1. Introduction
Legumes are important sources of affordable alternative protein to poor resource people in many tropical especially in Africa and Asia where they are predominantly consumed
. In the developing countries, research attention is being paid to better utilization of legumes in addressing protein malnutrition and food security issues.
Afzelia africana “Akparata”,
Mucuna sloanei “Ukpo”,
Brachystegia eurycoma “Achi”
and
Detarium microcarpum “Ofor” are legumes commonly used as soup thickeners in the South-Eastern part of Nigeria and they belong to the same family
leguminosae as well as the same sub-family
caesalpiniacea [8] | Igwenyi, I. O. and Azoro, B. N. Proximate and Phytochemical composition of flour from indigenous seeds used as soup thickeners in Ebonyi state, Nigeria. J. of Environmental Science, Toxicology and Food Technology, 2014, 8(6), 35-40. https://doi.org/10.9790/2402-08623540 |
[8]
. Flours from these seeds are used as thickeners, emulsifiers and flavouring agents in traditional soups (for eating gari, pounded yam or cocoyam and cassava fufu), as a result of their inherent gum contents essential in thickening and gel formation. The gums are extracted from the seeds and serve as natural hydrocolloids, when crushed to flour and in powdered form they have the ability to swell in water and thus are able to influence the flow and consistency of the liquid.
Food gums are diverse group of long chain polymers characterized by their property of forming viscous dispersions and/or gels in water. The presence of large number of hydroxyl groups increases their affinity for binding water molecules, and so belongs to the group of hydrophilic compounds. According to
[12] | Juszczac, L., Witczak, M., Fortuna, T. and Babachowicz, A. Effect of some hydrocolloids on the rheological properties of rye starch. International Journal of Food Science and Technology, 2004, 10(2), 125-131. https://doi.org/10.1177/1082013204043764 |
[12]
, food gum produces dispersion, which is intermediate between a true solution and a suspension, and exhibits the properties of a colloid. Considering these two properties, they are appropriately regarded as hydrophilic colloids or hydrocolloids. Hydrocolloids have a wide array of functional properties in foods including; thickening, gelling, emulsifying, stabilization and coating. The primary reason behind the use of hydrocolloids in foods is their ability to modify the rheology of food systems
. This includes two basic properties of food systems that is, flow behavior (viscosity) and mechanical solid property (texture) which in turns affect its sensory properties.
The world hydrocolloid market which is valued at about USD 4.4 billion per annum, with a total volume of about 260,000 tonnes in the year 2000. This reflects a remarkable demand for hydrocolloids which has influenced the price and availability
[32] | Williams, P. A. and Phillips, G. O. Introduction to food hydrocolloids. In Handbook of Hydrocolloids; Phillips, G. O, Williams, P. A., Eds.; Woodhead Publishing Ltd: Cambridge, UK, 2000, pp. 1-19.y |
[32]
. Sequel to the increase in the hydrocolloid market demand, it is therefore imperative to exploit some new raw materials as potential and alternative sources of food hydrocolloids and seed gums
. Studies on the extraction of the hydrocolloids from seeds such as:
Mucuna sloanei and
Irivingia gabonensis and their visco-elastic properties have been reported
[26] | Onweluzo, J. C., Obanu, Z. A. and Okwandu, M. C. Potentials of Gum from Detarium microcarpum (DM) and Mucuna flagellipes (MF) Seeds as Raw Beef Burger Stabilizers. Plants Food for Human Nutrition. 2005, 59(4), 137-141. |
[26]
. The gums from the cotyledon of these legumes have not found much use in food systems unlike the tapioca starch which is used in numerous industrial and food applications, as thickening and gelling agents
[8] | Igwenyi, I. O. and Azoro, B. N. Proximate and Phytochemical composition of flour from indigenous seeds used as soup thickeners in Ebonyi state, Nigeria. J. of Environmental Science, Toxicology and Food Technology, 2014, 8(6), 35-40. https://doi.org/10.9790/2402-08623540 |
[8]
. The method of processing of food commodities generally affects their functional behavior
[26] | Onweluzo, J. C., Obanu, Z. A. and Okwandu, M. C. Potentials of Gum from Detarium microcarpum (DM) and Mucuna flagellipes (MF) Seeds as Raw Beef Burger Stabilizers. Plants Food for Human Nutrition. 2005, 59(4), 137-141. |
[26]
. This work is aimed at the determining the effect of processing methods on the physical property of gum extracts from selected legume seeds.
2. Materials and Method
2.1. Material Collection
Mucuna sloanei “ukpo”, Detarium microcarpium “ofor”, Brachysteia eurycoma “Achi)” Afzelia africana “akparata”, seeds were obtained from “Ekeikpa” (a local market) in Ihitte/ Uboma, Imo state, Nigeria. Petroleum ether, distilled water and propane-2-ol were purchased from a scientific laboratory in Owerri, Imo state, Nigeria and were of analytical grade. Other reagents and equipment/facilities were obtained from the department of Food Science and Technology of University of Agriculture and Environmental Sciences.
2.2. Processing of Seed Flour
The seeds of ‘Ukpo’, ‘Achi’, ‘Akparata’ and ‘Ofor’ were cleaned to remove dirt. The whole and healthy seeds were weighed separately and manually cracked with the use of a wooden hammer (Mallet). They were divided into four equal portions each; the first three portions were subjected to boiling, roasting and soaking respectively while the fourth portion was processed raw.
