Abstract

Modified porang flour by lactic acid and conventional heating using waterbath (PAW) and microwave radiation (PAM) were determined its functional group using FTIR, the chemical structure were studied using H1NMR, molecular weight were measured using HPLC-SEC and its microstructure were studied using SEM, particles size were measured using PSA and rheology characteristics were determined using Rheometer. The results showed that modified porang either PAW and PAM showed changes on functional group peaks compared to one of native porang flour included OH, CH₃, C-C, C = O, C-O-C, mannose and glucose groups. H¹NMR spectra of modified porang flour (PAW and PAM) were similar mainly in proton of CH₃ and CH₂, molecular weight were higher at PAW 2.0×10⁶ and PAM 3.0×10⁶, while particles size of PAW and PAM were smaller. The microstructure of PAW and PAM were porous and spongy indicated that PAW and PAM had higher moisture accessability on the amorph site. Storage modulus (G’) dan loss modulus (G”) PAW and PAM decreasing with the increased temperature. Lower G’ compared to G” and modulus (G’ and G”) did not showed crossing indicated that PAW and PAM have a stable visco-elasticity. It can be concluded that functional group peaks of modified porang flour (PAW and PAM) changed differently compared to native porang flour, H¹ -NMR spectra of modified porang flour were similar, with bigger moleculer weight of PAM than PAW, the microstructure were porous and spongy and rheology characteristics indicated that an unchanged visco-elastic system by thermal treatments.

Keywords:

Lactic acid, microwave, modified porang, porang flour, waterbath,

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