Rekayasa proses produksi mono-digliserida dari palm fatty acid distillate serta aplikasinya sebagai emulsifier dalam pembuatan margarin berbahan minyak sawit merah

Abstract

Kebutuhan dunia industri terhadap produk emulsifier pada tahun 2017 cukup tinggi yaitu sebesar 2,7 juta ton, dimana 70% emulsifier yang digunakan, terlebih pada industri pangan adalah mono-digliserida (MDG). MDG merupakan ester dari alkohol trihidroksi (gliserol) dengan satu atau dua gugus hidroksil diesterifikasi dengan asam lemak rantai panjang. MDG merupakan surfaktan non-ionik, memiliki gugus hidrofobik asil panjang dan gugus hidrofilik. MDG berstatus Generally Recognized as Safe (GRAS) dan termasuk kedalam jenis pengemulsi pada bahan tambahan pangan (BTP). MDG dapat diproduksi dari palm fatty acid distillate (PFAD) dan gliserol melalui reaksi esterifikasi yang bersifat reversible. Berbagai upaya untuk memperoleh MDG dengan kemurnian dan rendemen tinggi perlu dilakukan, seperti mempelajari kondisi reaksi, pengaruh waktu reaksi, dan proses pemurnian produk hasil esterifikasi. Selain itu, peningkatan skala produksi perlu dilakukan melalui penggunaan reaktor kontiniu, serta aplikasi MDG pada produk hilir berbasis pangan perlu untuk dikaji lebih lanjut. Aplikasi MDG dari PFAD pada produk hilir yang sangat berpotensi untuk dikembangkan adalah margarin. Margarin adalah produk pangan berbentuk plastis yang merupakan emulsi air dalam minyak (water in oil (w/o)) dengan penambahan emulsifier. Selain itu, warna kuning margarin dapat diperoleh dari kandungan karoten pada minyak sawit merah (MSM). MSM mengandung karoten (pro-vitamin A), tokoferol dan tokotrienol (vitamin E) tinggi. Sehingga, dalam pembuatan margarin berbahan MSM dapat meminimalisasi biaya produksi karena tidak memerlukan penambahan pewarna (dari karoten) dan vitamin E (dari tokoferol dan tokotrienol). Penelitian ini dilakukan bertujuan untuk melakukan review terhadap sintesis MDG dengan bahan baku PFAD, mereview tentang minyak sawit dan minyak sawit merah, serta melakukan rekayasa proses produksi MDG dari PFAD pada reaktor batch berpengaduk dan reaktor kontiniu static mixer serta sirkulasi campuran bahan baku pada design reaktor kontiniu dan aplikasi MDG sebagai emulsifier dalam pembuatan margarin berbahan minyak sawit merah, yang kemudian diaplikasikan pada pembuatan bolu kukus. Penelitian ini dilakukan dalam tiga tahap. Pada tahap pertama, sintesis MDG dari PFAD dan gliserol dilakukan menggunakan reaktor berpengaduk kapasitas 20 kg/batch pada rasio mol substrat 1:6 katalis para-toluena sulfonic acid (PTSA) sebanyak 1,5% dari berat PFAD, suhu 150 °C, kecepatan pengadukan 400 rpm, serta lama reaksi 15, 30, 45, 60, dan 75 menit. Produk esterifikasi pada lama reaksi terbaik dimurnikan menggunakan metode ekstraksi pelarut heksana dan etanol. Residu fraksi heksana (dari proses pemurnian heksana) di analisis komposisi MG, DG, TG, dan ALB, kemudian dimanfaatkan kembali melalui pemurnian sebagai upaya peningkatan rendemen, dan di esterifikasi menggunakan gliserol sisa esterifikasi PFAD untuk melihat kemampuannya digunakan secara langsung di dalam reaksi tanpa proses pemurnian terlebih dahulu, sebagai dasar untuk sintesis MDG secara kontiniu. Pada tahap kedua, sintesis MDG dilakukan menggunakan reaktor kontiniu static mixer pada kondisi lama reaksi terbaik pada proses batch dengan variasi residence time (60, 75, dan 120 menit), dan sintesis MDG menggunakan design pada reaktor kontiniu melalui sirkulasi campuran bahan baku pada lama reaksi (60, 90, 120, 150, 180, 210, 240, 270, dan 300 menit). Pada tahap ketiga, MDG dari PFAD digunakan sebagai emulsifier dalam pembuatan margarin berbahan minyak sawit dan minyak sawit merah (MSM), yang