Judul: OPTIMIZATION OF PRE-TREATMENTS TOWARDS REHYDRATABLE TORCH GINGER (Etlingera elatior) FLOWER CHARACTERISTICS
Abstrak: Torch ginger (Etlingera elatior) is an indigenous plant found in South-Asian region which is known for its attractive appearance, pink color, and health benefits. The torch ginger flower shows potential for its rehydratable form development to increase added value, convenience, and shelf life. Some of the most important characteristics in the rehydratable torch ginger flower development are moisture content, color difference, rehydration ratio, and antioxidant activity. Cabinet drier has been used widely in the development of dehydrated food due to its affordability, however shows problem in the degradation of quality. On the other hand, pre-treatments such as steam blanching and sodium metabisulphite soaking has been known to retard quality degradation during drying in dehydrated products. In this study, optimization was done using Response Surface Methodology (RSM) in Design Expert v11.0 software with 13 combination runs of steam blanching time (ranging from 30-180 seconds) and sodium metabisulphite soaking concentration (ranging from 0.15%-0.40%). The optimum pre-treatments in the experiment were found to be 180 seconds of steam blanching continued by soaking in 0.331% sodium metabisulphite solution which resulted in moisture content of 7.96%, rehydration ratio of 4.65, color difference of 12.56, and antioxidant activity of 39.36% with the desirability of 0.719.
Keyword: optimization, torch ginger, rehydratable, blanching, sodium metabisulphite

Judul: Uji Performansi Alat Pengering Tipe Rak dan Pengaruh Perlakuan Awal terhadap Mutu Jahe Kering (Zingiber officinale Rosc.)
Abstrak: Ginger (Zingiber officinale Rosc.) is one of spices and medicinal plant which has high economic value and have been widely recognized by the Indonesian people. Fresh ginger has moisture content between 85-91% wet basis causes reduction quality of ginger if it is not eventually to be processed or dried. Generally, farmers and traders dried the ginger by using sun drying which require a lot of time, so that the artificial drying is needed to produce dried ginger with better quality and can shorten the drying time. The objectives of the research are to conduct the performance assessment of Sunbeam Food Dehydrator, which is rack-type dryer that using electrical energy as heat source; to assess the effect of immersion in lime solution (Ca(OH)2) at concentration of 2%, 4% and 6% to the quality of dried ginger; as well as studying the temperature distribution and air flow patterns in the dryer using Computational Fluid Dynamics (CFD). The results of the research showed that the dryer has capacity about 1kg of ginger slice and drying efficiency of 25.09%. It also shown that the immersion in lime solution gave a significant effect on increasing ash content and lightness of dried ginger, but it gave no significant effect on essential oil content of dried ginger. The treatment of immersion in 6% concentration of lime solution produce dry ginger with ash content that beyond of quality standard limit. The simulation of temperature and air flow patterns inside the dryer showed the accuracy of 97.09% and resulting linear regression of the relationship between measurement temperature and simulation temperature of 0.943. This shows that the CFD simulation gives good results in predicting the distribution of air temperature and air flow patterns inside the dryer.
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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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