Characterization of microbial inactivation in clear and turbid juices processed by short-wave ultraviolet light

Abstract

The aim of this study was to analyze the inactivation of a wide spectrum of microorganisms in clear as well as turbid juices processed by ultraviolet light (UV‐C: 0–1720 mJ/cm2). A biodosimetry assay was used to determine the equivalent UV‐reduction dose (3.1 mJ/cm2). UV‐C effectiveness increased in melon (3.2 and 4.4 log‐reductions of Saccharomyces cerevisiae and Escherichia coli) and orange‐tangerine juices (4.7 log‐reductions of E. coli) compared to carrot (2.7, 2.9, and 4.2 log‐reductions of S. cerevisiae, Candida parapsilosis and Pseudomonas fluorescens), orange (1.7, 2.0, 2.9 and 4.0 log‐reductions of S. cerevisiae, Zygosaccharomyces bailii, Listeria innocua, and E. coli), and orange‐carrot juices (2.5, 2.5 and 2.9 log‐reductions of S. cerevisiae, P. fluorescens, and E. coli). The Coroller model allowed a better fit compared to the Weibull and modified Gompertz models. UV‐C effectiveness in clear juices was related to low absorbance at 254 nm, color, and turbidity; whereas, in the turbid juices, it was also linked to the presence of particle aggregates. Practical applications Short‐wave ultraviolet light (UV‐C) is a promising preservation technology to partially or totally replace traditional thermal treatments, which severely alter product quality. The present study allowed to interpret how physicochemical properties of clear and turbid juices affected the inactivation of a wide spectrum of microorganisms processed by short‐wave ultraviolet light (UV‐C, up to 1,720 mJ/cm2). UV‐C effectiveness was related to high UV‐C transmittance, low absorbance, and turbidity in clear juices. Whereas, in the turbid ones, other parameters such as the presence of particle aggregates stemmed the disinfection process. Moreover, the optical properties of the juices were used in the estimation of UV dose distribution. Mathematical modeling revealed differences in microbial sensitivities and the existence of subpopulations with different resistance to UV‐C treatment. These results suggest that UV‐C light represents a promissory alternative for the processing of a variety of juices and blends with significant differences in their physicochemical characteristics.

Investigating the Use of Ultraviolet Light Emitting Diodes (UV-LEDs) for the Inactivation of Bacteria in Powdered Food Ingredients

“…In chilli powder, despite a significant reduction in cell numbers for all four strains following 40 s treatment (between 0.75–1.3 log 10 CFU/g), the overall levels of inactivation were lower than those observed in the other three powders. The physiochemical properties of the powder have been shown to influence UV inactivation efficacy in food matrices [ 11 , 33 , 43 ]. Therefore, particle size and water activity were determined ( Table 1 ); however, in our study, smaller particle size and higher water activity were not associated with increased inactivation.…”

“…Therefore, curves which show a sharp initial decline followed by a tailing phase are generally described well by the biphasic model and it was statistically the best fit for L. monocytogenes (R 2 adj = 0.975, RMSE = 0.180) and B. subtilis (R 2 adj = 0.942, RMSE = 0.217) in cheese and onion powder. In contrast, the behaviour of E. coli and S. Typhimurium in this powder were best described using the Weibull model which has been used in other studies to describe UV-C inactivation [ 43 , 44 ]. The Geeraerd-shoulder-tail model, which describes inactivation curves incorporating both shoulder and tailing phases, was the statistical best fit for all of the strain data in both garlic powder and onion powder.…”

“…Bacterial strains were most and least susceptible to UVC-LED inactivation in cheese and onion powder and chilli powder, respectively. Other studies have also shown the efficacy of UV treatment to be dependent on the matrix [ 11 , 12 , 33 , 43 , 56 ], with differences commonly attributed to the ingredient composition and the chemical and physical properties of the food. The particle size of the food sample is one such characteristic which can impact UV-LED inactivation of microorganism.…”

“…The fitting of inactivation models to the data confirmed that the bacteria did not show linear behaviour during inactivation, with both shoulders and/or tails observed in most curves and the Geeraerd shoulder–tail model being the most accurate of the models assessed. A number of studies have observed inactivation curves with shoulders following UV treatment of microbes in culture media [ 17 , 57 , 58 ] and liquid foods such as fruit and vegetable juices [ 43 , 59 , 60 , 61 ] However, as each study differs in the choice of UV device and treatment protocol, it is possible that the presence/absence of a shoulder may be dependent on the UV-LED dosage. For example, some studies report bacterial log reductions following a single UV treatment [ 16 , 22 , 56 ] while Liu et al (2012) and Arroyo et al (2017) did not observe shoulders following the inactivation of C. sakazakii in PIF; however, higher initial doses were used [ 15 , 21 ].…”

Effects of protein–polysaccharide interactions on the physical and textural characteristics of low‐fat whipped cream

“…Homogenized samples were then injected into the instrument until 60% to 80% of light passed through the solution. The average particle size (d 32 ) was calculated using Equation (3) and the surface area of the particles was obtained using the software (Fenoglio, Ferrario, García Carrillo, Schenk, & Guerrero, 2020). …”