Effect of infrared radiation on chemical and physical properties on Duku’s peel

Laila Rahmawati,Daniel Saputra,Gatot Priyanto,Kaprawi Sahim

doi:10.5219/985

Abstract

Infrared radiation has a potential for drying agricultural commodities such as the peel of duku. Drying of duku's peel in a whole duku using infrared radiation could become an effective method to eliminate the water on the peel but not in the flesh and could increase the shelf life of duku. The objective of this study was to investigate the potential of using infrared radiation for drying the peel of duku which would increase the shelf life of duku during storage. Duku's peel drying process was achieved by means of heating duku using a pairs of electric infrared emitters (IRE) facing each other with the emitter distance of 6 cm and 10 cm for a relatively short heating time of 50, 60, 70 and 80 seconds and after that stored at a cool room at the temperature of 15 °C for the length of one month. During storage, the physical and chemical changes of duku were then evaluated. It was found that the weight loss, fruit firmness, and total soluble solid of duku dried by means of exposing to Infra Red Emitter (IRE) were significantly affected by the distance of IRE, the temperature of IRE and the time exposed to IRE. However the titratable acidity only affected significantly by the distance of IRE. There were no significantly changes of browning index on duku during drying by exposing to IRE and while stored up to 25th day of storage. Drying duku by exposing it to IRE show a slightly better shelf life than the previous work.

Highlights

Lansium domesticum corr. is a tropical fruit of South East Asia with its member known as langsat, longkong and duku
Infrared radiation has a potential for drying agricultural commodities such as the peel of duku
Drying of duku’s peel in a whole duku using infrared radiation could become an effective method to eliminate the water on the peel but not in the flesh and could increase the shelf life of duku

Summary

Introduction

Lansium domesticum corr. is a tropical fruit of South East Asia with its member known as langsat, longkong and duku. Duku has a thicker peel and no latex while langsat has a peel that contains a milky sticky sap. There are 4 to 12 fruits per bunches for duku and 15 to 25 fruits for langsat. Both of them have five separate segments, with one to five seeds in it (Paull, 2014). Peel color (green for the immature to yellow for the mature one) and the lack of latex could be used as an indicator for the level of fruit maturity. The fresh peel contains 0.2% of a light yellow, volatile oil, a brown resin and reducing acids. A dark, semi-liquid oleoresin composed of 0.17% volatile oil and 22% resin could be extracted from the dried peel. The extract of Lansium domesticum fruit was found to have an antioxidant as evaluated by the DPPH free radical assay and the dried hydro-ethanol extract of Lansium domesticum fruit could be used as cosmetic (Tilaar et al, 2008)

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Conclusion