Judul: Comparison of Total Phenol and Total Phenolic Acid of Bogor Arabica Coffee from Different Postharvest and Roasting Processes
Abstrak: Kopi mengandung senyawa fenolik, yang dapat dianalisis dari kandungan total fenolik atau senyawa fenolik tertentu. Komposisi dan konsentrasi fenolik dalam kopi dipengaruhi oleh proses pascapanen dan tingkat penyangraiant. Penelitian ini bertujuan untuk membandingkan rasio asam fenolat (diukur sebagai asam klorogenat) terhadap total kandungan fenolik dalam kopi arabika Bogor, dengan mempertimbangkan perlakuan pascapanen dan tingkat penyangraian yang berbeda. Sampel kopi diberikan perlakuan pascapanen (kering, basah, dan madu) dan penyangraian (ringan dan gelap). Proses penyangraian melibatkan pemanasan kopi pada suhu antara 147,9°C hingga 178,8°C untuk penyangraian ringan, dan 190,2°C hingga 200°C untuk penyangraian gelap (masing-masing selama 10 menit). Biji kopi hijau digunakan sebagai kontrol. Warna biji kopi, konsentrasi asam fenolik dalam ekstrak kopi, dan konsentrasi fenolik total dalam ekstrak kopi dianalisis dengan colorimeter, HPLC, dan spektrofotometer secara berturut-turut. Hasil penelitian menunjukkan bahwa penyangraian secara signifikan memperkuat warna gelap kopi arabika Bogor. Di antara asam fenolat, isomer 5-CQA muncul sebagai yang paling dominan dan juga paling rentan terhadap degradasi selama penyangraian. Seiring dengan peningkatan tingkat penyangraian, konsentrasi asam fenolat secara konsisten menurun. Kandungan total fenolik pada awalnya meningkat pada kopi ringan namun kembali menurun pada kopi gelap. Biji kopi hijau memiliki proporsi asam fenolat tertinggi (83%), sedangkan kopi gelap memiliki proporsi terendah (19%). Meskipun kopi ringan memiliki kandungan total fenolik tertinggi, konsentrasi asam fenolat menurun secara signifikan dibandingkan dengan biji kopi hijau., Coffee contains abundant phenolic compounds, which can be evaluated either collectively as total phenolics or individually as specific phenolic components. The presence and amount of phenolics in coffee are influenced by various factors, including postharvest treatments and the roasting process. This study aimed to compare the ratio of phenolic acid, specifically chlorogenic acid, to the total phenolic content in Bogor arabica coffee, considering different postharvest treatments and roasting levels. The coffee samples underwent different postharvest treatments (dry, wet, and honey) and were subjected to two types of roasting processes (light and dark). Green coffee beans were used as the control. The roasting procedure involved heating the coffee within the temperature range of 147.9°C to 178.8°C for light roasting and 190.2°C to 200°C for dark roasting (each for 10 minutes). The color of the coffee beans, the concentration of phenolic acid in the coffee extract, and the total phenolic content in the coffee extract were analyzed using a colorimeter, high-performance liquid chromatography (HPLC), and spectrophotometer, respectively. The findings revealed that roasting significantly intensified the dark color of Bogor arabica coffee. Among the phenolic acids, the 5-CQA isomer emerged as the most dominant and was also the most susceptible to degradation during the roasting process. As the roasting level increased, the concentration of phenolic acid consistently decreased. Interestingly, the total phenolic content initially increased in light-roasted coffee but decreased in dark-roasted coffee. Green coffee beans exhibited the highest proportion of phenolic acid (83%), whereas dark-roasted coffee had the lowest proportion (19%). Although light-roasted coffee had the highest total phenolic content, its phenolic acid concentration decreased significantly compared to green coffee beans.
Keyword: asam fenolat, kopi arabika, penyangraian, perlakuan pascapanen, total fenolat

Judul: Pattern of Chlorogenic Acid Degradation on Arabica Coffee Roasting Process
Abstrak: Arabica coffee (Coffea arabica L.) contains phenolic compounds that have an important role in the formation of flavor and beneficial for health. One of the main phenolic compounds is chlorogenic acid. Chlorogenic acid has a subgroup with the largest content in coffee, namely caffeoylquinic acid (CQA) but this subgroup is very sensitive to heat damage. This study objective is to understand the effect of the roasting on chlorogenic acid concentration in coffee beans. Measurement of physicochemical characteristics (moisture content, density, yield, and color) was carried out to see the effect of roasting process on characteristic of coffee beans. Meanwhile, the analysis and quantification of chlorogenic acid was carried out using the HPLC method. The results obtained showed that there was a degradation of chlorogenic acid content in the arabica coffee after the roasting process. Higher roasting rate will cause greater damage of chlorogenic acid content. Each isomer such as 3-CQA, 4-CQA, or 5-CQA has a certain pattern of damage due to the roasting process. 5-CQA has pattern that is directly proportional to the roasting level. However, the others, 3-CQA and 4-CQA have different patterns due to an increase on concentration level in certain sampels after the roasting process., Kopi arabika (Coffea arabica L.) memiliki kandungan senyawa fenolik yang berperan penting dalam pembentukan sensori dan bermanfaat bagi kesehatan. Salah satu senyawa fenolik utama yang berperan adalah asam klorogenat. Asam klorogenat memiliki subgrup dengan kandungan terbesar dalam biji kopi yaitu asam caffeoylquinic (CQA), namun subgrup tersebut sangat sensitif terhadap kerusakan akibat panas. Penelitian ini bertujuan mempelajari pengaruh proses penyangraian terhadap konsentrasi asam klorogenat pada biji kopi. Pengukuran karakteristik fisikokimia (kadar air, densitas kamba, rendemen, dan warna) dilakukan untuk melihat pengaruh proses penyangraian terhadap karakteristik biji kopi. Sementara itu, analisis dan kuantifikasi asam klorogenat dilakukan dengan metode HPLC. Hasil penelitian yang diperoleh menunjukkan adanya degradasi kandungan asam klorogenat pada kopi arabika setelah proses penyangraian. Semakin tinggi tingkat penyangraian akan menyebabkan tingginya kerusakan kandungan asam klorogenat. Masing-masing isomer asam klorogenat seperti 3-CQA, 4-CQA, dan 5-CQA memiliki pola kerusakan tertentu akibat proses penyangraian. 5-CQA memiliki pola kerusakan yang berbanding lurus dengan tingkat penyangraian. Namun, isomer lainnya yaitu 3-CQA dan 4-CQA memiliki pola kerusakan berbeda yang disebabkan oleh adanya kenaikan konsentrasi pada sampel tertentu setelah proses penyangraian.
Keyword: arabica coffee, chlorogenic acid, damage pattern, hplc, roasting

Judul: Pengaruh vaksinasi terhadap dinamika populasi pada model SIR (Susceptible-Infected-Recovered)
Abstrak: SIR model can be used to model the spread of diseases in a closed population based on certain assumptions. In this research, the SIR model is formulated by including the factor of vaccination. As the result, the model has been shown to have two equilibrium points, i.e. disease free and endemic equilibrium. A simulation study is carried out to illustrate the model. The results show that some equilibrium points are asymptotically stable. Moreover, a minimum level of vaccination has been defined. For the vaccination level less than the minimum level, increase in the vaccination level results in decrease of the proportion of infected individuals in the corresponding equilibrium point. On the other hand, for the vaccination level greater than the minimum level, increase in the vaccination level results in decrease the proportion of susceptible individuals in the corresponding equilibrium point. Furthermore, when vaccination level is greater than the minimum level, it is found that the time needed for the disease to extinct is shorter.
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