Sifat-Sifat Fisikokimia Pati Ubi Kayu Terfermentasi Khamir Indigenus Tapai
Authors: Widyatmoko Heru , Subagio Achmad , Nurhayati Nurhayati 
Published: August 2018

Tapai is a cassava food product fermented by yeast starter (“Ragi”). Among the amylolitic yeasts that had been isolated from the tapai were Candida guilliermondii, C. tropicalis, Trichosporon mucoides, and Saccharomycopsis fibuligera. The aim of this research was to characterize the physicochemical properties of fermented cassava starch by amylolytic yeasts of indigenus tapai i.e. C. guilliermondii, C. tropicalis, T. mucoides, and S. fibuligera. The process of fermentation of cassava starch was done by inoculating each pure isolate by 5% v / v (105 CFU / ml) into cassava starch suspension 50% b/v (100g starch into 200ml sterile distilled water). The incubation was carried out at 28 °C for 24 h, 48 h, and 72 h. The fermented cassava starch was dried at 50 °C for 24 h. Characterization of physicochemical properties of cassava starch included chemical properties (amylose content), paste properties (RVA), thermal properties (DSC), physical properties (SEM granule macrostructure) and functional groups (FT-IR) of unfermented (native) or fermented cassava starch. The results showed that during the fermentation process, the yeast was able to grow up to 7 log10 CFU/ml and the acidity decreased to pH 3,9. The amylose content of fermented cassava starch decreased to 11,22% from native starch amylose content (15,85%). The paste properties of fermented cassava starch increased at the value of trough viscosity, breakdown, final viscosity, and swelling power. The thermal properties of fermented cassava starch increased to 64,7-67 °C for the initial temperature value of gelatinization (To), 69,1-71,2 °C for gelatinization peak temperature (Tp), 73,9-75 °C for the final temperature of gelatinization (Tc), but decreased gelatinization enthalpy in the range of ΔH 4,84-6,38 J/g. The macrostructure of the longest fermented starch granules (72 hours)occurred liberation into irregular granular shapes. The profile of fermented cassava starch functional groups had a similarity with native cassava starch that had the highest absorption spectra at 3291,2 cm-1 peak (vibration of the O-H bonding group) and 2920 cm-1 peak (C-H group vibration). ABSTRAKTapai merupakan produk pangan ubi kayu yang terfermentasi oleh starter khamir (ragi). Di antara khamir amilolitik yang sudah diisolasi dari tapai yaitu Candida guilliermondii, C. tropicalis, Trichosporon mucoides, dan Saccharomycopsis fibuligera. Tujuan penelitian ini adalah melakukan karakterisasi sifat-sifat fisikokimia pati ubi kayu yang difermentasi oleh khamir amilolitik indigenus tapai yaitu C. guilliermondii, C. tropicalis, T. mucoides, dan S. fibuligera. Proses fermentasi pati ubi kayu dilakukan dengan menginokulasikan masing-masing isolat murni sebanyak 5% v/v (105 CFU/ml) ke dalam suspensi pati ubi kayu 50% b/v (100g pati ke dalam 200ml akuades steril). Selanjutnya dilakukan inkubasi pada suhu 28 °C selama 24, 48, dan 72 jam. Pati ubi kayu terfermentasi dikeringkan pada suhu 50 oC selama 24 jam. Karakterisasi sifat-sifat fisikokimia pati ubi kayu meliputi sifat kimia (kadar amilosa), sifat pasta (RVA), sifat termal (DSC), sifat fisik (makrostruktur granula SEM) dan gugus fungsi (FT-IR) pati ubi kayu alami maupun pati ubi kayu terfermentasi. Hasil penelitian menunjukkan bahwa selama proses fermentasi, khamir mampu tumbuh hingga mencapai 7 log10 CFU/ml dan derajat keasaman mengalami penurunan mencapai pH 3,9. Kadar amilosa pati ubi kayu terfermentasi mengalami penurunan menjadi 11,22% dari kadar amilosa pati alami (15,85%). Sifat pasta pati ubi kayu terfermentasi khamir mengalami peningkatan pada nilai viskositas trough, breakdown, viskositas akhir, dan daya kembang. Sifat termal pati ubi kayu terfermentasi menglamai peningkatan menjadi 64,7-67 °C untuk nilai suhu awal gelatinisasi (To), 69,1-71,2 °C untuk suhu puncak gelatinisasi (Tp), 73,9-75 °C untuk suhu akhir gelatinisasi (Tc), tetapi mengalami penurunan entalpi gelatinisasi pada kisaran ∆H 4,84-6,38 J/g. Makrostruktur granula pati yang terfermentasi paling lama (72 jam) mengalami liberasi dengan bentuk granula yang tidak beraturan. Profil gugus fungsi pati ubi kayu terfermentasi oleh khamir memiliki kemiripan dengan pati ubi kayu alami yaitu memiliki spektra penyerapan tertinggi pada puncak 3291,2 cm-1 (getaran gugus ikatan O-H) dan puncak 2920 cm-1 (getaran gugus C-H).