Electronic Theses and Dissertation

Umbi janeng (Dioscorea hispida Dennst) atau yang dikenal secara umum/botani ialah
umbi gadung merupakan salah satu umbi-umbian yang dapat tumbuh liar di hutan,
pekarangan ataupun perkebunan yang dapat dijadikan sebagai sumber pangan lokal alternatif
yang kaya karbohidrat, namun pemanfaatannya masih terbatas karena mengandung senyawa
toksik berupa asam sianida (HCN) yang berbahaya bagi kesehatan. Kadar HCN pada umbi
gadung segar tergolong tinggi yaitu sekitar 469 ppm (Rahayu, 2018) sementara itu ambang
batas aman konsumsi manusia menurut SNI 7622:2011 tentang syarat mutu tepung mocaf
maksimal 10 mg/kg, sehingga diperlukan proses pengolahan yang tepat untuk mengurangi
kandungan asam sianida (HCN). Berbagai metode telah dikembangkan, namun pemilihan
metode yang efektif, mudah diterapkan, serta menggunakan bahan yang mudah diperoleh
menjadi pertimbangan utama. Oleh karena itu, penelitian ini mengambil topik pengurangan
kadar HCN pada pembuatan tepung umbi janeng melalui perendaman menggunakan larutan
garam, larutan kapur, dan kombinasi keduanya sebagai alternatif metode yang aplikatif dan
efisien. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh perlakuan perendaman
larutan garam, kapur dan kombinasi (garam-kapur) terhadap perubahan sifat fisiko-kimia
tepung umbi janeng.
Metode penelitian yang digunakan adalah Rancangan Acak Lengkap (RAL) faktorial
dengan dua faktor, yaitu jenis air rendaman (larutan garam, larutan kapur, dan kombinasi
garam–kapur) serta lama perendaman (48, 72, dan 96 jam), masing-masing dengan tiga
ulangan. Bahan utama yang digunakan adalah umbi janeng yang berasal dari Aceh Tengah,
kemudian umbi diparut, direndam sesuai perlakuan, dikeringkan, kemudian ditepungkan dan
diayak 80 mesh. Parameter penelitian meliputi sifat kimia dan fisik tepung janeng, yaitu kadar
HCN, kadar air, kadar abu, kadar protein, pH, warna (L*), daya serap air, dan rendemen. Data
dianalisis menggunakan ANOVA dan uji lanjut DMRT, serta penentuan perlakuan terbaik
dilakukan dengan metode deGarmo.
Hasil penelitian menunjukkan bahwa jenis air rendaman berpengaruh terhadap penurunan
kadar HCN tepung janeng. Perlakuan kapur sirih menghasilkan kadar HCN terendah tetapi
masih berada di atas batas aman konsumsi. Selain itu, perlakuan jenis air rendaman dan lama
perendaman juga memengaruhi karakteristik fisikokimia tepung janeng. Lama perendaman dan
jenis air rendaman menurunkan kadar air, pH, warna L* sehingga menghasilkan warna tepung
yang gelap, namun meningkatkan kadar protein. Sedangkan jenis air rendaman meningkatkan
kadar abu tepung, namun tidak memberikan pengaruh terhadap rendemen dan daya serap air.
Berdasarkan uji deGarmo, perlakuan larutan kapur sirih dengan lama perendaman 96 jam
(A3T3) ditetapkan sebagai perlakuan terbaik secara keseluruhan dengan kadar HCN 36,83 ppm,
kadar air 7,19%, kadar protein 6,13%, pH 9,65, kadar abu 1,54% dan warna L* 96,83.

Janeng tuber (Dioscorea hispida Dennst), commonly known as gadung, is a wild tuber found in forests, residential yards, and plantations. It has the potential to serve as an alternative carbohydrate-rich local food source; however, its utilization remains limited due to the presence of hydrogen cyanide (HCN), a toxic compound hazardous to human health. The HCN content in fresh janeng tubers is considerably high, at approximately 469 ppm (Rahayu, 2018), whereas the safe threshold for human consumption—according to the SNI 7622:2011 quality standards for mocaf flour—is a maximum of 10 mg/kg. Therefore, appropriate processing methods are required to reduce the HCN content. While various methods have been developed, selecting an effective, easily applicable method using readily available materials is essential. Consequently, this study aimed to determine the effect of soaking treatments using salt, lime, and a combination of both solutions on the physicochemical properties of janeng tuber flour to establish an applicable and efficient detoxification method. This study employed a Factorial Completely Randomized Design (CRD) with two factors: the soaking solution type (salt, lime, and a salt–lime combination) and the soaking duration (48, 72, and 96 hours), with each treatment replicated three times. Janeng tubers sourced from Central Aceh were grated, soaked according to the respective treatments, dried, milled, and sifted through an 80-mesh sieve. The research parameters evaluated the chemical and physical properties of the flour, specifically HCN content, moisture content, ash content, protein content, pH, color lightness (L* value), water absorption capacity, and yield. Data were analyzed using Analysis of Variance (ANOVA) followed by Duncan's Multiple Range Test (DMRT). The optimal treatment was determined using the DeGarmo method. The results demonstrated that the type of soaking solution significantly affected the reduction of HCN content in janeng flour. The lime solution treatment produced the lowest HCN content, although it remained above the safe consumption threshold. Furthermore, both the soaking solution type and soaking duration significantly influenced the physicochemical characteristics of the flour. Prolonged soaking durations decreased the moisture content, pH, and L* value (resulting in a darker flour), while increasing the protein content. The solution type significantly impacted the ash content but exerted no significant effect on the yield or water absorption capacity. Based on the DeGarmo index, soaking in a lime solution for 96 hours (A3T3) was identified as the optimal treatment, yielding an HCN content of 36.83 ppm, moisture content of 7.19%, protein content of 6.13%, pH of 9.65, ash content of 1.54%, and a color L* value of 96.83.