- Teks
- Sejarah
ing temperature fraction [i.e., pal
ing temperature fraction [i.e., palm stearin (PS), full or partially
hydrogenated oils] is interesterified with a particular vegetable
oil in the manufacture of trans-free margarine and vegetable
shortening (12,13).
An additional alternative involves the direct blending of a
high-melting temperature fraction with a vegetable oil (i.e.,
sesame oil). This last process has the additional advantage that
no chemical process is involved, consistent with the consumer
trend toward natural products. The aim of this study was to investigate the crystallization kinetics of PS, a palm oil fraction
constituted mainly by triglycerides of high-melting temperature, in blends with sesame seed oil. This process constitutes a
feasible alternative to expand the use of sesame oil through the
development of value-added products such as squeezable margarines, spreads, or low-fat margarines. According to the National Association of Margarine Manufacturers, the consumption of margarine-type products grew from 2.6 to 9.1 pounds
per capita for the period between 1930 and 1996 (10). In contrast, butter consumption dropped from 17.6 to 4.3 pounds per
person (10).
PS is obtained through fractional crystallization of refined,
bleached, and deodorized palm oil (12). Tripalmitin (TP) is the
triglyceride with the highest melting temperature in both palm
oil (5–10% w/w) and PS (12–56% w/w), depending on the
fractionation temperature) (14). As a consequence, TP should
affect crystallization kinetics and polymorphic behavior of
palm oil and PS. Our previous research (8,15) on crystallization has indicated that solutions of pure TP in sesame oil behave like binary solutions formed by saturated triglycerides
(i.e., TP) and unsaturated triglycerides (i.e., sesame oil). In the
present study, we evaluate whether this behavior holds in a
more complex crystallization system, i.e., mixtures of PS in
sesame oil.
MATERIALS AND METHODS
Materials.Whole-seed refined sesame oil was obtained from a
local company (DIPASA de México, Celaya, Gto., México).
The oil was stored at 4°C in the dark. The same batch was used
in all the experiments.
Pure TP (>99% pure, experimentally confirmed by gas chromatography and DSC) was obtained from Sigma Chemical Co.
(St. Louis, MO). Refined, bleached, and deodorized PS was
provided by the Palm Oil Research Institute of Malaysia (Kuala
Lumpur, Malaysia). Both TP and PS were used without further
purification.
Chemical analysis.The fatty acids composition of sesame
oil and PS was determined by gas chromatography utilizing a
Shimadzu chromatograph GC-9A (Shimadzu Corp., Kyoto,
Japan) with flame-ionization detector and a Supelco (Bellefonte, PA) glass column (2.6 m ×2.1 mm) packed with GP 10%
SP 2330 on Chromosorb 100/120. The analysis conditions have
been previously reported (8).
The triglyceride profile for PS was determined by high-performance liquid chromatography (HPLC) following the conditions described previously by Che Man et al.(14) utilizing a
Waters 600 E instrument (Waters Millipore Co., Milford, MA)
with a refractive index detector and a Nova Pack C18
column
(3.9 ×300 mm) (Water Millipore Co.). Triglyceride peaks were
assigned based on the retention time of triglyceride standards.
The particular concentration of TP in PS was determined by
gas chromatography of the saturated triglyceride fraction isolated by silver ion thin-layer chromatography (TLC) following
the conditions described by Nikolova-Damyanova (16)
DSC. A PerkinElmer differential scanning calorimeter
(model DSC-7; PerkinElmer, Norwalk, CT) equipped with a
dry box was used in all cases. The temperature calibration of
the equipment was done with indium (onset temperature for
melting = 429.8 K) and n-hexatriacontane (onset temperature
for melting = 349.3 K), and the baseline was developed with
an empty aluminum pan. The calibration for heat involved in
phase changes (i.e., melting/crystallization) was made only
with indium (∆Hfor melting = 28.45 J/g).