2.2.1. Processing of Flour from Boiled Seeds
The first portion of the cracked seeds was divided into three equal portions and placed in boiling distilled water in the ratio of 1/5 (w/v) for durations of 10 min, 20 min and 30 min. They were drained and allowed to cool to ambient temperature. They were de-decoated to obtain the seeds endosperms by scraping the seed coats with a stainless-steel knife and washed in surplus water (1/5 w/v) and milled using an attrition mill. The flours were dried in a moisture extraction oven (DHG- 9053 Model) at 65°C to a constant weight, cooled to ambient temperature and sieved through a 500 µm mesh-sized sieve to generate fine flour. They were packaged in airtight containers and stored at ambient conditions for further analysis and application. The production flow chart is as shown in
Figure 1.
2.2.2. Processing of Flour from Roasted Seeds
The second portion of the cracked seeds were divided into three equal portions, and toasted in a pre- heated locally fabricated oven at 130°C for 10 min, 20 min and 30 min, allowed to cool to ambient temperature. They were de-coated to obtain the seeds endosperms by scraping the seed coats with a stainless-steel knife and washed in surplus water (1/10 w/v) and milled using an attrition mill. The flour was dried in a moisture extraction oven (DHG- 9053 Model) at 65°C to a constant weight, cooled to ambient temperature and sieved through a 500 µm mesh-sized sieve to generate fine flour. They were packaged in airtight containers and stored at ambient conditions for further analysis and application. The production steps are as shown in
Figure 2.
Figure 1. Flow Chart for the Preparation of Flour from Boiled Seeds (Ukpo, Ofor, Achi and Akparata).
Figure 2. Flow Chart for the Preparation of Flour from Roasted Seeds (Ukpo, Ofor, Achi and Akparata).
2.2.3. Processing of Flour from Soaked Seeds
The third portion of the cracked seeds were soaked in distilled water in the ratio of 1/10(w/v) at ambient temperature for 8 h, 16 h and 24 h. The soaking liquors were drained at the elapse of each soaking time, de-coated to obtain the seeds endosperms by scraping the seed coats with a stainless-steel knife and washed in surplus water (1/5 w/v) and milled using an attrition mill. The flour was dried in a moisture extraction oven (DHG- 9053 Model) at 65°C to a constant weight, cooled to ambient temperature and sieved through a 500 µm mesh-sized sieved to generate fine flour. They were packaged in airtight containers and stored at ambient conditions for further analysis and application. The processing steps are as shown in
Figure 3.
Figure 3. Flow Chart for the Preparation of Flour from Soaked Seeds Sample (Ukpo, Ofor, Achi and Akparata).
2.2.4. Processing of Flour from Raw Seeds
The fourth portion of the cracked seeds was de-coated raw to obtain the seeds endosperms by scraping the seed coats with a stainless-steel knife and washed in surplus water (1/5 w/v) and milled using an attrition mill. The flour was dried in a moisture extraction oven (DHG- 9053 Model) at 65°C to a constant weight, cooled to ambient temperature and sieved through a 500 µm mesh-sized sieved to generate fine flour. They were packaged in airtight containers and stored at ambient conditions for further analysis and application. The processing steps are as shown in
Figure 4.
Figure 4. Flow Chart for the Preparation of Flour from Raw Seeds Sample (Ukpo, Ofor, Achi and Akparata).
2.3. De-fatting of Seed Flours
Cold (bulk) extraction method of
[1] | Abah, S. E. and Egwari, L. O. Methods of Extraction and Antimicrobial Susceptibility Testing of Plant Extracts. In: African Journal of Basic and Applied Sciences. 2011, 3 (5), 205-209. |
[1]
was used for the de-fatting of the flours. The full-fat flour (200 g) was wrapped in a white cotton fabric and soaked in 400 ml of Petroleum ether in an enclosed transparent glass jar and allow for a period of 72 hours. The wrapped flour was removed and rinsed in fresh Petroleum ether and manually squeezed to express out the entrapped solvent. The de-fatted flour was spread on a stainless tray for 4 hours to allow the trapped solvent to volatilize. The flour was sieved through a 500 µm mesh sized sieve, packaged in air-tight container and stored at ambient condition for further analysis and applications.
2.4. Seed Gum Extraction
The method of
was adopted for gum extraction from the de-fatted seed flours. Five (5) g of the flour samples were dispersed in 400 ml distilled water and hydrated continuously by means of a magnetic stirrer (FBI 15001, Fischer Scientific, UK) for 6 h. Four hundred (400) ml of Propane -2-ol was gradually (drop by drop) added to the hydrated flour solution. The precipitated gums that spool out of the solution were gently separated from the mother liquor with the use of perforated spoon. The clear liquor was decanted, while the trapped solvent was removed by filtering under suction in a Buchner funnel. The precipitates were dried in a moisture extraction oven (DHG-9053 Model) at 60°C till a flaky- dried gum (
Figure 5) could be easily scrapped off the drying tray. The resultant gums were cooled in desiccators to ambient temperature pulverized using the dry section of an electric blender and stored at ambient temperature in a sealed container.
2.5. Determination of Physical Properties of Gum Extracts
Physical properties (foaming capacity/stability, bulk density, water absorption capacity, oil absorption capacity, gelation temperature, wettability and swelling index) were determined on the extracted seed gums.
2.5.1. Foam Capacity/ Stability Determination
The method of
[27] | Onwuka, G. I. Functional properties and Food Toxicants In: Food Analysis and Instrumentation - Theory and Practice. Naphtali Prints Lagos. 2nd edition. 2018, Pp. 341 -381. |
[27]
was used. Two gram (2 g) of gum sample was blended with 100 ml distilled water in a warring blender (the suspension was whipped at 1000 rpm for 5 minutes). The mixture was poured into a 250 ml measuring cylinder and the volume was recorded after 30 seconds. Foam capacity was expressed as percent increase in volume using the formula (equation
1) below:
(1)
The foam stability was determined by recording the foam volume after 15, 30, 60 and 120 seconds after whipping. Foam stability was calculated using equation
2.
