Judul: Formulation of High-Fiber Extruded Purple Sweet Potato (Ipomoea batatas L.) and Red Kidney Bean (Phaseolus vulgaris)
Abstrak: Rendahnya asupan serat pangan yang berkaitan erat dengan peningkatan risiko beragam penyakit tidak menular (PTM) masih menjadi masalah kesehatan terkait gizi pada masyarakat luas. Ubi ungu dan kacang merah merupakan pangan tinggi serat yang terjangkau dan mudah diakses di Indonesia. Penelitian ini bertujuan mengembangkan formulasi olahan ubi ungu dan kacang merah berupa ekstrudat tinggi serat. Tahapan penelitian terdiri dari optimasi formula, evaluasi sensori, uji karakteristik fisik yakni analisis warna dan tekstur, analisis proksimat, analisis serat pangan, baik larut dan tidak larut, dan analisis aktivitas air. Optimasi formula dilakukan menggunakan empat formulasi dengan perbandingan penggunaan tepung ubi ungu dan tepung kacang merah yang berbeda-beda yakni F0 (100:0), F1 (80:20), F2 (70:30), dan F3 (60:40). Ekstrudat diekstrusi pada suhu 60°C dan kecepatan ulir, umpan, serta pisau sebesar berturut-turut 45, 45, dan 50 Hz. Formula terpilih yakni formula F2 ditentukan berdasarkan hasil seluruh analisis. Satu takaran saji ekstrudat formula F2 diketahui mengandung mengandung energi, protein, lemak, karbohidrat, dan total serat pangan berturut-turut sebesar 129 kkal, 4,0 g, 0,3 g, 27,7 g, dan 6,0 g, serta memenuhi 6,0% kebutuhan energi serta 19,9% kebutuhan serat orang dewasa. Analisis aktivitas air menunjukkan bahwa formula terpilih memiliki aktivitas air sebesar 0,44%. Formula ekstrudat terpilih berpotensi memenuhi klaim sebagai pangan tinggi serat dan rendah lemak dengan umur simpan yang cukup panjang., The low intake of dietary fiber, which is closely related to the increased risks of various non-communicable diseases (NCDs), is still considered as a major health problem related to nutrition globally. Purple sweet potatoes and red kidney bean are high-fiber foods that are affordable and readily accessible in Indonesia. This research aimed to develop a formulation of high-fiber extrudate made from purple sweet potato and red kidney bean. This research was conducted through formula optimization, sensory evaluation, and analyses of color, texture, proximate, dietary fiber, and water activity. Optimization of the formula was carried out using four formulations with different ratios of purple sweet potato and red kidney bean flours, i.e. F0 (100:0), F1 (80:20), F2 (70:30), and F3 (60:40). The extrudate was extruded using a double-screw extruder at the temperature of 60°C, with the screw, feed and cutter speeds of 45, 45, and 50 Hz, respectively. The selected extrudate formula, formula F2, was determined based on the results of all analyses. A single serving of F2 extrudate was shown to contain energy, protein, fat, carbohydrates and total dietary fiber of 129 kcal, 4.0 g, 0.3 g, 27.7 g, and 6.0 g respectively, and contributes to 6.0% and 19.9% of energy and fiber needs for adults. Water activity analysis showed that the selected formula had a water activity of 0.44%. The results of all analyses showed that this extrudate was well accepted and may potentially be claimed as a high-fiber and low-fat food with long shelf life.
Keyword: analisis proksimat, makanan ekstrudat tinggi serat, kacang merah, optimasi formula, ubi ungu, formula optimisation, high-fiber extruded food, proximate analysis, purple sweet potato, red kidney bean

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: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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