Sains Malaysiana 40(4)(2011): 359–367

Effect of Super Olein and Sunflower Oil on the Rheological Properties of Chocolate Syrup

(Kesan Minyak Super Olein dan Bunga Matahari ke Atas Ciri Reologi Sirap Coklat)

Nazaruddin Ramli* & Foo Shih Ying

School of Chemical Sciences and Food Technology, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Received: 9 December 2009 / Accepted: 21 October 2010

ABSTRACT

This study was carried out to determine the effect of super olein (POo) and sunflower oil (SFO) on the rheological properties of chocolate syrup. The formulation of chocolate syrup was modified from that used in a preliminary study consisting of 49.1% water, 30% sugar, 15% cocoa powder, 5% vegetable fats (POo and SFO), 0.5% lecithin and 0.4% vanilla flavour. The rheology of chocolate syrup was measured at a shear rate of 0.01-60 s-1 using a rotational rheometer equipped with a parallel plate at 4°C and 25°C. The shear stress and shear rate data were entered into the Power Law model to determine the apparent viscosity, flow behaviour index (n) and consistency index (K) of the chocolate syrup. In this study, the apparent viscosity of the chocolate syrup was determined at a shear rate of 30 s-1. The apparent viscosity of POo chocolate syrup was the highest at 14.62 ± 1.97 Pa.s (4°C) and 3.91 ± 0.21 Pa s (25°C), followed by SFO chocolate syrup, with apparent viscosities of 5.42 ± 0.40 Pa s (4°C) and 1.203 ± 0.076 Pa s (25°C). The apparent viscosity of Hershey’s chocolate syrup was the lowest, at 2.15 ± 0.070 Pa.s (4°C) and 0.6734 ± 0.027 Pa s (25°C). All of the chocolate syrups exhibited shear-thinning behaviours with n<1 at 4°C and 25°C. The consistency index of chocolate syrup increased in the order of KHershey<KSFO<KPOo at 4°C and 25°C. For sensory evaluation, it was found that POo and SFO chocolate syrups were preferred by the panellists over Hershey’s syrup (p<0.05). There was no significant difference between the POo and SFO chocolate syrups with respect to panellists’ preferences. In conclusion, POo and SFO can be potentially utilised in the preparation of chocolate syrups.

Keywords: Chocolate syrup; rheology; sunflower oil; super olein; viscosity

ABSTRAK

Kajian ini dijalankan untuk menentukan kesan minyak super olein (POo) dan bunga matahari (SFO) ke atas ciri reologi sirap coklat. Formulasi sirap coklat adalah diubahsuai daripada kajian awal yang mengandungi 49.1% air, 30% gula, 15% serbuk koko, 5% lemak sayuran (POo dan SFO), 0.5% lesitin dan 0.4% perisa vanilla. Reologi sirap coklat diukur pada kadar ricihan 0.01-60 s-1 menggunakan reometer berputar yang dilengkapi dengan plat selari pada 4°C dan 25°C. Data tekanan ricihan dan kadar ricihan dimasukkan ke dalam model Hukum Kuasa untuk menentukan kelikatan ketara, indeks kelakuan aliran (n) dan indeks konsistensi (K) sirap coklat. Dalam kajian ini, kelikatan ketara bagi sirap coklat ditentukan pada kadar ricihan 30 s-1. Kelikatan ketara bagi sirap coklat POo adalah yang tertinggi, pada 14.62 ± 1.97 Pa s (4°C) dan 3.91 ± 0.21 Pa.s (25°C), diikuti dengan sirap coklat SFO, dengan kelikatan ketara 5.42 ± 0.40 Pa.s (4°C) dan 1.203 ± 0.076 Pa s (25°C). Kelikatan ketara bagi sirap coklat Hershey adalah yang terendah, pada 2.15 ± 0.070 Pa s (4°C) dan 0.6734 ± 0.027 Pa s (25°C). Kesemua sirap coklat mempunyai kelakuan ricihan penipisan n<1 pada 4°C dan 25°C. Indeks konsistensi bagi sirap coklat meningkat mengikut urutan KHershey<KSFO<KPOo pada 4°C dan 25°C. Bagi penilaian sensori, didapati sirap coklat POo dan SFO lebih disukai oleh ahli panel berbanding sirap Hershey (p<0.05). Tiada perbezaan ketara diantara sirap coklat POo dan SFO dengan kesukaan ahli panel. Kesimpulannya, POo dan SFO adalah berpotensi untuk digunakan di dalam penyediaan sirap coklat.

Kata kunci: Kelikatan; minyak bunga matahari; reologi; sirap coklat; super olein

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*Corresponding author; email: naza@ukm.my