Judul: The potency of jambolan (Syzygium cumini) fruit anthocyanins as natural food colorant with antioxidation capability
Abstrak: There is a worldwide interest in the use of natural red colorant in foods. Anthocyanins have been suggested as potential colorants due to their attractive red colors and non-toxicity. Jambolan (Syzygium cumini) fruit, a tropical fruit is found in Indonesia, is rich in anthocyanin pigments especially in its peel part. It has a potency for natural food colorant. In this study, the utilization of jambolan anthocyanins for natural food colorant was studied. The anthocyanins of jambolan fruit were characterized for their composition, stability properties, improvement of color intensity and stability through intermolecular copigmentation reaction, and capability as antioxidant. The content of total monomeric anthocyanin in the ripe fruit was 161 mg/100 g fresh fruit (731 mg/100 g skin on wet basis). Anthocyanins were identified as 3,5-diglucoside derivatives of delphinidin (41%), petunidin (28%), malvidin (26%), cyanidin (4%), and peonidin (1%). Native jambolan anthocyanins had low color intensity with pH ranging from 1 to 8 and relatively unstable during heating at 80 and 98oC, exposed to white fluorescent light and storage at room and refrigeration temperature, absence of light. However, they showed better stability to all treatments tested than enocianin, a commercial anthocyanin colorant. During light exposure and storage treatment, native jambolan anthocyanins showed comparable stability to red cabbage anthocyanins (acylated structure). Intermolecular copigmentation of jambolan anthocyanins with cinnamic acid (sinapic acid, ferulic acid, caffeic acid) and rosemary polyphenol extract increased the color intensity. Copigmentation with rosemary polyphenol extract produced the best color enhancement. Copigmentation with sinapic acid, caffeic acid, and rosemary polyphenol extract also increased stability on light exposure and storage treatments (room and refrigeration temperatures), not on heat treatments at 80 and 98oC. Moreover, jambolan anthocyanins, native or copigmented, in the form of extract, isolate, or added to a model beverage as colorant showed antioxidant activities. The anthocyanin isolate showed higher antioxidant activity as compared to extract from pulp or peel. Copigmentation jambolan anthocyanins with sinapic acid, caffeic acid, ferulic acid, and rosemary polyphenol extract on a model beverage increased the total polyphenol content and antioxidant activity as compared to model beverage with native anthocyanins. These results indicated that anthocyanins obtained from jambolan fruit can be utilized as a functional natural colorant for low pH foods.
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Judul: Kajian Pemanfaatan dan Pengembangan Potensi Ekstrak Manggis Merah (Garcinia forbesii) sebagai Minuman Fungsional Kaya Antioksidan dan Kestabilannya
Abstrak: Red Mangosteen (Garcinia forbesii) is a fruit that comes from South Kalimantan and rarely used by people. Red mangosteen fruit has white flesh with sweet flavor and fresh red rind with strong sour taste. Red mangosteen rind has a potency to be processed into functional beverage. This study is aimed to determine the functional beverage formulas made from red mangosteen rind extract (M) and emprit ginger extract (J) with the addition of pekak extract (P) and cinnamon extract (K) and then analyzed the characterization of physicochemical properties, functional and determination of its stability at high temperatures. Raw Material M obtained in the form of extracts with 1.4 TPT oBrix while J , P and K obtained by water extraction with water and spices ratio of 1:10 for J and 1:5 for P and K. Formula drink based on M and J was made in three concentration ratio, which is 5:1 (MJ 1), 5:2 (MJ 2), and 5:3 (MJ 3) (v/v). MJ 1 formula is selected as the basic formula based on hedonic rating test and antioxidant capacity. MJ 1 formula is given each addition P extracts and K extract which is made in three different concentrations, are 5%, 10%, and 15%. Formula MJP 5% and MJK 5% is chosen as the selected formula to determine its stability. Formula MJP 5% has the antioxidant capacity 6,46 mg AEAC/mL and total phenol content 20,38 mg GAE/mL, while MJP 5% has 7,95 mg AEAC/mL antioxidant capacity and total phenol content 21,17 mg GAE/mL. Determination of stability MJP 5% and MJK 5% to 85% usable quality was conducted by using the Arrhenius method with antioxidant capacity and total phenol content as parameters. Both formulas packaged in vials dark bottles of 10 ml volume without heating treatment processes, such as pasteurization and sterilization and stored in an incubator at temperature 35°C, 45°C and 55°C. Stability of MJK 5% stored at 35°C, 45°C and 55°C are 8 days, 5 days and 4 days based on the antioxidant capacity parameter and 7 days, 6 days, and 5 days based on total phenol parameters, while the stability of MJP 5% is 9 days, 6 days, and 5 days based on antioxidant capacity parameter and 7 days, 6 days, and 5 days based on total phenol parameter. The observation results showed that the formula mixture of red mangosteen rind extract and ginger extract by the addition of pekak extract and cinnamon extract could potentially be developed as a functional drink from the utilization of rare fruit cultivation, red mangosteen fruit.
Keyword: Arrhenius, cinnamon, pekak, emprit ginger, red mangosteen rind, functional drink

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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