the temperature of 600◦C was 25% in

the temperature of 600
◦
C was 25% in mass of the starting material. This lowering of the degradation temperature of agar acetate
compared to raw agar was probably due to the presence of acetyl
ester group, which has adverse effect on the thermal stability of agar
molecule. This result was different from other polysaccharides such
as starch and xylan which thermal stability were increased after
acetylation (Fundador, Enomoto-Rogers, Takemura, & Iwata, 2012;
Xia, Wenyuan, Qianqian, Luqi, & Changxiao, 2011; Zhang, Xie, Zhao,
Liu, & Gao, 2009).
4. Conclusions
A series of agar acetates with different DS were prepared, and
their properties were determined and analyzed contrastively with
the raw agar. The results showed that the gelling temperature, gel
melting temperature, gel strength and apparent viscosity of agar
acetates were all decreased with the increase of DS. The variation
process of agar molecules in solution from coil to helix could be
observed through the optical rotation measurement, which could
be carried out not only in a higher concentration (0.25 wt%) at which
it could form a gel, but also in a lower concentration (0.05 wt%) at
which even it could not form a gel. The temperature of the transition
beginning point(from coil to helix) of the agar molecule was higher
in higher concentration(0.25 wt%) than that in lower concentration(0.05 wt%), but its temperature of the transition end point(from
coil to helix) was almost the same in both higher and lower concentration. According to the texture profile analysis (TPA), the
hardness, the fracturability and the springiness of agar acetate gels
all decreased except that the cohesiveness of agar acetate gels
increased with the increase of DS. The Cyro-SEM showed that the
gel skeleton microstructures of both agar acetate gel and raw agar
gel were of porous network structure, the size of the water droplet
trapped in gel skeleton structure of agar acetate gels were smaller
than the one of raw agar gel, and become even smaller with the
DS increase of agar acetate. After acetylation, the water holding
capacity of the agar was improved, but its thermal stability was
lowered

Hasil (Bahasa Indonesia) 1:

suhu 600◦C adalah 25% massa bahan awal. Ini menurunkan suhu degradasi agar-agar asetatdibandingkan dengan mentah agar itu mungkin karena adanya asetilEster group, yang memiliki efek buruk pada stabilitas termal agarmolekul. Hasil ini adalah berbeda dari polisakarida lainnya sepertisebagai pati dan stabilitas termal yang meningkat setelah xylanacetylation (Fundador, Enomoto-Rogers, Takemura, & Iwata, 2012;Xia, Wenyuan, Qianqian, Luqi, & Changxiao, 2011; Zhang, Xie, Zhao,Liu, & Gao, 2009).4. kesimpulanSerangkaian asetat agar-agar dengan berbeda DS yang dipersiapkan, dansifat mereka ditentukan dan dianalisis contrastively denganagar-agar mentah. Hasil penelitian menunjukkan bahwa suhu gelling, geltemperatur leleh, gel kekuatan dan jelas viskositas agarasetat semua menurun dengan peningkatan DS. Variasiproses agar-agar molekul dalam solusi dari coil untuk helixdiamati melalui pengukuran optik rotasi, yang bisadilakukan tidak hanya dalam konsentrasi yang lebih tinggi (0.25 wt %) di manabisa membentuk gel, tetapi juga dalam konsentrasi yang lebih rendah (0.05 wt %) diitu yang bahkan tidak bisa membentuk gel. Suhu transisimulai titik (dari coil untuk helix) agar molekul adalah lebih tinggidalam konsentrasi yang lebih tinggi (0.25 wt %) daripada dalam konsentrasi yang lebih rendah (0.05 wt %), tetapi suhu dari titik akhir transisi (dariCoil untuk helix) adalah hampir sama dalam konsentrasi tinggi dan rendah. Menurut analisis profil tekstur (TPA),kekerasan, fracturability, dan springiness agar asetat gelsemuanya menurun kecuali bahwa kesinambungan agar-agar asetat gelmeningkat dengan kenaikan DS. Cyro-SEM menunjukkan bahwagel kerangka mikro agar asetat gel dan mentah agargel adalah struktur jaringan berpori, ukuran tetesan airterperangkap dalam gel kerangka struktur agar-agar asetat gel yang lebih kecildaripada yang mentah agar-agar gel, dan menjadi lebih kecil denganDS meningkatkan agar asetat. Setelah acetylation, memegang airkapasitas agar-agar ditingkatkan, tetapi adalah stabilitas termalmenurunkan