Malaysian Journal of Analytical Sciences Vol 22 No 4 (2018): 667 - 675

EFFECT OF INCORPORATING PURPLE-FLESHED SWEET POTATO IN BISCUIT ON ANTIOXIDANT CONTENT, ANTIOXIDANT CAPACITY AND COLOUR CHARACTERISTICS

(Kesan Penambahan Keledek Ungu ke dalam Biskut Terhadap Kandungan Antioksida, Kapasiti Antioksidan dan Ciri-Ciri Warna)

Azni A. Aziz^1,3, Alyani Mohd Padzil¹, Ida Idayu Muhamad^1,2*

¹Bioprocess and Polymer Engineering Department, School of Chemical and Energy Engineering, Faculty of Engineering

²Cardiac Biomaterials Cluster, IJN-UTM Cardiovascular Engineering Center, School of Biomedical Engineering

and Health Sciences, Faculty of Engineering

Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia

³Technology and Natural Resources Department, Faculty of Applied Sciences and Technology,

Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor, Malaysia

*Corresponding author: idaidayu@utm.my

Received: 16 April 2017; Accepted: 7 April 2018

Abstract

Purple flesh sweet potato (PFSP) is considered to be a nutritionally rich crop. It also contain abundant amount of anthocyanin pigment which possess disease preventive properties. This work aims to study the effect of incorporating different form of processed PFSP, namely fresh, flour, and paste in biscuit formulation. Analysis was performed on the total phenolic, total anthocyanin content, antioxidant capacity, and colour characteristics. The analyses were made on samples, before and after the incorporation of PFSP in the biscuit. PFSP flour was prepared by directly using hot air-drying at 65 ºC for 18 hours while PFSP paste was steamed for 30 minutes at 100 ºC. The PFSP fresh contained total anthocyanin content at 21.40 mg CyE/100 g fw, and the content increased when processed into the form of flour and paste approximately at 38.90 mg CyE/100 g fw and 52.48 mg CyE/100 g fw, respectively. All forms of processed PFSP enhanced the purple colour when incorporated into the biscuit formulation. The experimental results showed that biscuit added with PFSP lost 15–36% of antioxidant capacity. Based on these findings, all forms of PFSP can be a natural colourant, a potential functional food ingredient, and can become a superior source for the production of foods with health benefits.

Keywords: purple-fleshed sweet potato, biscuit, phenolic, anthocyanin, antioxidant capacity, colour

Abstrak

Keledek ungu (PFSP) dianggap sebagai tanaman kaya khasiat. Ia juga mengandungi sejumlah besar pigmen antosianin yang mempunyai sifat pencegah penyakit. Kajian ini bertujuan untuk mengkaji kesan penambahan PFSP yang diproses dalam beberapa bentuk berbeza iaitu mentah, tepung, dan pes ke dalam formulasi biskut. Analisis dilakukan terhadap jumlah fenolik, jumlah kandungan antosianin, kapasiti antioksidan, dan ciri-ciri warna. Analisis kajian dijalankan terhadap sampel, sebelum dan selepas PFSP dimasukkan ke dalam biskut. Tepung PFSP disediakan dengan menggunakan pengeringan udara panas pada suhu 65 ºC selama 18 jam manakala pes PFSP dikukus selama 30 minit pada suhu 100 ºC. PFSP mentah mengandungi jumlah kandungan antosianin sebanyak 21.40 mg CyE/100 g fw, dan kandungannya meningkat apabila diproses ke dalam bentuk tepung dan pes iaitu masing-masing sebanyak 38.90 mg CyE/100g fw dan 52.48 mg CyE/100g fw. Kesemua bentuk PFSP yang diproses meningkatkan warna ungu apabila dimasukkan ke dalam formulasi biskut. Keputusan eksperimen menunjukkan biskut yang ditambah PFSP hilang kapasiti antioksidan sebanyak 15–36%. Berdasarkan dapatan ini, semua bentuk PFSP dapat menjadi pewarna semula jadi, berpotensi sebagai bahan makanan berfungsi, dan boleh menjadi sumber penting untuk pengeluaran makanan dengan manfaat kesihatan.

Kata kunci: keledek ungu, biskut, fenolik, antosianin, kapasiti antioksidan, warna

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