ofGracilariaspecies must be adapted

ofGracilariaspecies must be adapted for each species and variables
like temperature and alkali concentration must be adjusted to obtain as much desulphation as possible, while still avoiding the yield
losses caused in the treatment (Armisen & Galatas, 1987; OrduñaRojas et al., 2008).
G. cliftoniiis an economically important resource due to its high
agar yield of 52%db (Byrne et al., 2002) but agar characteristics of
this species are yet to be reported. In addition, no studies have
been reported on the alkali treatment ofG. cliftonii. The agar
extraction process ofG. cliftoniiwas evaluated to maximise the
agar yield by investigating the effects of five variablesviz.soaking
time, soaking temperature, seaweed–water ratio and time and
temperature of extraction. The aim of the current research was
to investigate the effects of extraction variables on chemical and
physical properties (gel strength, gelling temperature, melting
point and sulphate content) of agar. In addition, the effect of alkali
treatments on the agar characteristics of G. cliftoniiat different
soaking temperatures was also investigated. This information provides the basis to standardise the procedure of agar extraction
from G. cliftoniito obtain agar with characteristics accepted by
industry.
2. Experimental
2.1. Sample preparation
G. cliftoniifronds were collected from shallow creeks around
Point Peron, Shoalwater Islands Marine Park (32 17
0
S, 115 42
0
E), Perth, WA by free diving and transported in containers filled
with ocean water to Curtin Aquatic Research Laboratory (CARL).
G. cliftoniisamples were washed with tap water to remove impurities. When the seaweed was free from visible impurities it was
then considered as ‘clean seaweed’. The ‘clean seaweed’ sample
was oven dried for 8 h at 60C and stored in sealed plastic bags
for agar extraction.
2.2. Agar extraction process
2.2.1. Soaking time
First lot of ‘Clean seaweed’ was divided into 12 samples of 5 g
(dry weight) each and nine samples from these 12 samples were
soaked for 1, 2 and 3 h at room temperature (25C) in triplicate
to hydrate. The remaining three samples were used as control
and were not soaked (0 h). Extraction was carried out by boiling
all samples for 2.5 h in 250 mL conical flasks with distilled water
at 90C in a water bath.
2.2.2. Soaking temperature
Second lot of ‘Clean seaweed’ was divided into 12 samples of 5 g
(dry weight) each and nine samples from these 12 samples were
soaked for 2 h at three different temperatures (30, 35 and 40C)
in triplicate. Three remaining samples were soaked at room temperature (25C) and used as control in triplicate. Extraction was
carried out by boiling all samples for 2.5 h in 250 mL conical flasks
with distilled water at 90C in a water bath.
2.2.3. Seaweed to water ratio
Third lot of ‘Clean seaweed’ was divided into 12 samples of 5 g
(dry weight) each and soaked for 2 h at 30C in different volume of
water to represent variable seaweed–water ratios. These four different seaweed–water ratios were 1:50, 1:100, 1:150 and 1:200.
All of them were used in triplicate and then transferred to water
bath for agar extraction. Extraction was carried out by boiling all
the samples for 2.5 h in 250 mL conical flasks with distilled water
at 90C in a water bath.
2.2.4. Extraction temperature
Fourth lot of ‘Clean seaweed’ was divided into 12 samples of 5 g
(dry weight) each and soaked for 2 h at 30C with seaweed–water
ratio of 1:150. Extraction was carried out at four different temperatures of 70, 80, 90 and 100C in triplicate by boiling the samples
for 2.5 h in four water baths.
2.2.5. Extraction time
The fifth and last lot of ‘Clean seaweed’ was divided into 12
samples of 5 g (dry weight) each and soaked for 2 h at 30C with
seaweed–water ratio of 1:150. Extraction from the samples was
carried out at 100C at five different times of 1.0, 1.5, 2.0, 2.5,
3.0 h in triplicate in a water bath.
2.2.6. Agar yield
The extracts from all the lots were filtered using a three-ply
cheesecloth and were transferred to plastic containers (500 mL).
The filtrate was frozen overnight, thawed and oven dried at 60C
for 24 h and weighed. Quantity of agar was determined in terms
of agar yield expressed as percentage dry basis and calculated from
the following equation
Agar Yield¼½ðDry weight of agarðgÞ=Dry weight of seaweedðgÞÞ 100 ð1Þ
2.2.7. Alkali preparation and treatments
Four concentrations of 1%, 2%, 3% and 5% alkali were prepared
dissolving analytical grade sodium hydroxide (NaOH) (Sigma

)in
distilled water. The dried samples ofG. cliftonii(5 g db) in triplicate
were soaked in each alkali concentrations of 1%, 2%, 3% and 5% for
3 h at room temperature in 250 mL conical flask. The flasks were
then placed for 1 h in a water bath at 60, 70 and 80C, respectively.
After alkali treatment, the samples were washed with running tap
water for 1 h to remove excess alkali. Extraction was carried out by
boiling the sample for 2.5 h in 250 mL of distilled water at 7.0–7.5
pH. The extracts were filtered using three-ply cheesecloth and
transferred to plastic containers (500 mL). The filtrate was allowed
to gel at room temperature, frozen overnight and thawed. Finally,
the agar was oven dried for 24 h at 60C, cooled and weighed to
calculate percent agar yield on dry weight basis (%db) and calculated from Eq. (1).
