Response Surface Methodology for Studying the Quality Characteristics of Cowpea (Vigna Unguiculata)‐based Tempeh

Response surface methodology was used to optimize the processing conditions in the preparation of cowpea tempeh. The independent factors studied were boiling time (varying from 5 to 30 min), incubation time (varying from 12 to 48 h) and incubation temperatures (varying from 25 to 50C), whereas the dependent factors were protein content, protein solubility, pH, titratable acidity and total color difference (using L, a* and b*). Regression models were generated and adequacy was tested with regression coefficients (R2) and the lack‐of‐fit tests. Optimum processing conditions were determined by method of superimposition. There was a strong and significant influence (P < 0.01) of the quadratic effect of the incubation time on the protein content of the cowpea tempeh, with similar significance (P < 0.01) noted in protein solubility with increasing boiling time. The optimum processing conditions observed for the preparation of cowpea tempeh were boiling time of about 20 min, incubation time of about 28 h and incubation temperature of about 37C. PRACTICAL APPLICATIONS Response surface methodology (RSM), as a statistical tool, has been effectively used in food process applications. This study embraced the use of RSM in the optimization of the processing conditions involved in the preparation of cowpea tempeh. Superimposition of the contour plots developed from the regression models indicated that cowpea with optimum quality characteristics should be processed at a boiling time of 20 min, incubation time of 28 h and incubation temperature of 37C. These conditions could be adopted for the industrial production of cowpea tempeh.