Sains Malaysiana 42(12)(2013): 1707–1714

Rheological Properties of Different Degree of Pregelatinized Rice Flour Batter

(Sifat Reologi bagi Larutan Bater Tepung Beras Tergelatin)

M.S. ROHAYA, M.Y. MASKAT*& A.G. MA'ARUF

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

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

Diserahkan: 28 November 2012/Diterima: 15 Ogos 2013

ABSTRACT

The effect of using rice flour at different degree of gelatinization on rheological properties of a batter system was studied. Rice flour was gelatinized by heated for 20, 40, 60 and 90 min. The treated rice flour was used to prepare batters by stirring it for 2 min. The batter were subjected to determination of apparent viscosity, consistency and flow behavior index and storage modulus G’. The results showed that degree of gelatinization, DG of rice flour increased with the increased heating period up to 60 min. All rice flour batter shown shear thinning behavior since the viscosity decreased with increasing shear rate. The behavior was proven by the value of consistency coefficient, K more than 0 and flow behavior index, n less than 1. Rice flour batter heated in a longer period has higher viscosity and could be attributed by lower water content. The storage modulus, G’ of heated rice flour were lower than G’ of commercial and unheated rice flour. This result was probably because of the lower amylose and protein content in the modified starch pastes.

Keywords: Degree of gelatinization; gelatinization; rheology; rice flour

ABSTRAK

Kesan menggunakan tepung beras pada darjah pengelatinan yang berbeza terhadap sifat reologi sistem bater telah dikaji. Tepung beras digelatinkan dengan memanaskannya selama 20, 40, 60 dan 90 min. Tepung beras yang terawat ini digunakan untuk menghasilan larutan bater dengan mengacaunya selama 2 min. Larutan bater ini digunakan untuk penentuan kelikatan, indeks konsistensi, indeks kelakuan aliran dan moduli keelastikan G'. Keputusan menunjukkan darjah pengelatinan, DG bagi tepung beras adalah meningkat apabila dipanaskan sehingga 60 min. Kesemua larutan bater tepung beras menunjukkan kelakuan penipisan ricihan disebabkan oleh kelikatannya menurun dengan peningkatan kadar ricihan. Kelakuan penipisan ricihan ini dibuktikan dengan nilai indeks konsistensi, K yang lebih daripada 0 dan indeks kelakuan aliran yang kurang daripada 1. Larutan bater beras yang dipanaskan lebih lama mempunyai kelikatan yang lebih tinggi dan mungkin disebabkan oleh kandungan lembapan yang kurang. Sifat kekenyalan, G' bagi tepung beras adalah lebih rendah daripada G' bagi tepung beras komersil dan tepung beras yang tidak dipanaskan. Penemuan ini mungkin disebabkan oleh kandungan amilosa dan protein yang rendah di dalam larutan kanji terubahsuai.

Kata kunci: Darjah pengelatinan; pengelatinan; reologi; tepung beras

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*Pengarang untuk surat-menyurat; email: maskatmy@yahoo.com