International Food Research Journal 26(5): 1469-1476 (October 2019) Journal homepage: http://www.ifrj.upm.edu.my Physico-chemical and antioxidant properties of mesocarp and exocarp from Borassus flabellifer 1,2Rodiah, M. H., 1*Jamilah, B., 1Sharifah Kharidah, S. M. and 1Russly, A. R. 1Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia 2Department of Science and Biotechnology, Faculty of Engineering and Life Sciences, Universiti Selangor, Bestari Jaya Campus, Jalan Timur Tambahan, 45600 Bestari Jaya, Selangor, Malaysia Article history Abstract Received: 17 November, 2018 The physico-chemical and antioxidant activity of the mesocarp and exocarp of Borassus Received in revised form: flabellifer were determined to assess the potential of the fruit as a food ingredient. Proximate 25 June, 2019 analysis indicated that both mesocarp and exocarp had a high fibre content of 23.92% and Accepted: 31 July, 2019 28.20%, respectively, of which 62.5% and 79.4% were insoluble dietary fibre. The soluble dietary fibre was < 0.50% for both samples. Hemicellulose was the major component in the Keywords exocarp followed by cellulose and lignin. Meanwhile for the mesocarp, cellulose was the highest component followed by hemicellulose and lignin. Fructose, galactose, glucose, mannose and Composition sucrose were detected in both samples. Phenol and tannins were present in both mesocarp and Antioxidants exocarp; however, saponin was only detected in the mesocarp. Radical scavenging activity Fibre (157.05 mM TE/g) and reducing power (213.05 mM Fe2+) of the exocarp were significantly Sugar higher as compared to those of the mesocarp. © All Rights Reserved Introduction cordials, jams and potable alcohol (Rupasena et al., 1995; Ariyasena et al., 2001; Perera et al., 2015). The Borassus flabellifer Linn. of the Arecaceae family pulp is rich in pectin, sugar, carotenoids, antioxidants, is known as kelapa laut Afrika in Malaysia. The vitamin C and minerals (Ariyasena et al., 2001; palmyrah palm is widely cultivated and distributed Tikkanen, 2007). The ripe fruit pulp can be processed in tropical Asian countries such as Bangladesh, into toffee, soft beverages, sweets and delicious food Thailand, Myanmar, India, Sri Lanka and Malaysia items (Das and Das, 2003). In Malaysia, B. flabellifer (Jansz et al., 1994; Ariyasena et al., 2000; 2001). In tree is grown in several states, and the immature soft 2002, there are about 140 million palmyrah palms juicy seed nuts are very popular as a natural drink. distributed worldwide (Naguleswaran et al., 2010). However, the husks which consist of the mesocarp To date, statistical data are not available on global and exocarp (40% - 55% w/w of fruit) are discarded. production and trade; however there are 10 million This discarded portion could be a potential source for palms on 25.000 ha (two-thirds in Jaffna district) in the food ingredient. Sri Lanka, and 60 million palms (two-thirds in Tamil Negligible reports are available on the chemical Nadu) in India were reported. Central Cambodia and composition of immature mesocarp and exocarp central Myanmar accounted to 1.8 million and 2.5 of the B. flabellifer fruit. To date, limited work has million palms, respectively on 25,000 ha. While, in been reported on the endosperm, seed coat and Central and East Java and Madura (Indonesia), there pulp from the mature fruit (Rupasena et al., 1995; are 0.5 million palms on 15 000 ha. Ariyasena et al., 2001; Alamelumangai et al., 2014). The fruit, sap and young shoots are consumed in A comprehensive study on the physico-chemical many parts of these tropical countries. In Sri Lanka, the composition and antioxidant properties of the pulp is eaten fresh or used for making confectionary, mesocarp and exocarp of the young B. flabellifer is *Corresponding author. Email: [email protected]; [email protected] 1470 Rodiah, M. H., Jamilah, B., Sharifah Kharidah, S. M. and Russly, A. R./IFRJ 26(5) : 1469-1476 still scarce. Hence, in the discussion, Cocos nucifera was kept constant at 60°C to precipitate SDF. The (coconut) is used for comparison as it is the closest precipitate was filtered by the Fibertec machine and palm family to B. flabellifer. Therefore, the objectives dried in a hot air oven at 105°C for 24 h, after which of the present work were to determine the physico- samples were weighed. Both SDF and IDF residues chemical content and antioxidant activities of the were corrected for ash (by incinerating the sample mesocarp and exocarp residues in order to assess at 525°C), protein (by the Kjeldahl procedure) and their potentials as a food ingredient. a blank for the final calculation of SDF and IDF contents. The blank sample was prepared as the Materials and methods unknown sample except minus of the sample. The blank sample was also employed to evaluate any Sample contribution of the reagents to the residue. The The mesocarp and exocarp of the young fruit of analyses were made in triplicates. 