Food Engineering / Gıda Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/12

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Subject: search.filters.subject.Saccharomyces cerevisiae

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  • Article
    Citation - WoS: 21
    Citation - Scopus: 28
    Effectiveness of Pulsed Light Treatments Assisted by Mild Heat on Saccharomyces Cerevisiae Inactivation in Verjuice and Evaluation of Its Quality During Storage
    (Elsevier, 2020) Martin Belloso, Olga; Ünlütürk, Sevcan; Soliva Fortuny, Robert; Kaya, Zehra; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The effects of pulsed light (PL) processing parameters such as depth of juice layer (1, 3, 5 mm), distance from the lamp (5, 10 cm) and number of pulses (0-50 pulses) on the inactivation of Saccharomyces cerevisiae in verjuice, a clarified beverage obtained from freshly-squeezed unripe grapes, were investigated. A reduction of 0.96 +/- 0.27 log CFU/mL was achieved by applying a dose of 34 J/cm(2) (1-mm layer depth, 5-cm distance, 50 pulses). PL was combined with mild heating (MH) at 43, 45 and 47 degrees C to increase its inactivation efficacy. Pasteurization was achieved by applying 17 J/cm(2) at 45 degrees C (PLMH45-3) and 6.12 J/cm(2) at 47 degrees C (PLMH47-3) to a 3-mm juice layer with S. cerevisiae reductions of 5.10 +/- 0.24 and 5.06 +/- 0.08 log CFU/mL, respectively. Quality properties of PLMH47-3-pasteurized verjuice were monitored during 6 weeks of storage at refrigerated (5 degrees C) and room temperature (25 degrees C), The results were compared to those of untreated and thermally pasteurized (72 degrees C/18 s) samples. Untreated juice spoiled within 2 weeks at 25 degrees C. No growth was detected in other conditions for 6 weeks. Among quality characteristics, only optical properties changed slightly during storage. It was concluded that mild MH-assisted pulsed light treatments have potential for verjuice pasteurization compared to conventional thermal pasteurization due to the better preservation of its fresh-like characteristics.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Temperature and Glycerol Formation: a Proposal To Explain the Causal Relationship Based on Glycolytic Enzyme Activities
    (American Society for Enology and Viticulture, 2019) Büyükkileci, Ceylan; Batur, Ayşem; Büyükkileci, Ali Oğuz; Hamamcı, Haluk; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Most yeast strains produce glycerol in larger quantities when cultivated at higher temperatures, which likely explains why red wines contain higher amounts of glycerol than white wines. In this work, we used a kinetic and thermodynamic approach to suggest a mechanistic explanation for this phenomenon. We began with a glycolytic model of the kinetics of the individual enzymes. The effects of temperature and ethanol on the apparent kinetics of individual enzymes were then determined and incorporated into the model. The activation energy for each enzyme was determined with the Arrhenius equation. The enzymes in the upper part of the glycolytic pathway were found to be more dependent on the temperature than those in the lower part. The model, as improved by these changes, could qualitatively simulate the ethanol and glycerol production curves and the production of more glycerol at higher temperatures. We propose that the differences in the temperature dependence of the enzymes around the glycerol branch are the reason for glycerol accumulation at higher temperatures.
  • Article
    Citation - WoS: 52
    Citation - Scopus: 72
    Production of Bioethanol From Apple Pomace by Using Cocultures: Conversion of Agro-Industrial Waste To Value Added Product
    (Elsevier Ltd., 2015) Evcan, Ezgi; Tarı, Canan; Tarı, Canan; Evcan, Ezgi; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Direct fermentation of cellulosic biomass to bioethanol has been very promising and hence attracted attention in recent years. In this study, bioethanol production from apple pomace hydrolysate (agro-industrial waste product) was investigated by coculturing Trichoderma harzianum, Aspergillus sojae and Saccharomyces cerevisiae using statistical approaches. Screening and optimization experiments were conducted in order to determine the significant factors and their optimum levels for maximum bioethanol production. Inoculation rates, aeration and agitation speed were considered as factor variables and bioethanol production as response variable. Highest bioethanol (EtOH) concentration and ethanol yield on total reducing sugar content (YP/S) were 8.748 g/L and 0.945 g/g, respectively. Optimum conditions were 6% (w/v) inoculation rates of T.harzianum and A.sojae, and 4% (v/v) inoculation rate of S.cerevisiae with vented aeration method and agitation speed of 200 rpm. To best of our knowledge to date, no reports are available in literature regarding the coculturing of T.harzianum, A.sojae and S.cerevisiae for bioethanol production. Therefore, this study will serve as a base line of initial studies in this field. The method can create a renewable alternative feedstock for fossil fuel production and suggest a feasible solution to multiple environmental problems simultaneously creating a sink for waste utilization.