(2)
2.5.2. Emulsification Capacity Determination
The Method of
[27] | Onwuka, G. I. Functional properties and Food Toxicants In: Food Analysis and Instrumentation - Theory and Practice. Naphtali Prints Lagos. 2nd edition. 2018, Pp. 341 -381. |
[27]
was adopted. Emulsification capacity was estimated by blending 2 g of gum sample with 25 ml distilled water at room temperature for 30 seconds in a warring blender at 1600 rpm. After complete dispersion, 25 ml of vegetable oil (groundnut Oil) was added and the blending was continued for another 30 seconds, then it was put into a centrifuge tube and centrifuged at 1600 rpm for 5 minutes. The volume of oil separated from the sample after centrifuging was read directly from the tube. Emulsion capacity is expressed as the amount of oil emulsified and held per gram of sample.
Emulsion Capacity (%)(3)
2.5.3. Bulk Density Determination
This was done according to
[24] | Onimawo, I. A. and Akubor, P. I. Functional properties of food. In: Food Chemistry. Integrated Approach with Biochemical Background. Ambik Press Limited, Benin City, Nigeria. 2005, Pp 208-221. https://doi.org/10.1007/s11130-004-0027-0 |
[24]
. Ten (10 ml) capacity graduated measuring cylinder was filled with the gum sample and the initial volume was recorded. The cylinder was tapped continuously to displace air and vacuum until the volume becomes constant. The final volume was noted after it was leveled, and bulk density of the samples was calculated as shown in equation
4.
Bulk density (g/ml)(4)
2.5.4. Water Absorption Capacity Determination
The method as was described by
[27] | Onwuka, G. I. Functional properties and Food Toxicants In: Food Analysis and Instrumentation - Theory and Practice. Naphtali Prints Lagos. 2nd edition. 2018, Pp. 341 -381. |
[27]
was adopted. A gram (1 g) of each gum samples were weighed separately and the weight of the samples in a clean dry centrifuge tube was also taken. The sample and 10 ml distilled water were mixed thoroughly for 30 seconds, then the sample was allowed to stand for 30 minutes at room temperature and then centrifuged at 5000 rpm for 30 minutes, then the volume of free water (supernatant) was read directly from the graduated centrifuge tube. Density of water was assumed to be 1.0 g/ml. The water absorption was expressed as the amount of water retained by 1 g of gum (g/ml).
Water absorption capacity (g/ml)(5)
2.5.5. Oil Absorption Capacity Determination
The method as described by
[27] | Onwuka, G. I. Functional properties and Food Toxicants In: Food Analysis and Instrumentation - Theory and Practice. Naphtali Prints Lagos. 2nd edition. 2018, Pp. 341 -381. |
[27]
was adopted. A gram (1 g) of each gum samples were weighed separately and the weight of the samples in a clean dry centrifuge tube was also taken. Oil was mixed with the sample to make up to 10 ml dispersion. The sample and oil were mixed thoroughly for 30 seconds; the sample was allowed to stand for 30 minutes at room temperature and then centrifuged at 5000 rpm for 30 minutes. The volume of free oil was read directly from the graduated centrifuge tube. Density of oil was assumed to be 0.38 g/ml. The Oil Absorption was expressed as the amount of oil bound by 1 g of gum (g/ml) estimated with equation
6.
Oil absorption capacity (g/ml)(6)
2.5.6. Gelatinization Temperature Determination
The method described by
[27] | Onwuka, G. I. Functional properties and Food Toxicants In: Food Analysis and Instrumentation - Theory and Practice. Naphtali Prints Lagos. 2nd edition. 2018, Pp. 341 -381. |
[27]
was used. Ten percent (10%) suspension of the gum sample was prepared in a test tube. The formed aqueous suspension was heated in a boiling water bath with continuous stirring. The temperature after 30 seconds after gelatinization was visually noticed was recorded as the gelatinization temperature.
2.5.7. Wettability Determination
The method of
[24] | Onimawo, I. A. and Akubor, P. I. Functional properties of food. In: Food Chemistry. Integrated Approach with Biochemical Background. Ambik Press Limited, Benin City, Nigeria. 2005, Pp 208-221. https://doi.org/10.1007/s11130-004-0027-0 |
[24]
was adopted. One gram of the gum sample was weighed into a clean, dry test tube and was covered. The tube was clamped in-vertically on a retort stand 15 cm over 200 cm
3 distilled water container in 250 cm
3 beaker at room temperature. Gently the paper covering the tube was removed and the sample was allowed to fall under gravity into the beaker. The wetting time was recorded as the time (seconds) required for all the powder to be wetted and penetrate the surface of the still water.
2.5.8. Swelling Index Determination
The procedure described by
[9] | Ikegwu, O. J., Okechukwu, P. E. and Ekumankana, E. O. Physico-chemical and pasting characteristics of flour and starch from achi (Brachystegia eurycoma) seeds. Journal of Food Technology. 2010, 8(2), 58-66. https://doi.org/10.3923/jftech.2010.58.66 |
[9]
was used to determine the swelling indexes of the gum samples. One gram the gum sample was mixed with 10 ml of distilled water in a centrifuge tube and heated at 80°C for 30 min under continuous agitation. After heating, the suspension was centrifuged at 1500 rpm for 15 min. The supernatant was decanted and the weight of the paste taken. The swelling index was calculated as follows:
Where: H2 = final height
H1 = initial height
2.6. Statistical Analysis
The data obtained were subjected to statistical analysis such as simple description mean and standard deviation, Analysis of variance (ANOVA), using General Linear Model (GLM) procedure. A comparison test (LSD) was used to separate the means where significant differences existed.
