Food Chemistry 128 (2011) 748–753

Contents lists available at ScienceDirect

Food Chemistry

journal homepage: www.elsevier .com/locate / foodchem

Chemical and functional properties of the native banana (Musa acuminata �balbisiana Colla cv. Awak) pseudo-stem and pseudo-stem tender core flours

Noor Aziah Abdul Aziz a,⇑, Lee-Hoon Ho a, Baharin Azahari b, Rajeev Bhat a, Lai-Hoong Cheng a,Mohamad Nasir Mohamad Ibrahim c

a Food Technology Division, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysiab Bioresource Paper & Coating Technology Division, School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysiac Industrial Chemistry Division, School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia

a r t i c l e i n f o

Article history:Received 12 November 2010Received in revised form 24 January 2011Accepted 23 March 2011Available online 29 March 2011

Keywords:Banana pseudo-stemTender core banana pseudo-stemMusa acuminata � balbisiana Colla cv. AwakChemical compositionFunctional properties

0308-8146/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.foodchem.2011.03.100

⇑ Corresponding author. Tel.: +60 194 705 254; faxE-mail address: naziah@usm.my (N.A.A. Aziz).

a b s t r a c t

This research was conducted to evaluate the differences in chemical composition and functional profilesof native banana pseudo-stem flour (NBPF) and boiled tender core of the banana pseudo-stem flour(TCBPF). Chemical analyses indicated that the proximate contents (moisture, fat, protein and ash), weresignificantly higher in TCBPF than in NBPF. The levels of total dietary fibre, insoluble dietary fibre, lignin,hemicellulose and cellulose were all higher in NBPF than TCBPF, while there was no significant differencein soluble dietary fibre. NBPF also had higher contents of polyphenols and flavonoids than TCBPF. Boththe antioxidant capacity and the free radical-scavenging capacity were higher in NBPF than in TCBPF.On the other hand, the TCBPF showed significantly higher swelling power, water holding capacity andsolubility, although its oil holding capacity was lower than NBPF. We conclude that banana pseudo-stemflour is a potential functional food ingredient for products containing high dietary fibre.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Banana, which belongs to the Musaceae family, is native to theIndonesian–Malaysian region of Asia. Bananas are produced inlarge quantities in the tropical and sub-tropical regions of theworld. The crop is of major importance to the people living inthe areas in which it grows because it provides a major portionof their annual income and is a primary source of food. Today, ba-nanas are the fourth most widespread fruit crop in the world.Annually, about 72.5 million tons of bananas are produced world-wide (FAO, 2006).

The production of bananas has considerable economic impor-tance. After harvesting, however, a large amount of pseudo-stemresidue is left behind in plantation soil to be used as organic mate-rial. It has been estimated that a few tons per hectare of bananapseudo-stem are produced annually (Cordeiro, Belgacem, Torres,& Moura, 2004). These crops have been utilised as a source of fibrein the pulping industry, and their decomposition generates energy(Cordeiro et al., 2004; Oliveira, Evtuguin, Cordeiro, & Silvestre,2009). Furthermore, according to Cordeiro et al. (2004) and Oli-veira, Cordeiro, Evtuguin, Torres, and Silvestre (2007), bananawaste materials are rich in minerals and nutrients. Recently, somestudies on the banana pseudo-stem (Musa acuminata Colla and

ll rights reserved.

: +60 4657 3678.

Musa sapientum species) have been reported, focusing on thechemical contents, such as monosaccharides, fibre compositionand mineral contents (Cordeiro et al., 2004; Mukhopadhyay, Fan-gueiro, Arpac, & Senturk, 2008; Oliveira et al., 2007). However, toour knowledge, there still is a lack of knowledge regarding theproximate composition, dietary fibre contents and antioxidantproperties of the banana pseudo-stem. The tender core of the bana-na pseudo-stem is located in the centre (core) of the banana stemand is tube-like, with a diameter of approximately 5–6 cm. Thetender core is edible and is consumed in many parts of India andMalaysia (Mohapatra, Mishra, & Sutar, 2010); in Malaysia, it iscommonly boiled before cooking so as to soften the texture ofthe stem.

Functional ingredients have been widely developed and appliedin the food industry. Oat bran, rice husks and barley bran havecommercial significance because of their use as fibre sources inbakery products. Dietary fibre is composed of edible parts of plantsor analogous carbohydrates that are resistant to digestion andabsorption in the human small intestine with complete or partialfermentation in the large intestine. Dietary fibre includes polysac-charides, oligosaccharides, lignin, and associated plant substances.It promotes beneficial physiological processes, including laxation,blood cholesterol and blood glucose attenuation (AACCI, 2001).Several studies have been carried out to determine the chemicaland functional properties of banana flour, banana starches andfibre-rich powder from unripe banana flour (Bello-Perez,

N.A.A. Aziz et al. / Food Chemistry 128 (2011) 748–753 749

Agama-Acevedo, Sanchez-Hernandez, & Paredes-Lopez, 1999;Mukhopadhyay et al., 2008; Rodriguez-Ambriz, Islas-Hernandez,Agama-Acevedo, Tovar, & Bello-Perez, 2008).