Nonisothermal DSC analysis.For dynamic runs, ≈12 mg of
TP solution in sesame oil (0.00, 0.32, 0.98, 1.80, 2.62, 10, and
25% wt/vol) or PS blend in sesame oil (0.00, 26, 42, 60, and
80% wt/vol) was sealed in a pan and held at 353 K for 30 min
before each DSC scan. The system was cooled at a rate of 10
K/min until a temperature of 243 K was achieved. After 2 min
at this temperature, the melting curve was obtained by heating
the system at 5 K/min until reaching 353 K. The temperature in
the maxima of both the exothermal peak of crystallization (T
Cr
)
and the endothermal melting peak (T
s
) were calculated using
the DSC-7 software library. In the same way, the heating and
cooling thermograms of pure TP and PS were determined.
The ideal behavior of the TP crystallization/melting in both
systems, TP/sesame oil and PS/sesame oil, was evaluated using
the Hildebrand equation (17):
ln(x) = ∆Hf
/R(1/T
s
−1/T
p
) [1]
where ∆Hf
is the enthalpy of fusion per mole of pure TP, T
p
and
T
s
are the melting temperature of pure TP and in the oil solutions, respectively (i.e., the temperature in the peak maximum
in the DSC endotherm), xis the mole fraction of TP in the system (i.e., TP/sesame oil and PS/sesame oil solutions), and Ris
the universal gas constant. An average molecular weight for
sesame oil triglycerides (874.93) and PS triglycerides (842.15)
was calculated from the fatty acid composition.
Isothermal DSC analysis.The PS/sesame oil solution (26,
42, 60, and 80% wt/vol) was heated at 353 K for 30 min and
then cooled (1.0 K/min) to a preset temperature (297.5–309 K)
and held at that temperature for crystallization. After complete
crystallization, the system was left at the isothermal temperature for additional 35 min. Afterward, the melting thermogram
was obtained by heating the system at a rate of 1.0 K/min. The
induction time for crystallization (T
i
) was calculated from the
isothermal thermogram as the time from the start of the isothermal process to the beginning of crystallization (i.e., time where
the heat capacity of the sample had a significant departure from
the baseline) using the DSC-7 software library. The cooling
rate was selected according to conditions used in previous stud-
hydrogenated oils] is interesterified with a particular vegetable
oil in the manufacture of trans-free margarine and vegetable
shortening (12,13).
An additional alternative involves the direct blending of a
high-melting temperature fraction with a vegetable oil (i.e.,
sesame oil). This last process has the additional advantage that
no chemical process is involved, consistent with the consumer
trend toward natural products. The aim of this study was to investigate the crystallization kinetics of PS, a palm oil fraction
constituted mainly by triglycerides of high-melting temperature, in blends with sesame seed oil. This process constitutes a
feasible alternative to expand the use of sesame oil through the
development of value-added products such as squeezable margarines, spreads, or low-fat margarines. According to the National Association of Margarine Manufacturers, the consumption of margarine-type products grew from 2.6 to 9.1 pounds
per capita for the period between 1930 and 1996 (10). In contrast, butter consumption dropped from 17.6 to 4.3 pounds per
person (10).
PS is obtained through fractional crystallization of refined,
bleached, and deodorized palm oil (12). Tripalmitin (TP) is the
triglyceride with the highest melting temperature in both palm
oil (5–10% w/w) and PS (12–56% w/w), depending on the
fractionation temperature) (14). As a consequence, TP should
affect crystallization kinetics and polymorphic behavior of
palm oil and PS. Our previous research (8,15) on crystallization has indicated that solutions of pure TP in sesame oil behave like binary solutions formed by saturated triglycerides
(i.e., TP) and unsaturated triglycerides (i.e., sesame oil). In the
present study, we evaluate whether this behavior holds in a
more complex crystallization system, i.e., mixtures of PS in
sesame oil.
MATERIALS AND METHODS
Materials.Whole-seed refined sesame oil was obtained from a
local company (DIPASA de México, Celaya, Gto., México).
The oil was stored at 4°C in the dark. The same batch was used
in all the experiments.
Pure TP (>99% pure, experimentally confirmed by gas chromatography and DSC) was obtained from Sigma Chemical Co.
(St. Louis, MO). Refined, bleached, and deodorized PS was
provided by the Palm Oil Research Institute of Malaysia (Kuala
Lumpur, Malaysia). Both TP and PS were used without further
purification.
