Turnip juice (Shalgam) is a traditional Turkish beverage with sour flavor and purplish red color, which is produced by the lactic acid fermentation of black carrot. Due to its rich antioxidant content, Turnip juice offers some health benefits. However, the preservation of Turnip juice is a main challenge for the producers. While the growth of bacteria is supressed by lactic acid, wild yeasts can readily grow in Turnip juice. In this study, the effect of pulsed UV light (PUV) on Candida inconspicua in Turnip juice was evaluated. Inoculated Turnip juice samples were treated in a pulsed UV light system at different distances from the quartz window (5, 8 and 13 cm) and for different times (5, 15, 30, 45 and 60 s). A maximum log reduction of 2.80 was obtained after treatment at 5 cm for 60 s. To describe the inactivation of C. inconspicua by pulsed UV light, the first-order kinetics and Weibull model were used. Weibull model was found to be suitable for fitting the inactivation data. PRACTICAL APPLICATIONSTurnip juice (Shalgam) is a traditional fermented beverage produced from black carrots, which is a suitable growth medium for yeasts. The wild yeast Candida inconspicua was identified as a microorganism causing spoilage in Shalgam. The only methods utilized in industry to preserve shalgam are heat pasteurization and addition of chemical food additives. Due to the fact that thermal methods can cause the loss of anthocynanins and colorants, a nonthermal method could be a good alternative to preserve Shalgam. In this research, the effect of pulsed UV light, a novel method considered to be nonthermal for short treatment times, on the yeast C. inconspicua which was isolated from Shalgam was investigated. The results were supported with models to understand the effect of pulsed UV light on C. inconspicua cells for future applications in food industry and to direct other related inactivation studies.

In this study, the effects of pulsed UV (PUV) light on the degradation kinetics of anthocyanins and physicochemical properties of turnip juice were investigated. PUV light was applied to turnip juice at 3 different distances (5, 8, 13 cm) from the quartz window of the xenon lamp for 5 different times (5, 15, 30, 45, 60 s). The pH, total acidity (% lactic acid), monomeric anthocyanin content, color density, hue, brightness, and percent color components (yellow, red, and blue) of turnip juice changed significantly after PUV-light treatments at each level. The maximum degradation of anthocyanin after PUV-light treatments was found to be about 63%. The anthocyanin degradation, brightness, yellow and blue color (%) increased, while red color (%) decreased with longer treatment time and shorter distance. The degradation of monomeric anthocyanins in turnip juice exposed to PUV light was described by the Weibull model (R 2 0.982-0.998, RMSE 0.087-0.133) more accurately than the first-order kinetics (R 2 0.906-0.992, RMSE 0.071-0.192).

The present research investigates the effect of different pretreatments on glucose and fructose consumption and ethanol production by four Saccharomyces cerevisiae wine strains, three isolated and identified from different wine regions in Turkey and one reference strain. A mild stress temperature (45 °C, 1 h) and the presence of ethanol (14% v/v) were selected as pretreatments applied to cell cultures prior to the fermentation step in synthetic must. The goodness fit of the mathematical models was estimated: linear, exponential decay function and sigmoidal model were evaluated with the model parameters R2 (regression coefficient), RMSE (root mean square error), MBE (mean bias error) and χ2 (reduced Chi-square). Sigmoidal function was determined as the most suitable model with the highest R2 and lower RMSE values. Temperature pretreatment allowed for an increase in fructose consumption rate by two strains, evidenced by a t90 value 10% lower than the control. One of the indigenous strains showed particular promise for mild temperature treatment (45 °C, 1 h) prior to the fermentation step to reduce residual glucose and fructose in wine. The described procedure may be effective for indigenous yeasts in preventing undesirable sweetness in wines.

Kohlrabi is a valuable crop due to its substantial amount of macro- and micronutrients. It is mostly consumed in fresh form, as jam or fermented product. This current work aimed to optimize the spontaneous fermentation conditions of kohlrabi in order to improve its product functionality and diversity. For this purpose, a Box Behnken design was employed to evaluate the effects of boiling time (0–8 min.), vinegar ratio (0–50%), and salt content (2–8%) on chemical and microbiological properties of fermented kohlrabi. Some chemical and microbiological analyses, including total phenolic content, total antioxidant capacity, total acidity, pH, salt content, total counts of yeast and molds, and mesophilic and lactic acid bacteria, were determined. The total antioxidant capacity of samples changed between 11.91 and 75.75 µmol Trolox/100 g, respectively. Both ANOVA results (p  <  0.05) and PCA model (R2  =  0.99; Q2  =  0.72) confirmed that boiling time is the important factor affecting the fermentation process. The optimal fermentation parameters for kohlrabi were determined to be 44.12% vinegar and 2.07% salt concentrations without the boiling step by response surface methodology.