Judul: Kajian Pengaruh Kadar Asam Lemak Bebas Terhadap Sifat Termal Minyak Sawit Kasar
Abstrak: Minyak sawit merupakan salah satu komoditas pertanian terbesar di Indonesia. Sejak tahun 2006, Indonesia bahkan tercatat sebagai produsen minyak sawit terbesar dunia. Pencapaian ini tentu didukung oleh industri minyak sawit kasar atau Crude Palm Oil (CPO) yang merupakan bahan baku minyak sawit. Indonesia mampu memproduksi 19,85 ton CPO pada tahun 2010 dengan 30,25% merupakan komoditas ekspor. CPO di Indonesia mengacu pada SNI 01-2901-2006 tentang minyak kelapa sawit kasar. Di dalam aturan tersebut CPO yang layak diperjualbelikan memiliki kadar asam lemak bebas (ALB) yang kurang dari 5%. Dalam prakteknya, industri masih merasa sulit untuk memenuhinya. Hal ini terutama disebabkan oleh proses penanganan yang kurang baik sehingga aktifitas enzim lipoksigenase dapat dengan mudah meningkatkan ALB. Dengan keadaan tersebut, mendorong terjadinya praktek adulterasi dengan cara mencampurkan CPO yang telah out of spec (kadar ALB lebih dari 5%) dengan CPO berkadar ALB kurang dari 5% sehingga didapatkan kadar ALB yang sesuai dengan standar. Proses pencampuran ini disinyalir dapat memberikan dampak pada sifat fisikokimia khususnya sifat termal serta memengaruhi proses awal pengolahan CPO, yakni fraksinasi. Hal ini disebabkan ALB, yang merupakan impurities, dicurigai memiliki pengaruh terhadap sifat termal CPO. Penelitian ini merupakan pemetaan awal dari sifat fisikokimia CPO yang dapat menjadi dasar untuk menemukan adanya parameter fisik yang mampu mendeteksi terjadinya proses pencampuran CPO. Penelitian ini dibatasi pada uji SNI 01-2901-2006 dan uji penentuan thermogram kristalisasi dan pelelehan. Hasil telah menunjukkan bahwa terdapat korelasi antara kadar ALB terhadap sifat termal dari CPO campuran. Namun korelasi yang kuat terjadi hanya pada beberapa sifat termal yaitu titik potong kurva kristalisasi, peak pelelehan olein, dan titik potong kurva pelelehan.
Keyword: Crude Palm Oil, asam lemak bebas, sifat termal, thermogram kristalisasi dan pelelehan

Judul: Kajian Sifat Kristalisasi Lemak pada Minyak Sawit Kasar
Abstrak: Indonesia is the biggest crude palm oil (CPO) producer in the world. Study on fat crystallization of CPO is needed to improve the knowledge of CPO handling during storage and transportation. The aim of this study is to characterize fat crystallization properties of CPO related to storage and transportation. Solid fat content (SFC) of CPO were decreased in higher temperature. After four weeks storage, SFC of CPO were increased at 20 ºC and 25 ºC, but were decreased at 30-40 ºC. CPO crystallized in slow cooling rate (0.2 ºC/minute) had higher SFC, meanwhile CPO crystallized in faster cooling rate (0.5 ºC/minute and 1 ºC/minute) had lower SFC. CPO which crystallized under slow cooling resulted higher Avrami constant (k) and lower Avrami exponent (n) than CPO which crystallized under fast cooling. The Avrami constant on cooling rate 0.2 ºC/minute, 0.5ºC/minute, and 1 ºC/minute were 0.013, 0.003, and 0.002 respectively. CPO which crystallized under fast cooling had higher induction time and crystallization half time. The Avrami exponent on cooling rate 0.2 ºC/minute, 0.5 ºC/minute, and 1 ºC/minute was 1.614, 2.032, and 2.170 repectively. Faster crystallization occured on higher shear rate. CPO which crystallized under higher shear rate had longer induction time than lower shear rate.
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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