Chemical analysis.The fatty acids composition of sesame
oil and PS was determined by gas chromatography utilizing a
Shimadzu chromatograph GC-9A (Shimadzu Corp., Kyoto,
Japan) with flame-ionization detector and a Supelco (Bellefonte, PA) glass column (2.6 m ×2.1 mm) packed with GP 10%
SP 2330 on Chromosorb 100/120. The analysis conditions have
been previously reported (8).
The triglyceride profile for PS was determined by high-performance liquid chromatography (HPLC) following the conditions described previously by Che Man et al.(14) utilizing a
Waters 600 E instrument (Waters Millipore Co., Milford, MA)
with a refractive index detector and a Nova Pack C18
column
(3.9 ×300 mm) (Water Millipore Co.). Triglyceride peaks were
assigned based on the retention time of triglyceride standards.
The particular concentration of TP in PS was determined by
gas chromatography of the saturated triglyceride fraction isolated by silver ion thin-layer chromatography (TLC) following
the conditions described by Nikolova-Damyanova (16)
DSC. A PerkinElmer differential scanning calorimeter
(model DSC-7; PerkinElmer, Norwalk, CT) equipped with a
dry box was used in all cases. The temperature calibration of
the equipment was done with indium (onset temperature for
melting = 429.8 K) and n-hexatriacontane (onset temperature
for melting = 349.3 K), and the baseline was developed with
an empty aluminum pan. The calibration for heat involved in
phase changes (i.e., melting/crystallization) was made only
with indium (∆Hfor melting = 28.45 J/g).
Nonisothermal DSC analysis.For dynamic runs, ≈12 mg of
TP solution in sesame oil (0.00, 0.32, 0.98, 1.80, 2.62, 10, and
25% wt/vol) or PS blend in sesame oil (0.00, 26, 42, 60, and
80% wt/vol) was sealed in a pan and held at 353 K for 30 min
before each DSC scan. The system was cooled at a rate of 10
K/min until a temperature of 243 K was achieved. After 2 min
at this temperature, the melting curve was obtained by heating
the system at 5 K/min until reaching 353 K. The temperature in
the maxima of both the exothermal peak of crystallization (T
Cr
)
and the endothermal melting peak (T
s
) were calculated using
the DSC-7 software library. In the same way, the heating and
cooling thermograms of pure TP and PS were determined.
The ideal behavior of the TP crystallization/melting in both
systems, TP/sesame oil and PS/sesame oil, was evaluated using
the Hildebrand equation (17):
ln(x) = ∆Hf
/R(1/T
s
−1/T
p
) [1]
where ∆Hf
is the enthalpy of fusion per mole of pure TP, T
p
and
T
s
are the melting temperature of pure TP and in the oil solutions, respectively (i.e., the temperature in the peak maximum
in the DSC endotherm), xis the mole fraction of TP in the system (i.e., TP/sesame oil and PS/sesame oil solutions), and Ris
the universal gas constant. An average molecular weight for
sesame oil triglycerides (874.93) and PS triglycerides (842.15)
was calculated from the fatty acid composition.
Isothermal DSC analysis.The PS/sesame oil solution (26,
42, 60, and 80% wt/vol) was heated at 353 K for 30 min and
then cooled (1.0 K/min) to a preset temperature (297.5–309 K)
and held at that temperature for crystallization. After complete
crystallization, the system was left at the isothermal temperature for additional 35 min. Afterward, the melting thermogram
was obtained by heating the system at a rate of 1.0 K/min. The
induction time for crystallization (T
i
) was calculated from the
isothermal thermogram as the time from the start of the isothermal process to the beginning of crystallization (i.e., time where
the heat capacity of the sample had a significant departure from
the baseline) using the DSC-7 software library. The cooling
rate was selected according to conditions used in previous stud-
0/5000
ing temperature fraction [i.e., palm stearin (PS), full or partiallyhydrogenated oils] is interesterified with a particular vegetableoil in the manufacture of trans-free margarine and vegetableshortening (12,13).An additional alternative involves the direct blending of ahigh-melting temperature fraction with a vegetable oil (i.e.,sesame oil). This last process has the additional advantage thatno chemical process is involved, consistent with the consumertrend toward natural products. The aim of this study was to investigate the crystallization kinetics of PS, a palm oil fractionconstituted mainly by triglycerides of high-melting temperature, in blends with sesame seed oil. This process constitutes afeasible alternative to expand the use of sesame oil through thedevelopment of value-added products such as squeezable margarines, spreads, or low-fat margarines. According to the National Association of Margarine Manufacturers, the consumption of margarine-type products grew from 2.6 to 9.1 poundsper capita for the period between 1930 and 1996 (10). In contrast, butter consumption dropped from 17.6 to 4.3 pounds perperson (10). PS is obtained through fractional crystallization of refined,bleached, and deodorized palm oil (12). Tripalmitin (TP) is thetriglyceride with the highest melting temperature in both palmoil (5–10% w/w) and PS (12–56% w/w), depending on thefractionation temperature) (14). As a consequence, TP shouldaffect crystallization kinetics and polymorphic behavior ofpalm oil and PS. Our previous research (8,15) on crystallization has indicated that solutions of pure TP in sesame oil behave like binary solutions formed by saturated triglycerides(i.e., TP) and unsaturated triglycerides (i.e., sesame oil). In thepresent study, we evaluate whether this behavior holds in amore complex crystallization system, i.e., mixtures of PS insesame oil.MATERIALS AND METHODSMaterials.Whole-seed refined sesame oil was obtained from alocal company (DIPASA de México, Celaya, Gto., México).The oil was stored at 4°C in the dark. The same batch was usedin all the experiments.Pure TP (>99% pure, experimentally confirmed by gas chromatography and DSC) was obtained from Sigma Chemical Co.(St. Louis, MO). Refined, bleached, and deodorized PS wasprovided by the Palm Oil Research Institute of Malaysia (KualaLumpur, Malaysia). Both TP and PS were used without furtherpurification.Chemical analysis.The fatty acids composition of sesameoil and PS was determined by gas chromatography utilizing aShimadzu chromatograph GC-9A (Shimadzu Corp., Kyoto,Japan) with flame-ionization detector and a Supelco (Bellefonte, PA) glass column (2.6 m ×2.1 mm) packed with GP 10%SP 2330 on Chromosorb 100/120. The analysis conditions havebeen previously reported (8).The triglyceride profile for PS was determined by high-performance liquid chromatography (HPLC) following the conditions described previously by Che Man et al.(14) utilizing aWaters 600 E instrument (Waters Millipore Co., Milford, MA)with a refractive index detector and a Nova Pack C18column(3.9 ×300 mm) (Water Millipore Co.). Triglyceride peaks wereassigned based on the retention time of triglyceride standards.The particular concentration of TP in PS was determined bygas chromatography of the saturated triglyceride fraction isolated by silver ion thin-layer chromatography (TLC) followingthe conditions described by Nikolova-Damyanova (16)DSC. A PerkinElmer differential scanning calorimeter(model DSC-7; PerkinElmer, Norwalk, CT) equipped with adry box was used in all cases. The temperature calibration ofthe equipment was done with indium (onset temperature formelting = 429.8 K) and n-hexatriacontane (onset temperaturefor melting = 349.3 K), and the baseline was developed withan empty aluminum pan. The calibration for heat involved inphase changes (i.e., melting/crystallization) was made onlywith indium (∆Hfor melting = 28.45 J/g).Nonisothermal DSC analysis.For dynamic runs, ≈12 mg ofTP solution in sesame oil (0.00, 0.32, 0.98, 1.80, 2.62, 10, and25% wt/vol) or PS blend in sesame oil (0.00, 26, 42, 60, and80% wt/vol) was sealed in a pan and held at 353 K for 30 minbefore each DSC scan. The system was cooled at a rate of 10K/min until a temperature of 243 K was achieved. After 2 minat this temperature, the melting curve was obtained by heatingthe system at 5 K/min until reaching 353 K. The temperature inthe maxima of both the exothermal peak of crystallization (TCr)and the endothermal melting peak (Ts) were calculated usingthe DSC-7 software library. In the same way, the heating andcooling thermograms of pure TP and PS were determined.The ideal behavior of the TP crystallization/melting in bothsystems, TP/sesame oil and PS/sesame oil, was evaluated usingthe Hildebrand equation (17):ln(x) = ∆Hf /R(1/Ts−1/Tp) [1]where ∆Hfis the enthalpy of fusion per mole of pure TP, TpandTsare the melting temperature of pure TP and in the oil solutions, respectively (i.e., the temperature in the peak maximumin the DSC endotherm), xis the mole fraction of TP in the system (i.e., TP/sesame oil and PS/sesame oil solutions), and Risthe universal gas constant. An average molecular weight forsesame oil triglycerides (874.93) and PS triglycerides (842.15)was calculated from the fatty acid composition.Isothermal DSC analysis.The PS/sesame oil solution (26,42, 60, and 80% wt/vol) was heated at 353 K for 30 min andthen cooled (1.0 K/min) to a preset temperature (297.5–309 K)and held at that temperature for crystallization. After completecrystallization, the system was left at the isothermal temperature for additional 35 min. Afterward, the melting thermogramwas obtained by heating the system at a rate of 1.0 K/min. Theinduction time for crystallization (Ti) was calculated from theisothermal thermogram as the time from the start of the isothermal process to the beginning of crystallization (i.e., time wherethe heat capacity of the sample had a significant departure fromthe baseline) using the DSC-7 software library. The coolingrate was selected according to conditions used in previous stud-
Sedang diterjemahkan, harap tunggu..
