Judul: Redistilled Liquid Smoke from Oil-Palm Shells and Its Application as Natural Rubber Coagulant
Abstrak: Abundant oil-palm shells waste which is generated annually as the result of the increasing production of palm oil can be utilized as source of liquid smoke. The acidic property of liquid smoke shows its potency as natural rubber coagulant. The objectives of this study are to redistill liquid smoke at 80, 90, and 100 ºC and also to examine the coagulation property of the RLS as compared to formic acid as a commercial coagulant. During redistillation, two collections of RLS were obtained from each temperature. The first collection was gathered at the first 5 min and the second one was gathered at the next 5 min. Each collection gave 5 L of RLS. The physical properties test showed that the RLS 100 ºC from the second collection was recommended as the natural rubber coagulant. This coagulant produced Wallace plasticity value that met the the Indonesian standard and high plasticity retention index value. The assumption of constituents in RLS which can prevent the storage hardening in rubber was not proven.
Keyword: Bogor Agricultural University (IPB), redistillation, oil-palm shells, natural rubber, coagulation

Judul: Pemanfaatan Redistilat Asap Cair Cangkang Kelapa Sawit sebagai Bahan Pengawet Alami pada Bakso Sapi
Abstrak: The misapplication of chemicals, such as formaldehyde, for preservative is still found in processed food ingredients. The use of these materials can be replaced by redistilled liquid smoke from oil palm shells. Identification using gas chromatography-mass spectrometer showed that there were no harmful compounds such as tar and polycyclic aromatic hydrocarbons. Acid level and pH of redistilled liquid smoke on 80 °C possess better result with the respectively values were 5.14% and 2.26. The LC50 value with brine shrimp lethality test method is 0.16%. Inhibition zone on the antibacterial test to Staphylococcus aureus with redistilled liquid smoke on 0.1% and 0.8% were respectively 6.11 mm and 6.08 mm while to Escherichia coli were respectively 0 mm and 6.95 mm. The inhibition zone redistilled liquid smoke was lower than 100 ppm chloramphenicol, which were 14.17 mm on S. aureus and 12.60 mm on E. coli. Redistilled liquid smoke with concentration of 0.8% was better than the concentration of 0.1% in inhibiting the growth of total microbial on the meatballs. The addition of redistilled liquid smoke was able to inhibit the growth of microbial up to 18 hours at room temperature.
Keyword: Bogor Agricultural University (IPB), redistilled liquid smoke, oil-palm shells, natural preservative, meatball

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf