Yam bean ( Pachyrhizus spp.) is legume crop that not only produces edible roots but also has a high yield of unutilized seeds. Although the yam bean seeds are rich in protein, they are not used due to a high content of toxic rotenone. In this study, yam bean seeds were detoxified and the nutritional and functional properties of their protein determined to assess the proteins’ potential for applications. Seeds of 10 accessions (2 accessions of P. erosus, 4 accessions of P. ahipa and 4 accessions of P. tuberosus) were analyzed for proximate composition, pasting and functional properties (bulk density, least gelation concentration, water absorption capacity, oil absorption capacity, emulsifying capacity, emulsion stability, foaming capacity, foam stability and protein solubility). The results showed that yam bean seeds contained: 29.2 - 32.1 g/100g proteins, 31.3 - 33.0 g/100 g carbohydrates, 24.1 - 25.6 g/100g total fat, 7.5 - 8.1 g/100g crude fiber and 3.4 - 4.1 g/100g ash. The defatted P. erosus seed flour contained 45.6 - 48.8 g/100g protein, 32.6 - 36.5 g/100g total carbohydrate, 6.7 - 7.1 g/100g crude fiber, 6.0 - 6.4 g/100g ash and 5.2/100 g crude fat. The defatted yam bean seed flour exhibited relatively high protein solubility (68.0% - 70.4%), least gelation concentration (14%), water absorption capacity (2.8% - 2.9%) and oil absorption capacity (1.5%). The defatted flour exhibited emulsifying capacity of 35.7% - 36.0%, emulsion stability of 33.2% - 33.5%, foaming capacities of 42% and foam stability of 25.1% - 25.8%. With respect to pasting properties, the defatted yam bean seed flours exhibited pasting temperature of 80.0?C - 81.3?C, peak viscosity of 145.5 - 146.7 RVU, trough viscosity of 95.1 - 102.0 RVU, break down of 43.5 - 51.6 RVU, set back of 252.9 - 258.1 RVU and final viscosity of 348 - 360 RVU. The results show that yam bean seed has potential for use in both food and non-food applications.
The yam bean crop belongs to the genus Pachyrhizus and is a close relative of soybeans and phaseolus bean [
There is a need to exploit the food (nutritional) and industrial potentials of yam bean seeds. However, this requires prior information and understanding of desirable functional properties and the behavior of the material in systems during processing, manufacturing, storage, preparation as well as consumption [
Yam bean is an underutilized crop and was only recently introduced in farming systems outside South America. There is relatively limited information on properties of yam bean seeds and their derivatives. The lack of information on many basic aspects of underutilized crops such as the yam bean hinders their development and sustainable utilization. There is a need to get more information and understand the characteristics of this crop for its optimal use and application in areas where it is newly introduced. Therefore, the objective of this study was to determine the nutrient composition of seeds of Pachyrhizus spp. as well as functional properties of its defatted seed flour as the first step in identifying potential food and technological applications.
Yam bean seed samples of P. ahipa, P. tuberosus and P. erosus were obtained from International Potato Center (CIP)-Uganda office. The seeds were planted and grown in Uganda at National Crops Resources Research Institute (NaCRRI)-Namulonge. Seed samples from a total of 10 selected accessions (
The collected yam bean seeds were cleaned to remove extraneous matter and then milled to fine flour using Hammer mill (8’ Laboratory Mill, Christy Hunt Agricultural Ltd, Suffolk-England) fitted with 0.5 mm screen. The flour was then stored in a refrigerator at 4˚C until use. The seed flour sample destined for the determination of functional properties was defatted by mixing with hexane at a flour/solvent ratio of 1:10 w/v, for 24 hour with
Species | Selected accessions* | |||
---|---|---|---|---|
P. ahipa | 209031(UYB19) | 209033 (UYB21) | 209035 (UYB23) | 209006 (UYB03) |
P. tuberosus | 209060 (UYB40) | 209061 (UYB41) | 209054 (UYB35) | 209058 (UYB38) |
P. erosus** | 209017 (UYB06) | 209018 (UYB07) |
*Accession codes in brackets are CIP-Uganda codes corresponding to CIP-Limacodes. **Two accessions (UYB 06 and UYB 07) from the P. erosus species were further selected for assessment of pasting and functional properties.
constantstirring. The solvent was separated by centrifuging with a Fisher Scientific Centrific (225; Fisher Scientific, Pittsburg, PA, USA) at 6500 rpm for 15 minutes followed by air drying of the flour at room temperature for 8 hours. The defatted flour was stored at 4˚C until use.
The proximate composition of the yam bean seed flours was determined by standard methods [
The bulk density of the defatted flour was determined according the method described by Butt and Batool [
This was determined according to the method described by Mugendi et al., [
Water and oil absorption capacities were determined according the method described by Appiah et al. [
Protein solubility was determined according to the method of Butt and Batool [
Emulsifying properties (emulsifying capacity and stability) were determined according to the method described by Butt and Batool [
Emulsion stability was determined in a similar way to that of emulsion capacity except that the emulsion was initially heated in a water bath at 85˚C for 30 minutes and subsequently cooled to 25˚C prior to centrifugation.