ing fraksi suhu [yaitu, stearin sawit (PS), penuh atau sebagian
minyak terhidrogenasi] adalah interesterified dengan sayuran tertentu
minyak dalam pembuatan margarin trans-bebas dan sayur
shortening (12,13).
Alternatif lain melibatkan pencampuran langsung sebuah
fraksi suhu tinggi-lebur dengan minyak sayur (misalnya,
minyak wijen). Proses terakhir ini memiliki keuntungan tambahan yang
tidak ada proses kimia yang terlibat, sesuai dengan konsumen
kecenderungan produk alami. Tujuan dari penelitian ini adalah untuk menyelidiki kinetika kristalisasi PS, fraksi minyak sawit
merupakan terutama oleh trigliserida dari suhu tinggi-lebur, dalam campuran dengan minyak biji wijen. Proses ini merupakan
alternatif yang layak untuk memperluas penggunaan minyak wijen melalui
pengembangan produk bernilai tambah seperti margarin mudah dipengaruhi, menyebar, atau margarin rendah lemak. Menurut National Association of Manufacturers Margarin, konsumsi margarin-jenis produk tumbuh 2,6-9,1 pounds
per kapita untuk periode antara 1930 dan 1996 (10). Sebaliknya, konsumsi mentega menurun 17,6-4,3 pound per
orang (10).
PS diperoleh melalui kristalisasi fraksional halus,
dikelantang, dan deodorized palm oil (12). Tripalmitin (TP) adalah
trigliserida dengan suhu tertinggi leleh di kedua telapak
minyak (5-10% b / b) dan PS (12-56% b / b), tergantung pada
suhu fraksinasi) (14). Akibatnya, TP harus
mempengaruhi kinetika kristalisasi dan perilaku polimorfik
kelapa sawit dan PS. Penelitian kami sebelumnya (8,15) pada kristalisasi telah menunjukkan bahwa solusi dari TP murni dalam minyak wijen berperilaku seperti solusi biner dibentuk oleh trigliserida jenuh
(yaitu, TP) dan trigliserida tidak jenuh (yaitu, minyak wijen). Dalam
studi ini, kami mengevaluasi apakah perilaku ini berlaku dalam
sistem kristalisasi yang lebih kompleks, yaitu campuran dari PS di
. minyak wijen
BAHAN DAN METODE
Materials.Whole-biji minyak wijen halus diperoleh dari
perusahaan lokal (DIPASA de México, Celaya , Gto., México).
Minyak disimpan pada suhu 4 ° C dalam gelap. Batch yang sama digunakan
dalam semua percobaan.
TP Murni (> 99% murni, eksperimen dikonfirmasi dengan kromatografi gas dan DSC) diperoleh dari Sigma Chemical Co.
