ORIGINAL ARTICLE Effect of Cooking Time on Some Nutrient and Antinutrient Components of Bambaragroundnut Seeds

Animal Science Journal (2009) 80, 52–56 doi: 10.1111/j.1740-0929.2008.00599.x

ORIGINAL ARTICLE Effect of cooking time on some nutrient and antinutrient components of bambaragroundnut seeds

Stanley Omoh OMOIKHOJE,1 Mohammed Bashiru ARUNA1 and Adeyemi Mustapha BAMGBOSE2 1Department of Animal Science, Ambrose Alli University, Ekpoma, Edo State, and 2Department of Animal Nutrition, University of Agriculture, Abeokuta, Ogun State, Nigeria

ABSTRACT

The proximate composition, gross energy, mineral composition, percentage sugar, oligosaccharides and antinutrient substances of bambaragroundnut seeds subjected to different cooking times were determined. The seeds were cooked for 30, 60, 90 and 120 min. Results of the proximate analysis showed that only the ether extract and ash were significantly (P < 0.05) reduced as the cooking time increased. In contrast, gross energy values significantly (P < 0.05) increased with increased cooking time. Amongst, the mineral elements assayed, calcium, magnesium and iron were significantly (P < 0.05) increased, while phosphorous, potassium, sodium and copper were reduced significantly (P > 0.05) with inreased cooking time. Percentage sucrose and glucose of bambaragroundnut seeds were significantly (P < 0.05) lowest in the raw form, but increased progressively with increased of cooking time. Raffinose and stachyose levels were reduced significantly by increased cookinf time (P < 0.05) with the least value in seeds cooked for 120 min. Trypsin inhibitor, hemagglutinin and tannin were completely eliminated in seeds cooked for 60 min or longer, but the phytin level was reduced significantly (P < 0.05) by cooking. For a significant detoxification of antinutrient substances and for optimal bioavailability of the component nutrients of bambaragroundnut seeds, an optimum cooking time of 60 min at 100°C is therefore recommended.

Key words: antinutrients, bambaragroundnut cooking time, nutrients.

INTRODUCTION known to be harmful to the nutritive value of legume seeds, which is why Brenes et al. (1973) reported an Most legumes are hard to cook, particularly after long optimal cooking time of 20 min at 120°C for pigeon storage periods, and this is a major constraint on their peas. In addition, Bender (1983) reported that cooking utilization. As the storage period of legumes increases, red beans for 45 min at 80°C resulted to a marked grains become harder to cook, so it takes longer to reduction in the agglutinating activity compared to the cook such legume seeds. With the incessant increases raw form. But, when the same beans were cooked for in the prices of petroleum products in Nigeria in recent the same length of time at 100°C, no agglutinating years, it has become very difﬁcult for average Nigeri- activity was observed. Similarly, Akinmutimi (2004) ans to afford these products, thereby preventing the asserted that to obtain appreciable values of crude rural poor from utilizing legume seeds for food. For protein and minerals, and higher percentage reduction instance, the hard-to-cook phenomenon of soybeans in antinutrient substances of Mucuna utilis seeds, an has been ascribed (Philips & McWalters 1991) to the presence of calcium pectate. Calcium pectate is an insoluble complex formed in the middle lamella, Correspondence: Stanley Omoh Omoikhoje, Department of Animal Science, Ambrose Alli University, P.M.B 14, Ekpoma, which delays the destruction of the middle lamella Edo State, Nigeria. (Email: [email protected]) during cooking (thereby resulting to a prolonged Received 12 July 2007; accepted for publication 12 February cooking time). However, prolonged heating has been 2008.