kemudian diaplikasikan pada pembuatan bolu kukus. Margarin diformulasi dengan mencampurkan lemak 81,8%, MDG 0,1-0,9% (sebagai kontrol digunakan lesitin 0,35%), antioksidan 0,01%, garam 2%, flavor 0,05%, dan air. Margarin dibuat dengan dua jenis campuran fraksi lemak yaitu formula 1 (refined bleached deodorized palm oil (RBDP Oil): MSM pada rasio berat 96,5:3,5) dan formula 2 (RBDP Stearin: MSM pada rasio berat 2,5:97,5). Margarin dengan formula terbaik diaplikasikan dalam pembuatan bolu kukus. Hasil penelitian tahap 1 menunjukkan bahwa lama reaksi terbaik untuk menghasilkan produk MDG kasar dengan rendemen dan kadar tertinggi sebesar 95,45 dan 49,98% diperoleh pada 75 menit reaksi. Pemurnian produk MDG kasar menggunakan ekstraksi pelarut heksana dan etanol menghasilkan rendemen dengan kadar berturut-turut sebesar 20,16% terhadap PFAD dan 94,08%. Residu fraksi heksana (dari proses pemurnian) mengandung MG (15,69%), DG (29,24%), ALB (17,75%), dan TG (37,31%). Dengan demikian, peningkatan rendemen MDG melalui pemanfaatan residu fraksi heksana tersebut dapat dilakukan melalui pemurnian dan esterifikasi kembali menggunakan gliserol murni dan gliserol sisa dari esterifikasi PFAD. Pemurnian kembali residu dari fraksi heksana menghasilkan MDG dengan kemurnian 96,98% dan meningkatkan rendemen MDG sebesar 8,43% (dari 20,16% menjadi 28,59% terhadap PFAD). Sedangkan, esterifikasi kembali residu dari fraksi heksana menghasilkan MDG dengan kemurnian 90,85% (dari gliserol murni) dan 90,90% (dari gliserol sisa) mengalami peningkatan rendemen MDG masing-masing sebesar 2,71% dan 2,31% (dari 20,16% menjadi 22,87% dan 22,47% terhadap PFAD), yang tidak berbeda signifikan. Hal ini menunjukkan bahwa gliserol sisa esterifikasi PFAD dapat digunakan langsung di dalam reaksi tanpa harus dimurnikan terlebih dahulu. MDG yang dihasilkan memiliki kadar air < 2%, kadar ALB < 6%, kadar gliserol bebas < 7%, pH 5, slip melting point (SMP) 48,75-56,25 °C, dan stabilitas emulsi > 80%. Hasil penelitian tahap kedua menunjukkan bahwa reaktor kontiniu static mixer belum dapat digunakan untuk mengkonversi PFAD menjadi MDG, yang ditunjukkan oleh rendahnya kadar MDG yang terbentuk (< 10%) dengan kadar ALB yang masih tinggi (> 80%) pada produk esterifikasi. Sementara itu, pada sintesis MDG menggunakan komponen pada reaktor kontiniu dengan sistem sirkulasi diperoleh MDG kasar dengan rendemen dan kadar berturut-turut pada range 46,34-51,75% dan 41,09-46,85%. Pemurnian MDG kasar menghasilkan rendemen dan kadar pada range 9,40-11,21% terhadap PFAD dan 95,07-97,73%. MDG hasil pemurnian memiliki kadar air < 2%, kadar ALB < 6%, kadar gliserol bebas < 7%, pH 5,25, SMP 56,63-61,75 °C, dan stabilitas emulsi > 85%. Hasil penelitian tahap ketiga menunjukkan bahwa sifat fisikokimia margarin formula 1 dan 2 menyerupai margarin komersial, namun warna margarin formula 2 lebih merah dibandingkan margarin formula 1 dan margarin komersial. Penambahan MDG 0,1-0,9% tidak berpengaruh signifikan terhadap kadar ALB, kadar karoten, dan SMP fraksi lemak serta kadar air margarin, sedangkan kadar asam oleat menurun, kadar asam palmitat meningkat, dengan nilai solid fat content (SFC) tidak berbeda signifikan. Margarin dengan penambahan MDG 0,1-0,9% memiliki stabilitas yang baik dibandingkan tanpa MDG, dan stabilitasnya menyerupai margarin kontrol dan margarin komersial. Margarin formula 1 dan 2 disukai panelis dari segi warna dan tekstur, dan nilainya menyerupai margarin kontrol dan margarin komersial, dengan nilai kesukaan terbaik diperoleh pada penambahan MDG 0,5%. Aplikasi margarin formula 1 dan 2 dalam pembuatan bolu kukus disukai panelis dari segi warna, tekstur, aroma, dan rasa. Bolu kukus berbahan margarin formula 2 lebih disukai dibandingkan bolu kukus berbahan margarin komersial.

