Physicochemical properties and cooking quality of four new cultivars of Nigerian cowpea (Vigna unguiculata L walp)

Abstract

Abstract:Four new cowpea cultivars (IT8 1 D-699, IT82E-18, IT84S-2246-4 and TVx 3236) were evaluated for their physicochemical properties and cooking quality. The four cultivars fell into two categories (rough and smooth) according to testa texture, and varied in seed dimensions and weights with IT81D-699 and IT84S-2246-4 having smaller seed volume than IT82E-18 and TVx 3236. Leached solids, swelling capacity and seed coat percentage were within a range of 0 , 3 3 4 9 4 g per 100 g, 77.0-1235 g per 100 g and 56-15.7% w/w of dry beans respectively. The total polyphenol content of the brown or cream-coloured beans were similar (1.53-1.96 mg g-') but higher than the amount (1.03 mg g-l) found in the white bean. Cooking time varied between 29 and 37 min and was reduced by about 21 % following a presoaking treatment in water for 12 h at room temperature (28 "C). Cooking time was significantly positively correlated ( P < 0.05) with seed weight ( r = 0.82) and seed volume ( r = 0.75). Water absorption was not related to cooking time, and was much lower for the cultivar with larger seeds. No significant difference in hardness was found betwecn unsoaked beans cooked for 30 min and soaked beans cooked for 10 min, suggesting that cookability for all cultivars was improved through soaking.

Evaluation of selected food characteristics of three advanced lines of Nigerian soybean (Glycine max (L.) Merr.)

“…After soaking (12hours), there were no significant (/9 > 0.05) differences between the cooking times of the lines. Reduction in cooking time as a result of presoaking treatment in water have been reported for soybeans [6], dry beans [15], and cowpeas [13,25]. The effect of soaking time on water absorption of the soybean lines is shown in Figure 1.…”

“…The final weight was expressed as a percentage of total initial seed weight. Leached solids and swelling capacity were determined using a modification [13] of the method described by Akinyele et al [12].…”

“…Seed volume and seed density were determined using the water displacement method described by Phirke et al [15]. For the determination of seed coat percentage, the procedure described by Phirke et al [15] as modified by Giami & Okwechime [13] was followed. Fifty seeds of each line were weighed and soaked in 100 ml distilled water for 1 hour at room temperature (28• 1 ~ The seed coats were removed manually, drained on filter paper, weighed wet and re-weighed after drying to constant weight (60 ~ 24 hours) by the air oven method [16].…”

“…In addition, the cooking quality of legumes has been shown to be affected by varietal differences [7], length and temperature of storage [8], and structure and composition of seeds [9]. Some physical properties, such as seed size or weight, seed volume, swelling capacity, percent seed coat and seed coat texture of certain beans have been associated with their cooking quality [4,[10][11][12][13].…”

Compositional and nutritional properties of selected newly developed lines of cowpea (Vigna unguiculata L.Walp).

“…Although characterization of these advanced lines of cowpeas (IT81D-699; IT82E-18; IT84S-2246-4; TVx 3236) for physicochemical, functional and cooking properties has been done (Giami and Okwechime, 1993;Giami et al, 2001), information on their chemical and nutritional properties, as influenced by heat treatment is lacking. Therefore, the aim of this study was to evaluate the chemical composition and protein quality of these advanced lines of cowpea and the changes brought about by boiling and steaming treatments of the seeds.…”