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<p>This study investigates continuous and pulsed ultraviolet (UV) LED irradiation for inactivating <i>Escherichia coli</i> in water and in a caramel solution simulating high-absorption fruit juice. A laboratory-scale setup equipped with a 271-nm UV-C LED (12 mW) was developed, and microbial inactivation was evaluated across water samples with absorption coefficients of 0.0429–11.253&#xa0;cm<sup>−1</sup>. Pulsed irradiation at 1 and 5&#xa0;Hz (50% duty cycle) was compared to continuous mode at equivalent UV doses. Results showed that higher absorption coefficients significantly reduced UV penetration and inactivation efficiency under continuous irradiation, particularly at doses above 6&#xa0;mJ&#xa0;cm<sup>−2</sup>. Pulsed irradiation substantially enhanced log reductions, with 5&#xa0;Hz outperforming both continuous and 1&#xa0;Hz modes. At 5&#xa0;mJ&#xa0;cm<sup>−2</sup>, log inactivation was 2.7 in continuous mode, 3.05 at 1&#xa0;Hz (+ 13%), and 3.8 at 5&#xa0;Hz (+ 41%). Statistical analysis (ANOVA with Tukey HSD) confirmed these differences were highly significant (<i>p</i> &lt; 0.001). The inactivation data were described using both linear and Weibull models, and a global Weibull model was developed that integrates UV dose and absorption coefficient into a single predictive framework (<i>R</i><sup>2</sup> = 0.864). Enhanced disinfection under pulsed mode is attributed to improved LED cooling, increased radiant output, and inhibition of bacterial DNA repair. These findings highlight pulsed UV-LED irradiation as a promising non-thermal, energy-efficient strategy for microbial inactivation in high-absorption liquids such as fruit juices.</p>

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Impact of Absorption Coefficient and Irradiation Mode on Escherichia coli Inactivation Using UVC-LEDs

  • 期刊论文

  • 发表日期：

    2026年2月7日

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  • Zahra Soltani Asli,
  • Saied Moghaddam,
  • Mohammad Dehghani,
  • Fatemeh Azarikia,
  • Iradj Ashrafi Tamai

摘要

This study investigates continuous and pulsed ultraviolet (UV) LED irradiation for inactivating Escherichia coli in water and in a caramel solution simulating high-absorption fruit juice. A laboratory-scale setup equipped with a 271-nm UV-C LED (12 mW) was developed, and microbial inactivation was evaluated across water samples with absorption coefficients of 0.0429–11.253 cm−1. Pulsed irradiation at 1 and 5 Hz (50% duty cycle) was compared to continuous mode at equivalent UV doses. Results showed that higher absorption coefficients significantly reduced UV penetration and inactivation efficiency under continuous irradiation, particularly at doses above 6 mJ cm−2. Pulsed irradiation substantially enhanced log reductions, with 5 Hz outperforming both continuous and 1 Hz modes. At 5 mJ cm−2, log inactivation was 2.7 in continuous mode, 3.05 at 1 Hz (+ 13%), and 3.8 at 5 Hz (+ 41%). Statistical analysis (ANOVA with Tukey HSD) confirmed these differences were highly significant (p < 0.001). The inactivation data were described using both linear and Weibull models, and a global Weibull model was developed that integrates UV dose and absorption coefficient into a single predictive framework (R2 = 0.864). Enhanced disinfection under pulsed mode is attributed to improved LED cooling, increased radiant output, and inhibition of bacterial DNA repair. These findings highlight pulsed UV-LED irradiation as a promising non-thermal, energy-efficient strategy for microbial inactivation in high-absorption liquids such as fruit juices.