The Effect of Ultraviolet Light on Microbial Inactivation and Quality Attributes of Apple Juice

Abstract

Non-thermal technologies such as UV irradiation can offer advantages for minimal processing of transparent beverages. In this study, reconstituted apple juice was exposed to UV light in a continuous laboratory scale system at energy dosages ranging from 2.66 to 53.10 J/cm 2 by changing the exposure time. Treated juices were then evaluated for microbial inactivation and selected physical and chemical attributes. Product quality was further assessed by sensory evaluation using a 30-member consumer panel. Microbiological analysis was performed by inoculating apple juice with Escherichia coli K12 and Listeria innocua and microbial numbers were counted preand post-processing. UV energy levels did not affect pH,°B rix, or total phenols content, but decreased non-enzymatic browning (p<0.01) and antioxidant capacity (p<0.05) compared to unprocessed juice. A colour-lightening effect was noted with increasing energy dose. All UV treatments applied (2.66 J/cm 2 and above) resulted in a reduction below the detection level (<1 log cfu/ml) for both E. coli and L. innocua in apple juice. Sensory evaluation showed that samples treated with energy dosages up to 10.62 J/cm 2 were comparable to the control in terms of acceptability, though higher dosages produced adverse effects in terms of flavour and colour. Based on these results, UV treatment with low energy dosages could represent a valid alternative to thermal processing to eliminate pathogenic microorganisms while maintaining quality in reconstituted apple juice.

Effect of UV-C irradiation and heat treatment on the shelf life stability of a lemon–melon juice blend: multivariate statistical approach

“…There were no significant differences between untreated (control), UV-C-treated and heat-treated LMJ blends in terms of pH (3.92-3.93) and titratable acidity (0.48-0.51%) (p b 0.05). Our results were in agreement with other studies reporting no significant changes in pH and titratable acidity of different types of fruit juices treated with UV-C light and heat treatment (Caminiti et al, 2012;Falguera, Pagan, & Ibarz, 2011;Noci et al, 2008;Pala & Toklucu, 2011.…”

Ultraviolet-C Light Effect on the Physicochemical and Antioxidant Properties of Blackberry, Blueberry, and Raspberry Nectars

“…In raspberry nectar (light reddish), it was observed a decrease in the antioxidant capacity during the UV-C light processing; a decrease from 65 to 15 mg T/100 mL of nectar was observed. Similar results were found by Caminiti, Palgan, Muñoz, Noci, Whyte, & Morgan (2012) who indicated that in clear juices, such as clarified apple juice and raspberry juice, as the exposition time increased, the antioxidant capacity decreased because of a greater penetration of the UV-C light. Another important factor that can contribute to a decrease in the antioxidant capacity of raspberry nectar is the ascorbic acid content.…”

“…The explanation to the reduction of pigments in fruit products is because UV-C light may affect the structures of some compounds. Pala & Toklucu (2011) reported no significant differences (p > 0.05) in the content of phenolic compounds in pomegranate juices after UV-C light treatment; the same findings were reported by Caminiti, Palgan, Muñoz, Noci, Whyte, & Morgan (2012) in apple juice. The nectar that was more effected on TPC by the UV-C light was the blueberry nectar; this fact can be attributed to the inactivation of phenolic such as hydroxycinnamic acids and, or flavonols (Manach, Scalbert, Morand, Remesy, & Jimé nez, 2004) found in this fruit.…”

Ultraviolet-C Light Effect on Pitaya (Stenocereus griseus) Juice

“…The average values of the total soluble solids and pH, after UV-C light treatment, were 6.79±0.04 and 5.93±0.07 %, respectively. A number of researchers have reported that UV-C light did not have effect on pH, total soluble solids, and titratable acidityof fruit juices (Noci, Riener, Walkling, Cronin, Morgan & Lying, 2008;Caminiti et al, 2010;Pala & Toklucu, 2011). Table 2 presents the L, a, b, and ΔE color parameters of pitaya juice treated with UV-C light for 25 minutes.…”

“…Despite of this and due to the presence of colored compounds, organic compounds, and suspended matter, characteristic that may affect the UV-C light penetration into the liquid food product, the light transmission might be attenuated. As a result theUV-C light efficiency could be reduced (Caminiti et al, 2010).…”