2.3. Agar properties
The dried agar from extraction process variables and alkali
treatments was reconstituted in 250 mL glass beakers with distilled water to obtain a 1.5% w/v agar solution. The hot gel was
poured into 50 mL sterile plastic containers and remaining in a
glass test tube (2.3 cm diameter, 16.5 cm height) to determine
gel strength, melting point and gelling temperature, of the agar.
The physical and chemical properties (gel strength, melting temperature, gelling temperature and sulphate content) of the agar
were determined after curing gel for 24 h at 25C.
Gel strength was determined as described byMarinho-Soriano
and Bourret (2005)with minor modifications. A texturometerTX-2iwith a 1-cm
2
plunger at a speed of 1 mm/s to depth 5 mm was
used on gel in 50 mL sterile containers. Melting point and gelling
temperature were determined using techniques described byFreile-Pelegrin and Murano (2005)with minor modifications. Melting
point of the gel in test tubes was measured by placing a glass bead
(5 mm diameter) on the gel surface. The test tube rack with test
tube was transferred to the water bath at boiling temperature.
The melting point was recorded with a digital thermometer when
the bead sank into the solution. Same test tubes were kept at room
temperature to measure the gelling temperature. The tubes were
tilted up and down in a water bath at room temperature until
the glass bead ceased moving. The gel temperature in the tube

Hasil (Bahasa Indonesia) 1:

ofGracilariaspecies harus disesuaikan untuk setiap spesies dan variabelseperti suhu dan alkali konsentrasi harus disesuaikan untuk mendapatkan desulphation sebanyak mungkin, sementara masih menghindari hasilkerugian yang disebabkan dalam pengobatan (Armisen & Galatas, 1987; OrduñaRojas et al., 2008).G. cliftoniiis sumber daya ekonomi penting karena tingginyaagar hasil dari 52% db (Byrne et al., 2002) tetapi agar karakteristikspesies ini masih belum dilaporkan. Selain itu, ada penelitian telahtelah dilaporkan pada ofG perlakuan alkali. cliftonii. Agar-agarofG proses ekstraksi. cliftoniiwas dievaluasi untuk memaksimalkanagar hasil oleh menyelidiki efek dari lima variablesviz.soakingwaktu, perendaman suhu, rumput laut-air rasio dan waktu dansuhu ekstraksi. Tujuan dari penelitian saat ini adalahuntuk menyelidiki efek dari ekstraksi variabel pada kimia dansifat fisik (gel kekuatan, gelling suhu mencairtitik dan sulfat konten) dari agar-agar. Selain itu, efek alkaliperawatan agar-agar karakteristik G. cliftoniiat berbedaperendaman suhu itu juga diselidiki. Informasi ini menyediakan dasar untuk membakukan prosedur ekstraksi agardari G. cliftoniito memperoleh agar-agar dengan karakteristik yang diterima olehindustri.2. eksperimental2.1. preparasi sampleG. cliftoniifronds dikumpulkan dari Sungai dangkal di sekitarTitik Peron, Portland Islands Marine Park (32 170S, 115 420E), Perth, WA oleh gratis menyelam dan diangkut dalam wadah penuhdengan air laut untuk Curtin akuatik penelitian laboratorium (CARL).G. cliftoniisamples dicuci dengan air keran untuk menghilangkan kotoran. Ketika rumput laut adalah bebas dari kotoran yang terlihatkemudian dianggap sebagai 'bersih rumput laut'. Sampel 'bersih rumput laut'oven dikeringkan untuk 8 h 60 c dan disimpan dalam kantong plastik tertutupuntuk ekstraksi agar-agar.2.2. agar proses ekstraksi2.2.1. perendaman waktuPertama banyak 'Rumput laut bersih' dibagi menjadi 12 sampel 5 g(kering berat) yang masing-masing dan sembilan sampel dari sampel ini 12direndam selama 1, 2 dan 3 h pada suhu kamar (25 C) dalam rangkap tigauntuk hidrat. Tersisa tiga sampel digunakan sebagai kontroldan tidak basah (0 h). Ekstraksi dilaksanakan oleh mendidihSemua sampel untuk 2,5 jam dalam 250 mL kerucut labu dengan air sulingpada 90 C dalam penangas air.2.2.2. perendaman suhuKedua banyak 'Rumput laut bersih' dibagi menjadi 12 sampel 5 g(kering berat) yang masing-masing dan sembilan sampel dari sampel ini 12direndam selama 2 h di tiga suhu yang berbeda (30, 35-40 C)dalam rangkap tiga. Tiga sisa sampel yang basah pada suhu kamar (25 C) dan digunakan sebagai kontrol