(St. Louis, MO). Halus, dikelantang, dan deodorized PS
disediakan oleh Palm Oil Research Institute of Malaysia (Kuala
Lumpur, Malaysia). Kedua TP dan PS digunakan tanpa lanjut
pemurnian.
asam lemak Kimia analysis.The komposisi wijen
minyak dan PS ditentukan dengan kromatografi gas memanfaatkan
Shimadzu kromatografi GC-9A (Shimadzu Corp, Kyoto,
Jepang) dengan detektor api ionisasi dan Supelco (Bellefonte, PA) kolom gelas (2,6 m × 2,1 mm) dikemas dengan GP 10%
SP 2330 pada Chromosorb 100/120. Kondisi analisis telah
telah dilaporkan sebelumnya (8).
Profil trigliserida untuk PS ditentukan dengan kromatografi cair kinerja tinggi (HPLC) mengikuti kondisi yang dijelaskan sebelumnya oleh Che Man et al. (14) memanfaatkan
Waters 600 E instrumen (Waters Millipore Co, Milford, MA)
dengan detektor indeks bias dan Nova Pack C18
kolom
(3,9 × 300 mm) (Air Millipore Co). Puncak trigliserida yang
ditetapkan berdasarkan waktu retensi standar trigliserida.
Konsentrasi tertentu TP di PS ditentukan dengan
kromatografi gas dari fraksi trigliserida jenuh diisolasi oleh ion perak kromatografi lapis tipis (TLC) mengikuti
kondisi yang dijelaskan oleh Nikolova-Damyanova ( 16)
DSC. Sebuah PerkinElmer diferensial scanning kalorimeter
(model DSC-7; PerkinElmer, Norwalk, CT) yang dilengkapi dengan
kotak kering digunakan dalam semua kasus. Kalibrasi temperatur
peralatan dilakukan dengan indium (suhu awal untuk
leleh = 429,8 K) dan n-hexatriacontane (suhu awal
untuk mencair = 349,3 K), dan baseline dikembangkan dengan
aluminium pan kosong. Kalibrasi untuk panas yang terlibat dalam
perubahan fase (yaitu, peleburan / kristalisasi) dibuat hanya
dengan indium (ΔHfor mencair = 28.45 J / g).
Nonisothermal DSC analysis.For berjalan dinamis, ≈12 mg
solusi TP dalam minyak wijen (0.00 , 0,32, 0,98, 1,80, 2,62, 10, dan
25% wt / vol) atau PS berbaur minyak wijen (0.00, 26, 42, 60, dan
80% wt / vol) disegel dalam panci dan diadakan di 353 K selama 30 menit
sebelum setiap scan DSC. Sistem ini didinginkan dengan laju 10
K / menit sampai suhu 243 K dicapai. Setelah 2 menit
pada suhu ini, kurva leleh diperoleh dengan memanaskan
sistem pada 5 K / menit hingga mencapai 353 K. Suhu di
maxima kedua puncak exothermal kristalisasi (T
Cr
)
dan puncak endothermal lebur (T
s
) dihitung dengan menggunakan
DSC-7 perpustakaan software. Dengan cara yang sama, pemanasan dan
pendinginan thermograms TP murni dan PS ditentukan.
Perilaku ideal kristalisasi TP / mencair di kedua
sistem, TP / minyak wijen dan PS / minyak wijen, dievaluasi menggunakan
persamaan Hildebrand (17) :
ln (x) = ΔHf
/ R (1 / T
s
-1 / T
p
) [1]
di mana ΔHf
adalah entalpi fusi per mol TP murni, T
p
dan
T
s
adalah suhu leleh murni TP dan dalam solusi minyak, masing-masing (yaitu, suhu di puncak maksimum
dalam endoterm DSC), X adalah fraksi mol TP dalam sistem (yaitu, TP / minyak wijen dan PS / solusi minyak wijen), dan Ris
universal konstanta gas. Berat molekul rata-rata untuk
trigliserida minyak wijen (874,93) dan PS trigliserida (842,15)
dihitung dari komposisi asam lemak.
