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

Hakguder Taze, Bengi, Unluturk, Sevcan
Scientia horticulturae 2018 v.233 pp. 370-377
Weibull statistics, aerobes, apricots, coliform bacteria, flora, lamps, light intensity, microbiological quality, models, molds (fungi), radiometry, regression analysis, ultraviolet radiation, yeasts
Inactivation of natural flora found on cv. ‘Şalak’ apricot surfaces was investigated using a newly designed UV-C treatment system equipped with four UV lamps and a rotating roller bearing. Multiple Point Source Summation (MPSS) Model was used to estimate UV light intensity field in this processing chamber. Although MPSS model over-predicted the UV intensity data, light intensity profile showed a good agreement with the radiometric measurements. UV-C treatment of apricots resulted in 3-log reduction in the number of total mesophilic aerobic bacteria (TAPC) at 32.3 W m−2 of average UV light intensity for 16 min at 31.01 kJ m−2 of UV dose whereas 2.38-log reduction was achieved for yeast and mould count (YMC) after 4 min of UV exposure at 7.75 kJ m−2 of UV dose. On the other hand, complete inactivation of coliform bacteria was observed after all treatments. Statistical analysis indicated that further extension of the exposure time did not cause any significant effect on the inactivation of natural flora of apricot surfaces. Additionally, the inactivation data obtained for TAPC and YMC were modelled by using log-linear regression, Biphasic model, log-linear + tail, Weibull model, Weibull + tail, double Weibull and biphasic + shoulder models. The inactivation kinetics of TAPC and YMC were best described by log linear + tail model with the smallest root mean squared error (RMSE) and the highest regression coefficient (R2 > 0.90). These results suggest that UV-C treatment can be applied to control the natural flora on cv. ‘Şalak’ apricots. Use of a rotating roller bearing is highly appreciated in UV-C systems to provide equal radiation among fruit surfaces.