Crude extracts of plant materials rich in phenolic compoundsare of increasing interest in the food industry because they retardoxidative degradation of lipids and thereby improve the qualityand nutritional value of food. The importance of the antioxidantconstituents of plant materials in the maintenance of health, andin protection from coronary heart disease and cancer, have re-sulted in an increased interest among scientists, food manufactur-ers, and consumers. The trend of the future is moving towardsfunctional foods with specific health effects (Kallay & Kerenyi,1999).

The objective of this paper is to study the chemical compositionand functional properties of processed native banana pseudo-stemand the tender core of banana pseudo-stem.

2. Materials and methods

2.1. Materials

The banana (M. acuminata � balbisiana Colla cv. Awak) pseudo-stem was collected from a local banana farm in Balik Pulau andin Gelugor, Penang. The banana pseudo-stem and the tender coreof the pseudo-stem flour were then processed as described below.

2.2. Flour processing

NBPF was processed by peeling off the epidermis (skin) of thestem manually with a sterile knife. Furthermore, to process theTCBPF, several layers of stem cells were peeled off to reach the cen-tral 4–5 cm core of the pith. The peeled pseudo-stem and the ten-der core were rinsed with running tap water and cut into smallpieces. The tender core was then boiled for 15 min. to removethe mucus content of the inner stem. Both samples were thensliced using a mechanical slicer (Robot Coupe, France) before beingdried in a ventilated dryer (Afos, Model Mini, No. CK 80520, Eng-land) at 60 �C for 24 h. The dried slices of both the pseudo-stemand tender core were then ground in a blender (Panasonic Model:PB-325, Malaysia) and further sieved through a 355-lm meshsieve. NBPF and TCBPF were then kept in airtight plastic containersand stored in a refrigerator at 4 �C prior to use.

2.3. Proximate analysis

Moisture, ash, crude fat, crude fibre, crude protein and carbohy-drate contents of NBPF and TCBPF were determined according tothe AACC method (2000). The moisture content of the sampleswas determined by oven-drying (method 44-15A), while ash wasquantified by dry ashing (method 08-01). Crude fat was deter-mined with the Soxhlet method using petroleum ether extraction,followed by evaporation to constant weight (method 30-25). Crudefibre was determined according to the gravimetric method (meth-od 32-10). Crude protein was analysed by the Kjeldahl method(method 46-13). Carbohydrate was determined as the remainingpercent weight according to the formula: [100 – (mois-ture + ash + crude fat + crude fibre + crude protein)].

2.4. Total dietary fibre determination

An enzymatic–gravimetric method was used to determine thetotal dietary fibre content (Method 985.29, AOAC (1997)). Thismethod involved gelatinisation of the defatted samples witha-amylase and a stable heat source at 95 �C for 15 min. The sam-ples were enzymatically digested with protease for 30 min at

60 �C, followed by amyloglucosidase for 30 min at 60 �C to removethe protein and starch content in the sample. Four volumes of 95%ethyl ethanol (pre-heated to 60 �C) were then added to precipitatesoluble dietary fibre overnight at room temperature. Precipitateswere filtered and washed successively with 78% ethyl ethanol,95% ethyl ethanol and acetone. The residue was then oven-dried(105 �C) overnight.

Values obtained by the enzymatic method were then correctedby determining nitrogen content with the Kjeldahl method andashing at 525 �C.

2.5. Lignin, cellulose and hemicellulose content determination

Acid detergent fibre (ADF) and lignin, as well as neutral deter-gent fibre (NDF), were measured according to method 973.18and method 2002.04, respectively (AOAC, 2005).

Reflux extraction was conducted on the samples in separatesolutions, a neutral detergent solution and acid detergent solution,for 65 min each. Neutral detergent solution consisted of sodiumhydroxide, EDTA, disodium hydrogen phosphate, sodium boratedecahydrate and sodium lauryl sulfate, all of which were dissolvedin distilled water. Triethylene glycol was then added into the solu-tion to suppress the formation of foam, and the pH (6.95–7.05) ofthe solution was determined (pH meter Model: ORION 410A,UK). The acid detergent solution was prepared by dissolving 20 gcetyl trimethylammonium bromide (technical grade) in l l 0.5 MH2SO4 (previously standardised).

