Judul: Inaktivasi Lipase Pada Biji Jarak Pagar  (Jatropha Curcas L.) Dengan Metode Pengukusan
Abstrak: Biodiesel is produced from trans-estherification process of vegetables oil with methanol and base catalyst. This process can be done if the free fatty acid content in oil is low. If the free fatty acid content is high, it can be taken care of with estherification process to convert some part of the free fatty acid to ester. However this process can make biodiesel production cost higher so it is not competitive enough with diesel fuel. Free fatty acid is produced from hydrolysis process of the oil by water and catalyzed by lipase enzyme. Lipase should be inactivated in order to prevent the increase of free fatty acid in post harvest handling. The objective of this research is to obtain the best steaming time to inactivate lipase in jatropha seeds. The jatropha seeds are steamed during 15, 30, 45, and 60 minutes at temperature of 100-110oC. The experiment design is completely randomized design with one factor, which is the steaming duration of jatropha seed (15, 30, 45, 60 minutes and control). This research is conducted with five times replications for every level of treatment. The parameters to be observed are oil yield, water content, free fatty acid content (FFA) and acid value. The analysis of variance (ANOVA) of oil yield at confidence level of 95% (α = 0,05) indicate that the duration of steaming made a significant effect on oil yield. The significance testing by Duncan test, show that every steaming duration treatment was different with the control (not steamed), but among steaming duration has no significant difference. The analysis showed that the steaming duration do not have a significant effect to the water content in the oil. The water content in oil on each treatment range between 0,0722% to 0,0816%. The steaming duration has a significant effect on increasing rate of FFA content. Increasing rate of FFA content on the steaming duration of 60 and 45 minutes do not have significant effect and both duration treatments have significant difference with control. Increasing rate of FFA content on the steaming duration of 30 and 15 minutes do not have significant effect and both of them do not have significant effect with control as well as 45 and 60 minutes steaming duration, with a tends that the longer of steaming duration the reduce of the FFA content increasing rate. The steaming duration has a significant effect on acid value increasing rate. Acid value increasing rate on the steaming duration of 45 and 60 minutes have significant differences with control. On steaming duration of 15 and 30 minutes have no difference neither with control nor with steaming duration of 45 and 60 minutes. The conclusion from this research is steaming process of 45 minutes was the best lipase inactivation. Steaming process at the same temperature and duration can also produce higher oil yield compared to seed without steaming.
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Judul: Transformation of jatropha seeds (Jatropha curcas L.)  into biodiesel by in situ transesterification
Abstrak: Biodiesel is defined as mono-alkyl esters from transesterification reaction of triglycerides with alkyl alcohol. In situ transesterification is a method to produce biodiesel from oil sources of material by eliminating process steps of oil extraction and refining. The purpose of this research is to study the transformation process of Jatropha seeds into biodiesel by in situ transesterification on the 10 liters scale by studying the influence of reaction time, stirring speed and ratio methanol/hexane/material on the yield and quality of biodiesel. In situ transesterification of Jatropha seeds was carried out under the following process condition: the moisture content of Jatropha seeds were less than 2%, the particles size were ± 20 mesh and KOH concentration was 0.075 mol/L methanol. Operating condition of in situ transesterification was varied at 4 and 6 hours reaction time, 200 and 600 rpm stirring speed and ratio methanol/hexane/material (v/v/w) were 3:3:1, 4:2:1 and 5:1:1. Analysis of variance showed that reaction time, stirring speed and ratio methanol/hexane/material did not significantly affected the yield, acid value, saponification value, ester value, viscosity and ash content of biodiesel. The biodiesel yield was produced between 82.54-87.57%. The best biodiesel yield on all of treatments was 87.57% with condition treatment were reaction time of 6 hours, stirring speed 600 rpm and ratio methanol/hexane/material (v/v/w) of 4:2:1. Acid value, saponification value and ester value of biodiesel were 0.20-0.26 mg KOH/g, 185.49-194.30 mg KOH/g and 185.29-194.10 mg KOH/g respectively. Viscosity of biodiesel was 3.49-6.36 cSt. The ash content of biodiesel was 0%, but the condition treatment, were reaction time of 4 hours, stirring speed of 600 rpm and ratio methanol/hexane/material (v/v/w) of 5:1:1, had ash content of 0.007%. Jatropha cakes had total volatile matter content 1.80-3.64% and extracted material content 3.94-11.42%.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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