Pengeringan daging buah nangka secara osmosis

WARDHANI, Dyah Hesti, Prof.Ir. Boma Wikan Tyoso, MSc.,PhD

2001 | Tesis | S2 Teknik Kimia

Untuk mengurangi kerusakan pada buah bila dikeringkan menggunakan panas maka perlu dipelajari cara pengeringan lain, salah satunya adalah pengeringan secara osmosis. Pengeringan secara osmosis dilakukan dengan merendam buah pada larutan gula berkonsentrasi tinggi sehingga air dari dalam buah berpindah ke larutan karena perbedaan tekanan osmosis. Penelitian ini bertujuan untuk menganalisa proses pengeringan secara osmosis pada daging buah nangka yang dilakukan melalui percobaan laboratorium dan pemodelan matematis. Di samping itu, dipelajari pengaruh suhu, konsentrasi gula dalam larutan dan rasio berat larutan terhadap bahan. Pada penelitian ini diajukan lima model teoritis. Penelitian dilakukan dengan merendam daging buah nangka ukuran tertentu pada larutan gula. Diukur kadar air pada daging buah nangka setelah direndam selang waktu tertentu. Ke lima model yang diajukan kemudian dicocokkan dengan data hasil percobaan. Dari hasil percobaan diperoleh bahwa model IV (cell to cell model) dan model V (continuum model) paling sesuai untuk memprediksi pengeringan secara osmosis pada daging buah nangka. Ralat rata-rata model IV antara 0,98% sampai 4,52% sedangkan model V antara 1,47% sampai 4,89%. Pada hakekatnya model V adalah penyederhanaan dari model IV. Pada suhu antara 300°K sampai 318°K semakin tinggi suhu maka proses dehidrasi semakin cepat. Pada konsentrasi gula dalam larutan 60% sampai 75% semakin tinggi konsentrasinya air yang terambil dalam waktu yang sama semakin banyak. Efek pengenceran pada rasio berat larutan dengan bahan 10 sampai 25 dapat diabaikan.

Dehydration is usually done by drying, in which water is vaporized by addition of heat. But for dehydration of fruit, heat treatment may cause degradation. So, there is a need in developing dehydration method with no heat treatment. One of the possible processes is osmotic dehydration. Osmotic dehydration is carried out by soaking the fruits into high concentration of sugar solution which forces the water inside the fruits move into the solution because of the difference of osmotic pressure. The objective of this research was to study the osmotic dehydration of flesh of jack fruits, which consists of laboratory experiment and mathematical modeling. This research is also examining the effects of temperature, sugar concentration of solution, weight ratio of solution to fruits. In this research, five theoretical models are proposed. This study is done by soaking the flesh of jack fruits at fixed size into sugar solution. After the flesh of jack fruits was soaked for certain time, the moisture was then be measured. The results of the five models were then compared to the experimental data. The results of the study show that model IV and V well predict osmotic dehydration of flesh of jack fruits. Average errors of model IV are in the range between 0,98% and 4,52% which ones of model V lie between 1,47% and 4,89%. Actually, model V is a simplification of model IV. The higher temperature, the faster osmotic dehydration process at temperature between 300°K and 318°K. At sugar concentration of solution range between 60% and 70%, the higher the concentration, the more the water would be taken into solution. When weight ratio of solution to fruits is 10 to 25, the dilution effect could be ignored.

Kata Kunci : Pengeringan Buah Nangka, Osmosis, osmotic dehydration, mass transfer, soaking, jack fruits