Judul: Identification of Distinguishing Indicators of Natural Formaldehyde Based on Parameters of Quality Deterioration Value in Freshwater Fish
Abstrak: Ikan nila, mas, dan patin merupakan ikan air tawar komersil dan dagingnya menjadi komoditas ekspor dalam bentuk segar atau dingin dan beku. Formalin menjadi salah satu bahan berbahaya yang penggunaannya sering disalahgunakan sebagai pengawet pada ikan untuk mencegah kerusakan ikan. Formaldehida dapat terbentuk secara alami pada ikan selama proses kemunduran mutu ikan melalui reaksi reduksi trimetilamin oksida (TMAO) yang terjadi secara enzimatik dengan hasil samping berupa dimetilamin (DMA). Penelitian ini bertujuan menentukan indikator pembeda dengan penambahan formalin dan tanpa penambahan formalin pada ikan nila, mas, dan patin selama 8 minggu dengan penyimpanan beku. Parameter yang diamati adalah morfometrik, organoleptik, pH, total volatile base (TVB), formaldehida (FA), dan dimetilamin (DMA). Parameter FA dan TVB dapat dijadikan sebagai indikator pembeda antara kedua perlakuan tersebut. Parameter mata juga dapat dijadikan sebagai indikator pembeda, akan tetapi bukan merupakan parameter yang kuat., Tilapia, carp, and pangas catfish are commercial freshwater fish and their meat is an export commodity in fresh or chilled and frozen form. Formalin is one of the hazardous materials whose use is often misused as a preservative in fish to prevent fish damage. Formaldehyde can be formed naturally in fish during the process of deterioration of fish quality through the reduction reaction of trimethylamine oxide (TMAO) which occurs enzymatically with by-products in the form of dimethylamine (DMA). This study aims to determine the differentiating indicators with and without the addition of formalin in tilapia, carp, and catfish for 8 weeks with frozen storage. Parameters observed were morphometric, organoleptic, pH, total volatile base (TVB), formaldehyde (FA), and dimethylamine (DMA). The the parameters FA and TVB can be used as indicators of the difference between the two treatments. The eye parameter can also be used as a indicator, but it is not a strong parameter.
Keyword: carp, natural formaldehyde, nile tilapia, pangas catfish, quality deterioration

Judul: Natural Formaldehyde Content and Deterioration of the  Quality of Scad Fish During Chilling Temperature Storage
Abstrak: Ikan layang merupakan ikan ekonomis tinggi yang banyak digemari masyarakat. Formaldehida pada ikan dapat terbentuk secara alami melalui pemecahan TMAO menjadi formaldehida dan DMA. Penelitian bertujuan menentukan kandungan formaldehida alami dan kaitannya terhadap kemunduran mutu ikan layang selama penyimpanan suhu chilling. Analisis yang dilakukan meliputi uji organoleptik, pH, total volatile base (TVB), trimetilamina (TMA), formaldehida (FA), dan dimetilamina (DMA) setiap 2 hari sekali. Uji organoleptik ikan layang menunjukkan penurunan selama penyimpanan. Nilai pH menurun dihari ke-2 dan terus meningkat setelah penyimpanan hari ke-8 hingga hari terakhir. Nilai TVB dan TMA ikan layang di hari ke-0 sebesar 5,44 mgN/100g dan 0,78 mgN/100g, kemudian meningkat hingga penyimpanan hari terakhir. Kandungan FA sudah terbentuk di awal penyimpanan dengan nilai tertinggi yaitu 10,21 ppm pada penyimpanan hari ke-10. Kadar DMA tertinggi terlihat pada penyimpanan hari ke-14 sebesar 9,29 ppm. Formaldehida alami memiliki korelasi yang tinggi dan cukup tinggi dengan parameter kemunduran mutu seperti pH, TVB, TMA, dan DMA., Scad fish is a high economic fish that is very popular with the public. Formaldehyde in fish can be formed naturally through the breakdown of TMAO into formaldehyde and DMA. The study aimed to determine the natural formaldehyde content and its relationship to the deterioration of the quality of scad fish during chilling temperature storage. The analysis includes an organoleptic test, pH, total volatile base (TVB), trimethylamine (TMA), formaldehyde (FA), and dimethylamine (DMA) every 2 days. The organoleptic test of scad showed a decrease during storage. The pH value decreased on the 2nd day and continued to increase after the 8th day of storage until the last day. The TVB and TMA values of scad fish on day 0 were 5.44 mgN/100g and 0.78 mgN/100g, then increased until the last day of storage. FA content was formed at the beginning of storage with the highest value of 10.21 ppm on the 10th day of storage. The highest DMA level was seen on the 14th day of storage at 9.29 ppm. Natural formaldehyde has a high and quite high correlation with quality deterioration parameters such as pH, TVB, TMA, and DMA.
Keyword: chilling temperature, formaldehyde, quality deterioration, scad fish

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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