The filtration residue was washed with hot distilled water andethanol (3 times or until no change in colour was observed) andthen oven-dried to constant weight. The difference in weight be-tween the starting material and the oven-dried sample was usedto calculate NDF and ADF content. The samples were then stirredat 20 �C for 3 h after sulphuric acid (72%) was added to the sam-ples. After washing with hot distilled water and filtering, the resi-dues were oven-dried to determine the amount of lignin. Finally,the content of cellulose and hemicellulose was calculated fromthe contents of NDF, ADF and lignin, as follows:

Hemicellulose ¼ NDF� ADF

Cellulose ¼ ADF� lignin:

2.6. Antioxidant properties

2.6.1. Preparation of flour extractNBPF and TCBPF samples were extracted using methanol, [1:10

(w/v)] at room temperature for 24 h in an orbital shaker at170 rpm. Supernatants were filtered through Whatman No. 1 filterpaper, and the filtrate was then collected. The extracts were con-centrated using a rotary evaporator under reduced pressure at40 �C for 5 h. The concentrated solutions were freeze–dried andstored at �20 �C for further use.

2.6.2. Determination of total phenolic compoundsTotal phenolic content of the NBPF and TCBPC were determined

using a Folin–Ciocalteu (FC) assay based on the method describedby Alothman, Bhat, and Karim (2009), with some modifications. Inbrief, freeze–dried extracts (1 mg) of NBPF and TCBPF were dis-solved in 4 ml of methanol. Furthermore, 400 ll of the resultingsolution were mixed with 2 ml of FC phenol reagent. The reagentwas pre-diluted, 10 times, with distilled water. After standing for5 min at room temperature, 1.6 ml of (7.5% w/v) sodium carbonatesolution was added. The solutions were mixed and allowed tostand for 1 h at room temperature. The absorbance was measuredat 765 nm, using a UV–visible spectrophotometer (Shimadzu UV-1601PC, Japan). A calibration curve was prepared, using a standard

Table 1Proximate composition of NBPF and TCBPF (n = 3 ± SD).

Composition (%) NBPF TCBPF

Moisture 8.34a ± 0.02 8.82b ± 0.21Fat 0.24a ± 0.08 1.18b ± 0.50Protein 0.89a ± 0.17 3.52b ± 0.37Ash 3.03a ± 0.04 10.08b ± 0.04Crude fibre 29.92b ± 0.63 19.51a±0.79Total carbohydrate 57.58a 56.89a

Values in the same row with the same superscript letter are not statistically sig-nificant from each other (p > 0.05). All the result reported on the dry weight basis.NBPF, native banana pseudo-stem; TCBPF, tender core of banana pseudo-stem flour.

750 N.A.A. Aziz et al. / Food Chemistry 128 (2011) 748–753

solution of gallic acid. Results were expressed as milligrams of gal-lic acid equivalents per hundred grams of freeze–dried extract (mgGAE/100 g of dry weight).

2.6.3. Total flavonoid assayTotal flavonoid content was measured by the aluminium chlo-

ride colorimetric assay (Alothman et al., 2009). One ml of properlydiluted freeze dried extract of NBPF and TCBPF was mixed with4 ml of distilled water. Initially 0.3 ml of (5% w/v) NaNO2 wasadded. After 5 min, 0.3 ml of (10% w/v) AlCl3 was added. At6 min, 2 ml of 1 M solution of NaOH were added. After that, thevolume was made up to 10 ml, immediately, by the addition of2.4 ml of distilled water. The mixture was shaken vigorously andthe absorbance of the mixture was read at 510 nm. A suitable cal-ibration curve was prepared using a standard solution of catechinand the results were also expressed on a dry weight basis as mgcatechin equivalents (CEQ)/100 g of sample.

2.6.4. Ferric reducing/antioxidant power assay (FRAP assay)The ability of NBPF and TCBPF to reduce ferric ions was mea-

sured according to the method described by Benzie and Strain(1996). The FRAP reagent was prepared using 300 mM sodium ace-tate buffer at pH 3.6, 20 mM iron chloride and 10 mM 2,4,6-tripyr-idyl-s-triazine dissolved in 40 mM hydrochloric acid at a ratio of10:1:1 (v/v). The reagent was incubated in a water bath at 37 �Cfor 5 min prior to use. Freeze–dried extracts (1 mg) of NBPF andTCBPF were dissolved in 4 ml of methanol. Following this, 0.1 mlof the resulting solution was then added to 2.9 ml of FRAP reagent.The solution was mixed well and kept in the dark for 30 min. Theabsorbance was measured against the FRAP reagent at 593 nm. Re-sults were expressed as micromoles of trolox equivalents per hun-dred grams of freeze–dried extract (lmole TEACFRAP/100 g; dryweight).

2.6.5. DPPH free radical-scavenging assayThe determination of DPPH free radical-scavenging by NBPF and

TCBPF were based on the method proposed by Mosquera, Correa,Buitrago, and Nino (2007), with sight modifications. Freeze–driedextracts (1 mg) of NBPF and TCBPF were dissolved in 4 ml of meth-anol. Afterwards, 0.1 ml of the resulting solution was mixed with3.9 ml of DPPH solution (0.025 g/l methanol). The mixture wasincubated at room temperature for 30 min. The DPPH solutionwithout extracts was prepared as a control. The absorbance wasmeasured at 517 nm using a spectrophotometer and against ablank of methanol without DPPH. Results were expressed as milli-grams of trolox equivalents per hundred grams of freeze–dried ex-tract (mg TEAC/100 g dry weight).