The foaming capacity and stability were determined according the method of Butt and Batool [
The pasting properties of defatted yam bean seed flours were analyzed with a Series 4 Rapid Visco Analyzer (RVA) (Newport Scientific from Australia) with Thermocline for Windows software. The analysis was done using standard one profile. The flour suspensions (6.72 g in 25.28 ml H2O) corrected to 14% moisture content were exposed to the following time/temperature sequence: 50˚C for 1 minute, heating from 50˚C to 95˚C at 12.16˚C /minute, maintained at 95˚C for 2.5 minutes, and cooled from 95˚C to 50˚C at 11.84˚C/minutes rate. The apparent viscosity was expressed in RVU.
All experimental analyses in this study were done in triplicates. All the data analysis was done using SPSS version 16.0 Software. Analysis of variance (ANOVA) was performed to generate treatment means and Least Significant Difference (LSD) (P < 0.05) values were used to separate the means.
Proximate composition (
the seeds P. erosus, P. tuberosus and P. ahipa except for crude fiber. The results for crude protein and total lipids content in this study are in agreement with those reported by Grüneberg et al. [
The results in this study revealed that the levels of protein and oil of yam bean seed are high compared to that of other legumes like chick peas which was reported to have 24.2 g/100g and 5.6 g/100g for crude protein and total fat, respectively [
Species (number of accessions from each) | |||
---|---|---|---|
Composition | P. erosus (n = 2) | P. ahipa (n = 4) | P. tuberosus (n = 4) |
Moisture content | 6.48c (1.27)* | 4.81a (0.72) | 5.97b (0.71) |
Crude protein | 30.13b (0.69) | 29.23a (2.07) | 32.16c (0.22) |
Total fat | 25.58c (0.82) | 25.04b (0.82) | 24.14a (2.28) |
Crude fiber | 8.07b (0.47) | 7.48b (0.65) | 4.18a (0.26) |
Total ash | 3.36a (0.04) | 3.91b (0.14) | 4.12c (0.25) |
Total carbohydrates | 32.10b (0.39) | 34.54c (2.70) | 28.67a (5.53) |
Means values in the same row with different superscript letters are significantly different (P ≤ 0.05). *Values in parentheses are standard error (SE) of the respective means.
Macarulla, Del Barrio and Martȋnez [
The oil content in the yam bean seeds is only lower than that of Arachis hypogaea (peanut) among legumes [
The results of proximate composition of defatted yam seed flour (
Defatting with hexane resulted in an apparent increase in the protein and other nutrient contents, which is attributable to the removal of the lipids and lipid soluble components. With regard to the high protein content, the yam bean seed flour has potential to be used in a variety of food and non food industrial applications. The direct use of defatted flours as functional ingredients play an important role in industries because of their lower production cost compared to that of protein concentrates [
The measured functional properties did not show significant difference between the two accessions of P. erosus studied (
Bulk density depicts the behaviour of the material in dry mixes and is an important parameter that can determine packaging requirements of the product [
Component | Defatted yam bean seed flour | |
---|---|---|
UYB06 (g/100g) | UYB07 (g/100g) | |
Moisture | 10.45a ± 0.11 | 10.47a ± 0.16 |
Crude protein | 45.57a ± 1.20 | 48.78b ± 2.63 |
Total fat | 5.16a ± 0.03 | 5.16a ± 0.06 |
Crude fiber | 6.74a ± 0.03 | 7.13a ± 0.10 |
Ash | 6.0a ± 0.03 | 6.38a ± 0.09 |
Total Carbohydrates | 36.50b ± 1.11 | 32.55a ± 2.41 |
The values in the table are means of triplicate determinations ± SD. Mean values in the same row with different superscript letters are significantly different (P ≤ 0.005).
Functional properties | Accession | |
---|---|---|
209017 (UYB 06) | 209018 (UYB 07) | |
Bulk density(g/cm3) | 0.59a ±0.00 | 0.59a ± 0.00 |
Least gelation concentration (%) | 14.00a ± 0.00 | 14.00a ± 0.00 |
Water absorption capacity (g/g) | 2.81a ± 0.02 | 2.90a ± 0.04 |
Oil absorption capacity (g/g) | 1.52a ± 0.02 | 1.48a ± 0.02 |
Emulsion capacity (%) | 35.70a ± 1.40 | 36.02a ± 2.80 |
Emulsion stability (%) | 33.45a ± 6.10 | 32.15a ± 8.37 |
Foaming capacity (%) | 42.00a ± 2.00 | 42.00a ± 3.46 |
Foam stability (%) | 25.80a ± 6.19 | 25.10a ± 5.22 |
Protein solubility (%) | 70.35a ± 1.25 | 68.00a ± 1.90 |
The values indicated in the table are means of triplicate determinations ± SD. Mean values in the same row with the same superscripts are not significantly different (P ≤ 0.05) for various functional properties of two accessions of yam bean seed flours.
