Judul: Karakteristik Whey Kefir dan Aktivitasnya terhadap Penghambatan Angiotensin Converting Enzyme (ACE)
Abstrak: Whey is by product of cheese process that could be reached 80% of milk as cheese raw material. Whey contain the high of organic matter that could be potential to be exploited. Microbial fermentation by kefir grain can be used to utilize the whey. Bacteria and yeasts are growth simultaneously in kefir grain. Milk based fermentation product may contain bioactive peptides as functional foods, such as antihypertensive. This bioactive peptide could inhibit the angiotensin converting enzyme (ACE) activity, an enzyme that plays a role in the Renin Angiotensin Aldosterone system as a function of blood pressure regulation in human body. This research was conducted to evaluate the characteristic of whey based kefir product and its activity to inhibit the ACE. Kefir was produced by many type of whey as a treatment, SK : skim milk based kefir (control); WK : gouda cheese whey based kefir; and WKB : commercial whey powder based kefir, in three replication. Kefirs were evaluated for physical and chemical properties (pH, total titratable acidity, viscosity, protein, fat, lactose, and alcohol), microbiological (Lactic acid bacteria and yeast population), peptide concentration, ACE inhibition, IC50 and Inhibition Efficiency Ratio (IER). Data were analyzed by ANOVA, and continued by multiple comparison tests using Tukey’s HSD method. The results showed that the types of whey used for kefir productions significantly affected the physical and chemical characteristic of the products (P<0.05). Characteristics of whey kefir products were complaid to the CODEX STAN 234-2003 standards. Total lactic acid bacteria and yeast population of the products were not significantly different among whey types (P>0.05). The peptide concentration and ACE inhibitor activity of WK was 1.54 ± 0.02 mg/ml and 73.07 ± 0.91 % respectively. The values were significantly higher (P<0.05) than that of the control and WKB. IC50 of WK was 0.83 ± 0.02 mg/ml, significantly lower than that of control (1.05 ± 0.01 mg/ml) and WKB (0.96 ± 0.01 mg/ml). IER of WK was (47.35 ± 0.09 % per mg/ml), not significantly different (P>0.05) compared with control (47.19 ± 0.09 % per mg/ml) but significantly higher (P<0.05) than that of WKB (45.75 ± 0.18 % per mg/ml). General organoleptic test shows that the type of whey significantly affected (P<0.05) the panelist preferences on the sensory characteristic of whey kefir products. General sensory test result of WK was lower than that of SK but higher than that of WKB. Based on the plot of the intensity of sensory attributes, WK was in general between SK and WKB. The sensory properties that dominate the whey kefir product were specific kefir flavor, sour, compact and viscous texture. It was concluded that whey could be utilized for whey kefir production. Whey kefir has capability to be peptide bioactive sources for antihypertention agent. Whey kefir made from the Gouda cheese whey showed the higher ACE inhibitor activity than that of kefir based from commercial whey. Process optimization is necessary to meet the consumer preferences. The type of ACE inhibitor bioactive peptide in whey kefir product is also need to be further investigated.
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Judul: Analysis of Angiotensin-Converting Enzyme (ACE) Inhibitor Activity of Bioactive Peptides from Etawah Crossbreed Goat Milk
Abstrak: Peptida bioaktif merupakan hasil pemecahan protein yang bermanfaat untuk kesehatan dengan bekerja sebagai antioksidan, antidiabetes, dan antihipertensi. Salah satu mekanisme dari sifat antihipertensi peptida bioaktif adalah inhibisi angiotensin-converting enzyme (ACE). Penghambatan ACE dengan inhibitor alami menjadi alternatif untuk menghindari efek samping obat sintetik. Penelitian ini bertujuan untuk mengetahui pengaruh proses hidrolisis terhadap kadar protein, inhibisi ACE, dan profil protein susu kambing peranakan Etawa. Dalam penelitian ini, susu kambing yang telah dipisahkan lemaknya dihidrolisis enzim papain dengan aktivitas spesifik 1,48 ± 0,04 U/mg pada suhu 55 oC selama 1, 4, dan 24 jam. Analisis kadar protein dilakukan dengan metode Bradford, aktivitas inhibitor ACE dengan ACE Kit-WST, dan profil protein dengan SDS-PAGE. Susu kambing yang dihidrolisis mengalami penurunan kadar protein dan peningkatan inhibisi ACE yang signifikan. Waktu hidrolisis yang lebih lama juga