Study of Response Surface Methodology to Optimization Post Harvest Handling (Study of Case Waxing Concentration and Storage Temperature of Mangosteen)

Abstract

Inappropriate post-harvest handling of mangosteen is one of the reasons that caused low quality and consumer rejection. Several practices in post-harvest handling of fresh mangosteen to preserve its self life and quality includes but is not limited to packaging techniques, storage temperature control, storage in modified atmosphere, waxing, or any combinations of the above. Researches on the most preferred procedure of combining temperature control and waxing are still ongoing. From the literature it is found out that the latest research was looking for optimum combinations by comparing the treatment variations. By creating a mathematical model the responses to the treatment (as the variables) can be estimated, even the optimum values can be found. Response Surface Methodology (RSM) is used to look for the conditions of the treatment (Temperature and Waxing Concentration) which exerts the optimum influence to the parameters under observation. The storing stages started with the waxing, followed with packaging with plastic stretch film, and lastly storing in cold storage with various temperatures. Responses noted were rate of respiration, weight reduction, the firmness and total soluble solid (TSS) value. The experiment had been performed using Central Composite Design (CCD) with two factors (variables). Variables being optimized were storage temperature (X1) 6°C, 8°C, 13°C, 18°C, 20°C, and waxing concentration (X2) 4%, 5%, 7,5%, 10%, 11%. Further, the response to TSS optimization in 2nd order yielded the best value. The validity of the RSM method was proven by the regression test result R2 of 79%, lack of fit was obtained at 0.065. The optimum temperature is 130C, wax concentration is 8% with TSS rate is 2,1oBrix/day. The format of the plot surface resulted was a maximum. Mathematical model obtained was: Y = -6,574 + 0,429X1 + 1,515X2 - 0,0008X1X2 - 0,016X1 2 - 0,096X2 2