optimum cooking time of 90 min at 100°C is adequate. titrated with standard iron (iii) chloride solution (0.00195 g Against this background, the present study was iron per mL). The endpoint was slightly brownish-yellow designed to determine the effect of cooking time on which persisted for 5 min. The percentage phytic acid was calculated using the formula: the nutrient and antinutrient components of bambaragroundnut seeds. %. Phytic acid=×χ 1 I 9 × 100 Where c=titer value ¥ 0.00195 g MATERIALS AND METHODS Tannic acid determination Bambaragroundnut seeds were purchased from the Idah Tannic acid levels in the seeds were determined by the open market in Kogi State, Nigeria. The processing and method of Maga (1982). This involved the weighing of 2 g laboratory analyzes of the seeds were carried out in the of each sample into a beaker and soaking with a solvent Department of Animal Science Laboratory of Ambrose Alli mixture (80 mL of acetone and 20 mL of glacial acetic acid) University, Ekpoma, Edo State, Nigeria. for 5 h to extract the tannin. Each filtrate was placed in a water bath for 4 h before they were removed. The samples Processing of bambaragroundnut seeds were then filtered through a double layer filter paper to obtain the filtrate. A set of standard solutions of tannic acid The raw bambaragroundnut seeds were divided into five was prepared ranging from 10 ppm to 50 ppm. The absor- groups of 0.5 kg each. The first group was raw, while the bance of the standard solution and that of the filtrate were second, third, fourth and fifth groups were cooked in water read at 50 nm on specteromic 20. The percentage tannin was in an aluminum pot heated by a naked dry wood fire for 30, calculated using the formula: 60, 90 and 120 min, respectively, at 100°C. Thereafter, the cooked seeds were strained (to remove the cooking water) % Tannin=× Absorbance Average gradient and sun-dried at the atmospheric temperature (28°C) for five × dilution factor days to obtain a constant moisture content of 10.99%. All the 10 000 samples were then milled, sieved in a 1.55 mm mesh and analyzed chemically in triplicate. Statistical analysis Analytical procedures Data obtained were subjected to a one-way analysis of vari- ance (ANOVA) and significant means were compared using The proximate composition and gross energy of the raw and the Duncan’s multiple range test as outlined by Steel and processed samples were determined by the method of AOAC Torrie (1990) with the aid of SAS (1999). (2000). Nitrogen free extract was determined by subtracting the summation of all other proximate fractions from 100%. Crude protein was determined as percentage nitrogen ¥ 6.25 RESULTS AND DISCUSSION using the micro Kjeldhal distillation unit. Amongst the minerals, sodium and potassium levels were determined using Results of the proximate analysis revealed that only the flame photometer, while phosphorous levels were deter- ether extract, ash and gross energy of bambaraground- mined by the phosphovanadomolybdate method (AOAC < 2000). Other mineral constituents were determined after a nut seeds were significantly (P 0.05) influenced by wet digestion with a mixture of trioxonitrate (v) acid (HNO3), cooking time (Table 1). The protein content was not tetraoxosulfate (vi) acid (H2SO4) and hydrochloric acid using significantly (P > 0.05) affected by cooking time, with an Atomic Absorption Spectrophotometer. Oligosaccharide the values decreasing from 19.61% to 17.08% in raw contents such as stachyose, raffinose and verbascose as well samples and samples cooked for 120 min (CBG120), as glucose and sucrose were determined by the method of Oke et al. (1999). Trypsin inhibitor and hemagglutinin levels respectively. The decrease in the crude protein level as were determined by the method of Kakade et al. (1973). the duration of cooking increased could be ascribed to the leaching of nutrients into the cooking medium Phytic acid determination (Akinmutimi & Onwukwe 2002; Akinmutimi 2004). Thus, the longer the cooking time, the more nutrients Phytic acid levels were determined using the method described by Lucas and Markakes (1975). Two grams of each were lost. Ether extract values followed a similar sample was weighed into 250 mL conical flasks. 100 mL of pattern, with a significant (P < 0.05) decrease observed 2% concentrated hydrochloric acid was used to soak each from 6.45% in raw bambaragroundnuts (RBG) to sample in the conical flask for 3 h. This was then filtered 5.87% in CBG120. However, the values obtained through a double layer of hardened filter paper. 50 mL of in samples cooked for 30 min (CBG30) to 90 min each filtrate was placed into a 250 mL beaker. 107 mL of distilled water was added in each case to give proper acidity. (CGB90) were statistically similar to that of RBG. This Thereafter, 10 mL of 0.3% ammonium thiocyanate solution implies that cooking of bambaragroudnut seeds for up was added to each solution as an indicator. This was then to 90 min is adequate if the seed is to be used as oil

Table 1 Proximate composition of raw and cooked bambaragroundnut seeds (% Dry matter basis) Cooking time (min) 0 30 60 90 120

Constituents RBG CBG30 CBG60 CBG90 CBG120 SEM Dry matter (DM) 91.38 91.18 89.32 89.01 88.88 0.86 Crude protein 19.61 18.59 18.34 17.44 17.08 0.24 Ether extract 6.45a 6.32a 6.27a 6.28a 5.87b 0.11 Crude ﬁber 3.64 3.62 3.61 3.55 3.42 0.02 Ash 4.45a 3.51ab 3.40bc 3.10c 2.94d 0.12 Nitrogen free extract 54.95 59.35 57.69 60.82 59.45 1.01 Gross energy (kCal/kg) 2540c 2627b 2630a 2635a 2640a 1.01 a,b,c,dMeans in the same row with varying superscripts differ signiﬁcantly (P < 0.05).

