Optimization of infrared drying condition for whole duku fruit using response surface methodology

Duku (Lansium domesticum), tropical exotic fruit, was successfully preserved by drying using exposure to infrared radiation emitters. Response surface methodology (RSM) is used to optimize independent variables (IRE distance of 6 cm and 10 cm, IRE temperature of 200 °C, 300 °C, 400 °C, and IRE exposure time of 50 s, 60 s, 70 s, and to produce response variables (weight loss, fruit firmness, titratable acidity, total soluble solid, and browning index). It could be concluded from the optimization performed that drying duku skin in a whole fruit by exposing the fruit to the infrared emitter resulted in a duku fruit with a relatively good physical and chemical conditions and still be consumable. The IRE distance of 6 cm gave a desirability value of 0.80 while the IRE distance of 10 cm gave a desirability value of 0.92 however the IRE distance of6 cm gave a better storage time. The IRE distance of 6 cm has an optimum value of weight loss 2.2%; optimum value of fruit firmness of 40.92 N; optimum value of total soluble solid of 17.48 brix; optimum value of titratable acidity of 0.33%; and optimum value of browning index of 0.9. The fitting model base on RSM resulted from this research indicated that this study could be used as the basis for alternative process in food processing of duku but still need further research to increase the shelf life and a better result in the chemical and physical characteristics of duku.