Judul: Evaluasi Pengawet untuk Nira Kelapa (Cocos nucifera L.)
Abstrak: Palm sap obtained from tapping palm bunches of coconut flowers. Palm sap rich in sugar with it content apporiximately 11% that make it is easily fermented and decrease its quality. This study aims to obtain an effective antimicrobial formula used to inhibit degradation of palm sap quality. The preservatives used were of ethyl paraben, potassium sorbate, sodium sulfite, and nisin as a single agent or their mixture. Evaluation was done in following steps: (1) evaluation of single preservative toward lactic acid bacteria and yeast, (2) evaluation of preservatives toward lactic acid bacteria and yeast using coconut sap as medium, (3) evaluation the most efficacy preservative toward a mixture of lactic acid bacteria and yeast using coconut sap as medium. Based on the results, the mixture of ethyl paraben+potassium sorbate and ethyl paraben+sodium sulfite could inhibit the growth of yeast, and nisin could inhibit the growth of lactic acid bacteria, and preserve the pH value. When the initial contamination was high (±106 cfu/mL), the mixture of preservatives which could be used were: ethyl paraben 750 ppm + potassium sorbate 250 ppm + nisin 25 ppm; ethyl paraben 750 ppm + potassium sorbate 250 ppm + nisin 50 ppm; ethyl paraben 750 ppm + potassium sorbate 250 ppm + nisin 100 ppm; ethyl paraben 750 ppm + sodium sulfite 125 ppm + nisin 50 ppm; ethyl paraben 750 ppm + sodium sulfite 125 ppm + nisin 100 ppm. However, when initial contamination was lower (±104 cfu/mL), the following mixture of preservatives ethyl paraben 375 ppm + potassium sorbate 125 ppm + nisin 50 ppm were effective to preserve coconut sap.
Keyword: nisin, sodium sulfite, ethyl paraben, palm sap, preservative

Judul: Profil Bakteri Asam Laktat dan Bakteri Pembentuk Asam pada Nira Kelapa (Cocos Nucifera L.)
Abstrak: Coconut sap has been widely used to produce coconut sugar in many countries. It is a liquid that coming out by tapping the unopened coconut flower. Coconut sap is rich in sugar (10~15%) and nearly at neutral pH condition. Those characteristics cause the coconut sap spontaneously fermented by certain microorganisms that present naturally in coconut flower due to unsanitary tapping process. This study aims to evaluate the profile of lactic acid bacteria and acidforming bacteria and to evaluate the effect of storage on coconut sap. Coconut sap was obtained from Sukabumi and Purbalingga. The initial amount of lactic acid bacteria and acid-forming bacteria in fresh coconut sap from Sukabumi and Purbalingga was already high. The average number of lactic acid bacteria in Sukabumi and Purbalingga fresh coconut sap respectively amounted to 7.38 log CFU/ml and 7.94 log CFU/ml, meanwhile the average number of acid-forming bacteria in Sukabumi and Purbalingga fresh coconut sap respectively amounted to 5.88 log CFU/ml and 7.95 log CFU/ml. The average pH value of fresh coconut sap from Sukabumi and Purbalingga were 5 dan 5.5 with total sugar 15 and 15.2o brix. Purbalingga coconut sap stored at room temperature for 4, 8, and 16 hours increased the number of lactic acid bacteria and acid-forming bacteria, as well as decreased its pH value. Those also happened in Sukabumi coconut sap stored for 18 hours at low temperature. Isolates from Sukabumi coconut sap was dominated by heterofermentative coccobacilli, 43 % isolated from MRSA medium and 62 % from GYC medium. Heterofermentative coccobacilli also dominated 81 % isolates in Purbalingga coconut sap obtained from MRSA medium, whereas isolates from GYC medium were dominated by heterofermentative bacilli (84%). Identification using API 50 CHL showed that coconut saps from both places were dominated by Weissella viridescens. Other lactic acid bacteria isolates were identified as Lactococcus lactis ssp lactis 1 and Leuconostoc mesenteroides ssp mesenteroides/dextranicum 1.
Keyword: lactic acid bacteria, coconut sap, acid-forming bacteria

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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