2.7. Swelling power, solubility profiles, and water and oil holdingcapacities

Swelling power and solubility were measured using the methodof Adebowale, Adeniyi Afolabi, and Lawal (2002), with slight mod-ifications. NBPF and TCBPF (0.5 g) were accurately weighed intopreviously tared 50 ml dry centrifuge tubes. Next, 20 ml of distilledwater was pipetted into the centrifuge tubes containing the sam-ples. The suspensions were then stirred with a magnetic stir barfor 30 min at room temperature and centrifuged (3500 rpm,30 min). The residues obtained after centrifugation were weighedas swollen granules (g of swollen granules per g of dry sample).Meanwhile, aliquots of the supernatants were dried to a constantweight at 110 �C. The residue obtained represented the amountof flour granules solubilised in water (g of dry weight at 110 �Cper g of dry sample).

The water holding and oil holding capacities were determinedbased on the standard methods (Heywood, Myers, Bailey, & John-

son, 2002; Traynham, Myers, Carriquiry, & Johnson, 2007). First,25 ml of distilled water (for water holding capacity, WHC) or com-mercial olive oil (for oil holding capacity, OHC) was added to250 mg of dry flour samples, stirred with a magnetic stir bar for30 min and left at room temperature for 30 min. After centrifuga-tion at 3500 rpm for 30 min, the supernatants were decanted, eachcentrifuge tube was weighed then the WHC and OHC was calcu-lated as g water or oil per g of dry sample, respectively.

2.8. Statistical analysis

Statistical analyses were conducted by using SPSS 14.0 software(SPSS Inc., Chicago, IL, USA). The results obtained in the presentstudy are represented as the mean values of three individualreplicates ± standard deviation (SD). The significant differences be-tween mean values were determined by the t-test at a significancelevel of p < 0.05.

3. Results and discussion

3.1. Proximate analysis

Results from Table 1 indicated that the proximate compositionsof the two samples were significantly (p < 0.05) different, with theexception of carbohydrate content. TCBPF had a significantly high-er (p < 0.05) content of moisture, fat, protein, and ash (8.82%, 1.18%,3.52% and 10.08%, respectively), than NBPF, but a lower level ofcrude fibre (19.51%). However, by comparison, the moisture con-tent of both NBPF and TCBPF were lower than commercial wheatflour, which had a value of 12.36% (Traynham et al., 2007). Themoisture of the dried product has a critical influence on storagestability. In addition, textural quality, chemical and biochemicalreactions, as well as microbial growth rates are greatly affectedby the moisture content of food products (Ovando-Martinez, Say-ago-Ayerdi, Agama-Acevedo, Goni, & Bello-Perez, 2009).

The fat contents of NBPF and TCBPF were found to be 0.24% and1.18%, respectively. These values were lower than those reportedby others for banana flour prepared from the whole fruit (pulpand peel) of unripe banana, which had a fat content of 2.7% (Juar-ez-Garcia, Agama-Acevedo, Sayago-Ayerdi, Rodriguez-Ambriz, &Bello-Perez, 2006). Others report fat content varying from 2.2% to10.9% at different stages of ripeness in banana and plantain peels(Happi Emaga, Herinavalona Andrianaivo, Wathelet, Tchango-Tch-ango, & Paquot, 2007). Based on the results, it was evident that thefat composition of NBPF and TCBPF is lower than the pulp and peelof the banana.

Protein content of NBPF and TCBPF was also lower (0.89% and3.52%, respectively), compared to wheat flour (13.31%) as reportedby Traynham et al. (2007). The higher protein content in TCBPFcompared with NBPF may be attributed to the boiling step appliedduring the processing of TCBPF, which dissolves certain water-sol-uble proteins (Rodriguez-Ambriz et al., 2008).

Table 3Hemicellulose, cellulose and lignin content in NBPF and TCBPF (n = 3 ± SD).

Composition (%) NBPF TCBPF

Acid detergent fibre 47.22b ± 0.91 32.02a ± 1.21Neutral detergent fibre 5.78b ± 1.17 43.89a ± 0.68Lignin 5.13b ± 0.08 4.60a ± 0.06Hemicellulose 18.56b ± 0.80 11.87a ± 0.55Cellulose 42.09b ± 0.85 27.42a ± 0.37

Values in the same row with the same superscript letter are not statistically sig-nificant from each other (p > 0.05). All the result reported on the dry weight basis.NBPF, native banana pseudo-stem flour and TCBPF, tender core of banana pseudo-stem flour.

