Judul: Characterization of Umami Fractions Obtained from Spirulina platensis and Its Acid Hydrolysate
Abstrak: Spirulina platensis is known as unicellular and fibrous blue-green phytoplankton which grows in both fresh and saltwater through photosynthesis. Spirulina platensis has high reproductive power because biomass can reach 20 times the initial weight within 4-6 days after cultivation. Dried Spirulina platensis has been consumed as a nutraceutical dietary supplement due to its health benefits. Spirulina platensis powder contains high protein which is dominated by glutamic acid. Due to its composition, Spirulina platensis exhibits a fairly high development potential for the umami material. This research is the first research to explore the umami compounds from Spirulina platensis. Hydrolyzed foods commonly have higher umami taste intensity than unhydrolyzed food, for example, the hydrolyze soybeans with strong acid such as acid-hydrolyzed vegetable protein (aHVP) have a much stronger umami taste. In this research, the Spirulina platensis was also hydrolyzed with strong acid to produce simple peptides and free amino acids that may increase the umami taste intensity. To identify the umami compounds, the water soluble extracts (WSEs) of unhydrolyzed and hydrolyzed Spirulina platensis were fractionated using ultrafiltration membrane and gel filtration chromatography. Determination of umami taste intensity in WSEs, ultrafiltration fractions, and chromatography fractions was carried out through the sensory evaluation using the taste dilution analysis (TDA). The analyses of SDS PAGE, pH, total salt, total sugar, total soluble protein, total peptide and amino acid, RP-HPLC profile, organic acid composition, amino acid composition, and peptide sequencing were carried out to determine some simple peptides that contribute to the umami taste in Spirulina platensis. The result showed that hydrolyzed WSE had umami intensity twice higher (DF = 1024) than unhydrolyzed WSE (DF = 512). Each WSE was fractionated using an ultrafiltration membrane (MWCO 3000 Da) to obtain two ultrafiltration fractions, < 3000 Da and > 3000 Da. The ultrafiltration fraction < 3000 Da of hydrolyzed WSE had four times (DF = 1024) higher umami intensity than another fraction, > 3000 Da (DF = 256). On the other hand, the ultrafiltration fraction < 3000 Da of unhydrolyzed WSE had twice (DF = 512) higher umami intensity than fraction > 3000 Da (DF = 256). The chemical composition, especially total peptide and amino acid was more abundant in the ultrafiltration fractions < 3000 Da compared with ultrafiltration fractions > 3000 Da in both treatments. Therefore, the peptides with molecular weight less than 3000 Da have the potential to give the umami taste in algal hydrolyzate. Both ultrafiltration fractions < 3000 Da were fractionated using a gel filtration chromatography (Sephadex-G25). The hydrolyzed fraction was separated into four chromatography fractions (H1, H2, H3, and H4) while the unhydrolyzed fraction was separated into three chromatography fractions (U1, U2,and U3). The umami fraction H2 and U3 had rich in salt with DF umami 512 and 256 which mean that they had high umami intensity. The free glutamic acid concentrations of fraction H2 and U3 were about 3 and 1,5 times higher than the glutamic acid threshold, however, their intensity of the umami taste can reach up to 256 and 512 times. This result indicated the role of peptides or other components
Keyword: algae, chromatography, hydrolysate, Spirulina platensis, umami peptide, umami taste

Judul: Extraction and Enzymatic Hydrolysis of Spirulina sp. Protein as Antioxidant Properties