Figure 5. Samples of Flaky Gum Extract.
3. Results and Discussions
3.1. Foaming Capacity of Seed Gums
Table 1 show that the gums' foaming capabilities under various processing techniques varied significantly (p < 0.05) among the legume varieties. Gums from roasted seeds showed the lowest foaming capabilities (15.43%), while those from boiled seeds had the highest (17.19%) on average.
A. africana gum exhibited the lowest foaming capacities among the gums that were removed from the cooked and soaked seeds, whereas
B. eurycoma gums had the highest foaming capacities. Their respective results fell between 15.43% and 18.97% and 15.85% and 18.90%. However,
M. sloanei gum exhibited the highest foaming capacity (17.04%) among the gums made from roasted seeds, whereas
D. microcarpum gum had the lowest (14.70%). According to
[22] | Odimegwu, E. N., Nwosu, J. N, Umelo, M. C., Olawuni, I. A. Akajiaku, L. O. and Oga, B. N. Effect of processing on the proximate and functional properties of “Akparata” (Afzelia africana) flour. European J. of Food Sci. and Tech. 2016, 4(2), 10-20. https://doi.org/10.2139/ssrn.4852192 |
[22]
, foaming capacity is influenced by factors such as: processing methods, temperature and nature of protein present which in turns affect the surface tension of the protein molecules in the food material. Reduction in the foaming capacities of the gum extracts from roasted seeds could be attributed to the nature and level of heat treatment involved which probably denatured the protein molecules responsible for foam formation
[21] | Nwosu, J. N., Ahotu, I., Ayozie, C., Udeozor, L. O. and Nwosu, N. N. The Proximate and Functional Properties of African Yam beans (S. sternocarpa) Seeds as affected by processing. Nigerian Food Jytournal. 2011, 29(2), 39-48. |
[21]
. The average foaming capacity of the gums from raw seeds as shown in
Table 2 was 16.44% and that of guar gum was 20.41%. Generally, increase in processing time significantly (p≤ 0.05) affected the foaming capacities of the gum extracts. Soaking increased this value to 17.04% (24 h), while boiling and roasting reduced the value to 16.27 % and 13.38% after 30 min processing time, respectively. From
Figure 7, the average foaming capacities of gum extracted from legume cultivars, slightly reduced from 16.71% to 16.70% with increase in pre-treatment levels. According to
[19] | Nwanekezi, E. C., Onugha, F. C., Arukwe, D. C. and Odimegwu, E. N. Proximate Composition and Hyperlipidaemia lowering potential of rice bran enriched with yam flour. Nigerian Food Journal. 2019, 37 (1), 11-23. |
[19]
, the foaming capacity of food material is related to the rate of reduction in the surface tension of air-water interface resulting from protein molecules absorption.
3.2. Foaming Stability of Seed Gums
For all the processing methods adopted in this research (
Table 1), the foaming stability of the gum extracted was as follows: 15.42% to 16.33%, 14.67% to 15.82% and 15.39% to 16.19%% for boiled, roasted and soaked seeds respectively. Flour from
D. microcarpum seeds generally had the lowest, while
A. africana had the highest value. According
, foaming stability is affected by so many factors which include: temperature, pH and processing methods. For all the cultivars, gums from boiled seeds had the highest foaming stability, while those from roasted seeds had the lowest. The same trend was followed in
Table 2 where roasting operation resulted to reduction (11.37%) in the foaming stability of the gum extracts after 30 min, while boiling (30 min) and soaking (24 h) slightly increased the foaming stability from 12.39% (raw) to 13.24% and 12.98%, respectively. According to
[29] | Peters, D. P. and Olapade, A. A. Effect of some processing methods on nutritional, functional and pasting characteristics of D. microcarpum Seed flours. Annals Food Science and Technology. 2017, 19(1), 69-78. |
[29]
, the minor decrease in the gums' ability to foam from the boiled and roasted seeds may be related to protein de-naturation brought on by heat processing (boiling and roasting). Food emulsions including ice cream, yoghurt, and salad creams could be stabilized by using gums with higher foam stability.
3.3. Emulsion Capacity of Seed Gum
As shown in
Table 1 and
Figure 5, gums from boiled seeds had the highest (28.99%), while those from roasted seeds had the lowest (25.77%) emulsion capacities. Moreover, increase in boiling time significantly (p ≤ 0.05) increased the emulsion capacities of the seed gums from 26.84% to 27.36%, while increase in roasting time as shown in
Table 2, significantly (p < 0.05) reduced the emulsion capacities of the seed gums from 26.84% to 21.66%. Gums from
A. africana seeds had the lowest emulsion capacities, whereas gums from
D. microcarpum seed had the highest emulsion capacities, with the exception of the gums from the roasted legume cultivars, where
M. sloanei had the highest concentration (32.99%). The emulsion capacity of the gum that legume seeds contain determines their ability to thicken soup, and according to
[25] | Onuegbu, N. C., Nworah, K. O., Essien, P. E., Nwosu, J. N. and Ojukwu, M. (2013). Proximate, Functional and Anti- nutritional properties of boiled Ukpo seeds (M. flagellips) Flour. Nigerian Food Journal, 31(1): 1-5. |
[25]
, boiling and other processing techniques increased the emulsion capacity of
Mucuna flagellips flour. Gums with high emulsion capacities will be suitable in the preparation of food emulsions such as ice- cream and yoghurt where they will serve as emulsifying agents. According to
[7] | Chinma, C. E., Azeez, S. O., Ezekiel, M. Y., Adetutu, M. A., Ocheme, O. B. and Danbaba, N. Functional Properties of Flours from Five Nigerian Rice Cultivars. Nigerian Food Journal, 2018, 36 (1), 141 - 149. L. |
[7]
, processing such as heat treatments can lead to a level of repulsion existing between the lipids and water which are the major components of an emulsion.
