Process optimization of soybean and mushroom incorporated steamed bread

Abstract

Steamed bread was prepared with incorporation of oyster mushroom powder and defatted soybean powder, aiming to minimize wheat flour and maximize soybean and mushroom powder content in the mix. Design expert software, mixture design was used for experimental design, in which level of soybean and mushroom powder within a range from 0 to 20 parts of each for formulation of steamed bread with varying refined wheat flour content by 80 to 100 parts. Similarly, Response surface methodology, central composite design was used to design another experiment for optimization of fermentation time within a range from 30 to 90 min at 35±2°C and steaming time for 10 to 20 min at normal atmospheric condition. For microbiological study, steamed bread samples were packaged in 40 μ LDPE zip lock bags and stored at ambient and refrigerated storage conditions at 30±2ºC and 5±1ºC respectively. Both samples were subjected to microbiological assessment daily until the microbial load had reached to a critical value of 5 log cfu/g. The optimum level of wheat flour, soybean powder and mushroom powder were found to be of 87.89, 10.03 and 2.08 parts respectively with magnitude of hardness, specific volume, spread ratio and L* (whiteness) were 2801.73 g, 1.75 ml/g, 1.58 and 73.87 respectively. Fermentation time of 67.04 min at 35±2°C and steaming time of 15.05 min under normal atmospheric pressure as optimized process conditions with magnitude of hardness, specific volume, spread ratio and L* (whiteness) were 2806.63 g, 1.74 ml/g, 1.49 and 75.07 respectively. Moisture, crude fat, crude protein, total ash, crude fiber and total carbohydrate content of optimized product on dry weight basis were found to be 41.20±0.23, 2.95±0.09, 18.16±0.17, 3.98±0.11, 0.99±0.09 and 73.13±0.47% respectively. Results of sensory evaluation showed that there was no significant difference (p>0.05) between soybean and mushroom incorporated steamed bread and the control product containing 100 parts refined wheat flour in terms of color and appearance, flavor, texture, taste and overall acceptability. Microbiological analysis of steamed bread packaged in 40 μ zip lock LDPE bags showed that the product was found to be safe for consumption within the first 5 days of storage under refrigerated storage at 5±1ºC and only a day at ambient storage at 30±2ºC. The cost and calorific value of the optimized product per 100 g was found to be NRs. 12 (as of 2021) and 230.35 Kcal respectively.