Novel edible films of pectins extracted from low-grade fruits and stalk wastes of sun-dried figs: Effects of pectin composition and molecular properties on film characteristics

• Published in: Food hydrocolloids 2023-02, Vol.135, p.108136, Article 108136
• Main Authors: Çavdaroğlu, Elif, Büyüktaş, Duygu, Farris, Stefano, Yemenicioğlu, Ahmet
• Format: Article
• Language: English
• Subjects: Barrier properties; Citrus pectin; Cross-linking; Edible film; Fig pectin; Mechanical properties
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2022.108136

This study aimed to explore the characteristics of novel fig pectin films. For this purpose, films of crude fig pectin (CFP) extracted from low-grade sun-dried fruits and films of crude (CSP) and purified (PSP) stalk pectins extracted from stalk waste of processed high-quality sun-dried figs were evaluated for their physicochemical properties. The properties of pristine (CFP, CSP, and PSP films) and CaCl2 cross-linked films (CFP–Ca++, CSP-Ca++and PSP-Ca++ films) of fig pectins were also compared with films of commercial citrus (CP and CP-Ca++) and apple (AP, AP-Ca++) pectins. The cross-linking improved the mechanical strength and barrier properties of most films. CP, CP-Ca++, PSP, and PSP-Ca++ films showed greater mechanical strength and stiffness than other films. PSP-Ca++, PSP and CP-Ca++ films showed the lowest water vapor permeability (6.28, 12.85, 14.96 g.mm.m−2.day−1.kPa−1, respectively) while CSP-Ca++, CP-Ca++, CP, PSP-Ca++ films showed the lowest oxygen permeability coefficients (5403, 8265, 10776, 11124 mL.μm.m−2.24h−1.atm−1, respectively). All cross-linked fig pectin films showed 2–3 fold lower degree of swelling than CP-Ca++ film. The CFP-Ca++ film showed the highest surface hydrophobicity (contact angle = 101.8°) but the lowest water solubility (32.8%) and degree of swelling. Analysis of Pearson's correlations between pectin properties and film characteristics revealed that galacturonic acid (GA) content affects the mechanical properties, while GA content, degree of esterification (DE), and acetylation affect the moisture barrier performance; finally, GA content and DE affect the oxygen barrier performance of pectin films. Films of stalk waste pectins showed some properties beyond the limits of those obtained from commercial pectins. [Display omitted] •Pectins were extracted from low-grade fruits and stalk wastes of sun-dried figs.•Mechanical and barrier properties of fig and commercial pectins films were compared.•Cross-linking of films improved their mechanical and barrier properties.•Stalk waste pectin films showed the highest moisture and gas barrier properties.•Pectin composition was correlated with film properties for the first time.