The industrial world's demand for emulsifier products in 2017 was 2.7 million tons, of which 70% of the emulsifier used was mono-diglyceride (MDG). MDG is an ester of trihydroxy alcohol (glycerol) with one or two hydroxyl groups esterified with long-chain fatty acids. MDG is a non-ionic surfactant, has an extended hydrophobic acyl group and a hydrophilic group. MDG status as Generally Recognized as Safe (GRAS) and is included in the type of emulsifier in food additives. MDG can be produced from palm fatty acid distillate (PFAD) and glycerol through a reversible esterification reaction. Various efforts to obtain MDG with high purity and yield need to be carried out, such as studying the reaction conditions, the effect of reaction time, and the purification process of esterified products. In addition, it is necessary to increase the scale of production through continuous reactors, and the application of MDGs to food-based downstream products needs to be studied further. PFAD-based MDG applications in downstream products that have the potential to be developed are margarine. Margarine is a plastic food product that is a water in oil (w/o) emulsion with an emulsifier. In addition, the carotene content in red palm oil (RPO) can obtain the yellow colour of margarine. RPO is high in carotenoids (pro-vitamin A), tocopherols and tocotrienols (vitamin E). Thus, the manufacture of margarine made from RPO can minimize production costs because it does not require the addition of dyes (from carotene) and vitamin E (from tocopherols and tocotrienols). This study was conducted to review the synthesis of MDG with PFAD as raw materials, reviewing palm oil and red palm oil, as well as engineering the production process of MDG from PFAD in a stirred batch reactor, continuous reactor with static mixer and the utilization of components in the continuous reactor design and application of MDG as an emulsifier in the manufacture of margarine made from red palm oil, which is then applied to the manufacture of steamed cakes. Three stages conducted this research. In the first stage, the synthesis of MDG from PFAD and glycerol was carried out using a stirred reactor with a capacity of 20 kg/batch at a substrate mole ratio of 1:6 with a 1.5% para-toluene sulfonic acid (PTSA) catalyst by weight of PFAD, a temperature of 150 °C, a speed of 1.5% by weight of PFAD. Stirring at 400 rpm, and reaction time of 15, 30, 45, 60, and 75 minutes. In the best reaction time, the esterification product was purified using hexane and ethanol solvent extraction methods. The residue of the hexane fraction (from the hexane purification process) was analyzed for the composition of MG, DG, TG, and ALB, then reused through purification as an effort to increase yield, and esterified using glycerol remaining from PFAD esterification to see its ability to be used directly in the reaction without a process purification as the basis for continuous MDG synthesis. In the second stage, the synthesis of MDG was carried out using a continuous reactor with a static mixer at the best reaction time conditions in the batch process with the addition of variations in residence time (60, 75, and 120 minutes), and the synthesis of MDG using components in a continuous reactor design through a circulation system for a long time reactions (60, 90, 120, 150, 180, 210, 240, 270, and 300 minutes). In the third stage, MDG from PFAD is used as an emulsifier in the manufacture of margarine made from palm oil and red palm oil (RPO), which is then applied to the manufacture of steamed cakes. Margarine was formulated by mixing 81.8% fat, 0.1-0.9% MDG (as a