dalam rangkap tiga. Ekstraksi adalahdilakukan oleh mendidih semua sampel untuk 2,5 jam dalam 250 mL labu berbentuk kerucutdengan air 90 c dalam penangas air suling.2.2.3. rumput laut untuk air rasioKetiga banyak 'Rumput laut bersih' dibagi menjadi 12 sampel 5 g(kering berat) setiap direndam selama 2 h 30 c dalam volume berbedaair untuk mewakili variabel rumput laut-air rasio. Ini empat rasio rumput laut-air yang berbeda adalah 1:50, 1: 100, 1:150, dan 1: 200.Semua dari mereka yang digunakan dalam rangkap tiga dan kemudian ditransfer ke airmandi untuk ekstraksi agar-agar. Ekstraksi dilaksanakan oleh mendidih semuasampel untuk 2,5 jam dalam 250 mL kerucut labu dengan air sulingpada 90 C dalam penangas air.2.2.4. suhu ekstraksiKeempat banyak 'Rumput laut bersih' dibagi menjadi 12 sampel 5 g(kering berat) setiap direndam selama 2 h 30 c dengan rumput laut-airrasio 1:150. Ekstraksi dilaksanakan di empat suhu yang berbeda dari 70, 80, 90 dan 100 C dalam rangkap dengan merebus sampelselama 2,5 h di empat pemandian air.2.2.5. waktu ekstraksiBanyak kelima dan terakhir 'Rumput laut bersih' dibagi menjadi 12sampel 5 g (berat kering) masing-masing dan direndam selama 2 h 30 c denganrumput laut-air rasio dari 1:150. Ekstraksi dari sampel adalahdilakukan di 100 C pada waktu yang berbeda lima 1.0, 1.5, 2.0, 2.5,h 3.0 dalam rangkap tiga dalam penangas air.2.2.6. agar hasilEkstrak dari semua banyak disaring menggunakan three-plykain katun tipis dan dipindahkan ke wadah plastik (500 mL).Filtrat membeku semalam, dicairkan dan kering oven c 60untuk 24 h dan ditimbang. Jumlah agar ditetapkan dalam persyaratanagar hasil dinyatakan sebagai persentase dasar kering dan dihitung daripersamaan berikutAgar Yield¼½ðDry berat agarðgÞ = berat kering seaweedðgÞÞ 100 ð1Þ2.2.7. persiapan alkali dan perawatanEmpat konsentrasi 1%, 2%, 3% dan 5% alkali disusunmelarutkan analisis kadar natrium hidroksida (NaOH) (Sigma) diair suling. OfG kering sampel. cliftonii (5 g db) dalam rangkap tigayang direndam dalam konsentrasi alkali setiap 1%, 2%, 3% dan 5% untuk3 h pada suhu kamar di labu berbentuk kerucut 250 mL. Labu yangkemudian ditempatkan untuk 1 h dalam penangas air pada 60, 70 dan 80 C, masing-masing.Setelah pengobatan alkali, sampel dicuci dengan menjalankan keranair untuk 1 h untuk menghilangkan kelebihan alkali. Ekstraksi dilaksanakan olehmendidih sampel untuk 2,5 jam dalam 250 mL air suling 7.0-7,5pH. Ekstrak disaring menggunakan kain katun tipis three-ply danditransfer ke wadah plastik (500 mL). Filtrat diizinkanke gel pada suhu kamar, beku dicairkan dan semalam. Akhirnya,agar-agar adalah oven kering selama 24 jam pada 60 C, didinginkan dan ditimbang untukmenghitung persen agar hasil atas dasar berat kering (% db) dan dihitung dari EQ (1).2.3. agar propertiAgar-agar kering dari ekstraksi proses variabel dan alkaliperawatan dilarutkan dalam gelas kaca 250 mL dengan air suling untuk mendapatkan solusi agar w/v 1,5%. Hot gel adalahdituangkan ke dalam wadah plastik steril 50 mL dan sisa ditabung gelas (diameter 2.3 cm, 16,5 cm tinggi) untuk menentukangel kekuatan, titik leleh dan suhu gelling, agar-agar.Sifat fisik dan kimia (gel kekuatan, temperatur leleh, gelling suhu dan kandungan sulfat) dari agar-agarditentukan setelah pengobatan gel untuk 24 h di 25 C.Gel kekuatan ditentukan sebagai byMarinho-Soriano dijelaskandan Bourret (2005) dengan modifikasi kecil. TexturometerTX-2iwith 1-cm2plunger pada kecepatan 1 mm/s ke kedalaman 5 mm adalahdigunakan pada gel dalam wadah steril 50 mL. Titik leleh dan gellingsuhu bertekad menggunakan teknik yang dijelaskan byFreile-Pelegrin dan Murano (2005) dengan modifikasi kecil. Pencairantitik gel dalam tabung diukur dengan menempatkan manik-manik kaca(diameter 5 mm) pada permukaan gel. Tabung rak dengan testabung dipindahkan ke penangas air pada suhu mendidih.Titik lebur direkam dengan termometer digital ketikamanik-manik tenggelam ke dalam larutan. Tabung sama disimpan di ruangsuhu untuk mengukur suhu gelling. Tabung yangmiring naik dan turun dalam penangas air pada suhu kamar sampaimanik-manik kaca berhenti bergerak. Suhu gel tabung