Pengaruh Perendaman dalam Asam Sitrat dan Blanching Terhadap Mutu Fisik, Kimia dan Fungsional Tepung Ubi Jalar Ungu dan Aplikasinya dalam Pembuatan Cake

Abstract

Purple sweet potato has a potential as functional food because of it’s antocyanin and antioxidant activity. Purple sweet potato is also a source of antocyanin, phenolic compounds, fibers, and glicemic index. Another additional plus from purple sweet potato is it’s fiber content that’s good for digestion system and it’s low to medium glicemic index. This research intent on knowing citric acid treatment and blanching effect toward the best purple sweet potato flour applied to cake making. The research Research design used was Completely Randomized Design (RAL) non factorial i.e., citric acid treatment (0,5% and 1% for 30 minutes) and citric acid treatment (0,5% and 1% for 30 minutes with steam blanching for 5 minutes). The physical analysis result like L color value 40,66-46,64; bulk density 0,69-0,78 g/ml, and browning index 0,76-1,13. Chemical quality such as moisture content of 5,16-8,16%; ash content 1,27-1,93%; fat content 0,52%; protein content 5,19-6,82%; fiber content 2,53-3,00%; total anthocyanin 105,57- 126,97 mg CyE/g; starch content 55,02-60,00%; amylose content 9,79-13,02%; amylopectin content of 39,16-43,99%; total sugar 24,55-45,04%, sugar reduction 3,22- 19,43%; total phenolic content (μgGAE / mg) 765,89-1288,36; and Degree of acid (NaOH/100g of material) 3,22-5,39. Meanwhile functional qualities like water absorption capacity 1,90-3,83 g/g; oil absorption capacity 1,26-1,73 g/g; swelling power 5,19-6,69 g/g; baking expansion 0,89-0,92 ml/g; solubility 3,43-3,61%. From the result of this research, all treatment affect chemical quality of purple sweet potato flour in which citric acid with higher concentration followed with blanching, the protein content will get lower. Meanwhile functional qualities of purple sweet potato flour, citric acid with higher concentration followed with blanching makes higher water absorption capacity and lower oil absorption capacity. According to hedonic test, purple sweet potato flour cake, best sweet potato flour, and wheat flour have the highest score (like moderately to like). Control purple sweet potato flour cake, best sweet potato flour, and wheat flour have volume expansion each 43,89 cm3/g, 44,87 cm3/g, and 50,43 cm3/g. The result of color analysis shows that wheat flour cake L value is 69,49, control purple sweet potato flour cake L value is 22,80, and best sweet potato flour L value is 21,07. The result of of best sweet potato flour’s chemical analysis, each value of moisture content, ash content, fat content, protein content, and fiber content in chronological order are 22,28%, 6,90%,12,22%, 5,16%, 46,57%, and 0,72%.

Ubi jalar ungu memiliki potensi untuk dimanfaatkan sebagai pangan fungsional karena memiliki antosianin dan aktivitas antioksidan. Pada ubi jalar ungu diperoleh antosianin, senyawa fenol, serat pangan dan indeks glikemik. Kandungan serat pangan yang bermanfaat untuk pencernaan dan indeks glikemiknya yang rendah sampai medium, juga merupakan nilai tambah ubi jalar sebagai pangan fungsional. Penelitian ini bertujuan untuk mengetahui pengaruh perendaman asam sitrat dan blanching terhadap mutu fisik, kimia dan fungsional, tepung ubi jalar ungu yang terbaik diaplikasikan pada pembuatan cake. Rancangan penelitian yang digunakan adalah Racangan Acak Lengkap (RAL) non faktorial yaitu perendaman asam sitrat (0,5% dan 1% selama 30 menit) dan perendaman asam sitrat (0,5% dan 1% selama 30 menit dengan blanching uap 5 menit). Hasil analisis mutu fisik seperti warna nilai L 40,66-46,64; densitas kamba 0,69-0,78 g/ml dan browning index 0,76-1,13. Mutu kimia seperti kadar air sebesar 5,16-8,16%; kadar abu 1,27-1,93%; kadar lemak 0,52%; kadar protein 5,19-6,82%; kadar serat 2,53-3,00%; total antosianin 105,57-126,97 mg CyE/g; kadar pati 55,02-60,00%; kadar amilosa 9,79- 13,02%; kadar amilopektin 39,16-43,99%; total gula 24,55-45,04%; gula reduksi 3,22- 19,43%; total fenolik (μgGAE/mg) 765,89-1288,36 dan Derajat asam (NaOH/100g bahan) 3,22-5,39. Sedangkan mutu fungsional seperti daya serap air 1,90-3,83 g/g; daya serap minyak 1,26-1,73 g/g; swelling power 5,19-6,69 g/g; baking expansion 0,89-0,98 ml/g; kelarutan 3,43-3,61%. Dari hasil penelitian ini, perlakuan berpengaruh terhadap mutu kimia tepung ubi jalar ungu dimana semakin besar konsentrasi asam sitrat dengan blanching, maka kadar protein semakin rendah. Sedangkan mutu fungsional tepung ubi jalar ungu, semakin besar konsentrasi asam sitrat (1%) dan diikuti proses blanching maka daya serap air semakin tinggi dan menurun daya serap minyak. Berdasarkan uji hadonik cake tepung kontrol ubi jalar ungu, tepung ubi jalar ungu terbaik dan tepung terigu memiliki nilai tertinggi (agak disukai hingga disukai). Cake tepung kontrol ubi jalar ungu, tepung ubi jalar ungu terbaik dan tepung terigu memiliki volume pengembangan masing-masing sebesar 43,89 cm3/g, 44,87 cm3/g dan 50,43 cm3/g. Hasil analisis warna menunjukkan bahwa cake tepung terigu dengan nilai L 69,49, cake tepung kontrol ubi jalar ungu nilai L 22,80, dan cake tepung ubi jalar ungu terbaik nilai L 21,07. Hasil analisis kimia cake tepung ubi jalar ungu terbaik masing masing dari kadar air, abu, lemak, protein, kabohidrat, dan serat adalah 22,28%, 6,90%, 12,22%, 5,16%, 46,57%, dan 0,72%.