Judul: The Substitution of Peel Puree to Dragon Fruit Ice Cream Improves Physical and Organoleptic Quality with Identical Calcium Bioavailability
Abstrak: Kalsium merupakan mineral makro yang memiliki peran penting dalam fungsionalitas tubuh. Kalsium yang diserap tubuh digambarkan oleh bioavailabilitas kalsium. Bioavailabilitas kalsium dapat dipengaruhi oleh zat anti-gizi yang dapat ditemukan dalam buah. Penelitian ini bertujuan mengkaji substitusi pure kulit buah naga dalam es krim buah naga merah. Desain penelitian ini adalah eksperimen dengan rancangan acak lengkap (RAL). Tahap penelitian terdiri dari formulasi, pembuatan produk, uji karakteristik fisik, organoleptik, proksimat, penentuan formula terpilih, analisis kandungan dan bioavailabilitas secara in vitro serta analisis kontribusi dan klaim gizi. Formula terpilih adalah F2 dengan rasio pure daging dan kulit buah naga merah 60:40. Es krim terpilih memiliki kadar air 63,6%; kadar abu 3,4%; lemak 12,0%; protein 13,0%; dan karbohidrat 8,1% dengan kontribusi energi 8,9% berdasarkan acuan label gizi (ALG). Kandungan kalsium es krim 264,90 mg/100 g dengan bioavailabilitas 70,55%. Kandungan dan bioavailabilitas es krim tidak berbeda antara es krim kontrol dan terpilih berdasarkan independent samples t-test (p>0,05). Es krim dapat diklaim sebagai makanan sumber kalsium dengan kontribusi sebesar 24,1%., Calcium is a macro mineral that has important roles in body functionality. Calcium absorbed by the body is described by the bioavailability of calcium. The bioavailability of calcium can be affected by anti-nutrients sometimes found in fruit. This study aims to examine dragon fruit peel puree substitution in red dragon fruit ice cream. The research design is an experiment with a completely randomized design (CRD). The research stages are formulation, product manufacture, physical characteristic, organoleptic, and proximate analysis, formula selection, analysis of calcium content and bioavailability in vitro as well as analysis of contribution and nutritional claims. The selected formula is F2 with a red dragon fruit pulp and peel puree ratio of 60:40. Ice cream has a moisture of 63.6%, ash 3.4%, fat 12.0%, protein 13.0%; and carbohydrates 8.1% with energy contribution 8.9% based on nutrition label reference. The calcium of ice cream is 264.90 mg/100 g with a bioavailability of 70.55%. The content and bioavailability of ice cream are identical between control and selected ice cream based on independent samples t-test (p>0.05). Ice cream can be claimed as a source of calcium with a contribution of 24.1%.
Keyword: calcium bioavailability, ice cream, red dragon fruit’s peel puree

Judul: Utilization of Soy Milk and Red  Dragon Fruit (Hylocereus lemairei (Hook.) Britton & Rose) as Low-Fat Ice Cream for Woman of Childbearing Age
Abstrak: Asupan lemak yang rendah dapat berkontribusi dalam mencegah dan menurunkan risiko obesitas dan dengan antioksidan dapat mencegah stress oksidatif akibat obesitas. Kedelai merupakan salah satu sumber protein nabati rendah lemak dan mengandung isoflavon yang berpotensi sebagai agen anti-obesitas. Buah naga merah merupakan salah satu buah yang dimanfaatkan sebagai sumber antioksidan. Penelitian ini bertujuan untuk mengembangkan es krim rendah lemak dan mengandung antioksidan dengan memanfaatkan susu kedelai dan buah naga merah. Tahap penelitian ini meliputi pembuatan formula, uji sensori, analisis kandungan gizi dan analisis karakteristik fisik, serta analisis kapasitas antioksidan. Penelitian ini menggunakan tiga formula dengan rasio susu kedelai dan buah naga merah yang berbeda, yaitu F1 (67:33), F2 (50:50), F3 (33:67). Berdasarkan hasil uji organoleptik, F3 merupakan formula terpilih. Kandungan gizi formula terpilih yaitu, kadar air 78,32%, abu 1,33%, lemak 3,35%, protein 6,18%, dan karbohidrat 10,81%. Kapasitas antioksidan es krim susu kedelai dan buah naga merah dinyatakan dalam IC50 sebesar 6816,66 ppm atau setara 13,56 mg Vitamin C/100 g. Satu takaran saji es krim susu kedelai dan buah naga merah dalam penelitian ini dapat memenuhi kebutuhan energi sebesar 98 kkal serta dapat memenuhi klaim rendah lemak., Low fat intake can contribute to preventing and reducing the risk of obesity and with antioxidants it can prevent oxidative stress due to obesity. Soybeans are a source of low-fat vegetable protein and contain isoflavones which have the potential to act as anti-obesity agents. Red dragon fruit is one fruit that is used as a source of antioxidants. This study aims to develop a low-fat ice cream contains antioxidant by utilizing soy milk and red dragon fruit, using a process that involves formulating, conducting sensory tests, analyzing nutritional content and physical characteristics, and evaluating antioxidant activity. This study tested three formulas containing soy milk and red dragon fruit in different ratios: F1 (67:33), F2 (50:50), and F3 (33:67). Formula F3 was chosen based on organoleptic test results. It contains 78.32% moisture, 1.33% ash, 3.35% fat, 6.18% protein, and 10.81% carbohydrates. The antioxidant capacity of the ice cream is stated in IC50 of 6816.66 ppm or equivalent to 13.56 mg vitamin C/100 g. One serving of soy milk ice cream and red dragon fruit in this study can meet energy needs of 98 kcal and fulfill claims of low-fat ice cream.
Keyword: antioxidant, ice cream, low-fat, red dragon fruit, soy milk

Judul: Bifurkasi Hopf pada siklus bisnis IS-LM tanpa dan dengan waktu tunda
Abstrak: One of business cycle models in dynamical economics is the IS-LM business cycle model with time delay, where the time delay lies in stock capital variables. It is a time delay between the existence of stock capital and the time to get ready to invest. In a model without time delay, changing the parameter of investment rate on income could affect the system stability. On the other hand, in a model with time delay, there exists critical time delay changing the system stability. This shows limit cycle, which can be concluded that Hopf bifurcation occurs
Keyword: Bogor Agricultural University (IPB), time delay, Hopf bifurcation, business cycle model