Table 2 Mineral composition of raw and cooked bambaragroundnut seeds Cooking time (min) Cooking time (min) 0 306090120

Contents RBG CBG30 CBG60 CBG90 CBG120 SEM Calcium (%) 2.64e 2.90d 2.93ab 2.92bc 2.95a 0.01 Phosphorous (%) 0.080a 0.067b 0.063b 0.062c 0.060c 0.001 Potassium (%) 0.94a 0.93a 0.91b 0.90b 0.80c 0.004 Sodium (%) 0.005a 0.005a 0.004b 0.004b 0.003c 0.0001 Magnesium (%) 0.67 0.70 0.69 0.72 0.70 0.012 Iron (p.p.m) 150.7d 161.7a 158.0b 153.7c 154.3c 0.23 Copper (mg/kgDm) 3.10a 2.73b 2.47c 2.33d 2.27d 0.03 a,b,c,d,eMeans in the same row with varying superscripts differ significantly (P < 0.05). seed. These values are higher than the range of ether tively high level of ash. The nitrogen free extract extract recorded by Olomu (1995) for conventional values were not significantly (P > 0.05) affected by protein sources such as groundnut cake (3.63%) and the period of cooking, but were higher than those soybeans (4.5%). The non-significant (P > 0.05) obtained in conventional protein sources such as decrease in the crude fiber value as the duration of groundnut cake (23.84%) and soybeans (28.60%) as cooking increases is in consonance with the report of reported by Amaefule and Obioha (1998). The gross Aletor and Ojo (1989), which stated that cooking gen- energy values were significantly (P < 0.05) increased erally reduces the crude fiber values in legumes. The by the length of cooking. The 2640 kcal/kg recorded in crude fiber values obtained in this study are lower seeds cooked for 120 min is an appreciable energy compared to those recorded by Akinmutimi (2004) in value which compares favorably with those of ground- conventional legumes such as groundnut cake (5.0%) nut cake (2640 kcal/kg) and boiled jackbeans and soybeans (6.5%). The lower value in crude fiber in (2970 kcal/kg) as recorded by Ogbonna et al. (2000). bambaragroundnut could therefore be an advantage This suggests the potentiality of the seeds as an energy to monogastric animals, which do not easily digest supplement, and it is worthy of note as protein utili- fibrous materials. The ash content of the raw bambara- zation and energy intake are closely interrelated. groundnut seeds was significantly (P < 0.05) higher The mineral concentration of bambaragroundnut than those of the processed samples. The values of the seeds as influenced by cooking time (Table 2) reflects processed samples significantly (P < 0.05) decreased that all he mineral elements determined except progressively as the duration of cooking increased. magnesium were significantly (P < 0.05) affected by This observation contradicts that of Akinmutimi cooking time. For macrominerals, only calcium values (2004) who reported a significant increase in the ash were increased significantly (P < 0.05), while those of content of Mucuna utilis with increased cooking time. phosphorous, potassium and sodium were signifi- This suggests that prolonged cooking could deplete the cantly (P < 0.05) decreased with increased cooking ash content of the legume, and therefore an optimum time. Although the values of magnesium were not cooking time of 60 min is adequate to retain a rela- significantly (P > 0.05) affected by cooking time, the

