Malaysian Journal of Analytical Sciences Vol 22 No 4 (2018): 612 - 618

PHYSICOCHEMICAL PROPERTIES OF ENCAPSULATED PURPLE SWEET POTATO EXTRACT; EFFECT OF MALTODEXTRIN CONCENTRATION, AND MICROWAVE DRYING POWER

(Sifat Fizikokimia Ekstrak Keledek Ungu yang Dikapsul; Kesan Kepekatan Maltodekstrin, dan Kuasa Pengeringan Gelombang Mikro)

Alyani Mohd Padzil¹*, Azni A. Aziz¹,Ida Idayu Muhamad^{1, 2}

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

²IJN-UTM Cardiovascular Engineering Center Level 2, Block B, Building V01, Faculty of Biomedical Engineering

Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia.

*Corresponding author: mpr.alyani@gmail.com

Received: 16 April 2017; Accepted: 7 March 2018

Purple sweet potato (PSP) is rich with anthocyanin and has a great potential as natural food colorant. In this study, investigation on the effect of maltodextrin (MD, DE 4.0–7.0) concentration as wall material and various microwave drying powers towards physicochemical properties of microwave assisted encapsulation of purple sweet potato extract (PSPE) has been conducted. The effects of microwave power (550 W and 330W) and MD concentration (20%, 25%, and 30%) were analysed for moisture content, water activity, colour, and total monomeric anthocyanin content (TMA). Both moisture content and water activity of the encapsulated PSPE were significantly decreased (p <0.05) as the MD concentration increased at 20% and 30%. With respect of anthocyanin content, increasing of MD concentration at 20% and 30% showed a statistically significant reduction (p < 0.05). PSPA with 20% concentration gave the highest TMA at both microwave drying power of 330 W and 550 W, with 385.93±10.81 mg/L and 419.28±10.89 mg/L respectively. However, moisture content, water activity, colour, and TMA were not significantly different with the changing of microwave drying power.

Keywords: purple sweet potato, anthocyanin, microwave-assisted encapsulation, natural colorants, maltodextrin

Abstrak

Ubi keledek ungu (PSP) kaya dengan antosianin dan berpotensi untuk digunakan sebagai pewarna makanan semula jadi. Dalam kajian ini, kajian tentang kesan kepekatan maltodekstrin (MD, DE 4,0-7,0) sebagai bahan pengkapsulan dan pelbagai kuasa gelombang mikro pengeringan terhadap sifat fizikokimia ekstrak keledek ungu yang dikapsul telah dijalankan. Kesan kuasa gelombang mikro pengeringan (550 W dan 330W) dan kepekatan maltodekstrin (MD) (20%, 25%, dan 30%) dianalisis untuk kandungan kelembapan, aktiviti air, warna, dan jumlah kandungan antosianin monomerik (TMA). Nilai kandungan kelembapan dan aktiviti air daripada ektsrak keledek ungu yang dikapsulkan ketara berkurangan (p <0.05) dengan peningkatan kepekatan MD pada 20% dan 30%. Peningkatan kepekatan MD pada 20% dan 30% menunjukkan pengurangan TMA secara signifikan (p <0.05). PSPA dengan 20% kepekatan MD menunjukkan kandungan tertinggi TMA pada kedua-dua kuasa pengeringan ketuhar mikro 330 W dan 550 W, dengan masing-masing 38593 ± 10.81 mg/L dan 41928 ± 10.89 mg/L. Walau bagaimanapun, kandungan kelembapan, aktiviti air, warna, dan kandungan TMA tidak berbeza signifikan dengan perubahan kuasa pengeringan ketuhar gelombang mikro.

Kata kunci: keledek ungu, antosianin, pengkapsulan dengan bantuan gelombang mikro, pewarna semulajadi, maltodekstrin

References

1. Ahmed, M., Akter, M. S. and Eun, J. B. (2010). Impact of α-amylase and maltodextrin on physicochemical, functional and antioxidant capacity of spray-dried purple sweet potato flour. Journal of the Science of Food and Agriculture, 90(3): 494-502.

2. Aishah, B., Nursabrina, M., Noriham, A., Norizzah, A. R. and Mohamad Shahrimi, H. (2013). Anthocyanins from Hibiscus sabdariffa, Melastoma malabathricum and Ipomoea batatas and its color properties. International Food Research Journal, 20(2): 827-834.

3. Li, J., Li, X. D., Zhang, Y., Zheng, Z. D., Qu, Z. Y., Liu, M., Zhu, S. H., Liu, S., Wang, M. and Qu, L. (2013). Identification and thermal stability of purple-fleshed sweet potato anthocyanins in aqueous solutions with various pH values and fruit juices. Food Chemistry, 136(3): 1429-1434.

4. Choi, I., Lee, J. Y., Lacroix, M. and Han, J. (2017). Intelligent pH indicator film composed of agar/potato starch and anthocyanin extracts from purple sweet potato. Food Chemistry, 218 (Supplement C): 122-128.

5. Zaidel, D. N. A., Aqilah, N. and Mohd, Y. M. (2015). Efficiency and thermal stability of encapsulated anthocyanins from red dragon fruit (Hylocereus polyrhizus (Weber) Britton & Rose ) using microwave-assisted technique. Chemical Engineering Transactions, 43: 127-132.

6. Mohd Nawi, N., Muhamad, I. I. and Mohd Marsin, A. (2015). The physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea Batatas as affected by different wall materials. Food Science and Nutrition, 3(2): 91-99.

7. Haghi, A. K. and Amanifard, N. (2008). Analysis of heat and mass transfer during microwave drying of food products. Brazilian Journal of Chemical Engineering, 25: 491-501.

8. Ahmed, M., Akter, M. S., Lee, J. C. and Eun, J. B. (2010). Encapsulation by spray drying of bioactive components, physicochemical and morphological properties from purple sweet potato. LWT - Food Science and Technology, 43(9): 1307-1312.

9. Peng, Z., Li, J., Guan, Y. and Zhao, G. (2013). Effect of carriers on physicochemical properties, antioxidant activities and biological components of spray-dried purple sweet potato flours. LWT - Food Science and Technology, 51(1): 348-355.

10. Quek, S. Y., Chok, N. K. and Swedlund, P. (2007). The physicochemical properties of spray-dried watermelon powders. Chemical Engineering and Processing: Process Intensification, 46(5): 386-392.

11. Giusti, M. M. and Wrolstad, R. E. (2001). Characterization and measurement of anthocyanins by UV-visible spectroscopy. Current Protocols in Food Analytical Chemistry, John Wiley & Sons, Inc, Hoboken, USA.

12. Caliskan, G. and Dirim, S. N. (2016). The effect of different drying processes and the amounts of maltodextrin addition on the powder properties of sumac extract powders. Powder Technology, 287 (Supplement C): 308-314.