Judul: Glycemic Index Value of Extrudates Made from Purple Sweet Potato (Ipomoea batatas L.) and Red Beans (Phaseolus vulgaris L.)
Abstrak: Ubi jalar ungu dan kacang merah merupakan bahan pangan lokal Indonesia yang dapat dikombinasikan menjadi makanan olahan yang lebih optimal, misalnya ekstrudat. Penelitian ini bertujuan untuk mengetahui nilai indeks glikemik ekstrudat ubi jalar ungu dan kacang merah serta faktor-faktor potensial yang dapat memengaruhinya. Penelitian eksperimental terdiri dari analisis pati resisten (protokol Megazyme International), analisis profil polifenol (Folin-Ciocalteu assay), dan indeks glikemik (metode IAUC, ISO 26642:2010). Tiga formula ekstrudat yang dianalisis meliputi F0, F1, dan F2 masing-masing dengan komposisi 0%, 30%, dan 40% tepung kacang merah. Penelitian menunjukkan ekstrudat F2 memiliki IG rendah (53,11), sedangkan ekstrudat F0 (77,41) dan F1 (74,68) memiliki IG tinggi. Terdapat hubungan yang signifikan (p<0,05) antara kadar protein, lemak, serat pangan, dan pati resisten dengan indeks glikemik. Tidak ada hubungan yang signifikan (p>0,05) pada kadar total fenol, tanin, dan non tanin dengan indeks glikemik. Substitusi kacang merah berpotensi meningkatkan kandungan protein dan serat, serta menurunkan nilai indeks glikemik., Purple sweet potato and red bean are local Indonesian food that can be combined into processed foods more optimally, for example, extrudates. This study aimed to determine the glycemic index value of purple sweet potato and red bean extrudates and the potential influence factors. An experimental research was consisted of analysis of resistant starch (Megazyme International protocol), polyphenol profile (Folin-Ciocalteu assay), and glycemic index (IAUC method, ISO 26642:2010). Three extrude formulas were developed e.i. F0, F1, and F2 with 0%, 30%, and 40% of red bean fluor, respectively. The results showed that extrudates F2 had a low GI (53.11). Meanwhile, extrudates F0 (77.41) and F1 (74.68) had a high GI. There is a significant relationship (p<0,05) between protein, fat, fiber, and resistant starch with glycemic index. There is a significant relationship (p>0,05) between total phenol, tannin, and non-tannin with glycemix index. Red bean flour substitution seems to be able to improve the nutritional quality particularly the protein and fibre content, and reduce the glycaemic index of extrudates.
Keyword: extruded food, fiber, low glycemic index, protein, resistant starch

Judul: Optimasi Formula dan Proses Ekstrusi Ubi Jalar Ungu dengan Response Surface Methodology
Abstrak: Ubi jalar ungu (Ipomoea batatas var. Ayamurasaki) sebagai salah satu komoditas pertanian yang unggul karena warnanya yang menarik, mudah didapat, dan manfaat kesehatannya. Industri keripik ubi jalar hanya menggunakan ubi jalar dengan ukuran tertentu. Petani pun terkena imbas karena penyerapan hasil panen oleh industri tidak maksimal. Pengolahan ubi jalar ungu menjadi produk olahan menggunakan ekstruder pada skala industri masih belum dapat ditemui. Penelitian ini bertujuan untuk menentukan formula dan parameter proses ekstrusi ubi jalar ungu yang optimum untuk menghasilkan produk dengan karakteristik mutu yang baik. Ubi jalar ungu yang diolah dengan teknik ekstrusi menggunakan ekstruder ulir ganda pemasak (BEX-DS-2256). Optimasi formula dan proses dilakukan menggunakan Response Surface Methodology (RSM) dengan rancangan Combine D-Optimal pada program Design Expert 12.0. Percobaan dilakukan dengan 22 perlakuan yang merupakan kombinasi faktor-faktor konsentrasi ubi jalar ungu (60–70%), tepung tapioka (20–25%), tepung ubi jalar ungu (10–15%), dan suhu ekstrusi (60–70 oC). Perlakuan yang optimum adalah dengan konsentrasi ubi jalar ungu 62.66%, tepung tapioka 22.34%, tepung ubi jalar ungu 15%, dan suhu ekstrusi 62.53 oC. Kombinasi formula dan proses tersebut menghasilkan adonan ubi jalar ungu dengan kadar air 49.34% (bb), kelengketan 711.67 gf, dan derajat gelatinisasi 52.06% dengan nilai desirability 0.76., Purple sweet potato (Ipomoea batatas var. Ayamurasaki) is one of the leading agricultural commodities due to its attractive color, availability, and health benefits. The sweet potato chip industry only uses sweet potatoes of a certain size. Farmers are also affected because the absorption of crops by the industry is not optimal. The development process of turning purple sweet potatoes into processed products using industrial scale extruders is still can’t be found. This study aimed to determine the optimum formula and extrusion process of the purple sweet potato to produce a product with good quality characteristics. Purple sweet potato was processed by extrusion technique using a double screw extruder (BEX-DS-2256). The optimization of formulas and processes was carried out using the Response Surface Methodology (RSM) with the Combine D-Optimal design in the Design Expert 12.0 program. The experiment conducted 22 treatments that were a combination of purple sweet potato concentration (60–70%), tapioca flour (20–25%), purple sweet potato flour (10–15%), and extrusion temperature (60–70 oC). The optimum treatment was with a concentration of 62.66% purple sweet potato, 22.34% tapioca flour, 15% purple sweet potato flour, and an extrusion temperature of 62.53 oC. The combination of these formulas and processes resulted in purple sweet potato dough with a moisture content of 49.34% (bb), stickiness of 711.67 gf, and degree of gelatinization of 52.06% with a desirability value of 0.76.
Keyword: derajat gelatinisasi, ekstruder, kelengketan, optimasi, ubi jalar ungu

Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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