Judul: Pengaruh Suhu dan Waktu Penyimpanan terhadap Aktivitas dan Total Fenol pada Minuman RTD Spirulina
Abstrak: Minuman RTD (ready to drink) spirulina diformulasikan agar spirulina dapat dikonsumsi secara langsung, praktis, dan memiliki sensori yang lebih baik, serta bermanfaat untuk tubuh dengan kandungan bioaktifnya yang berfungsi sebagai antioksidan. Sayangnya, komponen bioaktif spirulina, termasuk polifenol, umumnya mudah mengalami kerusakan akibat suhu panas selama penyimpanan. Tujuan penelitian ini adalah mengevaluasi pengaruh suhu (35°C, 45°C, dan 55°C) dan lama penyimpanan (21 hari) terhadap total senyawa fenolik dan aktivitas antioksidan dari produk. Ditentukan pula kinetika degradasi dan umur simpan produk menggunakan metode ASLT model Arrhenius dengan kedua parameter tersebut. Hasil penelitian menunjukkan bahwa suhu dan lama penyimpanan sangat memengaruhi kandungan total fenol dan aktivitas antioksidan pada minuman (Sig.<0,05). Secara umum, kedua parameter mengalami penurunan seiring penyimpanan berjalan pada ketiga suhu. Penurunan terjadi sebesar 27,61%; 31,07%; dan 33,50% untuk aktivitas antioksidan, dan 25,23%; 21,97%; 17,53% untuk total fenol, pada suhu 35°C, 45°C, dan 55°C hingga akhir masa penyimpanan. Penurunan aktivitas antioksidan dan total fenol tercepat terjadi pada suhu 45°C dan 35°C berturut-turut, ditandai dengan nilai k yang besar. Faktor matriks pangan berpengaruh pada kestabilan kedua parameter teruji. Umur simpan tidak dapat ditentukan karena kedua parameter dianggap kurang cocok dijadikan parameter ASLT menggunakan model Arrhenius akibat nilai R2 yang kecil (R2<0,7)., RTD (ready-to-drink) spirulina beverages are formulated to allow spirulina to be consumed directly, practically, and with improved sensory acceptance while providing health benefits due to its bioactive compounds that function as antioxidants. Unfortunately, the bioactive components of spirulina, including polyphenols, are generally susceptible to degradation due to heat during storage. The aim of this study is to evaluate the effects of temperature (35°C, 45°C, and 55°C) and storage duration (21 days) on the total phenolic content and antioxidant activity of the product. The degradation kinetics and shelf life of the product were also determined using the ASLT method with the Arrhenius model for both parameters. The results showed that temperature and storage duration significantly affected the total phenol content and antioxidant activity in the beverage (Sig.<0.05). In general, both parameters decreased over the storage period at all three temperatures. The reductions were 27,61%; 31,07%; and 33,50% for antioxidant activity, and 25,23%; 21,97%; and 17,53% for total phenols, at 35°C, 45°C, and 55°C, respectively, until the end of the storage period. The fastest decreases in antioxidant activity and total phenols occurred at 45°C and 35°C, respectively indicated by large k values. The food matrix factor influenced the stability of the tested parameters. Shelf life could not be determined because both parameters were deemed unsuitable for ASLT parameters using the Arrhenius model due to low R2 values (R2<0.7).
Keyword: shelf life, antioxidant activity, RTD beverages, spirulina, total phenols

Judul: Estimating the Shelf Life of Spirulina Drinks with Total Chlorophyll Parameters Using the Arrhenius Model ASLT Method
Abstrak: Umur simpan sangat penting diketahui karena berkaitan langsung dengan keamanan dan mutu produk ketika berada di tangan konsumen. Umur simpan minuman RTD spirulina ditentukan menggunakan pendekatan penurunan mutu berdasarkan degradasi total klorofil. Penelitian ini bertujuan menentukan kinetika degradasi total klorofil minuman spirulina serta menduga umur simpannya menggunakan metode accelerated shelf-life testing (ASLT) model Arrhenius. Analisis total klorofil dilakukan menggunakan spektrofotometer UV-VIS. Sampel minuman disimpan pada suhu 35°C, 45°C, 55°C selama 21 hari. Hasil penelitian menunjukkan bahwa total klorofil mengalami penurunan seiring dengan meningkatnya suhu dan lama penyimpanan. Intensitas warna coklat dan pH minuman spirulina meningkat seiring dengan peningkatan suhu dan lama penyimpanan. Kinetika degradasi total klorofil pada minuman RTD spirulina mengikuti reaksi ordo satu. Umur simpan minuman RTD spirulina diperoleh selama 64,93 hari pada suhu 20°C, 55,04 hari pada suhu 25°C, dan 51,60 hari pada suhu 27°C., Shelf life was very important to know because it was directly related to the safety and quality of food products. The shelf life of RTD spirulina beverages was determined using a quality degradation approach based on total chlorophyll degradation. This study aimed to determine the kinetics of total chlorophyll degradation in spirulina beverages and to estimate their shelf life using the accelerated shelf-life testing (ASLT) method with the Arrhenius model. Total chlorophyll analysis was conducted using a UV-VIS spectrophotometer. Beverage samples were stored at temperatures of 35°C, 45°C, and 55°C for 21 days. The results showed that total chlorophyll decreased with increasing temperature and storage time. The brown color intensity and pH of the spirulina beverages increased with rising temperature and storage time. The kinetics of total chlorophyll degradation in RTD spirulina beverages followed a first-order reaction. The shelf life of RTD spirulina beverages was 64,93 days at 20°C, 55,04 days at 25°C, and 51,60 days at 27°C.
Keyword: Arrhenius, shelf life, Total chlorophyll

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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