Food Engineering / Gıda Mühendisliği

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

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  • Article
    Citation - WoS: 3
    Citation - Scopus: 5
    Assessing the Impact of Non-Thermal and Thermal Treatment on the Shelf-Life of Onion Juice
    (Czech Academy of Agricultural Sciences, 2018) Demir, Hande; Yıldız, Mustafa Kemal; Becerikli, İsmail; Ünlütürk, Sevcan; Kaya, Zehra
    Onion (Allium cepa L.) juice is a marinating agent for meat and fish marination and readily usable sauce for any meal that has onion in its formulation. This study aims to assess the microbiological and physicochemical changes in the onion juice processed by UV-C irradiation (0.5 mm sample depth, 30 min exposure time, 7.5 mW/cm(2) UV incident intensity) and conventional heat treatment (74.5 degrees C, 12 min) during its storage. Microbiological results showed processing by UV-C irradiation or heat treatment under optimum conditions extended the microbial shelf-life of untreated onion juice by minimum 6-times. Total colour change of heat-treated samples was lower than that of untreated and UV-C treated samples for 12 weeks. Also, pH, total titratable acidity, total soluble solids content, turbidity, NEBI and total phenolic content were monitored for 12 weeks. The results of this study will form scientific infrastructure for onion juice manufacturers to decide on the processing method with respect to its shelf-life.
  • Article
    Citation - WoS: 82
    Citation - Scopus: 103
    Effect of Uv-C Irradiation and Heat Treatment on the Shelf Life Stability of a Lemon-Melon Juice Blend: Multivariate Statistical Approach
    (Elsevier Ltd., 2015) Kaya, Zehra; Yıldız, Semanur; Ünlütürk, Sevcan
    Heat treatment and UV-C irradiation of lemon and melon juice (LMJ) blends were comparatively evaluated by examining their impact on E. coli K12 (ATCC 25253) and their physicochemical properties, i.e., total soluble solids (TSS), pH, titratable acidity (TA), color, turbidity and absorbance coefficient, both immediately after processing and during 30 days of refrigerated storage. The newly formulated LMJ blend containing 12% (v/v) lemon juice (pH 3.92 ± 0.01) scored the highest in the consumer acceptance test. Upon UV-C irradiation (2.461 J/mL) and heat treatment (72 °C, 71 s), the E. coli K12 population in LMJ blend was reduced by > 6 log10 CFU/mL. Principal component analysis (PCA) and hierarchical cluster analyses (HCA) showed a clear discrimination among the physicochemical properties of the control and the UV-C and heat-treated LMJ blends during storage, suggesting that UV-C irradiation has a comparable effect on microbial stability at 4 °C and better quality preservation performance than heat treatment. Industrial relevance Melon juice has many beneficial health effects. It has high sugar content, pH (5.6-6.0) and a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics has markedly expanded in recent years. In this study, an alternative lemon-melon juice (LMJ) blend formulation was developed, and pasteurized using both UV-C irradiation and mild heat treatment. The shelf life stability of pasteurized LMJ blends was assessed by means of principal component analysis and hierarchical cluster analysis. The shelf life of LMJ blends treated by both methods was increased from 2 days to 30 days. The multivariate data analysis was successfully applied as a tool for an overall evaluation of the shelf-life of the product. UV-C irradiation has a comparable effect on microbial stability at 4 °C and better quality preservation performance than heat treatment for obtaining both shelf-stable and fresh-like LMJ blends. This would be a major advantage in processing of nutritious juice products.
  • Article
    Citation - WoS: 38
    Citation - Scopus: 48
    The Impact of Uv-C Irradiation on Spoilage Microorganisms and Colour of Orange Juice
    (Springer Verlag, 2013) Hakgüder Taze, Bengi; Ünlütürk, Sevcan; Buzrul, Sencer; Alpas, Hami
    The effect of UV-C irradiation on inactivation of spoilage microorganisms and colour of freshly squeezed orange juice were investigated. Orange juice samples were intentionally fermented in order to increase the natural microflora which were mostly composed of yeasts and then exposed to UV-C irradiation at an intensity level of 1.32 mW/cm2 and sample depth of 0.153 cm for several exposure times by using a collimated beam apparatus. Applied UV dose was in the range of 0 and 108.42 mJ/cm2. Resistance of yeast to UV light and existence of suspended particles limited the effectiveness of the process. Survival data obtained for yeasts was either described by the Weibull or traditional first-order model and goodness-of-fit of these models was investigated. Weibull model produced a better fit to the data with higher adjusted determination coefficient (R2 adj) and lower mean square error (MSE) values which were 0.99 and 0.003, respectively. Time and UV dose of first decimal reduction were obtained as 5.7 min and 31 mJ/cm2, respectively. The data suggests that biodosimetric studies performed by using inoculated microorganisms for assesment of the efficiency of UV irradiation treatment in the shelf life extension of juices must be carefully evaluated. UV-C irradiation had no influence on the colour of orange juice.