N.A.A. Aziz et al. / Food Chemistry 128 (2011) 748–753 751

Ash content determination indicated that TCBPF (10.08%) con-tained significantly higher mineral levels than NBPF (3.03%). Theash content in banana and plantain peels (6.4–12.8% dry matter)was composed of high levels of potassium, magnesium and cal-cium (Happi Emaga et al., 2007).

NBPF and TCBPF were composed of 29.92% and 19.51% crude fi-bre, respectively. The lower content of crude fibre in TCBPF com-pared with NBPF might be attributed to the solubilisation ofpolysaccharides during the thermal treatment on processingTCBPF, which results in a decrease of the content of total fibre(Tatjana, Terezija, Milica, & Plestenjak, 2002).

3.2. Dietary fibre contents

The results of dietary fibre content are shown in Table 2. Dietaryfibre is composed of total dietary fibre (TDF), which includes bothsoluble (SDF) and insoluble dietary fibre (IDF).

The TDF content of NBPF and TCBPF (67.07% and 47.98%, respec-tively), indicated that NBPF contained higher levels of fibre thanTCBPF. Both pseudo-stem samples contained much higher levelsof fibre than rice bran and oat bran (27.04% and 26.40%, respec-tively), (Abdul-Hamid & Luan, 2000; Chen, Rubenthaler, Leung, &Baranowski, 1988, respectively). This result is important, especiallywhen considering the application of the banana pseudo-stem flouras a high-fibre substitute in food products. The dominant portion offibre was insoluble in both NBPF (64.49% and 67.07%, for IDF andTDF, respectively), and TCBPF (46.09% and 47.98%, for IDF andTDF, respectively). Hence, these banana pseudo-stem fibres maypromote intestinal regulation by providing bulk, a healthful conse-quence of consuming insoluble fibres. Similarly, IDF was found tobe the major fibre fraction in the dietary fibre composition of bana-na and plantain peels (Happi Emaga et al., 2007). The dietary fibreanalysis in this study indicates that banana pseudo-stem flourshows promise as a food fibre replacement for oats and sorghumin the development of new food products.

3.3. Hemicellulose, cellulose and lignin contents

The chemical composition of the banana pseudo-stem and itstender core are shown in Table 3. Cellulose, hemicellulose and lig-nin are components of plant fibres that are classified as insoluble.Among these, lignin is resistant to digestion.

Within the dietary fibre fraction, cellulose was the most abun-dant component, followed by hemicellulose and then lignin in bothNBPF and TCBPF (42.09%, 18.56%, 5.13% and 27.42%, 11.87%, 4.60%,respectively). Thus, banana pseudo-stem has higher amounts ofcellulose than both banana (7.5–9.6%) and plantain (6.4–7.8%) atvarious stages of maturation (Happi Emaga, Robert, Ronkart, Wath-elet, & Paquot, 2008). The high content of cellulose in banana pseu-do-stem can be explained by the fact that cellulose is the mainsubstance that forms the primary and secondary walls of plantcells. The cellulose content of NBPF reported in this study is similarto the cellulose content in the outer bark material of pseudo-stemsof M. acuminata Colla (40.2%), as reported by Cordeiro et al. (2004).The high content of cellulose in NBPF may also correspond to the

Table 2Total dietary fibre content in NBPF and TCBPF (n = 3 ± SD).

Composition (%) NBPF TCBPF

Insoluble dietary fibre 64.49b ± 0.22 46.09a ± 0.16Soluble dietary fibre 2.58a ± 0.35 1.89a ± 0.19Total dietary fibre 67.07b ± 0.13 47.98a ± 0.03

Values in the same row with the same superscript letter are not statistically sig-nificant from each other (p > 0.05). All the result reported on the dry weight basis.NBPF, native banana pseudo-stem; TCBPF, tender core of banana pseudo-stem flour.

high acid detergent fibre content (47.22%). Interestingly, Rose, Ing-lett, and Liu (2010) reported that the major constituent of cornbran fibre was hemicellulose (70%), followed by cellulose (28%),whereas the results from our present study showed the reverse.

Both NBPF and TCBPF have higher lignin content than wheatand soy meal, which contain only 0.88% and 0.58% lignin, respec-tively, as reported by Moller (2009). On the other hand, lignin lev-els are considerably lower in NBPF and TCBPF as compared withother wood-based materials such as sawdust (20.33%) (Moller,2009). In addition, both NBPF and TCBPF contained less lignin thanbanana (pulp) (6.0–12.1%) and plantain (green banana) (14.3–16.8%) (Happi Emaga et al., 2008). Moreover, Mukhopadhyayet al. (2008) have reported the lignin content in banana pseudo-stem fibres of Musa sapientum species (15.07%) to be much higherthan the results obtained in our present study.