control used lecithin 0.35%), 0.01% antioxidant, 2% salt, 0.05% flavor, and water. Margarine is made with two types of fat fraction mixture, namely formula 1 (refined, bleached deodorized palm oil (RBDP Oil): RPO at a weight ratio of 96.5:3.5) and formula 2 (RBDP Stearin: RPO at a weight ratio of 2.5:97,5). With the best formulation, margarine is applied in the manufacture of steamed sponges. The first stage results showed that 75 minutes reaction obtained the best reaction time to produce crude MDG product with the highest yield and concentration of 95.45 and 49.98%. Purification of crude MDG products using hexane and ethanol solvent extraction resulted in yields of 20.16% against PFAD and 94.08%, respectively. The hexane fraction residue (from the purification process) contains MG (15.69%), DG (29.24%), FFA (17.75%), and TG (37.31%). Thus, the increase in MDG yield through the utilization of the residual hexane fraction can be carried out through purification and re-esterification using pure glycerol and residual glycerol from PFAD esterification. Purification of residue from the hexane fraction produced MDG with a purity of 96.98% and increased the yield of MDG by 8.43% (from 20.16% to 28.59% against PFAD). Meanwhile, re-esterification of the residue from the hexane fraction resulted in MDG with a purity of 90.85% (from pure glycerol) and 90.90% (from residual glycerol), which increased the yield of MDG by 2.71% and 2.31%, respectively (from 20.16% to 22.87% and 22.47% to PFAD), which are not significantly different. Re-esterification of residue shows that the residual glycerol of PFAD esterification can be used directly in the reaction without being purified first. The resulting MDG has a water content < 2%, FFA content < 6%, free glycerol content < 7%, pH 5, slip melting point (SMP) 48.75-56.25 °C, and emulsion stability > 80%. The results of the second stage of the study showed that a continuous reactor with a static mixer could not be used to convert PFAD into MDG, which was indicated by the low levels of MDG formed (< 10%) with high FFA levels (> 80%) in the esterification product. Meanwhile, in the synthesis of MDG using components in a continuous reactor with a circulation system, crude MDG was obtained with yields and levels in the range of 46.34-51.75% and 41.09-46.85%, respectively. Purification of crude MDG produces yields and levels in the range of 9.40-11.21% for PFAD and 95.07-97.73%. The purified MDG had water content < 2%, FFA content < 6%, free glycerol content < 7%, pH 5.25, SMP 56.63-61.75°C, and emulsion stability > 85%. The third stage results showed that the physicochemical properties of margarine formulas 1 and 2 resembled commercial margarine. Still, margarine formula 2 was redder than margarine formula one and commercial margarine. The addition of 0.1-0.9% MDG had no significant effect on FFA levels, carotene levels, SMP fat fraction and water content of margarine. In contrast, oleic acid levels decreased, palmitic acid levels increased, with no different solid fat content (SFC) values significant. With the addition of 0.1-0.9% MDG, Margarine has good stability compared to without MDG, and its stability is similar to that of control margarine and commercial margarine. Margarine formulas 1 and 2 were favoured by panellists in terms of colour and texture. Their values resembled control margarine and commercial margarine, with the best preference value obtained at the addition of 0.5% MDG. The application of margarine formulas 1 and 2 in the steamed cake favoured panellists in terms of colour, texture, aroma, and taste. Steamed sponge cake made from margarine formula 2 is preferable to steamed cake made from commercial margarine.