3.4. Bulk Density of Seed Gums
The bulk density of the seed gums was as follows: 0.48 g/ml to 0.57 g/ml (boiled), 0.54 g/ml to 0.74 g/ml (roasted) and 0.51 g/ml to 0.69 g/ml (soaked).
M. sloanei gums had the lowest bulk density for all processing methods while
B. eurycoma had the highest bulk densities (
Table 1). Generally, gums from roasted seeds had the highest (0.60 g/ml) bulk densities while those from boiled seeds had the lowest (0.52 g/ml). Increase in bulk density increases the rate of starch dispersion during reconstitution. As shown in
Table 2, the bulk density of gums from raw seeds was /ml. For gums extracted from seed roasted for 30 minutes, this value rose to 0.72 g/ml. All of the gum extracts from the various legume seeds had average bulk densities that were greater than the guar gum's (0.48 g/ml). According to
[6] | Bello, F. A., Udo, I. I. and Mbak, D. L. Proximate composition and functional properties of sprouted sorghum (Sorghum bicolor) and defatted fluted pumpkin seed (Telfairia occidentalis) flour blends. American Journal of Innovative Research and Applied Sciences, 2017, 3, 1-15. |
[6]
, bulk density increases with increase in particle size and low bulk density may be caused by the texture, density and loose structure of the starch polymers. It is therefore an important functional property in the prediction of packaging requirement, handling and wet- processing in the food industry
[4] | Aluge, O. O., Akinola, S. A. and Osundahunsi, O. F. Effect of malted sorghum on quality characteristics of wheat- sorghum-soybean flour for potential use in confectionaries. Food and Nutrition Sciences. 2016, 7, 1241-1252. https://doi.org/10.4236/fns.2016.713114 |
[4]
. Researchers have shown that low bulk density is desirable in granular material because it results to lower dietary bulk and reduces paste thickness during reconstitution.
3.5. Water Absorption Capacity of Seed Gums
Table 1 showed that the water absorption capacities of the gums extracted from the legume seeds under study significantly (p ≤ 0.05) varied from each other. For all the processing methods,
A. africana seed gums had the highest water absorption capacity. Moreover, on the average, gums from roasted seeds had the highest (5.25 g/ml) water absorption capacity, while those from boiled samples had the lowest (4.70 g/ml). The high-water absorption capacity of the gums from the roasted seeds could be associated with increase in the level of moisture lost from the seeds during the roasting process. From this research, gums from the roasted seeds with high water absorption capacities could be better applied in soup and sauce thickening where high water absorption capacities is of high importance
[7] | Chinma, C. E., Azeez, S. O., Ezekiel, M. Y., Adetutu, M. A., Ocheme, O. B. and Danbaba, N. Functional Properties of Flours from Five Nigerian Rice Cultivars. Nigerian Food Journal, 2018, 36 (1), 141 - 149. L. |
[7]
. Increase water absorption capacity is desirable in bakery products because the starch molecules need to imbibe moisture in dough formation. According to
[13] | Kaur, M. and Singh, N. Studies on functional, thermal and pasting properties of flour from different Chickpea (Cicer arietinum L.) Cultivars. Food Chemistry. 2005, 91(3), 403-411. https://doi.org/10.1016/j.foodchem.2004.06.015 |
[13]
, water absorption capacity of granular food materials is affected by the presence of hydrophobic amino acids in the sample and as an index of starch gelation measures the level of water that the starch is able to absorb
[28] | Onyeka, E. U. and Dibia, I. Malted weaning food made from maize, soya bean, groundnut and banana. J. Sci. Food Agric.2002, 82(5), 34-38. https://doi.org/10.1002/jsfa.1060 |
[28]
.
Table 2 showed that average water absorption capacity of gum extracted from raw seeds was 4.90 g/ml. Boiling and soaking treatments significantly (p ≤ 0.05) reduced the water absorption capacities of the extracted gums to 3.76 g/ml and 4.58 g/ml after 30 min and 24 h respectively, while roasting (30 min) significantly (p ≤ 0.05) increased it to 5.33 g/ml with increase in processing time. These results were in agreement with the findings of
[29] | Peters, D. P. and Olapade, A. A. Effect of some processing methods on nutritional, functional and pasting characteristics of D. microcarpum Seed flours. Annals Food Science and Technology. 2017, 19(1), 69-78. |
[29]
on the effect of processing methods on the functional properties of
Deterium microcarpum seed flours
. Although there were no significant differences (p > 0.05), the average water absorption capacity of seed gums decreased from 5.04 g/ml to 4.90 g/ml as pre-treatment levels increased. Guar gum had a higher water absorption capacity (5.89 g/ml) than the extracted gums from this study. Water absorption capacity is directly proportional to the level of starch molecules and gel-forming capacity of the macromolecules. Water absorption capacity of flour and gum is important in the determination of their utilization in aqueous food formulations such as dough and related products because flour with high water absorption capacity will reduce firming of bread by providing initial softness and smoothness of the dough before and after baking. The variation in the water absorption capacities of the gum extracted from the different legume seeds could be as a result of variations in the physico- chemical nature of the different legume seeds
[30] | Shimelis, A. E., Meaza, M. and Rakshit, S. Physico-chemical Properties, Pasting Behaviour and Functional Characteristics of Flours and Starches from Improved Bean (Phaseolus Vulgaris L.) varieties Grown in East Africa. CIGR E-journal. 2006, 8, 1-18. |
[30]
.