isotermal DSC analysis.The PS / solusi wijen minyak (26,
42, 60, dan 80% wt / vol) adalah dipanaskan pada 353 K selama 30 menit dan
kemudian didinginkan (1,0 K / min) ke suhu yang telah ditetapkan (297,5-309 K)
dan diadakan pada suhu untuk kristalisasi. Setelah selesai
kristalisasi, sistem yang tersisa pada suhu isotermal untuk tambahan 35 menit. Setelah itu, termogram leleh
diperoleh dengan memanaskan sistem pada tingkat 1,0 K / min. The
waktu induksi untuk kristalisasi (T
i
) dihitung dari
termogram isotermal sebagai waktu dari awal proses isotermal ke awal kristalisasi (yaitu, waktu di mana
kapasitas panas dari sampel memiliki keberangkatan yang signifikan dari
baseline) dengan menggunakan perpustakaan software DSC-7. Pendinginan
Tingkat dipilih sesuai dengan kondisi yang digunakan dalam-studi sebelumnya
minyak terhidrogenasi] adalah interesterified dengan sayuran tertentu
minyak dalam pembuatan margarin trans-bebas dan sayur
shortening (12,13).
Alternatif lain melibatkan pencampuran langsung sebuah
fraksi suhu tinggi-lebur dengan minyak sayur (misalnya,
minyak wijen). Proses terakhir ini memiliki keuntungan tambahan yang
tidak ada proses kimia yang terlibat, sesuai dengan konsumen
kecenderungan produk alami. Tujuan dari penelitian ini adalah untuk menyelidiki kinetika kristalisasi PS, fraksi minyak sawit
merupakan terutama oleh trigliserida dari suhu tinggi-lebur, dalam campuran dengan minyak biji wijen. Proses ini merupakan
alternatif yang layak untuk memperluas penggunaan minyak wijen melalui
pengembangan produk bernilai tambah seperti margarin mudah dipengaruhi, menyebar, atau margarin rendah lemak. Menurut National Association of Manufacturers Margarin, konsumsi margarin-jenis produk tumbuh 2,6-9,1 pounds
per kapita untuk periode antara 1930 dan 1996 (10). Sebaliknya, konsumsi mentega menurun 17,6-4,3 pound per
orang (10).
PS diperoleh melalui kristalisasi fraksional halus,
dikelantang, dan deodorized palm oil (12). Tripalmitin (TP) adalah
trigliserida dengan suhu tertinggi leleh di kedua telapak
minyak (5-10% b / b) dan PS (12-56% b / b), tergantung pada
suhu fraksinasi) (14). Akibatnya, TP harus
mempengaruhi kinetika kristalisasi dan perilaku polimorfik
kelapa sawit dan PS. Penelitian kami sebelumnya (8,15) pada kristalisasi telah menunjukkan bahwa solusi dari TP murni dalam minyak wijen berperilaku seperti solusi biner dibentuk oleh trigliserida jenuh
(yaitu, TP) dan trigliserida tidak jenuh (yaitu, minyak wijen). Dalam
studi ini, kami mengevaluasi apakah perilaku ini berlaku dalam
sistem kristalisasi yang lebih kompleks, yaitu campuran dari PS di
. minyak wijen
BAHAN DAN METODE
Materials.Whole-biji minyak wijen halus diperoleh dari
perusahaan lokal (DIPASA de México, Celaya , Gto., México).
Minyak disimpan pada suhu 4 ° C dalam gelap. Batch yang sama digunakan
dalam semua percobaan.
TP Murni (> 99% murni, eksperimen dikonfirmasi dengan kromatografi gas dan DSC) diperoleh dari Sigma Chemical Co.
(St. Louis, MO). Halus, dikelantang, dan deodorized PS
disediakan oleh Palm Oil Research Institute of Malaysia (Kuala
Lumpur, Malaysia). Kedua TP dan PS digunakan tanpa lanjut
pemurnian.
asam lemak Kimia analysis.The komposisi wijen
minyak dan PS ditentukan dengan kromatografi gas memanfaatkan
Shimadzu kromatografi GC-9A (Shimadzu Corp, Kyoto,
Jepang) dengan detektor api ionisasi dan Supelco (Bellefonte, PA) kolom gelas (2,6 m × 2,1 mm) dikemas dengan GP 10%
SP 2330 pada Chromosorb 100/120. Kondisi analisis telah
telah dilaporkan sebelumnya (8).
