Microwave Drying of Black Olive Slices : Effects on Total Phenolic Contents and Colour

Abstract

In this study, the drying behaviour of black olive slices using microwave was investigated and the effects of microwave power on total phenolic content and colour were determined. Black olive slices were dried at different power levels (180, 360, and 540 W) using a microwave cabin. The results showed that the drying time of the olive slices decreased considerably as the microwave power increased. The total phenolic content of the product dried at 540 W was found to be significantly lower than those dried at 180 or 360 W. For the microwave power range studied, the use of an irreversible first-order model adequately described the decrease in the total phenolic content. The effects of microwave power level on changes of the surface temperatures and weight loss of the olive slices were also determined. The temperature increase and the weight loss were the highest at 540 W during drying. Changes in the colour values (L*, a*, and b*) of the black olive slices during drying were statistically different (P<0.05) for each microwave power level and the maximum change in brightness occurred drying at 360 W. It is thought that results obtained in this study will provide valuable data for the design of microwave drying systems used for drying of olive slices in pilot or industrial scales.

Keywords

• olive, microwave, kinetic, modeling, total phenolic content, colour.

Siyah Zeytin Dilimlerinin Mikrodalga ile Kurutulması ve Toplam Fenolik Madde ve Renk Üzerine Etkileri

Abstract

Bu çalışmada, mikrodalga kullanılarak siyah zeytin dilimlerinin kuruma davranışları incelenmiş ve mikrodalga gücünün toplam fenolik madde ve renk üzerine etkileri belirlenmiştir. Siyah zeytin dilimleri üç farklı güç seviyesinde (180, 360 ve 540 W) mikrodalga kabin kullanılarak kurutulmuştur. Sonuçlar zeytin dilimlerinin kuruma süresinin mikrodalga gücü arttıkça önemli ölçüde azaldığını göstermiştir. 540 W gücünde kurutulan ürünün toplam fenolik madde içeriğinin, 180 ve 360 W güçlerinde kurutulanlarınkinden önemli ölçüde daha düşük olduğu belirlenmiştir. Çalışılan mikrodalga güç aralığı için, tersinmez birinci dereceden kinetik modelin kullanılması toplam fenolik madde içeriğindekiazalmayı başarıyla tanımlamıştır. Mikrodalga güç seviyesinin yüzey sıcaklığı ve ağırlık kaybı değişimi üzerine etkileri de incelenmiştir. 540 W gücünde kurutma sırasında sıcaklık artışı ve ağırlık kaybı en fazla olmuştur. Kurutma sırasında her mikrodalga güç seviyesi için siyah zeytin dilimlerinin renk değerlerindeki (L*, a*, b*) değişim istatistiksel olarak anlamlı bulunmuştur (P<0.05) ve en fazla parlaklık değişimi 360 W gücünde kurutmada gerçekleşmiştir. Bu çalışmada elde edilen sonuçların zeytin dilimlerinin pilot veya endüstriyel ölçekte kurutulması amacıyla kullanılacak mikrodalga kurutma sistemlerinin tasarımları için değerli veri sağlayacağı düşünülmektedir.

Keywords

• zeytin, mikrodalga, kinetik, modelleme, toplam fenolik madde, renk

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