Unlike lignin, the higher hemicellulose content in NBPF corre-sponded with the higher content of neutral detergent fibre(65.78%). The relative amounts of hemicellulose and cellulose inour study are in accordance with those published by Mukhopadhy-ay et al. (2008), who also reported lower hemicellulose content ascompared to cellulose in banana pseudo-stem. However, the fibredata obtained in the present study are different from those re-ported by Mukhopadhyay et al. (2008) (14.98% hemicellulose and31.27% cellulose). This discrepancy may be due to the differencesin the banana species used in these two studies.

3.4. Antioxidant properties

The total phenolic content in the methanolic extracts of NBPFand TCBPF, is shown in Table 4. The phenolic content of NBPF(6532 mg GAE/100 g of dry weight) was significantly higher thanthe phenolic content of TCBPF (1245 mg GAE/100 g of dry weight).This difference might be attributed to the fact that different plantscontain different phenolic compounds and hence show variation intheir total phenolic content (Zhang & Wang, 2001). In addition, thisobservation may also indicate that the outer layers of the bananapseudo-stem have greater concentrations of phenolic compoundsthan the pith. We conclude that phenolic compounds are moreabundant in banana pseudo-stem than in the pulp and peel(232 mg/100 g weight and 907 mg/100 g dry weight, respectively)(Someya, Yoshiki, & Okubo, 2002). However, further studies arewarranted to identify individual phenolic compounds present inNBPF and TCBPF, which might provide more details.

With regard to the total flavonoid content, NBPF had a highertotal flavonoids (4500 mg CEQ/100 g of dry weight) than the TCBPF(1042 mg CEQ/100 g of dry weight) (Table 4). The correlations per-formed between total phenolics and total flavonoid assays showedit to be 0.901 and 0.929 for NBPF and TCBPF, respectively.

In general, phenolic compounds are widely distributed in theplant kingdom and they have been reported to possess strong anti-oxidant properties (Mosquera et al., 2007). The antioxidant activityof banana pseudo-stem flours is expressed as mg TEAC/100 g, andinhibition of DPPH radicals corresponds to the antioxidant activity.

Table 4Total phenolic content and antioxidant activity in NBPF and TCBPF (n = 3 ± SD).

NBPF TCBPF

Total phenolics (mg GAE/100 g of dry weight) 6532b ± 272.22 1245a ± 92.34Total flavonoids (mg CEQ/100 g of dry weight) 4500b ± 235.71 1042a ± 176.78DPPH value (mg TEAC/100 g of dry weight) 2422b ± 104.5 842a ± 20.70FRAP value (lmol TEACFRAP/100 g of dry weight) 16667b ± 628.54 2222a ± 314.27

Values in the same row with the same superscript letter are not statistically significant from each other(p > 0.05). NBPF, native banana pseudo-stem flour; TCBPF, tender core of banana pseudo-stem flour.

752 N.A.A. Aziz et al. / Food Chemistry 128 (2011) 748–753

The antioxidant activity of NBPF extracts was found to be signifi-cantly (p < 0.05) higher (2422 mg TEAC/100 g of dry weight) thanthat of TCBPF extracts (842 mg TEAC/100 g of dry weight). The find-ing that NBPF was enriched in antioxidant activity was attributed tothe relative abundance of phenolic compounds and the more robustproton-donating activity present in NBPF (Mosquera et al., 2007). Acorrelation between the DPPH value and total phenolics (r2 = 0.772and r2 = 0.879, respectively), indicated phenolic as the major com-ponent responsible for the antioxidant effects on the NBPF andTCBPF. These results are consistent with the general observationsthat the phenolic fraction contains the bulk of the antioxidant activ-ity in plants and that the distribution of phenolic compounds variesamong different structures within the same plant.

Another method was adopted for the evaluation of the totalantioxidant activity, FRAP assay is commonly used to study theantioxidant capacity of plant materials. In the present study, thetotal antioxidant power of NBPF (16667 lmol TEACFRAP/100 g ofdry sample) was found to be significantly higher (p < 0.05) thanthat of the TCBPF (2222 lmol TEACFRAP/100 g of dry sample). Ahigh correlation was found between the FRAP value and DPPH va-lue for NBPF and TCBPF (r2 = 0.805 and r2 = 0.878, respectively).This correlation could be due to the same mechanism that DPPHand FRAP methods rely on (Alothman et al., 2009). Another corre-lation analysis was performed on the phenolic content and FRAPvalue for the two flours. The correlation values were 0.719 and0.947 for NBPF and TCBPF, respectively. These correlations re-con-firm that the phenolic compounds are the main componentsresponsible for the antioxidant activities in these flours.