3.6. Oil Absorption Capacity of Seed Gums
The oil absorption capabilities of seed gums differed considerably (p < 0.05) from one another (
Table 1). Generally, the oil absorption capacity of the gums from roasted seeds was the highest (4.64 g/ml), while that of boiled seeds was the lowest (4.12 g/ml). Among the legume cultivars, gums from
M. sloanei showed the lowest oil absorption capacity, while those from
A. africana had the highest for all of the processing methods tested. The results are as follows: (3.25-5.13) g/ml for boiled seeds, (3.26-6.53) g/ml for roasted seeds, and (2.99-6.17) g/ml for soaking seeds. Oil absorption capacity of granular particles is usually a measure of the ability of their components such as protein and starch to physically bind fat through capillary attraction
[10] | Issoufou, A., Mahamadou, E. G., Tidjani, A., Moutaleb, O. H. and Gou-Wei, L. Functional and sensory Properties of tuwan aduwa: A traditional meal made from foxtail millet and dessert date. Nigerian Food Journal. 2017, 35(1), 1-7. |
[10]
. According to
[3] | Alimi, B. A., Workneh, T. S. and Meireles, M. A. A. Effect of hydro-thermal modifications on the functional, pasting and structural properties of false banana (E. ventricosum) starch, Food Biophysics. 2016, 11, 30, 248-256. https://doi.org/10:1007/s11483-016-9435-6 |
[3]
, this property is of great importance where emulsification is required and is usually affected by particle size, shape, pH, and ionic strength
[31] | Tharise, N., Julianti, E. and Nurminah, M. Evaluation of physico- chemical and functional properties of composite flour from cassava, rice, potato, soybean and xathan gum as alternative of wheat flour. International Food Research Journal. 2014, 21 (4), 1641 -1649. |
[31]
. From
Table 2, the oil absorption capacities of the extracted gums increased significantly (p ≤ 0.05) with increase in the roasting (4.42-4.63) g/ml and soaking (3.98-4.01) g/ml time, but reduced significantly (p ≤ 0.05) with increase in boiling (3.99-3.26) g/ml time. The oil absorption capacities of both the gums from the different raw and processed seeds were all lower than that of the guar gum (5.75 g/ml). The increase in the oil absorption capacities of gum extracts from roasted seeds could be attributed to the fact 22 that heat processing facilitates the oil absorption capacities of food particles. Oil absorption capacity of granular substances is an indication of the level of hydrophobic proteins which determines the level of binding of lipids. Researches have shown that high oil absorption capacity aids in flavour retention and increases sensory attributes such as mouth-feel, gum extracts from roasted seeds will be preferred for use in food formulations such as baked and pasta products where such sensory attributes are required
[21] | Nwosu, J. N., Ahotu, I., Ayozie, C., Udeozor, L. O. and Nwosu, N. N. The Proximate and Functional Properties of African Yam beans (S. sternocarpa) Seeds as affected by processing. Nigerian Food Jytournal. 2011, 29(2), 39-48. |
[21]
.
3.7. Gelation Temperature of Seed Gums
Table 1 showed that no particular trend was followed on gelation temperatures of the gum extracted from the different cultivars under different processing methods and levels of pre- treatments. There was no significant (p > 0.05) difference between the gelation temperatures of the gum from boiled
B. eurycoma (73.09°C) and boiled
A. africana (72.18°C) seeds. Gums from roasted seeds had the highest average gelation temperature (74.56°C), while those from boiled seeds had the lowest (70.08°C). These also reflected in
Table 2 where the average gelation temperature of the gums from raw seeds (68.47°C) increased with increase in roasting and soaking time to 77.72°C (30 min) and 70.18°C (24 h) respectively while those from boiled seeds slightly reduced with increase (30 min) in boiling time (67.47°C). There were no significant (p > 0.05) differences observed in the gelation temperatures of guar gum (76.27°C) and those from roasted (20 and 30) min seeds. Also, increasing the soaking duration had no significant (p > 0.05) effect on the gelation temperatures of the generated gums. Gelation temperature is the temperature at which starch molecules absorb moisture and swell to create a viscous mass known as gel. According to
[22] | Odimegwu, E. N., Nwosu, J. N, Umelo, M. C., Olawuni, I. A. Akajiaku, L. O. and Oga, B. N. Effect of processing on the proximate and functional properties of “Akparata” (Afzelia africana) flour. European J. of Food Sci. and Tech. 2016, 4(2), 10-20. https://doi.org/10.2139/ssrn.4852192 |
[22]
, gelation temperature of starch is a function of the degree of starches contained in the food, and different types of starchy materials experience this at different temperature levels due to changes in their chemistry
[15] | Malomo, O., Ogunmoyela, O. A. B., Adekoyeni, O. O., Jimoh O., Oluwajoba, S. O. and Sobanwa, M. O. Rheological and functional properties of soy-poundo yam flour. Int J Food Sci. Nutr. Eng. 2012, 2(6), 101-107. https://doi.org/10.5923/j/food.20120206.01 |
[15]
.
