Pulsed multifrequency thermosonication induced sonoporation in Alicyclobacillus acidoterrestris spores and vegetative cells

• Published in: Food research international 2022-06, Vol.156, p.111087-111087, Article 111087
• Main Authors: Wahia, Hafida, Zhang, Long, Zhou, Cunshan, Mustapha, Abdullateef Taiye, Fakayode, Olugbenga Abiola, Amanor-Atiemoh, Robert, Ma, Haile, Dabbour, Mokhtar
• Format: Article
• Language: English
• Subjects: Alicyclobacillus acidoterrestris inactivation; Dual-frequency ultrasound; FTIR; Reactive oxygen species
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2022.111087

[Display omitted] •A.acidoterrestris (AAT) was inactivated by 5 logs via cell sonoporation.•Double-frequency ultrasound (DFUS) waves induced ROS and caused DNA damage.•Microstructure analysis showed that DFTS had a greater bactericidal effectiveness.•FTIR detected modifications in AAT proteins, nucleic acids and lipids, induced by ROS. Alicyclobacillus acidoterrestris (AAT) was proposed as an index of pasteurization design for high-acid fruit products due to its spore resistance and repeated spoilage incidences in fruit juices. This study aimed to determine the effectiveness of pulsed multifrequency ultrasound to minimize AAT spores and vegetative cells in aqueous suspension. For this research, an investigation of the reactive oxygen species and antioxidant activity was performed to examine the effect of temperature and frequency on AAT spore inoculation. Total decreases in AAT bacteria were 5.99, 5.74 Log CFU/mL in vegetative cells for dual-frequency thermosonication (DFTS) and dual-frequency ultrasonication (DFUS), respectively, while 5.90 and 5.38 Log CFU/mL in spores for both DFUS and DFTS, respectively. The loss of the percentage of cells in ultrasound (US) and thermosonication (TS) treatments was inversely associated with the rate of O2−and H2O2 development. The fluorescence microscopy revealed a higher bactericidal efficacy of DFTS compared to the DFUS and control. Scanning Electron Microscopy (SEM) and Transmission electron microscopy (TEM) demonstrated ultra-structural modifications such as the interruption of cell walls by cavitation and pores in the membrane structure of the AAT bacteria induced by sonoporation. Several TS frequencies of 20/40/60, 20/40, and 20 kHz treated spores had a higher electrical conductivity than untreated ones, with an improvement of 7.94, 5.68, and 3.72 %, respectively. Fourier-transform infrared (FTIR) spectroscopy revealed major changes in the spectral region of membrane fatty acids and proteins of AAT. Simultaneously, AAT inactivation specific energy rate was significantly reduced using dual-frequency ultrasound, compared to mono-frequency thermosonication. The significant results of this work recommended pulsed DFUS as an alternative application to mono-frequency US in beverage industries.