Judul: Pendugaan Umur Simpan Kelopak Bunga Rosela (Hibiscus sabdariffa L.) Kering.
Abstrak: Roselle is a kind of plant from genus Hibiscus. Calyx of roselle flower from variety of sabdariffa has a lot of uses as a food material. Utilization of roselle (Hibiscus sabdariffa L.) has increased because many researches mentioned that roselle have chemical content which have many functions for human health, especially high content of vitamin C. Prediction of shelf life aims to know shelf life of dry calyx of roselle in certain condition. Determination shelf life product with ASS (Accelerated Storage Studies) method using environmental condition parameter enables to accelerate degradation process of quality of food product. The right packaging and storage is expected to increase shelf life and detain deterioration rate of dry calyx of roselle. The objectives of the research is to know quality changing, to determine shelf life, and to obtain better packaging to defend quality of dry calyx of roselle. The packaging materials which are used in this research were craft paper and plastic PP. Storage temperatures are held at 25°C, 35°C, and 45°C. Storage time in this research is 3 months. The analysis of dry calyx of roselle were water content, total of acid titration, total soluble solid, pH, vitamin C content, total mould, and sensory evaluation analysis. Based on this research, it is showed that dry calyx of roselle quality changed during 3 months of storage. Water content of dry calyx of roselle in craft paper packaging at storage temperature of 25°C increased by 0.12% per day and at temperature of 35oC and 45°C decreased by 0.03% and 0.04% per day respectively. In plastic PP packaging, water content of roselle at storage temperature of 25°C and 35°C increased by 0.06% and 0.04% per day respectively, while at 45°C it decreased by 0.03% per day. Total of acid titration of dry calyx of roselle in craft paper packaging at storage temperature of 25°C, 35°C, and 45°C decreased by 0.0007% per day, while in plastic PP at temperature of 25°C, 35°C, and 45°C decreased by 0.0008%, 0.0009%, and 0.0016% per day respectively. pH of dry calyx of roselle in craft paper packaging at storage temperature of 25°C, 35°C, and 45°C decreased by 0.0004% per day, while in plastic PP packaging at 25°C, 35°C, and 45°C, it decreased by 0.0003%, 0.0004%, and 0.0005% per day respectively. Vitamin C of dry calyx of roselle at storage temperature of 25°C, 35°C, and 45°C in craft paper packaging decreased by 0.0072%, 0.0136%, and 0.0142% per day respectively, while in plastic PP, it decreased by 0.0096%, 0.0161%, and 0.0166% per day respectively. Total soluble solid of dry calyx roselle in craft paper at 25°C, 35°C, and 45°C of storage temperatures increased by 0.0061%, 0.0067%, and 0.0077% per day respectively. In plastic PP, total soluble solid of dry calyx roselle at storage temperature of 25°C, 35°C, and 45°C increased by 0.0060%, 0.0071%, and 0.0076% per day respectively. During 3 months of storage, there was no mould found in dry calyx of roselle. There was no panelists refusal at assessment of common acceptance attribute of dry and extract calyx of roselle until 91 days of
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Judul: Hibiscus sabdariffa Linn
Abstrak: Es krim adalah makanan beku semi padat hasil olahan susu yang dibuat dengan melewati berbagai proses, yaitu pasteurisasi, homogenisasi, pematangan es krim, pengadukan untuk membentuk rongga udara pada adonan es krim, serta pembekuan dalam lemari es. Bunga rosella memiliki kandungan antioksidan yang tinggi. Kandungan antosianin pada bunga rosella mencapai 96 mg dan vitamin C mencapai 280 mg setiap 100 g. Antosianin pada bunga rosella mampu memberikan efek perlindungan terhadap penyakit kardiovaskuler, termasuk penyakit hipertensi. Penelitian ini bertujuan untuk menganalisis sifat fisikokimia, organoleptik dan aktivitas antioksidan es krim yang diberi penambahan bubuk bunga rosella. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan perlakuan persentase penambahan bubuk bunga rosella berbeda beda yaitu 0%, 5%, 10% dan 15%. Hasil penelitian menunjukkan bahwa penambahan bubuk bunga rosella pada es krim berpengaruh nyata (P<0.05) terhadap nilai pH, kadar air, aktivitas antioksidan, kapasitas antioksidan, daya leleh dan karakteristik organoleptik. Penambahan bunga rosella tidak berpengaruh nyata (P>0.05) pada nilai aw dan overrun. Persentase terbaik ditemukan pada penambahan rosella perlakuan 5%., Ice cream is a semi-solid frozen food processed by milk which is made by going through various processes, namely pasteurization, homogenization, ripening of ice cream, stirring to form air cavities in the ice cream dough, and freezing in the refrigerator. Rosella flowers have high nutritional content and antioxidant compounds. The anthocyanin content in rosella flowers reaches 96 mg and vitamin C reaches 280 mg for every 100 g. Anthocyanins in rosella flowers are able to provide a protective effect against cardiovascular disease, including hypertension. This study aims to analyze the physicochemical, organoleptic and antioxidant activity of ice cream which was added with rosella flower. This study used a completely randomized design (CRD) with different percentages, namely 0%, 5%, 10% and 15%. The results showed that the addition of rosella flowers to ice cream had a significant effect (P<0.05) on the pH value, water content, antioxidant activity, antioxidant capacity, melting power and organoleptic characteristics. The addition of rosella flowers had no significant effect (P>0.05) on the aw and overrun values. The best percentage was found in the addition of 5% rosella treatment.
Keyword: antioxidant, ice cream, rosella flower, milk

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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