Judul: Kualitas Mikrobiologi Minuman Susu Aneka  Rasa yang Dijual di Sekitar Kampus IPB Dramaga Berdasarkan Jumlah  Mikroorganisme
Abstrak: Various ready-to-drink milk is commonly sold by street vendors around the Dramaga campus of IPB University. Vending locations, hygiene of vendors, equipment sanitation, food handling and storage during sales can affect the safety of beverages sold by these street vendors. The aim of this study was to determine the microbiological quality of flavoured ready-to-drink milk and to measure the increase in the number of microorganisms of the milk before and after adding flavours. Samples used in this study were plain milk and milk that had been added with strawberry and chocolate flavour but without the addition of sugar and ice. Samples were obtained from four street vendors around the Dramaga campus of IPB University. One sample of each flavour was purchased three times per vendor. A total of 36 milk samples were analysed to determine the total number of microorganisms using the total plate count (TPC) method by the pour plate method. The data obtained was analysed descriptively. The results indicated that almost all samples had a total number of microorganisms which was above the threshold of microbial contamination according to SNI 7388:2009, that is 5 × 104 cfu/ml. The average total number of microorganisms in strawberry flavoured milk (6,74 × 106 ± 7,25 × 106 cfu/ml) was higher than chocolate flavoured milk (6,18 × 105 ± 4,86 × 105 cfu/ml). The average total number of microorganisms in unflavoured milk was 7,31 × 104 ± 8,02 × 104 cfu/ml. The total number of microorganisms in milk before and after the addition of flavours showed a significant increase. Total microorganisms in milk that had been added with strawberry flavour increased by 92 times, with a significant difference (p<0,05). An 8-fold increase of total microorganisms without a significant difference (p>0,05) was found in milk that had been added with chocolate flavour. The total number of microorganisms of flavoured milk sold by street vendors around the Dramaga campus of IPB University were very high. Provision of food safety education and adequate sanitary facilities at vending sites are highly recommended to improve the food safety of the products sold., Minuman susu aneka rasa siap minum banyak dijual oleh pedagang kaki lima di sekitar kampus IPB Dramaga. Lokasi penjualan, kondisi kebersihan penjual dan sanitasi peralatan, serta penanganan dan penyimpanan makanan selama penjualan dapat mempengaruhi keamanan pangan dari berbagai minuman yang dijual oleh pedagang kaki lima. Tujuan penelitian ini adalah mengetahui kualitas mikrobiologi minuman susu aneka rasa dan mengukur pertambahan jumlah mikroorganisme dari susu sebelum dan setelah ditambahkan perisa. Sampel berupa susu tanpa rasa (plain) dan susu yang telah ditambah dengan perisa stroberi dan coklat namun tanpa ada tambahan gula dan es batu. Sampel diperoleh dari empat pedagang kaki lima di sekitar kampus IPB Dramaga, yang diambil sebanyak satu sampel dengan tiga kali ulangan. Sebanyak 36 sampel susu dihitung jumlah total mikroorganisme (TPC) menggunakan metode hitungan cawan dengan cara tuang. Data yang diperoleh diolah secara deskriptif. Hasil penelitian ini menunjukkan sebagian besar sampel memiliki jumlah total mikroorganisme di atas ambang batas maksimum cemaran mikroba dalam pangan menurut SNI 7388:2009, yaitu 5 × 104 cfu/ml. Rata-rata jumlah total mikroorganisme
Keyword: flavoured milk, total microorganisms, jumlah mikroorganisme, minuman susu aneka rasa

Judul: Jumlah Pseudomonas spp. dan Bakteri Psikotrofik Lainnya pada Minuman Susu Aneka Rasa yang Dijual di Sekitar Kampus Dramaga dan Cilibende IPB University.
Abstrak: Minuman aneka rasa dengan bahan utama susu merupakan salah satu bahan pangan yang memiliki komposisi gizi tinggi, serta berpotensi sangat baik dalam pertumbuhan mikroba. Pseudomonas spp. merupakan salah satu golongan bakteri psikotrofik yang dapat mencemari susu sehingga dapat menurunkan kualitas olahan susu dan berpotensi mengganggu kesehatan manusia. Penelitian ini bertujuan mengukur tingkat cemaran Pseudomonas spp. dan bakteri.psikotrofik lainnya pada olahan susu yang dijual di sekitar Kampus Dramaga dan Cilibende IPB University. Sampel susu diambil dari setiap kedai susu, masing-masing satu sampel dan dilakukan pengulangan sebanyak 3 kali. Berdasarkan hasil survei terdapat 13 kedai susu di sekitar kampus sehingga total sampel sebanyak 39. Sampel susu diambil tanpa penambahan gula, varian rasa, yogurt dan es batu, hanya susu tawar (plain). Pengujian jumlah Pseudomonas spp. dan bakteri psikotrofik lainnya menggunakan metode hitungan cawan dengan cara sebar. Hasil penelitian ini menunjukkan rata-rata jumlah Pseudomonas spp. dalam susu sebesar 3.3 log cfu/ml (Dramaga) dan 4.7 log cfu/ml (Cilibende). Jumlah bakteri psikotrofik dalam susu berturut-turut yaitu, 4.30 ± 4.54 log cfu/ml; 4.36 ± 4.50 log cfu/ml. Sebanyak 93.33% sampel Dramaga dan 87.50% sampel Cilibende di bawah batas maksimum cemaran mikroba (BMCM), sedangkan sebanyak 6.67% sampel Dramaga dan 12.5% sampel Cilibende di atas ambang batas BMCM. Berdasarkan hasil wawancara didapatkan hubungan yang tidak signifikan antara variabel-variabel yang berasal dari karakteristik umum penjual susu siap minum (variabel asal susu, cara pengolahan, penyimpanan susu, tempat penyimpanan susu, peralatan, dan jarak dari keramaian) dengan keberadaan bakteri psikotrofik. Cemaran Pseudomonas spp. dan bakteri psikotrofik dalam minuman susu aneka rasa disebabkan penerapan sanitasi dan higiene personal yang kurang baik di tingkat penjual, sehingga dapat menurunkan kualitas olahan susu yang disimpan dingin.
Keyword: Bakteri Psikotrofik, Minuman Aneka Rasa, Pseudomonas spp., Susu

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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