3 - 4 weeks old (380 - 590 g) were collected from Cameron Highland, Pahang, Malaysia. The samples %IDF or %SDF = were carefully selected from the heap of discards, (Weight of Residue - protein - ash) - blank) x 100 freed of surface dirt and transported to the laboratory Weight of Sample in insulated boxes (4°C). (Eq. 1) Composition and physicochemical analysis %TDF = %IDF + %SDF (Eq. 2) Sample preparation The collected fresh mesocarp was separated from the exocarp, cut into smaller pieces measuring 2 × 3 Total soluble solids and pH cm, and oven-dried at 50°C for 24 h. The oven-dried The total soluble solids and pH were samples were ground in a grinder for 5 min (FZ- determined using a refractometer (Mettler Toledo, 240, Zhong Xing, Malaysia), sieved through a 0.5 Schwerzenbach, Switzerland) and a pH meter (HI mm sieve and packed in air-tight containers. Packed 221, Hanna, India), respectively. Briefly, 10 g of the samples were stored at room temperature (30°C) sample was ground with 50 mL of distilled water away from light until further analysis. and filtered through filter paper (Whatman No1, USA). The filtrate was collected and the volume was Proximate composition made up to 100 mL. The total soluble solids and pH The proximate composition (protein, lipid, measurement of triplicate samples were determined moisture and ash) of the mesocarp and exocarp and recorded. were determined in triplicate based on AOAC (2012). Carbohydrate content was determined by the Colour difference. Colour of the powdered mesocarp and exocarp were analysed using a chroma meter (00328QO, Crude, soluble and insoluble dietary fibre Konika Minolta, Japan) where L* was for lightness The crude fibre was determined based on from 0 (black) to 100 (white); a* and b* for redness AOAC (2012). An enzymatic-gravimetric procedure (+a) to greenness (−a) and yellowness (+b) to blueness (AOAC, 2012) was employed for the determination (−b), respectively (Reddy et al., 2015). Samples were of total dietary fibre (TDF), soluble dietary fibre analysed in triplicate. (SDF) and insoluble dietary fibre (IDF) contents of samples. About 1 g of sample powder was Sugar composition treated with α-amylase (EC 3.2.1.1, Sigma-Aldrich, Sugar composition of mesocarp and exocarp was Germany) before digesting the sample with protease determined according to Puwastien et al. (2011) and (EC 3.4.21.62, Sigma-Aldrich, Germany) and adopted from AOAC (1993a; 1993b). Briefly, 5 g of samples was neutralised with 3 g of CaCO before amyloglucosidase (EC 3.2.1.3, Sigma-Aldrich, 3 Germany). The enzymatic treatments were conducted 25 mL of 85% ethanol was mixed to the sample. The to remove protein and starch present in the sample. sample was then incubated at 60°C in a shaker bath Consequently, IDF was filtered using the Fibertec for 1 h, then filtered and re-extracted three times machine (E1023, USA) and the residue was rinsed using 25 mL of 85% ethanol for each extraction. with warm distilled water. Four volumes of 95% (v/v) The combined filtrate was then evaporated at 45°C ethanol were added to the filtrate and the temperature until the remaining solution was approximately 3 Rodiah, M. H., Jamilah, B., Sharifah Kharidah, S. M. and Russly, A. R./IFRJ 26(5) : 1469-1476 1471 mL. The concentrated filtrate was made up to 10 mL with 1.5 mL of 0.566 M Na2CO3 and incubated at using distilled water before being filtered with 0.45 room temperature for 90 min. The absorbance µm cellulose acetate filter prior to sample injection. of the mixture was measured at 725 nm by a The identification and quantification of sugar were spectrophotometer (Genesys 20, USA). Triplicates of performed using HPLC (Agilent 1200 Series, USA) each sample were made for each analysis. Standard with refractive index detector and the separation gallic acid ranging from 0 - 125 µg/mL was treated was performed by a Hypersil (APS2) NH2 column similarly as 200 µL of the sample above. The result (250 mm × 4.6 mm × 5 µm) of Thermo Scientific was expressed as mg of GAE/g sample. (USA). A mixture of acetonitrile:water:ethanol (82:17.5:0.5; v/v) was used as the mobile phase with Determination of tannins a flow rate of 1.5 mL/min. The column and detector Tannin content in the extract was evaluated temperature were maintained at 25 - 30°C. Standard according to Eleazu et al. (2012). Briefly, 1 mL of sugars used were glucose, fructose, mannose, sucrose sample extract was mixed with 20 mL of distilled and galactose (Sigma-Aldrich, USA). Duplicate water, 2.5 mL of Folin-Denis reagent and 10 mL of injections were carried out for each sample. Sugars 17% Na2CO3 into 50 mL volumetric flask, and mixed were quantified by the generation of a three-point thoroughly.