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Production of Pectin From Wastes and Low-Grade Products of Sun-Dried Fig Processing: Optimization of Pectin Extraction and Characterization of Its Major Properties
(01. Izmir Institute of Technology, 2023) Çavdaroğlu, Elif; Yemenicioğlu, Ahmet
This thesis aimed extraction and characterization of pectin from processing wastes as stalks and low-grade fruits of sun-dried figs as an alternative pectin source. The extraction performed with three techniques (hot acidic, ultrasonic, enzymatic extraction) was optimized for key parameters. The hot acidic extraction, the most feasible method, yielded 11.7% crude fig stalk pectin (CSP) and 9.4% crude low-grade fig pectin (CFP) at optimal extraction conditions. The CSP had higher galacturonic acid content (GA: 34.2%) and degree of esterification (DE: 45%) than CFP (GA: 32.2% and DE: 36.7%). Purification of CSP gave pectin (PSP) with the highest GA (63%) and DE (65.9%). Despite differences in sugar compositions (D-glucose, L-rhamnose, D-galactose and L-arabinose), fig and citrus pectins displayed similar molecular weights and FT-IR profiles. The fig pectins were characterized for their gelation, antioxidant activity, water/oil absorption, emulsification/foaming capacities and stabilities, and viscosity. The properties of edible fig pectin films obtained with or without CaCl2 crosslinking were also investigated. PSP films showed greater mechanical strength (15.6-19.1 MPa), but lower water vapor permeability (6.28-12.85 g.mm/m2.day.kPa) than other films. The crosslinked CFP film exhibited the lowest solubility (32.8%) and degree of swelling. The emulsion films of CFP with eugenol (EUG) characterized and applied as a coating on whole melons effectively inhibited Listeria innocua (-2.2 log reduction) within 1 weeks at 10 °C. Fig pectins exhibited comparable or superior functional properties than commercial pectins, thus, utilization of low-quality figs and fig stalks into pectin could provide huge economic benefits to Turkish dried-fruit industry.
Innovative Food Applications of Novel Multifunctional Active Edible Gel Fillings and Coatings
(01. Izmir Institute of Technology, 2022) Barış Kavur, Pelin; Yemenicioğlu, Ahmet
This thesis organized as two chapters aimed to develop and test multifunctional novel gel filling and coating. In Chapter 1, the thesis focuses on developing antimicrobial and antibrowning gelatin based gel filling to produce safe caramel apples. For this purpose, water holding capacity and mechanical stability of gelatin (GEL) gels were improved by the incorporation of soy proteins (SP) and inulin (IN), respectively. The water activity (aw) of gels was also reduced to < 0.9 by the addition of sucrose (SUC). The apples were cored and the void cores were filled with GEL-SP-IN-SUC blend gel solution containing synergetic antimicrobials, nisin and lysozyme, and antibrowning agent ascorbic acid (each at 1% in gel). Candy sticks were then placed into gel-filled void cores, and apples were kept at 4oC for 20 h for gelation of filling before caramel dipcoating. The caramel apples with antimicrobial GEL-SP-IN-SUC filling showed 2.4 – 2.9 D lower Listeria count than traditional caramel apples during 7-day cold storage. The active blend gel-filling also prevented discoloration of apple core. In Chapter 2, the thesis focuses on controlling postharvest sprouting and microbial risks associated with shallot bulbs by active chitosan based coating loaded with eugenol (EUG). The sustained release of EUG was achieved by applying ultrasonic homogenization (US) to prepare a composite of chitosan (CHI) with chickpea proteins (CP) (CHI:CP ratio of films = 2). The CHI-CPEUG coating successfully reduced the sprouting and inhibited the inoculated E. coli and L. innocua in shallot bulbs by 2.3 log and 1.7 log, respectively.

Phd Degree / Doktora

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