Judul: . Total Phenolic, Flavonoid, and Antioxidant of Scoby Kombucha Tea Camellia sinensis (L.) Kuntze with Variation of Sucrose Concentration
Abstrak: Mother of SCOBY sebagai inokulum utama dalam pembuatan kombucha, berfungsi memastikan pertumbuhan bakteri dan ragi yang sesuai. Penelitian ini menganalisis dan mengukur kadar total fenolik, kadar total flavonoid, dan aktivitas antioksidan mother of SCOBY metode FRP (Ferric Reduction Power), DPPH, dan AEAC (Ascorbic acid Equivalent Antioxidant Capacity) dengan konsentrasi sukrosa berbeda. Mother of SCOBY dibuat dalam enam formula kombucha dengan konsentrasi sukrosa 0% (F1), 5% (F2), 7.5% (F3), 10% (F4), 12.5% (F5), dan 15% (F6). Hasil menunjukkan kadar fenolik tertinggi ditemukan pada F5 dan terendah pada F6, kadar flavonoid tertinggi pada F4 dan terendah pada F6. Aktivitas antioksidan paling kuat pada F5 dan paling lemah pada F6, seperti yang ditunjukkan oleh nilai inhibisi dan IC50. Uji FRP menunjukkan nilai tertinggi pada F4 dan terendah pada F6. Kata kunci: antioksidan, kombucha, mother of SCOBY, sukrosa, Mother of SCOBY as the main inoculum in making kombucha, serves to ensure the growth of appropriate bacteria and yeast. This study analyzed and measured total phenolic content, total flavonoid content, and antioxidant activity of mother of SCOBY using FRP (Ferric Reduction Power), DPPH, and AEAC (Ascorbic acid Equivalent Antioxidant Capacity) methods with different sucrose concentrations. Mother of SCOBY was made into six kombucha formulas with sucrose concentrations of 0% (F1), 5% (F2), 7.5% (F3), 10% (F4), 12.5% (F5), and 15% (F6). Results showed the highest phenolic content was found in F5 and the lowest in F6, the highest flavonoid content in F4 and the lowest in F6. Antioxidant activity was strongest in F5 and weakest in F6, as indicated by the inhibition and IC50 values. FRP assay showed the highest value in F4 and the lowest in F6. Keywords: antioxidant, kombucha, mother of SCOBY, sucrose
Keyword: Kombucha, Fenolik, flavonoid, Antioksidan, scoby

Judul: Antioxidant Activity of Kombucha from Ganoderma lucidum and Camellia sinensis (L.) Kuntze Substrates with Various Fermentation Times
Abstrak: Kombucha merupakan produk minuman fungsional hasil fermentasi bakteri dan ragi. Penelitian ini bertujuan menentukan formula dan waktu fermentasi terbaik dari kombucha dengan substrat G. lucidum dan teh hijau berdasarkan kandungan fenolik, flavonoid, dan aktivitas antioksidan optimum. Sampel simplisia G. lucidum dan teh hijau dibuat menjadi 5 formula dengan perbandingan 1:0, 3:1, 1:1, 1:3, 0:1. Berdasarkan metode DPPH dan ferric reducing power (FRP), formula yang memiliki aktivitas antioksidan tertinggi didapatkan pada kombucha teh hijau (F5), dengan persen inhibisi dan IC50 DPPH paling optimum (rata-rata H-0 hingga H-17 sebesar 92,05% dan 22,302 µL/mL) serta potensi daya reduksi paling kuat di antara formula lainnya (absorbansi 0,523 pada 700 nm). Kandungan fenolik dan flavonoid pada F5 mencapai 479,729 mg GAE/L kombucha dan 95,766 mg QE/L kombucha. Sementara itu, kombucha G. lucidum (F1) menghasilkan fenolik dan flavonoid yang lebih rendah (nilai optimum 100,407 mg GAE/L kombucha dan 18,564 mg QE/L kombucha). F1 juga menunjukkan aktivitas antioksidan yang rendah, dengan rata-rata nilai inhibisi 32,45% dan IC50 DPPH 78,530 µL/mL serta potensi daya reduksi yang lebih lemah (absorbansi 0,150 pada 700 nm). Adapun variasi waktu fermentasi hampir tidak mempengaruhi aktivitas antioksidan DPPH kombucha., Kombucha is a functional beverage produced by bacterial-yeast fermentation. This study aimed to determine the best formula and fermentation time of kombucha with G. lucidum and green tea substrates for phenolic, flavonoid, and antioxidant content. Samples of G. lucidum and green tea simplisia were made into 5 formulas with ratios of 1:0, 3:1, 1:1, 1:3, 0:1. Based on the DPPH and ferric reducing power (FRP) methods, the formula with the highest antioxidant activity was found to be green tea kombucha (F5), with the most optimal percent inhibition and IC50 DPPH values (D-0 to D-17 average is 92.05% and 22.302 µL/mL) and the strongest reducing power potential among other formulas (absorbance 0.523 at 700 nm). The phenolic and flavonoid contents in F5 reached 479.729 mg GAE/L kombucha and 95.766 mg QE/L kombucha. Meanwhile, G. lucidum kombucha (F1) produced lower phenolics and flavonoids (optimum value of 100.407 mg GAE/L kombucha and 18.564 mg QE/L kombucha). F1 also showed lower antioxidant activity, with an average inhibition value of 32.45% and IC50 DPPH 78.530 µL/mL and weaker reducing potential (absorbance 0.150 at 700 nm). The variation of fermentation time barely affected the DPPH antioxidant activity of kombucha.
Keyword: antioxidant, Camellia sinensis, Ganoderma lucidum, kombucha

Judul: The Solution of Nonlinear Volterra Integral Equation using Linearization Method.
Abstrak: Many natural phenomena can be explained by mathematical models. One of those models is in the form of Volterra integral equation, which is usually nonlinear. Analitically, a nonlinear form is difficult to solve. Therefore, this research is aimed to discuss solution of Volterra integral equation using linearization method. Linearization is done to nonlinear integrand with Taylor series expansion. According to this linearization, a numerical solution of Volterra integral equation is obtained using MATLAB 7.0.1 software. Validity of this method is tested by comparing the approximate with the exact solution. The result of this research shows that the numerical solution agree with the exact solution quite well.
Keyword: