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    Development of gelatine-based edible film by addition of whey powders with different demineralisation ratios: Physicochemical, thermal, mechanical and microstructural characterisation
    (Wiley, 2021) Sert, Durmus; Ucok, Gamze; Kara, Ummugulsum; Mercan, Emin
    The effects of using whey powders with different demineralisation rates on the physicochemical, thermal, mechanical, and microstructural properties of gelatine-based edible films were investigated. Films were produced from film-forming solutions (FFS) containing whey powder (WP) and 50, 70 and 90% demineralised whey powder (50DWP, 70DWP, 90DWP). The addition of whey powders increased the pH and particle size values of FFS. The zeta potential decreased significantly in the WP sample and gradually reduced depending on the demineralisation rate in the DWP samples. The addition of whey powders partially increased the density of the films. WP addition reduced the hydrophobicity of the film, while the addition of DWPs did not cause any change. The addition of whey powders decreased the L* and a* values of the films while increasing the b* values. Control was the most transparent, while 70DWP and 90DWP films had higher opacity. WP films had the most uniform and smooth surface. The highest degradation temperature (269.64 degrees C) was observed in the control sample. The weight loss of the control was 95%, whereas those of WP and DWP samples were 88-89%. WP addition reduced the tensile strength and increased the elasticity of the films.
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    Growth kinetics and biomass characteristics of Lactobacillus plantarum L14 isolated from sourdough: Effect of fermentation time on dough machinability
    (Elsevier, 2020) Ucok, Gamze; Sert, Durmus
    Screening of the kinetic behavior of microorganisms is essential for industrial production planning, determining the changes depending on environmental factors and designing technologically the optimum reactor. In this study, the growth kinetics of Lactobacillus plantarum L14 naturally existing in sourdough was investigated in order to determine its biotechnological performance and the role of the effect on the fermentation process during dough-making. Growth kinetics of L. plantarum L14 were examined at 37 degrees C for 28 h fermentation using MRS medium. The maximum specific rate of L. plantarum L14 in the exponential phase was calculated to be 0.551 h(-1) and the productivity was 1.08 g/Lh. When the stationary phase was reached, maximum increase of 2.9 log cfu/mL was observed and average biomass productivity was determined as 9.19 g/L (2.14 g/L on dry matter basis). Cell sizes of L. plantarum L14 were examined using a particle size analyzer; D(4,3 )and D-90 results were measured as 4.38 and 9.01 mu m, respectively. Wheat doughs prepared by adding L. plantarum L14 biomass were fermented for 1, 15, 20 and 25 h and the acidity, cell number and machinability properties of the doughs were investigated. With increasing acidity during fermentation, more cohesive and sticky dough formation was detected.
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    Physical, mechanical, and thermal properties of gelatine-based edible film made using kefir: Monitoring Aspergillus flavus and A. parasiticus growth on the film surface
    (Wiley, 2022) Ucok, Gamze; Kara, Ummugulsum; Sert, Durmus
    In present work, the effect of kefir use on edible film quality was characterized, and the mold growth on the films was monitored. Kefir was used in the production of gelatine-based film at concentrations ranging from 10% to 50%. The thickness of the films did not change with the use of kefir, however, their density increased. Hydrophilic properties of the films increased due to the decrease in the contact angle values of the films. The addition of kefir increased the greenness and yellowness of films and more significantly the opacity. The surface morphology of the films improved with the use of kefir, however cloudy structures were observed with excessive use. Kefir has also slightly reduced the mechanical properties of the films. Maximum thermogravimetric weight loss was determined on films with 30 and 50% kefir added. While no growth of Aspergillus flavus and A. paraciticus was observed on the film surface for 10 days. Novelty impact statement In the food and packaging industry, efforts to increase the use of natural packaging materials such as environmentally friendly, biodegradable coating, and edible films that can be used instead of petrochemical packaging materials are gaining importance. For this purpose, in this study, the use of kefir in the production of edible films was considered as an alternative. The use of kefir, which has many health benefits, contains a wide variety of antimicrobials and is the source of some probiotic strains, in the production of edible films gains importance in terms of functional food development.
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    Trial productions of freeze-dried Lactobacillus plantarum culture using dairy by-products as cryoprotectants: Viability and characterization of cultures
    (Elsevier, 2022) Ucok, Gamze; Sert, Durmus
    This study is a research on the utilization of dairy industry by-products in the practical production and long-term preservation of industrial microbial cultures. Accordingly, lyophilized cultures were obtained by freeze-drying of Lactobacillus plantarum bacteria in large quantities and for a constant period of time in skimmed milk-based medium containing 5% acid casein, rennet casein, whey and demineralized whey. The cryoprotectants did not have significant protection against freeze-drying process, moreover, the use of rennet casein significantly reduced viability. The efficiency of the preservatives in preserving the viability during storage was very successful compared to the control culture. Casein-enriched cultures had high water activity and moisture, but high viability was maintained during storage. The powder morphologies of the cultures were differentiated by the use of different cryoprotectants. Particle sizes of the cultures were parallel to the moisture content. Particle size and distribution increased with storage. By thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis, it was determined that the addition of casein protein increased the degradation temperature of the cultures. The production of freeze-dried cultures became difficult with the use of casein. However, it was generally concluded that the protective properties of skimmed milk used for the preservation of L. plantarum could be improved by the addition of dairy by-products as a protective agent.