Effect of extraction condition on properties of pectin from banana peels and its function as fat replacer in salad cream

Abstract

Banana peels are wasted from banana processing industry. Pectin is a soluble dietary fibre usually prepared from fruit and vegetable processing wastes. Pectin extraction from banana peels thus should be an effective way of waste utilization. This study aimed to determine the effect of extraction condition on the properties of pectin from peels of Nam Wa banana (Musa (ABB group) 'Kluai Nam Wa') and its role as fat replacer in salad cream. Banana peel pectin (BPP) was extracted with HCl (pH 1.5) and water (pH 6.0) for 30-120 min at 90 ± 5 °C. Acid extraction yielded 7-11% pectin on a dry basis with galacturonic acid content (GalA), degree of methylation (DM), and viscosity-average molecular weight (M_v) of 42-47, 57-61%, and 17-40 kDa, respectively; while water-extracted BPP contained lower DM but higher GalA and M_v. Prolonged extraction raised the pectin yield but lowered the M_v of BPP and the viscosity of their solutions. Incorporation of BPP obtained from 60 min acid- and water-extraction into salad cream at 30% oil substitution level resulted in the decreases in viscosity and lightness. All reduced-fat samples were stable to cream separation during 3-weeks storage although the formula containing water-extracted BPP had larger oil droplet size and greater extent of droplet flocculation. There was no difference in sensory scores rated by 50 panelists on thickness, smoothness, and overall acceptability of the full- and reduced-fat salad creams. Therefore, Nam Wa banana peels can be an alternative source of pectin with potential application as fat replacer in food products.

Keywords: Banana peel; Chemical structure; Fat replacer; Pectin; Salad cream.

Fig. 1

Typical FTIR spectra of BPP extracted using acid (a) and water (b) at 90 ± 5 °C for 60 min

Fig. 2

Extraction yield (a), galacturonic acid content (b), degree of methylation (c), viscosity-average molecular weight (d), and apparent viscosity at 122 s⁻¹ of 2.5% (w/v) solutions (e) of BPP extracted at 90 ± 5 °C for 30, 60 and 120 min. Filled bars represent acid-extracted BPP; open bars represent water-extracted BPP

Fig. 3

Shear stress (a) and apparent viscosity (b) of (circle) control salad cream, and reduced-fat salad creams containing 2% (w/v) solution of (square) acid-extracted and (triangle) water-extracted BPP as fat replacer at 30% oil substitution level. Measurements were carried out at room temperature (28 °C)

Fig. 4

Particle size distribution (a, c, e) and optical micrographs taken (b, d, f) of control salad cream (a, b), and reduced-fat salad creams containing 2% (w/v) solution of acid-extracted (c, d) and water-extracted BPP (e, f) as fat replacer at 30% oil substitution level. Scale bar represents 100 μm. The arrow points the flocculated droplets