8342937112

Pertanika 14(1). 59-64 (1991)

Effects of Gamma-Irradiation on Peroxide Formation in Palm Olein

K.ENDINKEAU¹ and T.W. WOODWARD²

¹ Department of Chemistry Facu Ity ofScien re and En vi ron men ta l St u d i es Unwersiti Pert atu a n Malaysia 43400 Ul Serda ng Se la ngo r / )a rn I Eh sa n, Ma lny s i a

2

Deparment of Chemistry and Applied Chemistry Un i ? tersi t y ofSa l ford Salford M5 4WT, England

Key words: palm olein, gamma-irradiation, hydroperoxides.

ABSTRAK

Sampel olein sawitdidedahkanpada sinar- y sehinggados l2kCy dałam keadaan beroksigen. Pembentukan pernksida diukur dengan ni la i peroksida (NP), ni la i asid tiobarbituńk (A TB) dan dien terkonjugat. I Zasil kajian menunjukkan peroksida berta mhah dengan pertambahan dos penyinaran dan beru ba h dengan repa I dałam tempoh penyimpanan selepas penyinaran. Setelah mencapai maksimum, dna han perta ma _t peroksida menu run kepada nilai yangrendah dałam kedua-dua sampel tersi nar pada 4 dan 12kGy. Wala u bagaimanapun, nilai ATB bagi sampel tersi nar dengan dos rendah (4kGy) adalah Ubili tinggi daripada sampel tersi nar dengan dos besar( 12 k( iy). Peroksida berła ku pada ()°C.tetapi nilainya rendah daripada nilaisuhu bilik. Kepekatan bahan antioksida (BHT) pada 200bpjmeremalkan peroksidaan walaupun sebahagian dańpadanya rosak ketika penyinaran.

ABSTRACT

Samples oj palm olein were irradiated wilh y -rays up to 12 kCy in the presence of oxygen. The extent of peroxidation was determined by peroxide value (PV), thiobarbituńc and (Tl3A) value and conjugated diene. Peroxideformation increasedwith increasingiiradialion doseandchangedrapidlyduńngposl-irradiutwnslorage. Afferreaehingmaxima. duringthefirst two days, theperoxidedeclined to relatinely lownalues in both samples irradiated with 4 and 12 k(>y. Hown/er, the TBA values of samples irradiated with Iow dose (4 k(iy), were higherthan that of samples irradiated with high dose (12 kCy), aflerfour days storage. Peroxidłformation ornured at 0°C but the yields were lower than that of

room temperaturę. Conrentralion of anlwxidant (BH P)« pa rtially destroyed byga m rna-i rradiation.

INTRODUCTION

One of the most important tasks of palm oil producers is to produce high (juality oil. Much work hasbeen clone recemly to improve itsqualitv which depends on the State of the oil palm fruits. Deteriorated fruits will produce a Iow quality oil due to high free fatty acid (FFA) con tent as a result of action of a lipase enzyme from microorganisms and fungi during post-harvest. This problem bas beengivengreateremphasisrecently. An alternative means of improving palm oil quality is by using gamma-irradiation. This technology has been shown to beapromising means of preventing food

1200ppm significantly inhibitsperoxidation although it was

spoilage and losses, besides extending shelf-life (Loaharanu 1985). However, the technique may cause problems sińce unsaturated fats are easily induced by radiation to form hydroperoxides. Oxidised oils and fats produce offensive odours and flavours, and morę importantly, oxidation decreases the nutritional quality and safety of food. Hydroproxides have been shown to be very toxic when injected intoanimals. (Horgon etal. 1957).

Palm olein contains substantial amounts of unsaturated acids which is aboui 54% of all acids. Therefore, it is likely that radiation, within the rangęofpresenationdoses (lessthan lOkGy) (Webb