Kajian Variasi Lama Perendaman Dalam Larutan Kalsium Hidroksida Pada Pembuatan Tepung Ubi Jalar Ungu

Penelitian ini bertujuan untuk mengkaji proses pembuatan tepung ubi jalar ungu dengan variasi lama perendaman dalam larutan kalsium hidroksida. Tahapan proses pembuatan tepung ubi jalar adalah pengupasan, pemotongan membentuk chips dengan ketebalan 1 cm, perendamandalam larutan kalsium hidroksida Ca(OH)2, blanching pada suhu 85oC selama 5 menit, pengeringan bertahap dengan penjemuranselama 2 hari dan pengeringan oven selama 6 jam pada suhu 60oC sampai kadar air 10%, penggilingan dan pengayakan. Perendaman dalam larutan Ca(OH)2 konsentrasi 1.000 ppm dilakukan dengan  variasi lama perendaman 0, 15, 30 dan 60 menit. Parameter yang diamati meliputi rendemen, susut bobot, kadar air, kandungan pati, vitamin C, derajat keasaman, dan warna. Hasil penelitian menunjukkan bahwa rendemen yang dihasilkan pada berbagai variasi lama perendaman dalam larutan Ca(OH)2adalah 10,63%-10,79%, sedangkan kadar air tepung ubi jalar ungu diperoleh pada kisaran 8,4-10,27%. Susut bobot tertinggi diperoleh pada proses pengeringan matahari yaitu mencapai ±36,36%, sedangkan susut bobot terendah terjadi pada proses pengayakan yaitu ±3,13%. Kandungan pati tepung ubi jalar ungu berada pada kisaran 74,47-84,83%. Vitamin Ctepung ubi jalar ungu terendah diperoleh pada perendaman 60 menit sebesar 4,40 mg/100g, sedangkanvitamin C tepung ubi jalar ungu tertinggi diperoleh pada perendaman 0 menit yaitu 17,60 mg/100g. Secara umum dapat disimpulkan bahwa terjadi penurunan vitamin C selama proses penepungan. Derajat keasaman tepung ubi jalar ungu diperoleh pada kisaran 4,96-5,27. Berdasarkan analisis warna diperoleh tepung ubi jalar ungu dengan warna ungu ke kehitaman (perendaman 0 menit), ungu pucat (perendaman 15 menit), ungu pekat (perendaman 30 menit), dan ungu keabu-abuan (perendaman 60 menit).The study aimed to evaluate the purple sweet potato flour processing under variations of soaking time in calcium hydroxide solution. The steps of flour processing were pilling, cutting with a thikcness of 1cm, soaking in calcium hidroxide solution, blanching at a temperature of 85 oC for 5 minutes, drying at two stages i.e sun drying for two day and oven drying for 6 hour at  60oC until 10% moisture content miling and sieving. Soaking in calcium hidroxide  concentration of 1,000 ppm was done by variation soaking time of 0, 15, 30 and 60 minutes. The parameters observed were yield, weight loss, moisture, starch content, vitamin C, acidity, and color. The results showed that the yield generated due to variations of soaking time in calsium hidroxide solution was 10.63-10.79%, while the moisture content of the purple sweet potato flour was in the range of 8.4-10.27%. The highest weight loss was obtained in the sun drying process (±36.36%), while the lowest weight loss was occured in the sieving process (± 3.13%). The starch content of purple sweet potato flour was in the range of 74.47-84.83%. The lowest vitamin C of purple sweet potato flour was obtained after 60 minutes soaking (4.40 mg/100g), while the highest vitamin C of purple sweet potato flour was obtained without soaking (17.60 mg/100g). In general it can be concluded that vitamin C had been declined during the flour processing. The acidity of purple sweet potato flour was in range of 4.96 to 5.27. The  color analysis by using L*a*b method showed that there was differences in color due to the variation of soaking time.