Judul: Chemical and Microbiological Quality of Ginger Beer with Spontaneous and Inoculated Fermentation.
Abstrak: Ginger had been one of the most consumed herbs around Southeast Asia. Ginger beer is one of the beverage innovation with ginger as its raw material. Through fermentation, the functional properties of the ginger are enhanced. But the difference in creating ginger beer with spontaneous fermentation with inoculated fermentation is still unknown. In this research, the total antimicrobial activity as well as the total LAB count, the total antioxidant and phenol content, and the total ethanol content was tested. Ginger beer was prepared with spontaneous fermentation and inoculated fermentation for 6 days in total. Antimicrobial activity of samples was measured by measuring the absorbance with spectrophotometer against E. coli and S. aureus. The phenol content of the sample was determined by using Folin-Ciocalteau’s reagent with sodium carbonate and incubated for 40 minutes at 45°C and the absorbance was measured at 765 nm using the spectrophotometer. The result of yeast addition showed significant effect on the beverage where the antioxidant content, alcohol concentration, antibacterial activity, and total LAB count of the beverage increased in correlation with the concentration of the yeast. Highest phenols and antioxidant content was obtained with 0.7 g/L yeast on the third day.
Keyword: Antibacterial activity, Antioxidant, Ginger beer, Phenolic content

Judul: Aktivitas antimikroba ekstrak jahe (Zingiber officinale Roscoe) terhadap beberapa bakteri patogen
Abstrak: hazards to the human health. Ginger (Zingiber officinale Roscoe) is commonly used as traditional medicine. It has a potential as antimicrobial agent by inhibit or kill microbes in dose dependent manner. The principle compounds of ginger are essential oils and non volatile compounds which maximum have antimicrobial activity. The objectives of this research are: (1) to study the yield of ginger extracts by multistage maceration with different polarity solvents, (2) to study antimicrobial activity of hexane, ethyl acetate and ethanol extract of ginger against foodborne pathogen such as Staphylococcus aureus, Bacillus cereus and Salmonella enterica serovar Typhimurium. Ginger extracts were prepared by multistage maceration method using solvent hexane, ethyl acetate and ethanol. The ginger extracts were assayed for antimicrobial activity by agar well diffusion method with Diameter Inhibition Zone (DIZ) and dillution broth method. The yield of hexane, ethyl acetate and ethanol ginger extracts from multistage maceration were respectively 3,57; 3,17; 3,02 g/100 g dry ginger. The DIZ value for Staphylococcus aureus were 5,0; 5,7; 1,3 mm with hexane, ethyl acetate and ethanol ginger extracts respectively 6,1; 6,6; 6,0 mm for Bacillus cereus and Salmonella Typhimurium were show no inhibitory zone. This results showed that the ginger extracts from multistage maceration have a weak antimicrobial activity (1,3 – 6,6 mm) against Gram-positive bacterial. The inhibition activity was determined for ethyl acetate ginger extract that showed the relatively highest inhibition zone. The minimum inhibition concentration did not reach in a range concentration between 5 – 20 mg/ml against Staphylococcus aureus and Bacillus cereus, therefore ginger extracts from multistage maceration with rotavapor temperature 50 o C and freeze dry process were not efficient to developed as natural antimicrobial.
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Judul: Analisis Kompleksitas Masalah Optimasi Linear Menggunakan Metode Interior Primal-Dual dengan Langkah Full-Newton.
Abstrak: Primal-dual interior method with full-Newton step is a method for solving linear optimization problems. This method is designed in such a way that an optimal solution is obtained an interior of the domain. It has polynomial complexity. This paper discusses and analyzes the complexity of linear optimization problems using primal-dual interior method with full-Newton steps. From the case studies that have been conducted, can be concluded that the number of iterations is in accordance with the complexity of the algorithm.
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