Susu merupakan sumber utama protein, kalsium, dan vitamin yang penting untuk pertumbuhan dan perkembangan. Meski konsumsi susu per kapita di Indonesia masih rendah, produksi susu domestik masih rendah karena populasi sapi perah yang terbatas dan harga susu yang tinggi. Untuk mengatasi masalah ini, dapat digunakan teknologi pemekatan susu untuk menghilangkan sebagian air, menghasilkan produk dengan kadar padatan lebih tinggi, salah satunya dengan metode forward osmosis. Forward osmosis memanfaatkan gradien tekanan osmotik untuk memisahkan air dari zat terlarut, mempertahankan nilai gizi dari susu. Kalsium klorida (CaCl2) digunakan sebagai larutan penarik karena memiliki tekanan osmotik tinggi. Penelitian ini menggunakan konsentrasi CaCl2 2M dan 3M dengan laju alir 0,6 LPM, jenis membran polyamide dan polyethersulfone, serta variasi tekanan 2 bar, 3 bar, dan 4 bar. Hasil penelitian menunjukkan bahwa membran PA dengan larutan penarik CaCl2 2M pada tekanan 4 bar menghasilkan water flux tertinggi yaitu 5,37 L/m2·h, dengan RSF 7,58 g/m2·h, nilai SRSF 1,00 g/L, dan koefisien rejeksi 89,17%. Sementara itu, membran PES pada kondisi serupa memberikan water flux lebih tinggi yaitu 6,22 L/m2·h, namun disertai RSF yang lebih besar. Dari segi komposisi nutrisi, kondisi terbaik untuk membran PA diperoleh pada larutan penarik CaCl2 3M dan tekanan 4 bar dengan penurunan kadar air 10,91%, kadar lemak 3,72%, dan kadar protein 4,06%. Untuk membran PES, kondisi terbaik terjadi pada CaCl2 3M, tekanan 4 bar dengan penurunan kadar air 8,19%, kadar lemak 3,61%, dan kadar protein 3,63%. Secara keseluruhan, kondisi optimum dicapai pada larutan penarik CaCl2 2M, tekanan 4 bar, dan membran PA karena mampu memberikan pengurangan kadar air tertinggi dengan mempertahankan kandungan nutrisi dan efisiensi energi.
Milk is a primary source of protein, calcium, and vitamins essential for growth and development. Although per capita milk consumption in Indonesia remains low, domestic production is also limited due to the small population of dairy cattle and high milk prices. To address this issue, milk concentration technology can be applied to remove part of the water and produce products with higher total solids, one of which is the forward osmosis (FO) method. Forward osmosis utilizes an osmotic pressure gradient to separate water from solutes while preserving the nutritional value of milk. Calcium chloride (CaCl2) is used as a draw solution due to its high osmotic pressure. This study applied CaCl2 at concentrations of 2M and 3M with a flow rate of 0.6 LPM, polyamide (PA) and polyethersulfone (PES) membranes, and applied pressures of 2, 3, and 4 bar. The results showed that the PA membrane with a 2M CaCl2 draw solution at 4 bar produced the highest water flux of 5.37 L/m2·h, with a reverse solute flux (RSF) of 7.58 g/m2·h, a specific reverse solute flux (SRSF) of 1.00 g/L, and a rejection coefficient of 89.17%. Meanwhile, the PES membrane under the same conditions produced a higher water flux of 6.22 L/m2·h but with a greater RSF. In terms of nutritional composition, the best condition for the PA membrane was achieved with a 3M CaCl2 draw solution at 4 bar, resulting in a reduction of water content by 10.91%, fat content of 3.72%, and protein content of 4.06%. For the PES membrane, the best condition occurred with 3M CaCl2 at 4 bar, yielding reductions in water content of 8.19%, fat content of 3.61%, and protein content of 3.63%. Overall, the optimum condition was achieved using a 2M CaCl2 draw solution, 4 bar pressure, and a PA membrane, as it provided the highest water reduction while maintaining nutritional quality and energy efficiency.
