PDF《Sains Malaysiana 41(1)(2012): 41–4》

Sains Malaysiana 41(1)(2012): 41C45 Extraction and Characterization of Pectin from Dragon Fruit (Hylocereus polyrhizus) using Various Extraction Conditions (Pengekstrakan dan Pencirian Pektin daripada Buah Naga (Hylocereus polyrhizus) Menggunakan Pelbagai Keadaan Pengekstrakan) NORAZELINA SAH MOHD.

ISMAIL, NAZARUDDIN RAMLI*, NORZIAH MOHD. HANI &

ZAINUDIN MEON ABSTRACT The extraction of pectin from dragon fruit (Hylocereus polyrhizus) peels under three different extraction conditions was identified as an alternative source of commercial pectin. In this work, dried alcohol-insoluble residues (AIR) of dragon fruit peels were treated separately with 0.25% ammonium oxalate/oxalic acid at a pH of 4.6 at 85o C;

0.03 M HCl at a pH of 1.5 at 85o C;

and de-ionized water at 75o C. The pectin obtained from these methods was compared in terms of yield, physicochemical properties and chemical structure. Fourier Transform Infrared Spectroscopy (FTIR) was used in the identification of dragon fruit pectins. The results showed that the pectin yield (14.96-20.14% based on dry weight), moisture content (11.13-11.33%), ash content (6.88-11.55%), equivalent weight (475.64-713.99), methoxyl content (2.98-4.34%), anhydrouronic acid (45.25-52.45%) and the degree of esterification (31.05-46.96%) varied significantly (p <

0.05) with the various extraction conditions used. Pectin extracted with ammonium oxalate gave the highest yield of pectin, with high purity and low ash content. Based on the value of methoxyl content and the degree of esterification, dragon fruit pectin can be categorized as low-methoxyl pectin. Keywords: Alcohol insoluble residue;

dragon fruit;

extraction conditions;

pectin ABSTRAK Pengekstrakan pektin daripada kulit buah naga (Hylocereus polyrhizus) dengan menggunakan tiga keadaan pengekstrakan yang berbeza telah dikenalpasti sebagai sumber alternatif kepada pektin komersial. Dalam kajian ini, pepejal tak larut alkohol (AIR) kulit buah naga telah diperlakukan secara berasingan dengan 0.25% ammonium oksalat/ asid oksalik pada pH 4.6 pada suhu 85o C;

0.03 M HCl pada pH1.5 pada suhu 85o C;

dan air ternyahion pada suhu 75o C. Pektin yang diperolehi daripada kaedah ini dibandingkan dari segi hasil, ciri fiziko-kimia dan struktur kimia. . Spektroskopi infra- merah (FTIR) digunakan dalam penentuan pektin buah naga. Keputusan menunjukkan hasil pektin (14.96- 20.14% berdasarkan berat kering), kandungan air (11.13- 11.33%), kandungan abu (6.88- 11.55%), beratara (475.64- 713.99), kandungan metoksil (2.98- 4.34%), asid anhidro uronik (42.25- 52.45%) dan darjah pengesteran (31.05- 46.96%) berbeza secara signifikan (p<

0.05) dengan pelbagai keadaan pengekstrakan yang digunakan. Pektin yang diekstrak dengan ammonium oksalat memberikan hasil pektin tertinggi, dengan ketulenan tinggi dan rendah kandungan abu. Berdasarkan kandungan metoksil dan darjah pengesteran, pektin buah naga boleh dikategorikan sebagai pektin metoksil rendah Kata kunci: Buah naga;

keadaan pengekstrakan;

pepejal tak larut alkohol;

pektin mostly waste materials resulting from the dragon fruit juice processing industry and are normally discarded. These discarded peels may cause an environmental problem, particularly water pollution. Thus, in addition to being fed to animals, the peels can be used in the production of pectin, which would then increase the potential return for the dragon fruit juice processing industry. Pectin is the methylated ester of polygalacturonic acid that contains 1,4-linked α-D-galacturonic acid residues (Levigne et al. 2002). It is commonly found in the cell walls and middle lamellae of higher plants. These polysaccharides consist of 300-1,000 chains of galacturonic acid units (Yeoh et al. 2008). Pectin is widely used in the food industry as a thickener, emulsifier, INTRODUCTION Dragon fruit (Hylocereus polyrhizus) or red pitaya is one of the tropical fruits that belongs to the cactus family, Cactaceae. The fruits contain high amounts of vitamin C and water-soluble fiber (Ruzainah et al. 2009). In Malaysia, dragon fruits are known as buah naga or buah mata naga , which were first introduced in