Sains Malaysiana 49(9)(2020): 2301-2309

http://dx.doi.org/10.17576/jsm-2020-4909-27

Thermal Treatments on the Oil Palm Fruits: Response Surface Optimization and Microstructure Study

(Rawatan Termal pada Buah Kelapa Sawit: Pengoptimuman Permukaan Respon dan Kajian Struktur Mikro)

NURUL HASIMAH KASMIN¹, SAIFUL IRWAN ZUBAIRI¹, AZWAN MAT LAZIM²* & ROILA AWANG³

¹Department of Food Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Department of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

³Engineering & Processing Research Division, Malaysian Palm Oil Board, No. 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor Darul Ehsan, Malaysia

Received: 15 October 2019/Accepted: 8 May 2020

ABSTRACT

Sterilization is the most important steps in the palm oil milling process prior to oil extraction. Experiments involving dry heating sterilization (SD) couple with solvent extraction of palm fruits were done to determine the relationship of palm oil yield and deterioration of bleachability index (DOBI). As a comparison, the conventional method of wet heating was used (SW). The optimum sterilization treatment parameters were determined by using response surface methodology (RSM). Central composite rotatable design (CCRD) was used to study the effects of sterilization temperature, X₁ (°C) and treatment time, X₂ (min) to oil yield (%), and DOBI. The sterilization temperature and time were conducted between 70 and 90°C and 20 to 90 min, respectively. Preliminary results proved increasing temperature and time of sterilization process increased oil yield for both SD and SW. Furthermore, the DOBI showed a similar trend as the oil yield. Optimization study using SD gave the optimal response through a combination of parameters, SD: X₁ = 90 °C and X₂ = 68 min, where the oil yield obtained was 43.21% and DOBI 4.05. However, sterilization treatment using SW showed insignificant results (p>0.05) between temperature and time since R² value was 0.4368 and the low degree of agreement between adjusted R² (0.03) and predicted R² (-2.43). It was also found SD treatment produced high DOBI value though the oil yield was lower than SW.

Keywords: DOBI; dry heating; oil yield; RSM; wet heating

ABSTRAK

Pensterilan ialah proses utama dalam pemprosesan minyak kelapa sawit sebelum pengekstrakan untuk mendapatkan minyak sawit mentah. Uji kaji melibatkan pensterilan buah sawit menggunakan rawatan kering (SD) diikuti dengan pengekstrakan menggunakan pelarut bagi menentukan hubungan antara hasil pengekstrakan minyak sawit dan kualiti indeks pemerosotan dan pelunturan (DOBI). Kaedah konvensional menggunakan rawatan basah (SW) juga dijalankan sebagai perbandingan. Parameter pensterilan optimum ditentukan menggunakan kaedah permukaan respon (RSM). Reka bentuk berputar komposit sentral (CCRD) digunakan bagi menentukan kesan suhu, X₁ (°C) dan tempoh masa pensterilan, X₂ (min) terhadap pengekstrakan minyak sawit (%) dan DOBI. Suhu dan tempoh masa pensterilan dijalankan masing-masing pada 70 hingga 90 °C dan 20 hingga 90 min. Kajian awal menunjukkan peningkatan suhu dan tempoh masa pensterilan meningkatkan hasil pengekstrakan minyak bagi kedua-dua kaedah SD dan SW. Selain itu, nilai DOBI menunjukkan tren yang sama seperti hasil pengekstrakan minyak. Kajian pengoptimuman menggunakan SD memberi tindak balas optimum dengan kombinasi parameter, SD: X₁ = 90 °C dan X₂ = 68 min dengan hasil pengekstrakan minyak sebanyak 43.21% dan DOBI 4.05 diperoleh. Namun, rawatan pensterilan menggunakan SW menunjukkan perbezaan yang tidak signifikan (p>0.05) antara suhu dan masa kerana nilai R² adalah 0.4368 dan nilai terlaras R² (0.03) dan telahan R² (-2.43) yang tidak menghampiri. Didapati rawatan SD telah menghasilkan nilai DOBI yang lebih tinggi walaupun hasil pengekstrakan minyaknya adalah lebih rendah berbanding SW.

Kata kunci: DOBI; pengekstrakan minyak; rawatan basah; rawatan kering; RSM

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*Corresponding author; email: azwanlazim@ukm.edu.my