Pengeringan rumput laut menggunakan pengering putar (rotary dryer)

YAHYA, Muhammad, Muslikhin Hidayat, S.T., M.T., Ph.D

2010 | Tesis | S2 Magister Sistem Teknik

Penelitian ini bertujuan untuk mengetahui pengaruh suhu dan lama pengeringan terhadap perubahan kadar air, tekstur dan warna rumput laut dengan menggunakan pengering putar. Penelitian ini menggunakan alat pengering putar berbahan bakar briket batu bara dan bahan rumput laut Gracilaria sp. Rancangan penelitian menggunakan 3 kali perlakuan pada suhu: 60 oC, 75oC, dan 90 oC, variasi lama pengeringan: 1,5 jam, 2,5 jam, 5 jam, dan 7,5 jam. Hasil rumput laut kering dilakukan uji: kadar air, tekstur, dan warna. Hasil penelitian sebagai berikut: (1) terdapat pengaruh suhu dan lama pengeringan terhadap penurunan kadar air rumput laut dengan menggunakan pengering putar. Semakin tinggi suhu pengeringan semakin cepat waktu penurunan kadar air rumput laut; (2) untuk mencapai kadar air standar rumput laut Gracilaria sp hingga 25% diperlukan waktu sebagai berikut: (a) pada suhu 60 oC diperlukan waktu pengeringan 3,59 jam, (b) suhu 75 oC diperlukan waktu pengeringan 3,18 jam, dan (c) suhu 90 oC diperlukan waktu pengeringan 2,92 jam. (3) besarnya biaya pengeringan berbanding terbalik dengan lama waktu pengeringan, semakin cepat waktu pengeringan semakin mahal biaya yang diperlukan. Untuk mengeringkan 5 kg rumput laut sampai kadar air standar 25%; pada suhu 60 oC ddengan waktu 3,59 jam dbutuhkan biaya Rp 4.520, pada suhu 75 oC dengan waktu 3,18 jam dibutuhkan biaya Rp 5.461, dan pada suhu 90 oC dengan waktu 2,92 jam dibutuhkan biaya Rp 6.358; (4) suhu dan lama waktu pengeringan berpengaruh terhadap tekstur rumput laut. Pada suhu 60 oC semakin lama dikeringkan semakin kuat teksturnya. Sebaliknya pada suhu 75 oC dan 90 oC semakin lama dikeringkan semakin rapuh teksturnya. Tekstur optimal rumput laut kering berkadar air 25% diperoleh pada suhu 60 oC dengan lama pengeringan 3,59 jam yaitu sebesar 0,179 kg/cm2, dan (5) Suhu dan lama pengeringan berpengaruh terhadap warna rumput laut. Pada pengeringan suhu 60 oC, 75 oC dan 90 oC warna rumput laut mengalami penurunan kehijauan, tetapi nilai hijaunya tetap meskipun kecil, berbeda dengan pengeringan matahari setelah dikeringkan > 5 jam warna rumput laut berubah menjadi kemerahan. Warna optimal kehijauan rumput laut kering dengan kadar air 25% diperoleh pada suhu 60 oC dengan lama pengeringan 3,59 jam sebesar -0,74.

This study aimed to investigate effects of the temperature and drying duration on changes in the seaweed water content, texture and color by means of a rotary dryer. This study used a rotary dryer fueled by coal briquettes and seaweed material Gracilaria sp. The research design employed 3 treatments under the temperatures of 600C, 750C, and 900C and the drying durations of 1.5 hours, 2.5 hours, and 7.5 hours. The resulting dry seaweed was tested on the water content, texture, and color. The results of the study were as follows: (1) there were effects of the temperature and drying duration on the reduction of the seaweed water content by means of a rotary dryer. The higher the drying temperature was, the shorter it was to reduce the seaweed water content; (2) to obtain the standard water content of seaweed Glacilaria Sp up to 25%, the time required was as follows: (a) under the temperature of 60 0C, the required drying duration was 3.59 hours, (b) under the temperature of 75 0C, the required drying duration was 3.18 hours, and (c) under the temperature of 90 0C, the required drying duration was 2.92 hours. (3) the drying cost was inversely proportional to the drying duration; the shorter the drying duration was, the higher the drying cost was. To 5 kg of dried seaweed to the water content of the standard 25%; under the temperature of 60 0C in 3.59 hours, the cost was Rp 4,250, under the temperature of 75 0C in 3.18 hours, the cost was Rp 5,461, and under the temperature of 90 0C in 2.92 hours, the cost was Rp 6,358; (4) the temperature and drying duration had effects on the seaweed texture. Under the temperature of 60 0C, the longer the drying duration was, the stronger the texture was. On the contrary, under the temperatures of 75 0C and 90 0C, the longer the drying duration was, the weaker the texture was. The optimum texture of dry seaweed with a water content of 25% obtained from the temperature of 60 0C in the drying duration of 3.59 hours was 0.179 kg/cm2, and (5) the temperature and drying duration had effects on the seaweed color. Under the temperature of 60 0C in the drying duration of 3.59 hours, the seaweed color showed a reduction in the greenish shade, but its green value remained although it became less; this was different from the solar drying process because after > 5 hours the seaweed color became reddish. The optimum greenish color of dry seaweed with a water content of 25% obtained from the temperature of 60 0C in the drying duration of 3.59 hours was – 0.74.

Kata Kunci : Pengering putar,Rumput laut,Kadar air,Lama pengeringan,Suhu,Tekstur dan warna ; rotary dryer, seaweed, water content, drying duration, temperature, texture, color