Foh, Kamara and Guo-Wei [
Gelation is an aggregation of denatured protein molecules. The LGC results for yam bean seed flours in this study were similar to the results reported for lupin seed flour (14%) [
Water and oil absorption capacities (WAC, OAC) are useful indices of the ability of the protein in the material to prevent fluid loss from a product during food storage or processing [
The results of WAC for the defatted yam bean seed flours exhibited no significant difference between the two accessions (UYB 06 and UYB 07) (
The defatted yam bean seed flour showed moderate oil absorption capacity (OAC) (
Interactions of water and oil with proteins are very important in food systems because of their effects on the flavor and texture of foods [
The formation and stability of emulsions is very important in food systems such in mayonnaise and the emulsifying properties are usually attributed to the flexibility of solutes and exposure of hydrophobic domains [
Several natural and processed foods, such as milk, egg yolk, coconut milk, soy milk, butter, margarine, mayonnaise, spreads, salad dressings, frozen desserts, frankfurter, sausage, and cakes, are emulsion-type products where proteins play an important role as emulsifiers [
Proteins with high emulsifying capacity such as egg york is good for products such as salad dressing, sausages, bologna, soups, confectionery, frozen dessert and cakes [
The foaming capacity (FC) of a protein refers to the amount of interfacial area that can be created by the protein while foam stability refers to the ability of protein to stabilize against gravitational and mechanical stresses. Foam formation and stability are a function of the type of protein, pH, processing methods, viscosity and surface tension [
Egg white powder which is widely used for its excellent foaming characteristics has been reported to have higher FC values of 97.5% and FS values of 78.3 % [
Protein solubility is probably the most critical functional property since it affects other properties such as emulsification, foaming and gelation (Fekria et al., 2012). Protein solubility is influenced by many factors such as origin of the protein, processing conditions, pH, ionic strength as well as presence of other ingredients [
Industrial application of proteins such as in the production of fibres, adhesives, ingredients of coating, emulsifiers, food additives and different food products depend upon bringing proteineous materials into solution [
When flours are heated in an aqueous environment, they undergo a series of changes known constituting gelatinization and pasting [
The pasting temperature provides an indication of the minimum temperature required for cooking [
Peak viscosity reflects the ability of starch to swell freely before their physical breakdown [
The peak viscosity indicates the water binding capacity of the flour [
The trough viscosity, which is the minimum value in constant temperature phase of the RVA profile, measures the ability of the paste to withstand breakdown during hot and constant shear conditions. The defatted yam bean seed flour for the two accessions (UYB 06 and UYB 07) of P. erosus exhibited lower trough viscosities compared to those reported for corn flour (225.5 RVU) and Brachystegia eurycoma seed flour (229.25 RVU) [
The final viscosity which is the viscosity after holding cooked starch at 50˚C and represents cooked starch
Viscosity/RVU | ||||||||
---|---|---|---|---|---|---|---|---|
Sample | Peak Time/Min | Pasting Temp/˚C | Peak Viscosity | Trough Viscosity | Break Down | Final Viscosity | Setback | |
UYB 06 | 6.15a ± 0.20 | 79.97a ± 0.06 | 145.50a ± 2.11 | 102.03a ± 2.14 | 43.47a ± 0.05 | 360.14a ± 5.55 | 258.11a ± 3.80 | |
UYB 07 | 6.11a ± 0.08 | 81.33b ± 0.46 | 146.72a ± 3.10 | 95.11b ± 0.83 | 51.61b ± 3.92 | 347.97a ± 10.46 | 252.86a ± 11.28 | |
*Values in the table are means of triplicate determinations± SD. Means in the same column with same superscript letter are significantly different (P ≤ 0.05).
stability. The final viscosity was almost twice the peak viscosity (
The study established that yam bean seed flour has good characteristics which can foster its use in both food and non food systems. The results of pasting and functional characteristics observed in the study indicated that defatted yam bean seed flour has potential industrial applications and these may include: manufacture of fillers, emulsifiers, stabiliser, paper, adhesives, bioplastics among others. Yam bean seed flour, however exhibited rather low emulsion and foaming capacities compared to other legume seed flours and therefore may not be suitable for use in products or systems that require emulsification or foaming. If rotenone can be economically and effectively removed from yam bean seed, the flour could gain application in food processing as a functional ingredient otherwise the starch and protein yam bean seed flour could be considered for non food industrial applications such as in the paper, adhesive, bioplastics and textile industries.
The authors acknowledge the International Potato Centre for the financial and technical support that made this work possible under her Belgium Technical Cooperation funded project “Enhancing the nutrient rich yam bean (Pachyrhizus spp.) to improve food quality and availability and sustainability of farming systems in Central and West Africa.”