Judul: Pengaruh Waktu Pemasakan dan Konsentrasi Terhadap Aktivitas Antioksidan dan Kadar Fenolik Total Brokoli (Brassica oleracea L. var. italica)
Abstrak: There are many plants that can be used as alternative medicine. One of them is broccoli which is known as vegetable that contain antioxidant, such as phenolic compounds. Antioxidant is capable to inhibit free radicals in human tuJy. This research was aimed to measure the effect of cooking time and concentration of broccoli on antioxidants activity tested by DPPH (1,I-diphenyl-2-pycrilhydrazil) method and total phenolic content. Butylated hydroxytoluene (BHT) was used as positive control with various concentrations, 2, 4, 6, and 8 ppm. Some samples were cooked by conventional boiling treatment for 10, 20, and 30 minutes, and then were extracted with methanol. The extracts were separated by flash chromatography with toluene:ethyl acetate (11:9) as mobile phase. The number of fractions were determined with bioautography thin layer chromatography that were sprayed with DPPH 0.004% to get the active fraction. The methanol extracts and the active fractions were diluted to various concentrations, 10, 30, 50, and 70 ppm and then were determined for their antioxidant activity and the total phenolic content. The results showed that cooking time of broccoli from 10 to 30 minutes were significantly decreased antioxidant activity of extracts while increasing concentration of extract and active fraction from 10 to 70 ppm increase antioxidant activity of both of them. The ICso value of methanol extracts and active fraction were 226.94 and 221.78 ~g/mL, respectively. The ICso value of BHT was 6.46 ~g/mL. The total phenolic content active fraction for raw vegetable, 10, 20, and 30 minutes cooking time were 764.91, 495.96, 441.19, dan 304.66 mg/lOOg, respectively. Total phenolic content of broccoli were significantly decreased during the cooking.
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Judul: ANTIOXIDANT ACTIVITY FERRIC REDUCING ANTIOXIDANT POWER (FRAP), VITAMIN C, AND SENSORY PROFILES OF BROCCOLI COOKED WITH DIFFERENT WATER
Abstrak: Brokoli (Brassica oleracea var. italica) merupakan salah satu sayuran yang memiliki kandungan mikronutrien yang berlimpah. Proses perebusan merupakan cara yang paling mudah dan umum dilakukan untuk mengolah brokoli. Namun, penggunaan jenis air yang berbeda memiliki karakteristik yang berbeda sehingga diduga dapat mempengaruhi kandungan nutrisi pada brokoli. Tujuan dari penelitian ini adalah untuk menentukan pengaruh penggunaan jenis air yang berbeda untuk perebusan serta lama waktu perebusan terhadap aktivitas antioksidan, vitamin C, serta sensori pada brokoli. Analisis antioksidan dilakukan dengan metode Ferric Reducing Antioxidant Power (FRAP), vitamin C dengan 2,6- dichlorophenolindophenol, serta analisis sensori dengan metode Quantitative Descriptive Analysis (QDA). Jenis air yang digunakan untuk merebus brokoli adalah air sumur padat penduduk di Jakarta (TWJB), air minum dalam kemasan (AMDK), dan air minum isi ulang reverse osmosis (RO). Aktivitas antioksidan FRAP pada brokoli rebus dipengaruhi oleh jenis air dan lama waktu perebusan (4 menit dan 6 menit) secara signifikan. Brokoli yang direbus dengan air TWJB, AMDK, dan RO serta lama waktu perebusan memiliki aktivitas antioksidan FRAP yang berbeda secara signifikan. Jenis air AMDK dan TWJB memiliki kadar vitamin C tertinggi yaitu 2756,52 mg/kg sampel dan 2456,48 mg/kg sampel pada lama waktu perebusan 4 menit serta berbeda signifikan dengan jenis air lainnya. Pada uji sensori, jenis air TWJB dengan perebusan 6 menit unggul pada atribut warna sedangkan jenis air AMDK dengan perebusan 4 menit unggul pada atribut rasa manis, aroma, dan kekerasan. Jenis air serta variasi lama waktu perebusan dapat mempengaruhi aktivitas antioksidan, vitamin C, serta sensori pada brokoli., Broccoli (Brassica oleracea var. italica) is a vegetable high in micronutrients. The simplest and most popular method for processing broccoli is boiling. However, different types of water has varied properties, which is thought to impact the nutritional value of broccoli. The aim of this study was to examine the effects of boiling broccoli in various types of water and for various amounts of time on antioxidant, vitamin C, and sensory profiles. Vitamin C analysis used 2,6- dichlorophenolindophenol, antioxidant analysis used the Ferric Reducing Antioxidant Power (FRAP) method, and sensory analysis used the quantitative descriptive analysis (QDA) method. Broccoli is cooked in three different types of water: bottled water (AMDK), reverse osmosis (RO) refillable water, and Jakarta's densely populated well water (TWJB). The antioxidant activity of FRAP in broccoli was affected by the type of water and the length of boiling (between 4 and 6 minutes) significantly. At a boiling period of 4 minute, the AMDK and TWJB water has the maximum vitamin C level which is 2756,52 mg/kg sampel and 2456,48 mg/kg sampel which is significantly different from other types of water. The TWJB water type with a 6 minute boil excelled at the majority of color attributes whereas the AMDK water type with a 4 minute boil excelled at the sweetness, odor, and hardness attributes. Broccoli's antioxidant, vitamin C, and sensory profiles can be impacted by the type of water used and differences in the amount of time it is boiled for.
Keyword: broccoli, antioxidant, vitamin C, sensory profiles, water

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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