Judul: Physical, Chemical Characteristics and Organoleptic Test of Gelato Yogurt with Addition of Plum Juice (Prunus salicina) as a Natural Flavour
Abstrak: Yogurt merupakan salah satu bentuk produk susu yang memanfaatkan mikroba dalam proses fermentasi susu segar menjadi produk dengan rasa asam. Pembuatan gelato bisa bervariasi dengan menambahkan berbagai jenis buah, salah satunya plum. Rasa buah plum yang manis dan asam dapat dijadikan sumber bahan penambah rasa alami yang rendah kalori dan aman dikonsumsi, Tujuan penelitian ini adalah untuk menganalisis pengaruh karakteristik fisik, kimia dan sifat organoleptik panelis terhadap yogurt gelato dengan penambahan sari buah plum (Prunus salicina) sebagai perisa alami. Penelitian ini menggunakan rancangan acak lengkap (RAL) dengan penambahan sari buah plum (Prunus salicina) yang berbeda yaitu 0%, 5%, dan 10%. Hasil penelitian menunjukkan bahwa penambahan sari buah plum pada gelato yogurt berpengaruh nyata (P<0,05) terhadap nilai viskositas, daya leleh, dan overrun tetapi tidak berpengaruh nyata (P>0,05) terhadap nilai pH, kadar lemak, dan kadar protein. Data sifat organoleptik uji hedonik menunjukan hasil penambahan sari buah plum berpengaruh nyata (P<0,05) terhadap parameter rasa gelato yogurt yang dihasilkan. Data sifat organoleptik uji mutu hedonik menunjukan hasil penambahan sari buah plum tidak berpengaruh nyata (P>0,05) terhadap parameter tekstur gelato yogurt yang dihasilkan., Yogurt is a form of dairy product that utilizes microbes in the fermentation process of fresh milk into a product with a sour taste. Making gelato can be varied by adding various types of fruit, one of which is plum. The sweet and sour taste of plums can be used as a source of natural flavor enhancers that are low in calories and safe for consumption. The purpose of this study was to analyze the effect of the physical, chemical and organoleptic characteristics of the panelists on yogurt gelato with the addition of plum juice (Prunus salicina) as a natural flavoring. This study used a completely randomized design (RAL) with different percentages of plum juice (Prunus salicina) addition namely 0%, 5%, and 10%. The results showed that the addition of plum juice to yogurt gelato had a significant (P<0,05) effect on the viscosity, melting time, and overrun but had no significant effect (P>0,05) on the pH, fat and protein contents. Data on the organoleptic properties of the hedonic test showed the results of plum juice addition had a significant effect (P<0,05) on the taste parameters of the resulting yogurt gelato. Data on the organoleptic properties of the hedonic quality test showed that the results of the plum juice addition had no significant effect (P>0,05) on the texture parameters of the yogurt gelato.
Keyword: plums, gelato, natural flavors, yogurt

Judul: Sifat Fisik, Kimia, dan Organoleptik Gelato dengan Penambahan Ekstrak Daun Kelor
Abstrak: Gelato adalah salah satu jenis es krim yang berasal Italia yang marak ditemui dan digemari masyarakat Indonesia namun memiliki zat gizi yang kurang lengkap. Penelitian ini bertujuan menganalisis karakteristik fisik, kimia, dan uji organoleptik gelato dengan penambahan ekstrak daun kelor. Rancangan Acak Kelompok (RAK) digunakan pada uji sifat fisik, kimia, dan organoleptik gelato dengan perlakuan persentase penambahan 0%, 3%, dan 6% dengan 3 kali pengulangan. Data dianalisa dengan ANOVA dan Friedman Test untuk data organoleptik. Hasil penelitian menunjukkan bahwa penambahan ekstrak daun kelor berpengaruh nyata terhadap sifat fisik yakni overrun, daya leleh, dan pH dan sifat kimia gelato. Hasil uji hedonik menunjukkan bahwa penambahan ekstrak daun kelor berpengaruh nyata (P<0,05) terhadap parameter warna sedangkan pada uji mutu hedonik berpengaruh nyata (P<0,05) terhadap parameter warna, rasa, dan aroma. Penggunaan ekstrak daun kelor 6% pada gelato merupakan formulasi terbaik pada penelitian ini berdasarkan pengujian fisik, kimia, dan organoleptik., Gelato is a type of ice cream that originates from Italy and is widely found and loved by the people of Indonesia but it has a less complete nutritional profile. This research aims to analyze the physical, chemical, and organoleptic characteristics of gelato with the addition of moringa leaf extract. A randomized complete block design (RAK) was used for the physical, chemical, and organoleptic properties of gelato with treatments of 0%, 3%, and 6% addition percentages with three times replicated. The data is analyzed using ANOVA and Friedman Test for organoleptic data. The results showed that the addition of moringa leaf extract significantly affected the physical properties such as overrun, meltdown resistance, and pH, and the chemical properties of gelato. Hedonic test results indicated significant effects (P<0.05) of moringa leaf extract addition on color parameters, while significant effects (P<0.05) were observed in hedonic quality tests for color, taste, and aroma parameters. The use of 6% moringa leaf extract in gelato was found to be the best formulation based on physical, chemical, and organoleptic tests in this study.
Keyword: daun kelor, sifat kimia, uji organoleptik, gelato, sifat fisik

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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