Sains Malaysiana 43(8)(2014): 1189–1195

Effect of Microwave Heating on Oxidative Degradation of Sunflower Oil

in the Presence of Palm Olein

(Kesan Pemanasan Gelombang Mikro Terhadap Pemerosotan Oksidatif Campuran

Minyak Bunga Matahari dalam Olein Sawit)

M. ABBAS ALI^1,2*, Z. BAMALLI NOURUDDEEN¹, IDA I. MUHAMAD¹, R. ABD LATIP³

& N. HIDAYU OTHMAN³

¹Department of Bioprocess Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim, Malaysia

²Department of Chemistry, Rajshahi University of Engineering & Technology

Rajshahi-6204, Bangladesh

³Sime Darby Research Sdn. Bhd., 42700 Banting, Selangor Darul Ehsan, Malaysia

Received: 1 November 2012/Accepted: 9 December 2013

ABSTRACT

The aim of this study was to evaluate on how heat treatments by microwave oven may affect the oxidative degradation of sunflower oil (SFO) and its blend with palm olein (PO). The blend was prepared in the volume ratio of 40:60 (PO: SFO, PSF). The samples were exposed to microwave heating at medium power setting, for different periods. In this study, refractive index, free fatty acid content, peroxide value, p-anisidine value, total oxidation (TOTOX), specific extinction, viscosity, polymer content, polar compounds and food oil sensor value of the oils all increased, whereas iodine value and C18:2/C16:0 ratio decreased as microwave heating progressed. Microwave heating temperature increased with increasing heating time and longer heating times resulted in a greater degree of oil deterioration. The percentage of linoleic acid tended to decrease, whereas the percentage of palmitic acid increased. The effect of adding PO to SFO on the formation of free fatty acids and conjugated dienes during microwave treatment was not significant (p< 0.05). No significant differences in food oil sensor value was observed between SFO and PSF. Based on the most oxidative stability criteria, it can be concluded that the microwave heating caused the formation of comparatively lower amounts of oxidation products in PSF compared to SFO, indicating a lower extent of oxidative degradation of PSF.

Keywords: Fatty acids; microwave heating; oxidative stability; polar compounds; sunflower oil

ABSTRAK

Tujuan kajian ini dijalankan adalah untuk menilai bagaimana olahan haba oleh ketuhar gelombang mikro boleh mempengaruhi kemerosotan oksidatif minyak bunga matahari (SFO) dan campuran dengan olein sawit (PO). Campuran telah disediakan dalam nisbah isi padu 40:60 (PO: SFO, PSF). Sampel didedahkan kepada pemanasan gelombang mikro pada tetapan kuasa sederhana untuk tempoh yang berbeza. Dalam kajian ini, indeks biasan, kandungan asid lemak bebas, nilai peroksida, nilai p-anisidine, pengoksidaan total (TOTOX), kepupusan spesifik, kelikatan, kandungan polimer, sebatian berkutub dan nilai sensor minyak makan bagi semua sampel minyak meningkat, manakala nilai iodin dan nisbah C18:2/C16:0 menurun semasa pemanasan gelombang mikro tersebut berlaku. Suhu pemanasan gelombang mikro meningkat dengan pertambahan masa pemanasan dan masa pemanasan yang lebih panjang mengakibatkan tahap kemerosotan minyak yang lebih besar. Peratusan asid linoleik cenderung berkurangan, manakala peratusan asid palmitik meningkat. Kesan menambah PO ke dalam SFO terhadap pembentukan asid lemak bebas dan diene berkonjugat hasil olahan gelombang mikro didapati tidak signifikan (p<0.05). Tiada perbezaan yang ketara dalam nilai sensor minyak makan yang diperhatikan antara SFO dan PSF. Berdasarkan kriteria kestabilan oksidatif paling utama, dapat disimpulkan bahawa pemanasan gelombang mikro telah menyebabkan pembentukan jumlah produk pengoksidaan yang agak rendah dalam PSF berbanding SFO dan ini menunjukkan tahap kemerosotan oksidatif PSF yang lebih rendah.

Kata kunci: Asid lemak; kestabilan oksidatif; minyak bunga matahari; pemanasan mikro gelombang; sebatian berkutub

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*Corresponding author; email: radwiya44@yahoo.com