Judul: The Development of Ice Cream Using Red Dragon Fruit Flesh and Skin on Antioxidant Activity and Organoleptic Quality
Abstrak: Es krim adalah produk olahan yang terbuat darisusu dan ditambahkan dengan komposisi bahan pembuat es krim, yang sering disebut bahan campuran es krim (ice cream mix), seperti krim, skim, stabilizer, emulsifier, sweetener, dan penambahan rasa (flavor) untuk menciptakan produk es krim yang lembut, enak dan rasa yang lezat. Tujuan penelitian ini adalah mendapatkan formula terbaik dari es krim dengan variasi rasio daging dan kulit buah naga merah sebagai cemilan tinggi antioksidan. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan rasio daging dan kulit buah naga (%), yaitu F0 (100:0), F1 (70:30), F2 (60:40), dan F3 (50:50). Hasil organoleptik menunjukkan keempat formula dapat diterima oleh panelis dan formula yang paling disukai adalah F2, yaitu es krim dengan rasio daging buah naga 60% dan kulit buah naga 40%. Produk es krim buah naga memiliki kandungan (basis basah) untuk air sebesar 63,01-63,81%, abu 3,11-3,43%, lemak 11,82-12,33%, protein 12,60-13,14%, dan karbohidrat 7,28-9,36%. Kandungan antioksidan pada semua formula es krim lebih dari 200 ppm sehingga dikategorikan sangat lemah., Ice cream is a processed product made from milk and added to the composition of ingredients for making ice cream, which are often called ice cream mix ingredients, such as cream, skim, stabilizer, emulsifier, sweetener, and added flavors to create soft, tasty and delicious ice cream products. The purpose of this study was to obtain the best formula of ice cream with variations in the ratio of red dragon fruit flesh and skin as a snack high in antioxidants. This study used a completely randomized design with a ratio of dragon fruit flesh and skin (%), namely F0 (100:0), F1 (70:30), F2 (60:40), and F3 (50:50). The organoleptic results showed that the four formulas were acceptable to the panelists and the most preferred formula was F2, namely ice cream with a ratio of 60% dragon fruit flesh and 40% dragon fruit skin. Dragon fruit ice cream products contain (wet base) water 63.01-63.81%, ash 3.11-3.43%, fat 11.82-12.33%, protein 12.60-13.14%, and carbohydrates 7.28-9.36%. The antioxidant content in all formulas is more than 200 ppm so it is categorized as very weak.
Keyword: antioksidan, buah naga merah, es krim, kulit buah naga

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 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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