© 2008 The Authors Animal Science Journal (2009) 80, 52–56 Journal compilation © 2008 Japanese Society of Animal Science COOKING TIME ON BAMBARAGROUNDNUT SEEDS 55 value recorded in the raw sample was numerically and 16.67%, 71.32% and 51.85%, 82.73% and lower than those of the processed samples. The signifi- 71.30%, 90.07% and 86.11%, respectively. However, cant (P < 0.05) decrease in the values of phosphorous, the increase in the levels of sucrose and glucose with potassium and sodium could be due to leaching of the corresponding decreases in the levels of raffinose and nutrients into the cooking medium. This is supported stachyose for all the cooking periods may be ascribed by the reports of Iyayi and Egharevba (1998), and to the breakdown of the m, D- galactopyranose residue Agbede and Aletor (2001) who recorded decreases in which binds to the glucose moiety of glucose (Akinlo- the values of these macroelements except calcium and sutun & Akinyele 1991; Muzquize et al. 1992). magnesium in Mucuna utilis. The micromineral results Data on antinutrient substances (Table 4) revealed showed a significant (P < 0.05) increase in the values that cooking time significantly (P < 0.05) influenced of iron and a significant (P > 0.05) decrease in the the trypsin inhibitor, hemagglutinin, tannin and values of copper for the duration of cooking. However, phytin activities of raw bambaragroudnut seeds. In the values obtained for iron and copper agree with the fact, cooking beyond 30 min totally eliminated the report of Akinmutimi (2004) who investigated the trypsin inhibitor activity (TIA), and the hemagglutinin effect of cooking periods on the nutrient composition and tannin contents of raw seeds. However, the origi- of Mucuna utilis. nal level of phytin in the intact seeds was progressively Table 3 shows the influence of cooking time on the reduced by 16.30%, 31.11%, 38.52% and 51.85% in percentage sugars and oligosaccharide contents of CBG30, CBG60, CBG90 and CBG120, respectively. The bambaragroundnut. The results revealed that cooking 38.52% reduction in phytin content of seeds cooked time significantly (P < 0.05) increased the levels of for 90 min agrees with the value (38.42%) reported sucrose and glucose, but significantly (P < 0.05) by Akinmutimi (2004) who cooked Mucuna utilis for decreased the raffinose and stachyose levels in intact 90 min, but appreciably higher than 16.47% reported seeds. Sucrose and glucose levels increased progres- by Akinmutimi and Onwukwe (2002) for lima beans sively with increased cooking time. Cooking of cooked in potash solution. This therefore suggests that bambaragroundnut seeds for 30, 60, 90 and 120 min cooking bambaragroudnut seeds for 60 min or more reduced the raffinose and stachyose levels by 60.66% can minimize the concern posed by the chelating and protein binding ability of phytin that is found naturally in food materials of plant origin. The complete elimi- Table 3 Percentage sugar and oligosaccharide contents of nation of tannin even at 60 min of cooking could be bambaragroundnut seeds as influenced by cooking time attributed to the hydrolysis of the intermolecular force Cooking time (min) that exists within tannin (Bathe-Smith 1973). There- fore, the use of bambaragroundnut seeds cooked for 0 306090120 60 min or more will prevent the formation of complex Levels (%) RBG CBG30 CBG60 CBG90 CBG120 SEM linkages of tannin with protein (Griffiths 1991), Sucrose 20.23d 22.17c 22.56b 22.58b 22.82a 0.01 thereby resulting in increased protein availability. Glucose 13.23d 13.91c 14.47b 16.55a 16.87a 0.04 Raffinose 2.72a 1.07b 0.78c 0.47d 0.27e 0.04 Stachyose 1.08a 0.90b 0.52c 0.31d 0.15e 0.02 Verbascose ND ND ND ND ND – Conclusion a,b,c,d,eMeans in the same row with varying superscripts differ The overall results reveal that for bambaragroundnut significantly (P < 0.05). ND, Not detected. seeds, a cooking time of 60 min at 100°C is optimal for

Table 4 Antinutrient substances of bambaragroundnut seeds as inﬂuenced by cooking time Cooking time (min) 0 306090120

Composition RBG CBG30 CBG60 CBG90 CBG120 SEM Trypsin inhibitor (mg/g) 19.8 7.8 0.0 0.0 0.0 0.06 Haemagglutinin (Hu/mg/N) 0.83 0.05 0.0 0.0 0.0 0.04 Tannin (mg/100 g) 0.12 0.07 0.0 0.0 0.0 0.02 Phytin (mg/100 g) 13.5a 11.3b 9.3c 8.3d 6.5e 0.20 a,b,c,d,eMeans in the same row with varying superscripts differ signiﬁcantly (P < 0.05).

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