The impact of UV-C irradiation on spoilage microorganisms and colour of orange juice

Abstract

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/cm(2) 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/cm(2). 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 (R(2) 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/cm(2), 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.

Ultraviolet irradiation detoxification of aflatoxins

“…Therefore, there are obvious changes in the chemical composition of food components and product quality deterioration when the UV light treatment is applied in high dose (Kolakowska, 2003). However, seen from the other reported results, UV irradiation can not cause any adverse effects, especially if UV irradiation is applied in moderate amounts (Caminiti et al, 2012;Hakguder Taze, Unluturk, Buzrul, & Alpas, 2013;Krishnamurthy, 2006(chap. 2); Tripathi & Mishra, 2010).…”

Effect of ultraviolet-C light and mild thermal treatment on the storage life of orange juice

“…On the other hand, moulds plus yeasts stored at 5 °C display an n value higher than 1, which indicates that the microorganisms become more sensitive to the storage condition. This is very important because the main problem in citric juices is the growth of moulds and/or yeasts (Hakguder et al 2015).…”

Effect of postharvest UV-C treatment on the microbial quality of ‘Şalak’ apricot

“…Electrons of the hydrogen bonds between paired nucleotides become energized which leads to the breakage of the bond and subsequently to the formation of cytotoxic and mutagenic lesions (Koutchma, 2014a). These mutagenic lesions are pyrimidine dimers, mainly formed by covalent linkages between two adjacent thymine bases (Koutchma, 2014a;Hakguder Taze et al, 2015). Furthermore, inactivation of microorganisms might be also related to the various biochemical reactions such as synthesis of compounds which are toxic to pathogens like phytoalexins and phenols, and induction of antifungal enzyme activities occurred in fresh products after UV-C light exposure (Gonz´alez-Aguilar et al, 2001;Guan et al, 2012).…”

“…The reason might be the differences in the UV sensitivities of the microorganisms of concern. Yeasts were reported to be more resistant to UV-C light than bacteria due to their big size, differences in genetic material and also in cell wall composition and thickness (Hakguder Taze et al, 2015).…”