Microbial inactivation and physicochemical properties of ultrasound processed pomegranate juice

• Published in: Journal of food protection 2015-03, Vol.78 (3), p.531-539
• Main Authors: Pala, Çiğdem Uysal, Zorba, Nükhet Nilüfer Demirel, Özcan, Gülçin
• Format: Article
• Language: English
• Subjects: Acids; Anthocyanins - analysis; Bacteria; Beverages - analysis; Beverages - microbiology; Chemical filters; Colony Count, Microbial; Color; E coli; Enzymes; Escherichia coli; Escherichia coli O157 - physiology; Food; Food contamination & poisoning; Food Handling - methods; Food Microbiology; Food preservation; Food Preservation - methods; Food safety; Food science; Fruit - chemistry; Fruit - microbiology; Fruit juices; Hydrogen-Ion Concentration; Inactivation; Lythraceae - microbiology; Mechanical properties; Microbial Viability; Microbiology; Microorganisms; Phenols; Phenols - analysis; Physicochemical properties; Saccharomyces cerevisiae; Saccharomyces cerevisiae - physiology; Sound waves; Ultrasonic imaging; Ultrasonics; Yeast
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X.JFP-14-290

The effects of ultrasound treatment at various amplitudes (50, 75, and 100%) and times (0, 6, 12, 18, 24, and 30 min) on Escherichia coli ATCC 25922 (a surrogate for E. coli O157:H7) and Saccharomyces cerevisiae ATCC 2366 levels and physicochemical characteristics (monomeric anthocyanins, color values, total phenolics, pH, and soluble solids) were determined in pomegranate juice. More than a 5-log inactivation of E. coli ATCC 25922 and a 1.36-log inactivation of S. cerevisiae ATCC 2366 were achieved after 30 min of ultrasound treatment at 100% amplitude. The log-linear and Weibull models were successfully used to estimate the microbial inactivation as a function of ultrasound treatment time (R(2) > 0.97). No significant changes were observed in total phenolics, pH, and soluble solids of the treated juice (P > 0.05). The ultrasound treatment for up to 30 min resulted in more than 92 and 89% anthocyanin retention at 75 and 100% amplitude, respectively. The redness (a*) of the juice did not change significantly after the ultrasound treatment at amplitudes of 75 and 100% for up to 24 and 12 min, respectively. No significant changes in L* and b* values were observed after ultrasound treatment at all amplitudes and after up to 30 min of treatment for 50 and 75% amplitudes. Small differences in juice color were noted based on total color difference scores.