983; Negi et al., 1979; Makkar et aL, 1988). This vast resource of greens could be exploited for feeding to livestock if a simple and economically viable process for removal or inactivation of tannins were developed. Alkalis have been shown to be very effective for detannification of various feedstuffs (Kumar & Singh, 1984; Reddy et al., 1985; Virk & Menke, 1986). A cheap source of alkalis is wood ash. It is easily available in the countries where the problem of feeding oak leaves exists. Moreover, ash is non-corrosive and farmers handle it regularly.
RESULTS AND DISCUSSION Treatment using ash of both oak and pine woods decreased the content of TP and CT. The removal of TP and CT increased with increase in the level of the soluble portion of the ash in the extracting system. The behaviour was similar for protein precipitation capacity (PPC) (Table 1) which is considered as a measure of biological activity of tannin-rich feeds and foods (gee Makkar, 1989). At 10% level of the oak wood ash, the decreases in the content of TP, CT and PPC were 66, 80 and 75% respectively, whereas these values for pine wood ash were 69, 85 and 80%. The pine wood ash was more effective, and this could be attributed to a higher level of alkalis in the pine wood
85 Bioresource Technology 0960-8524/92/S05.00 © 1992 Elsevier Science Publishers Ltd, England. Printed in Great Britain
86
H. P. S. Makkar, B. Singh
Table 1. Reduction in the contents of total phenols (TP), condensed tannins (CT) and protein precipitation capacity (PPC) in oak leaves using oak and pine wood ashes Ash
Reduction (%) in:
(,r,,)
TP
CT
PPC
ACKNOWLEDGEMENT T h e authors thank the D i r e c t o r of the Institute for facilities.
REFERENCES
Oakwood 1 2 3 5 10 Pinewood 1 2 3 5 10
39.7±4.1 50.9±4.4 51.7±2.8 58.6±3.7 65.5±4.6
49.2±3.6 57.5±4.7 67.1±3.9 69.2±4.3 80.0±5.6
43.8±5.0 55.1±6.4 65.3±5.2 66.9±6.1 75.3±5.8
44.6±2-3 52,7±3.6 56.4±4.1 63-6±5"3 69"0±5"3
57.4±3.5 63.9±4.2 68"9±3.9 78.7±5.3 85"3±6"1
54"5±4.2 60"1±4.1 64"8±5.0 75.3±6.5 80"3±6'2
Treatment conditions: 20 rain with shaking at room temperature. Values are mean + SD (n = 4).
ash ( p H values of 10% ash solutions of pine and oak w o o d s were 11.3 and 10.5, respectively). Price et al. (1979) have also r e p o r t e d 8 5 % tannin inactivation in sorghum grain using a water extract of h a r d w o o d ash. Magadi soda, a n o t h e r unrefined material containing alkalis (sodium sesquicarbonate, Na2CO3 N a H C O 3 . H 2 0 ) has also b e e n shown to r e d u c e assayable tannins in sorghum grain by 4 0 - 5 7 % (Muindi et al., 1981). W o o d ash solutions have also b e e n traditionally used in U g a n d a and R w a n d a for treatment of high-tannin containing sorghums and millets for h u m a n consumption (Doggett, 1977). T h e present study and that of Price et al. (1979) p r o v i d e a scientific explanation for this tradition. O a k and pine w o o d s are generally used as fuel in rural areas of the H i m a l a y a n region in India and adjoining countries. W o o d ash is also used for cleaning utensils and is spread in the fields, as farmers believe that it is g o o d for crops. So ash is easily available to the farmers of the H i m a l a y a n region w h e r e o a k is abundant. M o r e o v e r , the use of this cheap source of alkali should also be exploited since the insoluble p o r t i o n of the ash could still b e used b y the farmers for traditional functions.
Doggett, H. (1977). Quality improvement in sorghums and millets. In Proceedings of the Symposium on Sorghum and Millets for Human Food. Tropical Products Institute, London, pp. 7-9. Kumar, R. & Singh, M. (1984). Tannins: their adverse role in ruminant nutrition. J. Agric. Food Chem., 32,447-53. Lohan, O. P., Laii, D., Vaid, J. & Negi, S. S. (1983). Utilization of oak tree (Quercus incana) fodder in cattle rations and fate of oak-leaf tannins in the ruminant system. Indian J. Anim. Sci., 53, 1057-63. Makkar, H. P. S. (1989). Protein precipitation methods for quantitation of tannins: a review. J. Agric. Food Chem., 37, 1197-202. Makkar, H. P. S., Dawra, R. K. & Singh, B. (1986). Can oak leaves be fed to animals? Farmers and Parliament, 24, 17-18. Makkar, H. P. S., Dawra, R. K. & Singh, B. (1988). Changes in tannin content, polymerisation and protein precipitation capacity in oak (Quercus incana)leaves with maturity. J. Sci. Food Agric., 44, 301-7. Martin, J. S. & Martin, M. M. (1982). Tannin assays in ecological studies: lack of correlations between phenolics, proanthocyanidins and protein-precipitation constituents, in mature foliage of six oak species. Oecologia, 54, 205-11. Muindi, P. J., Thomke, S. & Ekman, R. (1981). Effect of magadi soda treatment on the tannin content and in-vitro nutritive value of grain sorghums. J. Sci. Food Agric., 32, 25-34. Negi, S. S., Pal, R. N. & Ehrich, C. (1979). Tree Fodders in Himachal Pradish. Germany Agency for Technical Cooperation, Eschborn, FRG, p. 41. Price, M. L., Butler, L. G., Rogler, J. C. & Featherston, W. R. (1979). Overcoming the nutritionally harmful effects of tannin in sorghum grain by treatment with inexpensive chemicals. J. Agric. Food Chem., 27, 441-5. Reddy, N. R., Pierson, M. D., Sathe, S. K. & Salunkhe, D. K. (1985). Dry bean tannins: a review of nutritional implications. JAOCS, 62, 541-9. Virk, A. S. & Menke, K.-H. (1986). Occurrence and nutritional significance of tannins present in unconventional feeds in India. Anim. Res. Dev., 24, 7-22.
H. P. S. Makkar & B. Singh Indian Veterinary Research Institute, Regional Station, Palampur, Kangra Valley, HP 176 061, India (Received 28 January 1991; revised version received 8 June 1991; accepted 12 June 1991)