meningkatkan inhibisi ACE. Pada larutan susu kambing konsentrasi 7,5 mg/mL, hidrolisat 24 jam menunjukkan aktivitas tertinggi sebesar 95,01 ± 1,13% dibandingkan nonhidrolisis sebesar 84,49 ± 0,93%. Obat kaptopril sebagai kontrol positif menunjukkan aktivitas sebesar 101,25 ± 0,56% pada konsentrasi ≥ 0,1 µg/mL. Hasil elektroforesis susu kambing menunjukkan enam pita protein dengan berat molekul 11-84 kDa. Setelah proses hidrolisis, hidrolisat protein hanya menunjukkan dua pita protein 11 dan 16 kDa, menunjukkan bahwa hidrolisis memotong protein berukuran besar menjadi peptida dengan berat molekul lebih kecil. Penelitian ini berpotensi pada pengembangan pangan fungsional yang dapat mencegah dan mengobati hipertensi. Kata kunci: antihipertensi, inhibitor ACE, peptida bioaktif, susu kambing, Bioactive peptides are the result of protein breakdown which are beneficial for health by working as antioxidant, antidiabetic, and antihypertensive. One mechanism of the antihypertensive properties from bioactive peptides is the inhibition of angiotensin-converting enzyme (ACE). Inhibiting ACE with natural inhibitors is an alternative to avoid the side effects of synthetic drugs. This study aims to determine the effect of hydrolysis on protein content, ACE inhibition, and the protein profile of Etawah crossbreed goat milk. In this study, goat milk that has had its fat separated was hydrolyzed by papain enzyme with specific activity of 1.48 ± 0.04 U/mg at 55 oC for 1, 4 and 24 hours. Analysis of protein content was carried out using the Bradford method, ACE inhibitor activity with ACE Kit-WST, and protein profile with SDS-PAGE. Hydrolyzed goat milk had a significant decrease in protein content and increase in ACE inhibition. Longer hydrolysis time also increases ACE inhibition. In the goat milk solution with a concentration of 7.5 mg/mL, 24-hour hydrolysate showed the highest activity at 95.01 ± 1.13% compared to non-hydrolysis at 84.49 ± 0.93%. The captopril as positive control showed activity at 101.25 ± 0.56% at a concentration of ≥ 0.1 µg/mL. The result of goat milk electrophoresis showed six protein bands with a molecular weight of 11-84 kDa. After hydrolysis, the protein hydrolysates only showed two protein bands of 11 and 16 kDa, indicating that hydrolysis cleaves large protein into peptides with smaller molecular weight. This research has the potential to develop functional foods that can prevent and treat hypertension. Keywords: ACE inhibitor, antihypertensive, bioactive peptide, goat milk
Keyword: ACE inhibitor, antihypertensive, bioactive peptide, goat milk

Judul: Teknik penentuan posisi bintang berdasarkan pelat foto overlapping
Abstrak: Bintang adalah salah satu objek langit yang menarik untuk diamati. Untuk itu, pengetahuan tentang posisi bintang sangat diperlukan. Posisi bintang di langit dapat dihitung melalui foto bintang. Fotografi astronomi atau astrometri merupakan ilmu yang mempelajari metode untuk menentukan posisi bendabenda langit seperti bintang berdasarkan pelat foto (Kamp, 1967). Sebuah pelat foto berisi citra bintang-bintang yang sudah diketahui posisinya berdasarkan katalog dan citra bintang-bintang yang belum diketahui posisinya. Posisi bintang yang ada di katalog dinyatakan dengan (a,3). Bintang yang belum diketahui posisinya lebih banyak jumlahnya daripada bintang yang sudah diketahui posisinya. Citra bintang pada pelat foto berupa sebuah titik dalam bentuk tetap. Posisinya pada pelat merupakan hasil pengukuran pada bidang kartesius dan dinyatakan dengan (1;,fl). Hasil pengukuran tersebut kemudian direduksi menjadi koordinat terukur (x,y). Hubungan antara (a,3) dan (x,y) didekati dengan sebuah deret dengan konstanta-konsranta deret merupakan konstanta pelat. Nilai konstanta pelat diperoleh dengan menggabungkan hasil pengukuran posisi bintang pada masing-masing pelat menjadi sebuah persamaan normal (Jefferys, 1963). Hasil akhir dari gugus persamaan normal tersebut dijabarkan dalam bentuk nOlasi matriks partisi dan berupa sebuah sistem persamaan linier Ax = b di mana A adalah matriks jarang, dan x merupakan konstanta pelar yang akan dicari nilainya. Untuk menyelesaikan sistem persamaan linier terse but digunakan metode transformasi given. Konstanta pelat yang sudah diperoleh dengan menyelesaikan sistem persamaan linier di atas, kemudian disubtitusi ke sebuah persamaan untuk memperoleh posisi bintang yang tidak tercantum dalam katalog. .
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