Profil trigliserida untuk PS ditentukan dengan kromatografi cair kinerja tinggi (HPLC) mengikuti kondisi yang dijelaskan sebelumnya oleh Che Man et al. (14) memanfaatkan
Waters 600 E instrumen (Waters Millipore Co, Milford, MA)
dengan detektor indeks bias dan Nova Pack C18
kolom
(3,9 × 300 mm) (Air Millipore Co). Puncak trigliserida yang
ditetapkan berdasarkan waktu retensi standar trigliserida.
Konsentrasi tertentu TP di PS ditentukan dengan
kromatografi gas dari fraksi trigliserida jenuh diisolasi oleh ion perak kromatografi lapis tipis (TLC) mengikuti
kondisi yang dijelaskan oleh Nikolova-Damyanova ( 16)
DSC. Sebuah PerkinElmer diferensial scanning kalorimeter
(model DSC-7; PerkinElmer, Norwalk, CT) yang dilengkapi dengan
kotak kering digunakan dalam semua kasus. Kalibrasi temperatur
peralatan dilakukan dengan indium (suhu awal untuk
leleh = 429,8 K) dan n-hexatriacontane (suhu awal
untuk mencair = 349,3 K), dan baseline dikembangkan dengan
aluminium pan kosong. Kalibrasi untuk panas yang terlibat dalam
perubahan fase (yaitu, peleburan / kristalisasi) dibuat hanya
dengan indium (ΔHfor mencair = 28.45 J / g).
Nonisothermal DSC analysis.For berjalan dinamis, ≈12 mg
solusi TP dalam minyak wijen (0.00 , 0,32, 0,98, 1,80, 2,62, 10, dan
25% wt / vol) atau PS berbaur minyak wijen (0.00, 26, 42, 60, dan
80% wt / vol) disegel dalam panci dan diadakan di 353 K selama 30 menit
sebelum setiap scan DSC. Sistem ini didinginkan dengan laju 10
K / menit sampai suhu 243 K dicapai. Setelah 2 menit
pada suhu ini, kurva leleh diperoleh dengan memanaskan
sistem pada 5 K / menit hingga mencapai 353 K. Suhu di
maxima kedua puncak exothermal kristalisasi (T
Cr
)
dan puncak endothermal lebur (T
s
) dihitung dengan menggunakan
DSC-7 perpustakaan software. Dengan cara yang sama, pemanasan dan
pendinginan thermograms TP murni dan PS ditentukan.
Perilaku ideal kristalisasi TP / mencair di kedua
sistem, TP / minyak wijen dan PS / minyak wijen, dievaluasi menggunakan
persamaan Hildebrand (17) :
ln (x) = ΔHf
/ R (1 / T
s
-1 / T
p
) [1]
di mana ΔHf
adalah entalpi fusi per mol TP murni, T
p
dan
T
s
adalah suhu leleh murni TP dan dalam solusi minyak, masing-masing (yaitu, suhu di puncak maksimum
dalam endoterm DSC), X adalah fraksi mol TP dalam sistem (yaitu, TP / minyak wijen dan PS / solusi minyak wijen), dan Ris
universal konstanta gas. Berat molekul rata-rata untuk
trigliserida minyak wijen (874,93) dan PS trigliserida (842,15)
dihitung dari komposisi asam lemak.
isotermal DSC analysis.The PS / solusi wijen minyak (26,
42, 60, dan 80% wt / vol) adalah dipanaskan pada 353 K selama 30 menit dan
kemudian didinginkan (1,0 K / min) ke suhu yang telah ditetapkan (297,5-309 K)
dan diadakan pada suhu untuk kristalisasi. Setelah selesai
kristalisasi, sistem yang tersisa pada suhu isotermal untuk tambahan 35 menit. Setelah itu, termogram leleh
diperoleh dengan memanaskan sistem pada tingkat 1,0 K / min. The
waktu induksi untuk kristalisasi (T
i
) dihitung dari
termogram isotermal sebagai waktu dari awal proses isotermal ke awal kristalisasi (yaitu, waktu di mana
kapasitas panas dari sampel memiliki keberangkatan yang signifikan dari
baseline) dengan menggunakan perpustakaan software DSC-7. Pendinginan
Tingkat dipilih sesuai dengan kondisi yang digunakan dalam-studi sebelumnya
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