3.8. Wettability of Seed Gums
The wettability of the gums from the various cultivars under different processing procedures differed slightly; gums from roasted seeds (
Table 1) had the highest (26.44 s), while those from boiled seeds had the lowest (22.54 s). The wettability of gums from seeds decreased slightly from 23.43 s (raw) to 22.09 s with increasing boiling time (30 min). However, increasing roasting time significantly (p ≤ 0.05) increased the wettability of the gum extracts, while no significant (p > 0.05) difference was observed in the wettability of the gums as soaking time increased (
Table 2). This is because according to
[17] | Mir, S. A. and Bosco, S. J. D. Cultivar difference in physicochemical properties of starches and flours from temperate rice of Indian Himalayas. Food Chemistry. 2014, 15, 448-456. https://doi.org/10.1016/j.foodchem.2014.02.057 |
[17]
, there is an increased tendency of fibrous materials to absorb moisture as was observed in the water absorption capacities previously discussed. The wettability of guar gum (21.27 s) was lower than that of the gums from the different legume cultivars under study. With respect to levels of pre-treatments, as shown in
Table 2, the wettabilities of gums from all the cultivars under examination had no significant (p > 0.05) differences as the pre-treatment levels increased. Wettability is a function on the nature and level of polysaccharides present in the sample and it has a correlation with water absorption capacity and swelling power
[23] | Oluwole, D. M. and Aderigbige, Y. E. Microbiology and proximate composition of ogiri, A pastry produced from different melon seeds. New York Science Journal, 2010, 3(4), 18-27. https://doi.org/10.7537/marsnys03410.03 |
[23]
.
3.9. Swelling Index of Seed Gums
The swelling indexes of the gums from different legume cultivars under different processing methods significantly (p ≤ 0.05) differed from each other. As shown in
Table 1 and
Figure 6, gums from roasted seeds had the highest average swelling index (5.30), while those from soaked seeds had the lowest (4.05). Comparing the gums from the different legume seeds,
A. africana gums had the lowest swelling index, while
D. microcarpum gums had the highest and they are as follows: (5.78) boiled, (6.09) roasted and (5.64) soaked. The average swelling index for the gum extracted from raw seeds was 4.09 and this significantly (p ≤ 0.05) increased with increase in roasting time and reduced with increase in boiling and soaking time (
Table 2). Roasting increased the swelling index to 5.59, while boiling and soaking reduced the swelling indexes of extracted gums to 3.75 and 3.23 after 30 min and 24 h processing, respectively. Results showed that the swelling indexes of both raw and processed seeds were all lower than that of guar gum (6.22). Lower swelling index observed in the gum extracts from raw seeds could be associated with the level of inertness of starch in the raw seeds. From the results, there is an indication that gums from the roasted seeds (high swelling index) would be better applied to bakery products in order to improve the baking performance of the dough
[5] | Amandikwa, C., Bede, E. N. and Eluchie, C. N. Effect of processing methods on proximate composition, mineral content and functional properties of ‘ofor’ (Deterium microcarpum) seed flour. International Journal of Science and Research. 2017, 6 (5), 966-970. https://doi.org/10.21275/ART20172977 |
[5]
. The average swelling indexes of the gums from the different legume seeds reduced slightly from 4.60 to 4.57 with increase in pre-treatment levels. According to
[22] | Odimegwu, E. N., Nwosu, J. N, Umelo, M. C., Olawuni, I. A. Akajiaku, L. O. and Oga, B. N. Effect of processing on the proximate and functional properties of “Akparata” (Afzelia africana) flour. European J. of Food Sci. and Tech. 2016, 4(2), 10-20. https://doi.org/10.2139/ssrn.4852192 |
[22]
, the swelling indexes of granular materials are determined by the capacity of some intermolecular hydrogen bonds to loosen during processing, such as heating, allowing for increased water absorption and granule expansion. The swelling power of most starch granules is quite low at cold temperatures and increases with heating. This is because, as the temperature rises, intermolecular hydrogen connections break and networks loosen, enabling more moisture to enter and granules to expand. Thus, there is a linear relationship between wettability, water absorption capacity and swelling index. Amylose in starch tend to retard and resist the swelling power of starch and the level of binding forces holding the granules is been shown on the swelling power of such starch
[7] | Chinma, C. E., Azeez, S. O., Ezekiel, M. Y., Adetutu, M. A., Ocheme, O. B. and Danbaba, N. Functional Properties of Flours from Five Nigerian Rice Cultivars. Nigerian Food Journal, 2018, 36 (1), 141 - 149. L. |
[7]
. The higher the binding forces, the lower the swelling. Moreover, in as much as this property is peculiar to starch, it is also being affected by the interaction of the starch with other components such as protein and fat
[2] | Agume, A. S. N., Njin tang, N. Y. and Mbofung, M. F. Effect of soaking and roasting on the physicochemical and pasting properties of soybean flour. Food. 2017, 6, 12. https://doi.org/10.3390/foods6020012 |
[2]
. The formation of potein- amylose complex according to
[30] | Shimelis, A. E., Meaza, M. and Rakshit, S. Physico-chemical Properties, Pasting Behaviour and Functional Characteristics of Flours and Starches from Improved Bean (Phaseolus Vulgaris L.) varieties Grown in East Africa. CIGR E-journal. 2006, 8, 1-18. |
[30]
lowers the swelling index of starch.
4. Conclusion
Data from water absorption capacity (5.25 g/ml) and oil absorption capacity (4.53 g/ml) of gums from roasted seeds are indications that they might find application in baked products. The swelling index (6.09) of D. microcarpum seed gum was very close to that of guar gum (6.22) and is an indication that it could compete favorably with guar gum in foods where increase in volume is required. Results from this research showed that food gums for industrial purposes is achievable from legume seeds used in this research.
Table 1. Effect of Processing Methods on Functional Properties of Gums from Selected Legume Seeds.