Abstrak: Spirulina sp. merupakan mikroalga yang dikonsumsi sebagai dietary supplement karena memiliki kandungan gizi utama protein dan aktivitas biologis dalam menginhibisi senyawa radikal bebas. Proses ekstraksi dan hidrolisis protein diduga mampu meningkatkan sifat fungsional serta aktivitas inhibisi radikal bebas 1,1-diphenyl-2-picryl-hydrazyl (DPPH) Spirulina sp.. Tujuan penelitian ini membandingkan pengaruh perbedaan metode ekstraksi terhadap konsentrasi protein, derajat hidrolisis, inhibisi radikal bebas DPPH, serta profil asam amino hidrolisat Spirulina sp.. Spirulina sp. diekstrak dengan metode fisik dan metode kimiawi. Ekstrak yang dihasilkan kemudian dianalisis konsentrasi protein dan dihidrolisis dengan enzim papain, lalu dianalisis derajat hidrolisis dan profil asam amino. Ekstrak dan hidrolisat Spirulina sp. dianalisis inhibisi radikal bebas DPPH pada hari ke-0 dan ke-210 setelah proses hidrolisis. Perbedaan metode ekstraksi berpengaruh signifikan (p < 0,05) terhadap konsentrasi protein ekstrak. Metode fisik menghasilkan ekstrak dengan konsentrasi protein 67,4 ± 14,35 mg/mL, sedangkan metode kimiawi 53,41 ± 3,90 mg/mL. Perbedaan metode ekstraksi berpengaruh signifikan (p < 0,05) terhadap derajat hidrolisis hidrolisat yang dihasilkan. Hidrolisat yang diekstrak dengan metode fisik memiliki derajat hidrolisis 77,14 ± 11,95%, sedangkan metode kimiawi 35,08 ± 15,88%. Hidrolisat dan ekstrak Spirulina sp. mengalami penurunan nilai inhibisi radikal bebas setelah penyimpanan beku. Kandungan asam amino hidrolisat ekstrak metode fisik yaitu 8.711,56 mg/kg, sedangkan metode kimiawi sebesar 3.391,56 mg/kg., Spirulina sp. is a microalgae species that is consumed as a dietary supplement due to its high nutrition content, especially protein and its bioactivity as a radical scavenger. Extraction and hydrolysis processes are expected to enhance Spirulina’s functional characteristic and its bioactivity to inhibit free radicals 1,1-diphenyl-2-picryl-hydrazyl (DPPH). The aim of this study was to compare the effect of two different extraction methods on protein concentration, degree of hydrolysis, DPPH free radical inhibition, and amino acid profile of Spirulina sp. hydrolysate. Spirulina sp. were extracted using two different methods, physical and chemical methods. The crude protein extracts was analyzed using Biuret method and hydrolysed using papain enzyme. The protein hydrolysate was finally run through some analysis such as hydrolysis degree, amino acid profile, and DPPH scavenging activity. The two different extraction methods effected on protein concentration and degree of hydrolysis significantly (p < 0,05). Protein concentration of Spirulina sp. that were extracted using physical method is 67,4 ± 14,35 mg/mL, while Spirulina sp. that were extracted using chemical method is 53,41 ± 3,90 mg/mL. Hydrolysis degree of protein hydrolysate extracted using physical method is 77,141 ± 11,945% while Spirulina sp. that were extracted using chemical method is 35,081 ± 15,884%. Both Spirulina sp. extract and hydrolysate %inhibition decreased after storage. Hydrolysate extracted using physical method contains 8.711,56 mg/kg of amino acid, while hydrolysate extracted using chemical method contains 3.391,56 mg/kg.
Keyword: DPPH radical inhibition, extraction, papain, protein, protein hydrolysate

Judul: Rantai Markov Pada Bilangan Biner
Abstrak: Ranlai Markov {Xn} yang didefinisikan pada ruang peluang (n, P, P) dilllana n = (O,I],dan 'Fadalah cr-lapangan Borel, lllelllpunyai ekspansi biner X n = 0, dl(n) din).. n = I, 2, ... Mengkonstruksi rantai Markov ini diawali dengan memilih sembarang bilangan ..Y o di (0,1], nyatakan bilangan Xo dalam ekspansi biner Xo =0, diD) diD) ... d~O) ... dimana { d~O) ,n = 1,2, ... } adalah barisan nol dan satu. Peubah acak XI ditentukan oleh .Xo dan asumsi berikut.
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