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    Development of a fermented ice-cream as influenced by in situ exopolysaccharide production: Rheological, molecular, microstructural and sensory characterization
    (Elsevier Ltd, 2016) Dertli E.; Toker O.S.; Durak M.Z.; Yilmaz M.T.; Tatlisu N.B.; Sagdic O.; Cankurt H.
    This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS+ Streptococcus thermophilus strains on physicochemical, rheological, molecular, microstructural and sensory properties of ice cream in order to develop a fermented and consequently functional ice-cream in which no stabilizers would be required in ice-cream production. For this purpose, the effect of EPS producing strains (control, strain 1, strain 2 and mixture) and fermentation conditions (fermentation temperature; 32, 37 and 42°C and time; 2, 3 and 4 h) on pH, S. thermophilus count, EPS amount, consistency coefficient (K), and apparent viscosity (?50) were investigated and optimized using single and multiple response optimization tools of response surface methodology. Optimization analyses indicated that functional ice-cream should be fermented with strain 1 or strain mixture at 40-42°C for 4 h in order to produce the most viscous ice-cream with maximum EPS content. Optimization analysis results also revealed that strain specific conditions appeared to be more effective factor on in situ EPS production amount, K and ?50 parameters than did fermentation temperature and time. The rheological analysis of the ice-cream produced by EPS+ strains revealed its high viscous and pseudoplastic non-Newtonian fluid behavior, which demonstrates potential of S. thermophilus EPS as thickening and gelling agent in dairy industry. FTIR analysis proved that the EPS in ice-cream corresponded to a typical EPS, as revealed by the presence of carboxyl, hydroxyl and amide groups with additional ?-glycosidic linkages. SEM studies demonstrated that it had a web-like compact microstructure with pores in ice-cream, revealing its application possibility in dairy products to improve their rheological properties. © 2015 Published by Elsevier Ltd.
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    A novel antifungal surface-coating application to limit postharvest decay on coated apples: Molecular, thermal and morphological properties of electrospun zein–nanofiber mats loaded with curcumin
    (Elsevier Ltd, 2016) Yilmaz A.; Bozkurt F.; Cicek P.K.; Dertli E.; Durak M.Z.; Yilmaz M.T.
    Coating surfaces of fruit with electrospun zein mats with functionalized antimicrobial properties can be a novel strategy to prevent fungal colonization on fruit surfaces. In this study, we tested curcumin-loaded electrospun zein nanofibers (CLZN) in terms of limitation of postharvest decay on CLZN–coated apples infected with Botrytis cinerea and Penicillium expansum. Mixtures of zein and curcumin (the curcumin amounts of 2.5 and 5 wt% based on the weight of zein powder) were electrospun to yield cylindrical and ultrafine (< 350 nm in diameter) polymeric nanofibers. In addition, molecular, thermal, zeta potential and morphological properties of the CLZN as well as their encapsulation efficiency and releasing kinetics were determined, revealing that the developed zein-based scaffolds showed high encapsulation efficiency, molecular interactions with curcumin within nanofibers, alterations in physical states of these components, smooth beadless structure and good thermal (an endothermic peak at 152 °C) and dispersion stability (? 24 mV of ? potential) properties. In vitro antifungal activity tests conducted at 27 °C for six days showed that CLZN were effective against growth of the tested fungal pathogens, exhibiting almost 40–50% inhibition of mycelial growth of the fungal pathogens; but the antifungal effect against P. expansum was but two-fold higher than that against B. cinerea. In vivo tests conducted at 23 °C with 75% humidity for six days confirmed in vitro test results in terms of both visual inspections on uncoated and coated apples, revealing almost 50% reduction in lesion diameter measured on coated apples infected with Penicillium expansum. Our results suggest that CLZN mats open up new opportunities for a novel application of edible and biodegradable antifungal coating material with the ability to hinder fungal proliferation on coated apples during storage period. Industrial relevance We coated the surfaces of fruits with electrospun mats with functionalized antimicrobial properties to prevent fungal colonization on fruit surface. The coating of apples with curcumin-loaded zein nanoparticles (CLZNs) limited the postharvest decay caused by the fungal pathogens, Penicillium expansum and Botrytis cinerea. This study showed that by encapsulation of curcumin into zein-based nanofibers considerably increased the antifungal effectiveness of curcumin. Our results highlighted the potential use of the CLZN as an effective fungicidal coating material against P. expansum and B. cinerea and suggested that CLZNs can be promising tools to compete with synthetic fungicide counterparts of curcumin. The results of this study should be of great importance to industrial applications in terms of development of natural, but effective preservatives as alternative to synthetic ones. © 2016 Elsevier Ltd