Processing methods | FC (%) | FS (%) | EC (%) | BD (g/ml) | WAC (g/ml) | OAC (g/ml) | GT(°C) | Wet (s) | SI |
Boiling | | | | | | | | | |
A. Africana | 15.43d | 16.33a | 20.31d | 0.53b | 5.78a | 5.13a | 72.18a | 24.30a | 2.97d |
M. sloanei | 17.08c | 16.10c | 33.08b | 0.48d | 4.11d | 3.25d | 65.78c | 22.63c | 5.49b |
D.microcarp | 17.28b | 15.42d | 33.62a | 0.49c | 4.17c | 4.10b | 69.26b | 20.29d | 5.78a |
B. eurycoma | 18.97a | 16.15b | 28.97c | 0.57a | 4.74b | 4.01c | 73.09a | 22.93b | 3.29c |
Mean | 17.19 | 16.00 | 28.99 | 0.52 | 4.70 | 4.12 | 70.08 | 22.54 | 4.38 |
Roasting | | | | | | | | | |
A. Africana | 14.92c | 15.82a | 20.22d | 0.55c | 7.14a | 6.53a | 76.52b | 26.02c | 3.90d |
M. sloanei | 17.04a | 15.74b | 32.99a | 0.54c | 4.19c | 3.26d | 66.79d | 24.99d | 5.53c |
D.microcarp | 14.70d | 14.67d | 25.59b | 0.59b | 4.84b | 4.33c | 81.29a | 28.15a | 6.09a |
B. eurycoma | 15.04b | 15.07c | 24.27c | 0.74a | 4.84b | 4.44b | 73.63c | 26.61b | 5.66b |
Mean | 15.43 | 15.32 | 25.77 | 0.60 | 5.25 | 4.64 | 74.56 | 26.44 | 5.30 |
Soaking | | | | | | | | | |
A. Africana | 15.85d | 16.19a | 20.41d | 0.50d | 6.56a | 6.17a | 73.12a | 26.02a | 3.31d |
M. sloanei | 17.99b | 15.96c | 29.69b | 0.51c | 5.02b | 2.99d | 71.73a | 26.95a | 3.92b |
D.microcarp | 17.31c | 15.39d | 32.27a | 0.54b | 4.13d | 4.02c | 69.79b | 20.27b | 5.64a |
B. eurycoma | 18.90a | 16.16b | 28.60c | 0.69a | 4.15c | 4.08b | 70.35b | 21.39b | 3.35c |
Mean | 17.51 | 15.92 | 27.99 | 0.55 | 4.96 | 4.32 | 71.50 | 23.66 | 4.05 |
Guar gum | 20.41 | 29.24 | 36.79 | 0.48 | 5.89 | 5.75 | 76.27 | 21.27 | 6.22 |
Means on the same column with different superscript are significantly (p ≤ 0.05) different from each other
Key: FC - Foaming Capacity, FS - Foaming Stability, EC - Emulsion Capacity, BD - Bulk Density, WAC - Water Absorption Capacity, OAC - Oil Absorption Capacity, GT - Gelation Temperature, Wet - Wettability, SI - Swelling Index
Table 2. Functional Properties of Gums from Selected Legume Seeds as affected by Processing Time.
Processing Time (min.) | FC (%) | FS (%) | EC (%) | BD (g/ml) | WAC (g/ml) | OAC (g/ml) | GT (°C) | Wet (s) | SI |
0 (Raw) | 16.44b | 12.39e | 26.84e | 0.54ab | 4.90b | 3.87c | 68.47bc | 23.43a | 4.09b |
Boiling | | | | | | | | | |
10 | 16.43bc | 12.41d | 28.87d | 0.55a | 4.63c | 3.99b | 69.47b | 23.41a | 3.97c |
20 | 16.42c | 12.73c | 27.11c | 0.53b | 4.32b | 3.76d | 68.72bc | 22.49b | 3.89d |
30 Roasting | 16.27d | 13.24b | 27.36b | 0.50c | 3.76e | 3.26e | 67.47c | 22.09c | 3.75e |
10 | 13.46c | 11.96e | 21.81c | 0.61c | 5.03d | 4.42d | 73.91b | 28.10c | 5.26d |
20 | 13.42d | 11.67d | 21.76d | 0.68b | 5.12c | 4.54c | 76.43a | 28.89b | 5.32c |
30 | 13.38e | 11.37e | 21.66e | 0.72a | 5.33b | 4.63b | 77.72a | 30.55a | 5.59b |
Soaking (h) | | | | | | | | | |
8 | 16.81d | 12.44d | 25.44d | 0.55bc | 4.77c | 3.98c | 71.43b | 25.36a | 3.39c |
16 | 16.87c | 12.59c | 25.38e | 0.56b | 4.68d | 3.97d | 71.14b | 25.47a | 3.35d |
24 | 17.04b | 12.98b | 25.51c | 0.62a | 4.58b | 4.01b | 70.18b | 25.44a | 3.23e |
Guar gum | 20.41a | 29.24a | 36.79a | 0.48d | 5.89a | 5.75a | 76.27a | 21.27b | 6.22a |
Means on the same column with different superscript are significantly (p ≤ 0.05) different from each other
Key: FC - Foaming Capacity, FS - Foaming Stability, EC - Emulsion Capacity, BD - Bulk Density, WAC - Water Absorption Capacity, OAC - Oil Absorption Capacity, GT - Gelation Temperature, Wet - Wettability, SI - Swelling Index
Figure 6. (a-c). Functional Properties of Legume Seed Gums as affected by Processing Methods.
Figure 7. (a-c). Functional Properties of Seed Gums as Affected by Pre-treatment Levels.