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: Pengaruh Kopigmentasi Terhadap Stabilitas Warna Antosianin Buah Duwet (Syzygium cumini)
Abstrak: Warna pada makanan memberi pengaruh pada kualitas produk pangan. Banyaknya masalah yang dapat diakibatkan karena ketidaktahuan masyarakat mengenai aturan kadar dan jenis pewarna buatan yang diizinkan membuat tren yang saat ini beredar dalam masyarakat adalah back to nature. Jenis pewarna yang potensial untuk dikembangkan dengan adanya trend back to nature adalah zat pewarna alami. Antosianin merupakan salah satu pewarna alami yang potensial digunakan untuk produk pangan. Salah satu bahan pangan yang potensial sebagai sumber antosianin adalah buah duwet (Syzygium cumini). Jenis antosianin yang terdapat dalam buah duwet ini diduga ada dua yaitu petunidin-3-rhamnosa dan sianidin-3-soporosa namun yang lebih dominan adalah petunidin-3-rhamnosa.
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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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