Judul: Mempelajari karakteristik penyimpanan segar selada kepala (krop) lettuce head (lactuca sativa L.)
Abstrak: Selada kepala tergolong dalam sayuran jenis baru dan merupakan salah satu jenis sayuran daun komoditi ekspor dengan nilai jual cukup tinggi. Di daerah tropis yang lembab, keadaan sayuran cepat mengalami kerusakan. Hal ini terutama disebabkan kondisi suhu dan kelembaban lingkungan yang relatif tinggi. Penyimpanan merupakan salah satu kegiatan penanganan pasca panen yang perlu mendapat perhatian lebih dalam kondisi tersebut, karena penyimpanan yang kurang sesuai menyebabkan sayuran lebih cepat busuk dan rusak. Perubahan mutu yang terjadi selama penyimpanan disebabkan sayuran masih mengalami proses kehidupan diantaranya respirasi. Laju respirasi tergantung dari suhu penyimpanan, ketersediaan oksigen dan karakteristik dari produk sayuran itu sendiri. Tujuan dari penelitian: 1) mempelajari laju aktifitas respirasi selada kepala segar pada beberapa tingkat suhu dan menentukan suhu penyimpanan yang optimum, 2) mempelajari pengaruh kombinasi konsentrasi gas CO₂ dan O₂ yang berbeda terhadap mutu selada kepala dan menentukan kombinasi konsentrasi gas CO2 dan O₂ yang optimum bagi penyimpanan segar selada kepala dan 3) mengamati perubahan mutu selada kepala segar selama penyimpanan. Bahan utama yang digunakan adalah sayuran selada kepala jenis Crisp Heading varietas Great lakes. Peralatan yang digunakan antara lain stoples PET 2.5 1, selang plastik, penjepit kertas, aerator, unit pengukur konsentrasi gas O₂ dan gas CO2, unit pendingin dan peralatan yang diperlukan untuk pengujian mutu.
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Judul: Pengaruh Suhu dan Lama Perendaman Blansir Terhadap Mutu Selada Kepala (Lactuca sativa L.) Terolah Minimal Selama Penyimpanan
Abstrak: The damage of minimally processed head lettuce (Lactuca sativa L.) is because of the activities of enzymes and microorganisms. The objectives of this research were (1) to determine the effect of treatment on quality of shredded blanched-lettuce, (2) to determine the best combination of temperature and immersion time on the handling of shredded blanched-lettuce and (3) to determine the Standard Operational Procedure (SOP) to treat minimally-processed lettuce head. The results of this research were blanching temperature of 50 °C with immersion time of 55 seconds and vacuum packaging could maintain the quality (weight, water content, brightness, hardness, and organoleptic) shredded blanched-lettuce could until 8-day storage. Standard Operational Procedure (SOP) for handling the shredded lettuce is sorting and peeling brown leaves, cuting and shredding with a size of 1.5 cm, immersing in water at 50 °C for 55 seconds, submerging in cold water 3-5 ° C for 1 minutes, centrifuging to reduce the excess water on the surface of shredded lettuce, packing with HDPE plastic, packaging in vacuum, and storaging with a temperature of 5 oC.
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Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model