Judul: Effect Of Pre-Treatment And Drying Temperature On The Properties Of Gac Powder
Abstrak: Gac fruit has a high content of antioxidant, especially carotenoids. These carotenoids are currently in special demand as they are natural antioxidants with potential to prevent cancers. The objectives of this research were to study the optimum drying condition to produce gac powder, study the waste utilization from gac skin as a powder, and investigate the physical and chemical properties of dried gac powder. Annova completely randomized factorial design was used to study the effect of different pre-treatment (blanching and adding of ascorbic acid) and dried using tray dryer at different temperature (50 and 60ºC) until moisture content in range of 5.8-6.4%. The results showed that the best dried gac powder was from the ascorbic acid pre-treated, using aril pulp and dried at 50°C due to the less amount of antioxidant loses. Physical properties showed bulk density value 0.65±0.02 g/mL and water solubility index (WSI) 36.42±3.11 %. Color properties showed lightness (23.55±2.43), with redness (a*) (23.48±1.27) and yellowness (b*) (39.72±2.97) (p<0.05). Aril and pulp mixture using ascorbic acid as pretreatment at 50ºC has the highest value in total carotenoid content (TCC) (93.49±11.35 mg β-carotene/100 mL samples),total phenolic compound (TPC) (467.44±7.64 μg GAE/g), DPPH (43.57±1.61 mmol Trolox/100g) and FRAP assay (598.22±18.59 μmol AAE/100g) (p<0.05) compared to other sample (p<0.05). Gac peel sample with blanching and dried at 60°C showed the lowest value of TCC (32.40±2.23 mg β-carotene/100 mL samples), TPC (0.62±0.03 mg GAE/g), DPPH (15.67±1.02 mmolTrolox/100g), and FRAP assay (194.00±7.84 μmol AAE/100g). The aril-pulp mixture showed the highest TCC, TPC, DPPH and FRAP value compared to peel significantly (p<0.05). Peel with ascorbic acid pre-treatment and dried at 50°C had the greatest antioxidant activities among the peel samples.
Keyword: antioxidant, carotene, gac fruits, gac powder supplement, peel, waste utilization

Judul: Development of functional drink from Gac fruit (Momordica cochichinensis S.) combined with Tomato (Lycopersicon esculentum) and Pineapple (Ananas comosus) juice
Abstrak: Carotenoid, flavonoid, polyphenol, and vitamin are classified as bioactive agents that give beneficial impacts for health as antioxidant. These components can be found in fruits such as gac fruit (Momordica cochinchinensis S.), pineapple and tomato. The objectives of this research were to develop functional drink from gac juice combined with pineapple and tomato juice, and to analyze the physical, chemical properties, bioactive compound and sensory evaluation of the product. Product formulation was done using Design-Expert® 7.00 software which containing 47% of gac juice, 45% mix of tomato and pineapple juice, and 8% of fructose, resulted in eight formulas. Research variables were the percent of tomato juice (TJ) and pineapple juices (PJ), while the analyzed responses were total polyphenol content (TPC), DPPH, FRAP, and total carotenoid. Different proportion of tomato and pineapple juice in functional drink significantly affect TPC, FRAP, DPPH, and total carotenoid (p<0.05). Formula with the highest proportion of PJ showed the highest content of TPC (396.91 ± 10.12 μg GAE/ml), FRAP (330.23 ± 16.21 μmol AAE/100 ml), and DPPH (277.70 ± 11.30 μM Trolox) (p<0.05). Meanwhile, formula with the highest proportion of TJ gave the highest content of total carotenoid (3748.65 ± 20.94 μg/100ml) (p<0.05). Optimization using D-Optimal generated three formulas with highest desirability values for sensory evaluation and proximate analysis. The optimum formula consisting of 47% gac juice, 39.33% pineapple, 8% fructose syrup, and 5.67% tomato was suitable for functional drink development.
Keyword: antioxidant capacity, carotenoid, functional drink, polyphenol

Judul: Bifurkasi lokal pada titik tetap non-hiperbolik
Abstrak: Bifurkasi menggambarkan perubahan pada struktur orbit di sekitar titik tetap. Titik tetap dibagi menjadi dua yaitu titik tetap hiperbolik dan titik tetap non-hiperbolik. Titik tetap non-hiperbolik terjadi jika ada nilai eigen dengan bagian real sama dengan nol. Kestabilan dari titik tetap dapat diketahui dari nilai eigen yang diperoleh dari pelinearan medan vektor. Pada bifurkasi satu-dimensi ditemukan kasus-kasus untuk bifurkasi saddle-node, bifurkasi transcritical dan bifurkasi pitchfork. Bifurkasi saddle-node terjadi jika satu sisi dari nilai parameter tidak terdapat titik tetap dan pada sisi lain terdapat dua titik tetap, dimana yang satu stabil dan yang lainnya tak-stabil. Bifurkasi transcritical terjadi jika terdapat pertukaran kestabilan, yaitu dari titik tetap stabil menjadi titik tetap tak-stabil dan sebaliknya. Sedangkan bifurkasi pitchfork dibagi menjadi dua, yaitu: bifurkasi pitchfork supercritical dan bifurkasi pitchfork subcritical. Bifurkasi pitchfork supercritical terjadi jika satu titik tetap stabil berubah menjadi dua titik tetap stabil dan satu titik tetap tak-stabil, dan bifurkasi pitchfork subcritical terjadi jika satu titik tetap stabil dan dua titik tetap tak-stabil berubah menjadi satu titik tetap tak-stabil. Bifurkasi Hopf (bifurkasi dua-dimensi) terjadi jika terdapat orbit periodik pada struktur orbitnya yang berupa lingkaran dengan jari-jari konstan. Ada atau tidaknya orbit periodik dapat diketahui setelah sistem ditransformasikan ke dalam koordinat polar. Orbit periodik ini dapat bersifat stabil maupun tak-stabil. Model periklanan (advertising) Feichtinger merupakan salah satu contoh penerapan bifurkasi Hopf Model ini menghasilkan satu titik tetap dan orbit periodik yang bersifat stabil.
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