title: Development of a fermented ice-cream as influenced by in situ exopolysaccharide production: Rheological, molecular, microstructural and sensory characterization.
abstract: 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 4h) on pH, S. thermophilus count, EPS amount, consistency coefficient (K), and apparent viscosity (η50) 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 4h 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 η50 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 α-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.
authors.affiliation: Bayburt University, Engineering Faculty, Food Engineering Department, 69000 Bayburt, Turkey.
authors.forename: Enes
authors.initials: E
authors.lastname: Dertli
authors.affiliation: Yildiz Technical University, Chemical and Metallurgical Engineering Faculty, Food Engineering Department, 34210 Istanbul, Turkey.
authors.forename: Omer S
authors.initials: OS
authors.lastname: Toker
authors.affiliation: Yildiz Technical University, Chemical and Metallurgical Engineering Faculty, Food Engineering Department, 34210 Istanbul, Turkey.
authors.forename: M Zeki
authors.initials: MZ
authors.lastname: Durak
authors.affiliation: Yildiz Technical University, Chemical and Metallurgical Engineering Faculty, Food Engineering Department, 34210 Istanbul, Turkey. Electronic address: mtyilmaz@yildiz.edu.tr.
authors.forename: Mustafa T
authors.initials: MT
authors.lastname: Yilmaz
authors.affiliation: İstanbul Gelişim University, Vocational School, Food Technology Division, 34310 İstanbul, Turkey.
authors.forename: Nevruz Berna
authors.initials: NB
authors.lastname: Tatlısu
authors.affiliation: Yildiz Technical University, Chemical and Metallurgical Engineering Faculty, Food Engineering Department, 34210 Istanbul, Turkey.
authors.forename: Osman
authors.initials: O
authors.lastname: Sagdic
authors.affiliation: Erciyes University, Safiye Cikrikcioglu Vocational School, Food Science Division, Kayseri, Turkey.
authors.forename: Hasan
authors.initials: H
authors.lastname: Cankurt
mesh_terms: D005285:Fermentation; D005524:Food Technology / Q000379:methods*; D007054:Ice Cream / Q000382:microbiology*; D007218:Industrial Microbiology / Q000379:methods*; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000378:metabolism*; D012212:Rheology; D048249:Streptococcus thermophilus / Q000378:metabolism
chemical_list: D011135:Polysaccharides, Bacterial; C098632:exopolysaccharide, Streptococcus
keywords: Ethanol (PubChem CID: 702); Exopolysaccharides (EPS); Fermentation conditions; Ice-cream; Optimization; Potassium bromide (PubChem CID: 253877); Rheology; Trichloroacetic acid (PubChem CID: 6421)