Optimization of design parameters for by-product feed fermentation using taguchi method

The study proposed a design factor to optimize the fermentation storage process by identifying the optimum fermentation condition of by-product stock-feed. This study is an initial step to develop a by-product stock-feed fermentation storage system. The Taguchi method was adopted and the L₉(3⁴) orthogonal array was used. Nine experiments were done in triplicate, totaling 27 runs. The study analyzed the fermentation quality utilizing three levels of the four controllable factors (i.e., temperature, moisture content, density, and fermentation period) and two uncontrollable factors (type of by-products). Quality score was calculated using the silage quality assessment method after measuring pH and total organic acid content (i.e., citric acid, malic acid, lactic acid, acetic acid, and butyric acid). Fermentation tank (φ300×400L) was constructed for the reproducible experiment. Fermentation pH, temperature, and changes in CO2 were measured and analyzed in real time. Results indicated that by-product stock-feed had the highest quality score at 20 °C, moisture content of 50%, a density of 0.6kg/m³ including a 96-hour fermentation period. Analysis showed that the order (from highest to the lowest) of influence exerted by control factors was temperature, density, moisture content and fermentation period. The reproducibility experiment showed that pH, temperature, and CO2 curves became gentle at the 36-hour mark and stabilized at 84 hours. The results indicated that fermentation of by-products was completed in 36 hours and entered into a stabilized stage. Sample after 96 hours showed an excellent quality score of 82.