Rapid screening methods to evaluate cowpea cooking characteristics

Abstract

Current methods of evaluating cooking quality of grain legumes are inefficient and costly. As a result, breeders tend to delay cooking quality evaluations until late in the breeding process after the number of breeding lines has been markedly reduced. Cooking quality evaluations conducted earlier in the process, when genetic variation for these traits is high and can be exploited by selection, would maximize the probability of developing cultivars with greater functionality and consumer acceptability. This study aimed to develop a rapid, low-cost screening method to evaluate the cooking quality attributes of cowpea (Vigna unguiculata L. Walp.) dry grain.

Replicate samples (5 g) of 56 genetically diverse cowpea cultivars grown in either one or two environments, were soaked for 16 h, boiled for 27 min, and grain and their broth separated for evaluation. The samples were evaluated in batches of 25 and were subjectively rated on a 1–5 scale for cooked doneness, tactile texture, aroma intensity and opacity of the broth. Water absorption, seed splitting, and soluble solid loss were also determined.

The method differentiated the cowpea samples in terms of cook doneness, tactile texture, bean and broth aroma and broth opacity. Cooked properties showed significant correlations with each other, but did not correlate with either uncooked grain size or seed coat color. Compression force determined with a texture analyzer (TA) and cooking times from the Mattson Bean Cooker (MBC) significantly correlated with doneness and tactile texture ratings done with the rapid technique, confirming the applicability of the subjective ratings. A procedure to determine solid losses during cooking using a refractometer, instead of the time-consuming oven-drying method, saved time and showed significant promise. The rapid cooking method requires 2 h on the first day (sample preparation and soaking) and 5 h on the second day (cooking and evaluation) to evaluate 25 samples (1 rep). The method is efficient, repeatable and uses inexpensive equipment and materials. It provides descriptive information on aroma and organoleptic properties and differentiates cowpea cultivars based on several important cooking properties. This method should be a useful tool for selecting cowpea breeding lines with desirable cooking characteristics and it should be possible to extend the method to other grain legumes with only slight modification. This method may also be useful in preliminary determinations of whether specific lots of grain meet specifications for purchase and processing.

Citation

Field Crops Research (2009) 112 (2-3) 245-252 [doi: 10.1016/j.fcr.2009.03.010]

Rapid screening methods to evaluate cowpea cooking characteristics

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