Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 13Citation - Scopus: 14Nanotubular Structures Developed From Whey-Based ?-Lactalbumin Fractions for Food Applications(John Wiley and Sons Inc., 2014) Tarhan, Özgür; Harsa, ŞebnemWhey proteins have high nutritional value providing use in dietary purposes and improvement of technological properties in processed foods. Functionality of the whey-based α-lactalbumin (α-La) may be increased when assembled in the form of nanotubes, promising novel potential applications subject to investigation. The purpose of this study was to extract highly pure α-La from whey protein isolate (WPI) and whey powder (WP) and to construct protein nanotubes from them for industrial applications. For protein fractionation, WPI was directly fed to chromatography, however, WP was first subjected to membrane filtration and the retentate fraction, whey protein concentrate (WPC), was obtained and then used for chromatographic separation. α-La and, additionally β-Lg, were purified at the same batches with the purities in the range of 95%-99%. After enzymatic hydrolysis, WPI-based α-La produced chain-like and long nanotubules with ∼20 nm width while WPC-based α-La produced thinner, miscellaneous, and fibril-like nanostructures by self-assembly. Raman and FT-IR spectroscopies revealed that α-La fractions, obtained from both sources and the nanostructures, developed using both fractions have some structural differences due to conformation of secondary structure elements. Nanotube formation induced gelation and nanotubular gel network entrapped a colorant uniformly with a transparent appearance. Dairy-based α-La protein nanotubules could be served as alternative gelling agents and the carriers of natural colorants in various food processes.Article Citation - WoS: 51Citation - Scopus: 55Kinetic Modelling of Lactic Acid Production From Whey by Lactobacillus Casei (nrrl B-441)(John Wiley and Sons Inc., 2006) Altıok, Duygu; Tokatlı, Figen; Harsa, Hayriye ŞebnemThe biomass growth, lactic acid production and lactose utilisation kinetics of lactic acid production from whey by Lactobacillus casei was studied. Batch fermentation experiments were performed at controlled pH and temperature with six different initial whey lactose concentrations (9-77 g dm-3) in a 3 dm3 working volume bioreactor. Biomass growth was well described by the logistic equation with a product inhibition term. In addition, biomass and product inhibition effects were defined with corresponding power terms, which enabled adjustment of the model for low- and high-substrate conditions. The Luedeking-Piret equation defined the product formation kinetics. Substrate consumption was explained by production rate and maintenance requirements. A maximum productivity of 2.5 g dm-3 h-1 was attained with an initial lactose concentration of 35.5 g dm-3.Article Citation - WoS: 29Citation - Scopus: 32Optimization of Lactic Acid Production From Whey by L Casei Nrrl B-441 Immobilized in Chitosan Stabilized Ca-Alginate Beads(John Wiley and Sons Inc., 2005) Göksungur, Mehmet Yekta; Gündüz, Meltem; Harsa, Hayriye ŞebnemThe production of lactic acid from whey by Lactobacillus casei NRRL B-441 immobilized in chitosan-stabilized Ca-alginate beads was investigated. Higher lactic acid production and lower cell leakage were observed with alginate-chitosan beads compared with Ca-alginate beads. The highest lactic acid concentration (131.2 g dm-3) was obtained with cells entrapped in 1.3-1.7 mm alginate-chitosan beads prepared from 2% (w/v) Na-alginate. The gel beads produced lactic acid for five consecutive batch fermentations without marked activity loss and deformation. Response surface methodology was used to investigate the effects of three fermentation parameters (initial sugar, yeast extract and calcium carbonate concentrations) on the concentration of lactic acid. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar, yeast extract and calcium carbonate concentrations had a strong linear effect on lactic acid production. The maximum lactic acid concentration of 136.3 g dm-3 was obtained at the optimum concentrations of process variables (initial sugar 147.35 g dm-3, yeast extract 28.81 g dm-3, CaCO3 97.55 g dm-3). These values were obtained by fitting of the experimental data to the model equation. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in lactic acid production using alginate-chitosan-immobilized cells.Article Citation - WoS: 72Citation - Scopus: 83Batch Production of L(+) Lactic Acid From Whey by Lactobacillus Casei (nrrl B-441)(John Wiley and Sons Inc., 2004) Büyükkileci, Ali Oğuz; Harsa, Hayriye ŞebnemThe effects of temperature, pH, and medium composition on lactic acid production by Lactobacillus casei were investigated. The highest lactic acid productivity values were obtained at 37 °C and pH 5.5. The productivity was 1.87 g dm-3 h-1 at 37 °C in shake flasks. In the fermenter, a productivity of 3.97 g dm-3 h-1 was obtained at pH 5.5. The most appropriate yeast extract concentration was 5.0 g dm-3. Whey yielded a higher productivity value than the analytical lactose and glucose. Initial whey lactose concentration did not affect lactic acid productivity. MnSO4·H2O was necessary for lactic acid production by L casei from whey. Product yields were approximately 0.93 g lactic acid g lactose-1.