Sains Malaysiana 39(5)(2010): 785-790

Melting Behaviour of Binary Mixtures of Palm Mid Fraction and Rice Bran Oil

(Kelakuan Peleburan Adunan Binari Fraksi Pertengahan  Sawit dan Minyak Dedak Padi)

Saadah Mastura Saidin & Nazaruddin Ramli*

Food Science Program, School of Chemical Science and Food Technology

Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 Bangi, Selangor D.E., Malaysia

Diserahkan: 14 April 2009 / Diterima: 12 Februari 2010

ABSTRACT

The melting and crystallization profile of cocoa butter substitute (CBS) formulation consisting of oil blends between palm mid fraction (PMF) and rice bran oil (RBO) were measured through solid fat content using pulsed Nuclear Magnetic Resonance (pNMR) Bruker Minispe. The isothermal melting and crystallization behaviour were determined via Differential Scanning Calorimeter (DSC). The formulations were developed through binary mixture of palm mid fraction and rice bran oil with different ratios created using Mixture Design, Design Expert version 6.0. Selected formulations had been studied for compositional modification through immobilized lipase catalyzed by interesterification using Novozyme® 435. Three selected parameters such as temperature (40-60 ^oC), catalyst concentration (2-10%) and time (4-48 h) at 200 rpm orbital shaking with 14 formulations acquired by applying D-Optimal experimental design had been applied. The results showed that blends of 75% palm mid fraction with 25% rice bran oil and its 14 enzymatic interesterification (EIE) yields have the potential to perform the desired behaviour as the crystals are completely melt at 32.48 - 38.28 ^oC. However, the yields of formulation with EIE condition of 60 ^oC, 10% lipase and 48 h incubation time (labeled N) formed stable β crystals during tempering as it had melting peak at 34.19 ^oC which was closer to melting point of cocoa butter required in tempering to form V crystals (~34 ^oC), that assured best chocolate appearance and texture.

Keywords: Melting and crystallization profile; palm mid fraction; rice bran oil; solid fat content; pulsed nuclear magnetic resonance

ABSTRAK

Profil peleburan dan penghabluran bagi formulasi gantian lemak koko yang terdiri daripada fraksi pertengahan sawit dan minyak dedak padi ditentukan menggunakan Resonans Nuklear Magnet Denyut (pNMR) dan Kalorimeter Pengimbasan Pembezaan (DSC). Gantian lemak koko dibangunkan melalui adunan binari lemak fraksi pertengahan sawit (PMF) dan minyak dedak padi (RBO). Adunan binari ini disediakan berdasarkan peratusan tertentu yang diterbitkan melalui aplikasi Mixture Design, Design Expert version 6.0. Adunan ini dipilih untuk pengubahsuaian sifat fizikokimia secara interesterifikasi berenzim (EIE) menggunakan enzim lipase iaitu Novozyme® 435 dengan parameter yang dikaji iaitu suhu (40-60 ^oC), peratus enzim (2-10%), dan masa (4-48 jam). Hasil analisis menunjukkan bahawa adunan lemak 75% fraksi pertengahan sawit dan 25% minyak dedak padi sebelum dan selepas EIE mempunyai potensi untuk dibangunkan sebagai gantian lemak koko kerana melebur sepenuhnya pada julat 32.48 hingga 38.28 ^oC. Walau bagaimanapun, adunan lemak hasil EIE menggunakan parameter 60 ^oC, 10% lipase dan 48 jam tempoh tindak balas (adunan N) boleh membentuk hablur β paling stabil semasa proses penyepuhan dan kerana mempunyai puncak suhu penghabluran pada 34.19 ^oC, iaitu suhu yang paling hampir bagi lemak koko untuk membentuk hablur bentuk V (~34 ^oC), yang memberikan tekstur dan rupa coklat yang terbaik.

Kata kunci: Fraksi pertengahan sawit; kandungan lemak pepejal; minyak dedak padi; profil peleburan dan penghabluran

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*Pengarang untuk surat-menyurat; email: naza@ukm.my