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: Kajian Stabilitas Komponen Volatil dan Atribut Mutu Sirup Campuran Jahe, Sereh, dan Madu selama Penyimpanan
Abstrak: Ginger (Zingiberofficinale) and lemongrass (Cymbopogoncitratus) are two types of spices which often used as flavoring ingredients in beverages or foods. In these products, honey is sometime added as a sweetener. These spices and honey are known to have functional properties. The aim of this study was to study the stability of volatile components and quality attributes of the best formulation of syrup made from ginger, lemongrass, and honey during storage at room temperature. In the preliminary study, ginger and lemongrass were extracted with water at 60 0C for 10 minutes, filtered and decantation at room temperature to obtain the clear beverages. Different concentrations of syrup formulas were made as follows; ginger extract of 20%, 25% and 30%, and lemongrass extract of 10% and 15% and to each of formula were added 10% of honey. Determination of the best formula syrup based on an organoleptic test and capacity antioxidant. On advance research, the best formula of syrup (25% ginger extract, 15% lemongrass extract, and 10% honey) put in a dark glass bottle then stored at room temperature for 8 weeks and observed every 2 weeks. The observation during storage related quality attribute was include antioxidant capacity, total phenols, total plate count, pH, total titrable acid, total dissolved solids, and viscosity. The quality attribute did not change significantly during storage. The chromatogram of day-0 showed 116 peaks but only 71 peaks could be identified, there were 10 volatile components had an area over 2%. Primary volatile components on syrups were citral, neral, zingiberene, curcumene, β- bisabolene, cineole (1,8), cymene(0-), β-phellandrene, β-sesquiphellandrene, and α-farnesene (E,E.) The area of citral, neral, curcumene, β-bisabolene and cymene decreased during storage, on the other hand the area cineole (1.8), zingiberene, β- phellandrene, β-sesquiphellandrene, and α-farnesene (E,E) increased apparently during storage. Thus, the syrup is potent as functional food.
Keyword: syrup, ginger, lemongrass, honey, quality attribute volatile components

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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