3.5. Swelling power, solubility profiles, and water and oil holdingcapacity

Swelling power, solubility, water and oil holding capacities ofNBPF and TCPBF are presented in Fig. 1. The TCBPF swelling power

Fig. 1. Swelling power (SP), water holding capacity (WHC), oil holding capacity (OHC) anand font types are not statistically significant from each other (p > 0.05). NBPF: Native b

(13.82 g swollen granules/g of dry matter) exceeded that of NBPF(9.48 g of swollen granules/g of dry matter). This result was dueto the boiling (100 �C) process applied in preparation of the bananatender core flour. According to Bello-Perez et al. (1999), high tem-peratures lead to the solubilisation of amylase during starch gela-tinisation. It is also possible that the high swelling power is due toa high amylopectin content; the latter possibility could be exploredusing structural studies. The extent of water retained in the swol-len granules of TCBPF was significantly (p < 0.05) greater thanNBPF and paralleled a higher percent solubility of TCBPF (33.28%)vs. NBPF (3.44%).

Both WHC and OHC are important functional properties thathave been widely studied in food, as they are associated with foodquality. NBPF and TCBPF had WHCs of 10.66 and 18.28 g of water/gof dry matter, respectively. These values far exceed those from thedietary fibres of oat bran, rice bran, soy flour and wheat bran,namely 2.10, 4.89, 4.79–6.75, and 5.03 g of water/g of dry matter,respectively (Abdul-Hamid & Luan, 2000; Chen et al., 1988; Hey-wood et al., 2002). Thus, NBPF and TCBPF are able to bind or entrapmore water than oat bran, rice bran and soy flour. In contrast, NBPFhas a WHC value on par with apple fibre (9.36 g of water/g of drymatter) as reported by Chen et al. (1988). This small difference maybe due to the structural differences in cell wall components be-tween the stem and fruit fibres (Chen et al., 1988). The lowerWHC value of NBPF as compared with TCBPF may be due to boilingTCBPF during processing. Starch granules present in NBPF are notaffected at high temperatures and have a low WHC, whereas thepreparation of TCBPF may have released amylose, which effectivelybinds water molecules (Rodriguez-Ambriz et al., 2008).

Another important functional property of the fibre ingredientsis the OHC which, in NBPF and TCBPF, was 5.48 and 3.88 g of oil/g of dry matter, respectively. The results showed that NBPF andTCBPF have higher OHC values than dietary fibre obtained fromcommercial preparations (1.29 g of oil/g of dry matter) as reported

d solubility of NBPF and TCBPF (n = 3 ± s.d.). Values with the same superscript letteranana pseudo-stem flour; TCBPF: Tender core of banana pseudo-stem flour.

N.A.A. Aziz et al. / Food Chemistry 128 (2011) 748–753 753

earlier by Abdul-Hamid and Luan (2000). The differences in OHCbetween NBPF and TCBPF might be attributed to their differencesin chemical and physical structure, as well as their differences inpreparation. NBPF may be potentially suitable for use in food prod-ucts as an aid in stabilising emulsions and as a rich source of die-tary fibre.

4. Conclusions

NBPF has a higher amount of fibre (crude fibre, insoluble dietaryfibre, total dietary fibre, cellulose, hemicellulose and lignin) thanTCBPF. The phenol content, flavonoid content, antioxidant capacityand free radical-scavenging capacity were all higher in NBPF thanin TCBPF. Boiling process increased the TCBPF functional profilein terms of swelling power, water holding capacity and solubility.Results from this research clearly showed that the high fibre, WHCand OHC of NBPF and TCBPF are potentially suitable for use in foodapplications as a new low-calorie, high-fibre ingredient.

Acknowledgements

One of the author (Ho Lee-Hoon) thank USM for financial sup-port; fellowship (RU: 1001/441/29301/CIPS/AUPE001) and RUGrant (1001/PTEKIND/815055).

References

AACC. (2000). American Association of Cereal Chemists Approved Methods (10th ed.).MN: St. Paul.

AACCI. (2001). The definition of dietary fiber. Cereal Food World, 46, 112–126.Abdul-Hamid, A., & Luan, S. Y. (2000). Functional properties of dietary fibre

prepared from defatted rice bran. Food Chemistry, 68, 15–19.Adebowale, K. O., Adeniyi Afolabi, T., & Lawal, O. S. (2002). Isolation, chemical

modification and physicochemical of Bambarra groundnut (Voandzeiasubterranean) starch and flour. Food Chemistry, 78, 305–311.

Alothman, M., Bhat, R., & Karim, A. A. (2009). Antioxidant capacity and phenoliccontent of selected tropical fruits from Malaysia, extracted with differentsolvents. Food Chemistry, 115, 785–788.

AOAC (2005). Official Methods of Analysis of AOAC International. Section 4.6.03 and4.6.04. Methods 973.18, and 2002.04. URL: http://www.aoac.org (accessed on23.02.10).

AOAC. (1997). Official Methods of Analysis of AOAC International (16th ed.).Washington, DC.

Bello-Perez, L. A., Agama-Acevedo, E., Sanchez-Hernandez, L., & Paredes-Lopez, O.(1999). Isolation and partial characterization of banana starches. Agriculture andFood Chemistry, 47, 854–857.

