UV-C Irradiation of Freshly Squeezed Grape Juice and Modeling Inactivation Kinetics

Inactivation of Bacillus and Clostridium Spores in Coconut Water by Ultraviolet Light

Bacterial spores are generally more resistant than vegetative bacteria to ultraviolet (UV) inactivation. The UV sensitivity of these spores must be known for implementing UV disinfection of low acid liquid foods. UV inactivation kinetics of bacterial spores in coconut water (CW) and distilled sterile water was studied. Populations of Bacillus cereus and Clostridium sporogenes dormant spores were reduced by more than 5.5 log₁₀ at the UV-C photon fluence of 1142 μE·m^-2 and 1919 μE·m^-2 respectively. C. sporogenes spores showed higher UV-C resistance than B. cereus, with the photon fluence 300 μE·m^-2 required for one log inactivation (D₁₀) and 194 μE·m^-2, respectively. No significant difference was observed in D₁₀ values of spores suspended in the two fluid types (p > 0.05). The inactivation kinetics of microorganisms were described by log linear models with low root mean square error and high coefficient of determination (R² > 0.98). This study clearly demonstrated that high levels of inactivation of bacterial spores can be achieved in CW. The baseline data generated from this study will be used to conduct spore inactivation studies in continuous flow UV systems. Further proliferation of the technology will include conducting extensive pilot studies.

Effect of soluble solids concentration on Neosartorya fischeri inactivation using UV-C light

Ascospores of Neosartorya fischeri are heat-resistant and can survive thermal commercial treatments normally applied to the juices, as apple juice. Non-thermal processing of food such as exposure to ultraviolet light (UV-C) is reported to induce minimal quality changes while reduces microbial load. The main objective of this study was to determine the effect at different soluble solids concentration (12, 25, 30, 40, 50, 60 and 70 °Brix) on N. fischeri ascospores inactivation in apple juice, using UV-C light intensity (38 W/m²). Weibull model was fitted to experimental data. Then, a secondary model was used to describe how the inactivation kinetic parameters varied with the changes in soluble solids concentration. Results showed that the UV-C light had influence on N. fischeri ascospores inactivation in apple juice even at the highest soluble solids concentrations used, reaching approximately 4 log reductions at all concentrations used. The inactivation parameters, obtained by Weibull model, were δ (dose for the first decimal reduction) and p (the shape factor). Exponential model was chosen to describe the influence of soluble solids concentration on δ and p parameters. It can be concluded that UV-C light is a promising treatment with a drastic impact on the loads of N. fischeri, especially when low soluble solids concentration is used and a model was obtained to describe Brix effect.

Preliminary study on the influence of UV-C irradiation on microorganism viability and polyphenol compounds content during winemaking of ‘Regent’ red grape cultivar

In this study, UV-C light was tested as an alternative method to inactivate microorganisms in the must of ‘Regent’ red grape cultivar. The control sample containing the microorganism diluted in a physiological NaCl solution was prepared to take into consideration different conditions of liquids, such as turbidity and colour. Additionally, the changes in the composition of polyphenol compounds in the ‘Regent’ must after UV-C exposure were evaluated. The viability of yeasts (Saccharomyces cerevisiae) and bacteria (Oenococcus oeni) significantly decreased with time; however, the highest decline was noted after the first hour of exposure. The polyphenol compound content was significantly lower after UV-C treatment and this was mainly the result of anthocyanin decomposition. The total content of flavan-3-ols and hydroxycinnamic acids and derivatives increased after irradiation.

Effects of Ultraviolet Light and High-Pressure Processing on Quality and Health-Related Constituents of Fresh Juice Products

Fresh juices are highly popular beverages in the global food market. They are perceived as wholesome, nutritious, all-day beverages. For a fast growing category of premium juice products such as cold-pressed juices, minimal-processing nonthermal techniques such as ultraviolet (UV) light and high-pressure processing (HPP) are expected to be used to extend shelf-life while retaining physicochemical, nutritional, and sensory characteristics with reduced microbial loads. Also, UV light and HPP are approved by regulatory agencies and recognized as one of the simplest and very environmentally friendly ways to destroy pathogenic organisms. One of the limitations to their more extensive commercial application lies in the lack of comparative effects on nutritional and quality-related compounds in juice products. This review provides a comparative analysis using 92 studies (UV light: 42, HPP: 50) mostly published between 2004 and 2015 to evaluate the effects of reported UV light and HPP processing conditions on the residual content or activity of bioactive compounds such as vitamins, polyphenols, antioxidants, and oxidative enzymes in 45 different fresh fruit and vegetable juices (low-acid, acid, and high-acid categories). Also, the effects of UV light and HPP on color and sensory characteristics of juices are summarized and discussed.

UVC dosage effects on the physico-chemical properties of lime (Citrus aurantifolia) juice

Lime juice is in high demand due to a sour taste. Commercial thermal pasteurization extends juice shelf-life; however, fruit juice subjected to thermal pasteurization tends to change color and lose vitamin content. Lime juice was irradiated with ultraviolet-C (UVC) at dosages of 22.76, 30.19, and 44.24 mJ/cm² to investigate effects on the physicochemical properties of lime juice. pH values of lime juice did not change while total soluble solids, turbidity, titratable acidity, sweetness, and color values of lime juice did change after UV treatments. Changes in quality index indicators were prominent at the highest UV dosage of 44.24 mJ/cm². A low UVC dosage was effective for treatment of lime juice with minimal changes in juice properties.