Abstract
Despite being a rich source of protein (28-34%), karanj (Pongamia glabra) cake is found to be bitter in taste and toxic in nature owing to the presence of flavonoid (karanjin), tannin and trypsin inhibitor, thereby restricting its safe inclusion in poultry rations. Feeding of karanj cake at higher levels (>10%) adversely affected the growth performance of poultry due to the presence of these toxic factors. Therefore, efforts were made to detoxify karanj cake by various physico-chemical methods such as dry heat, water washing, pressure cooking, alkali and acid treatments and microbiological treatment with Sacchraromyces cerevisiae (strain S-49). The level of residual karanjin in raw and variously processed cake was quantified by high performance liquid chromatography and tannin and trypsin inhibitor was quantified by titrametric and colorimetric methods, respectively. The karanjin, tannin and trypsin inhibitor levels in such solvent and expeller pressed karanj cake were 0.132, 3.766 and 6.550 and 0.324, 3.172 and 8.513%, respectively. Pressure-cooking of solvent extracted karanj cake (SKC) substantially reduced the karanjin content at a cake:water ratio of 1:0.5 with 30-minute cooking. Among chemical methods, 1.5% (w/w) NaOH was very effective in reducing the karanjin content. Ca (OH) 2 treatment was also equally effective in karanjin reduction, but at a higher concentration of 3.0% (w/w). A similar trend was noticed with respect to treatment of expeller pressed karanj cake (EKC). Pressure cooking of EKC was effective in reducing the karanjin level of the cake. Among chemical methods alkali treatment [2% (w/w) NaOH] substantially reduced the karanjin levels of the cake. Other methods such as water washing, dry heat, HCl, glacial acetic acid, urea-ammoniation, combined acid and alkali, and microbiological treatments marginally reduced the karanjin concentration of SKC and EKC. Treatment of both SKC and EKC with 1.5% and 2.0% NaOH (w/w) was the most effective method in reducing the tannin content. Among the various methods of detoxification, dry heat, pressure cooking and microbiological treatment with Saccharomyces cerevisiae were substantially effective in reducing the trypsin inhibitor activity in both SKC and EKC. Based on reduction in karanjin, in addition to tannin and trypsin inhibitor activity, detoxification of SKC with either 1.5% NaOH or 3% Ca (OH) 2 , w/w) and with 2% NaOH were more effective. Despite the effectiveness of pressure cooking in reducing the karanjin content, it could not be recommended for detoxification because of the practical difficulties in adopting the technology as well as for economic considerations.
Highlights
Poultry production in India has gained momentum during the last three decades, which on today assumed the shape of an industry
Various processing methods such as physical, chemical and microbiological methods were tried at laboratory scale to detoxify the solvent extracted and expeller pressed karanj cake, which were obtained from the local market
The concentration of karanjin and tannin and trypsin inhibitor activity in raw and variously processed solvent extracted (SKC) and expeller pressed karanj cake (EKC) at laboratory scale are presented in Table 1 to 3
Summary
Poultry production in India has gained momentum during the last three decades, which on today assumed the shape of an industry. Karanj seed cake (KSC), the residue left after oil extraction, could not be utilized for poultry feeding even at lower levels due to the presence of toxic principle, karanjin, a furanoflavonoid. The expeller and solvent extracted cake contain trypsin inhibitor upto 8.2% and 8.7% of protein and tannins to the extent of 3.16 and 3.41%, respectively (Natanam et al, 1989b). Efforts could be made to convert karanj cake into a wholesome poultry feed after suitable processing and quantifying the residual toxins left back in the processed cake, which could be adopted by farmers and feed compounding industry. Keeping the above facts in view, the present investigations were undertaken to detoxify karanj cake by adopting various physicochemical methods like solvent extraction, water washing, pressure cooking, alkali and acid treatments and microbiological methods and to estimate residual karanjin, tannin and trypsin inhibitors left back in the treated cakes
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