Benzie, I. F. F., & Strain, J. J. (1996). The ferric reducing ability of plasma (FRAP) as ameasure of ‘‘antioxidant power’’: The FRAP Assay. Analytical Biochemistry,239(1), 70–76.

Chen, H., Rubenthaler, G. L., Leung, H. K., & Baranowski, J. D. (1988). Chemical,physical, and baking properties of apple fiber compared with wheat and oatbran. Cereal Chemistry, 65(3), 244–247.

Cordeiro, N., Belgacem, M. N., Torres, I. C., & Moura, J. C. V. P. (2004). Chemicalcomposition and pulping of banana pseudo-stems. Industrial Crops and Products,19, 147–154.

FAO (2006). FAO statistical databases. URL.http://faostat.fao.org/site (accessed on29.03. 2010).

Happi Emaga, T., Herinavalona Andrianaivo, R., Wathelet, B., Tchango-Tchango, J., &Paquot, M. (2007). Effects of the stage of maturation and varieties on thechemical composition of banana and plantain peels. Food Chemistry, 103,590–600.

Happi Emaga, T., Robert, C., Ronkart, S. N., Wathelet, B., & Paquot, M. (2008). Dietaryfibre components and pectin chemical features of peels during ripening inbanana and plantain varieties. Bioresource Technology, 99, 4346–4354.

Heywood, A. A., Myers, D. J., Bailey, T. B., & Johnson, L. A. (2002). Functionalproperties of low-fat soy flour produced by an extrusion-expelling system.American Oil Chemists’ Society, 79(12), 1249–1253.

Juarez-Garcia, E., Agama-Acevedo, E., Sayago-Ayerdi, S. G., Rodriguez-Ambriz, S. L., &Bello-Perez, L. A. (2006). Composition, digestibility and application inbreadmaking of banana flour. Plant Foods for Human Nutrition, 61, 131–137.

Kallay, M., & Kerenyi, Z. (1999). Occurrence and identification of procyanidins inhungarian grapes and wines. Hungarian Agricultural Research, 4, 17–20.

Mohapatra, D., Mishra, S., & Sutar, N. (2010). Banana and its by-product utilisation:an overview. Scientific and Industrial Research, 69, 323–329.

Moller, J. (2009). Gravimetric determination of acid detergent fiber and lignin infeed: interlaboratory study. AOAC International, 92(1), 74–90.

Mosquera, O. M., Correa, Y. M., Buitrago, D. C., & Nino, J. (2007). Antioxidant activityof twenty five plants from Colombian biodiversity. Bioline International, 102(5),631–634.

Mukhopadhyay, S., Fangueiro, R., Arpac, Y., & Senturk, U. (2008). Banana fibers–variability and fracture behaviour. Engineered Fibers and Fabrics, 3(2), 39–45.

Oliveira, L., Cordeiro, N., Evtuguin, D. V., Torres, I. C., & Silvestre, A. J. D. (2007).Chemical composition of different morphological parts from ‘Dwarf Cavendish’banana plant and their potential as a non-wood renewable source of naturalproducts. Industrial Crops Production, 26, 163–172.

Oliveira, L., Evtuguin, D., Cordeiro, N., & Silvestre, A. J. D. (2009). Structuralcharacterization of stalk lignin from banana plant. Industrial Crops and Products,29, 86–95.

Ovando-Martinez, M., Sayago-Ayerdi, S., Agama-Acevedo, E., Goni, I., & Bello-Perez,L. A. (2009). Unripe banana flour as an ingredient to increase the undigestiblecarbohydrates of pasta. Food Chemistry, 113, 121–126.

Rodriguez-Ambriz, S. L., Islas-Hernandez, J. J., Agama-Acevedo, E., Tovar, J., & Bello-Perez, L. A. (2008). Characterization of a fibre-rich powder prepared byliquefaction of unripe banana flour. Food Chemistry, 107, 1515–1521.

Rose, D. J., Inglett, G. E., & Liu, S. X. (2010). Utilisation of corn (Zeamays) bran andcorn fiber in the production of food components. Science of Food and Agriculture,90, 915–924.

Someya, S., Yoshiki, Y., & Okubo, K. (2002). Antioxidant compounds from banana(Musa cavendish). Food Chemistry, 79, 351–354.

Tatjana, K., Terezija, G., Milica, K., & Plestenjak, A. (2002). Dietary fibre content ofdry and processed beans. Food Chemistry, 80, 231–235.

Traynham, T. L., Myers, D. J., Carriquiry, A. L., & Johnson, L. A. (2007). Evaluation ofwater-holding capacity for wheat-soy flour blends. American Oil Chemists’, 84,151–155.

Zhang, W., & Wang, S. Y. (2001). Antioxidant in selected medical and culinary herbs.Journal of Agricultural and Food Chemistry, 49, 5165–5170.