Synergistic effects of antimicrobials combined with pressure assisted thermal processing against Alicyclobacillus acidoterrestris spores in orange juice

Abstract

The preservation of acidic beverages is challenged by the resistance of Alicyclobacillus acidoterrestris spores to conventional treatments. The effects of four antimicrobials (nisin (NIS) at 20 and 50 mg/L, vanillic acid (VA) at 200 and 500 mg/L, coumaric acid (CA) at 100 and 200 mg/L, and sinapic acid (SA) at 100 and 200 mg/L) combined with pressure-assisted thermal processing (PATP), high-pressure processing (HPP) at room temperature (RT), and thermal processing (TP) on A. acidoterrestris spores' inactivation and guaiacol production in orange juice were investigated. Samples inoculated at 105 cfu/mL for total cells and spores were enriched with antimicrobials and subjected to: i) PATP (T500/70: 500 MPa at 70 ◦C and T600/65: 600 MPa at 65 ◦C), ii) HPP (T500/RT: 500 MPa at RT and T600/RT: 600 MPa at RT), and iii) TP (T0.1/70: 0.1 MPa at 70 ◦C and T0.1/65: 0.1 MPa at 65 ◦C) for 5 min. Juices were incubated at 45 ◦C for 12 days. PATP reduced total cells and spores below detection limit (< 1.4 log cfu/mL) and prevented growth, with guaiacol levels between 4.1 and 10.0 ng/mL. VA inhibited growth but not guaiacol production (>300 ng/mL). Under HPP at RT, higher doses of NIS, CA, and SA reduced guaiacol production (5.7–8.3 ng/mL). NIS under T0.1/70 maintained populations at 4.5 log cfu/mL and guaiacol below quantification limit (< 4 ng/mL). Results confirm that PATP combined with NIS, CA, and SA is a promising strategy to control A. acidoterrestris spores and prevent guaiacol spoilage.

The authors are pleased to acknowledge to Spanish Ministry of Science and Innovation, research project QUALISAFEJUICE PID-2019- 106645RB-I00, for its financial support. I. Neggazi thanks the University of Lleida for its predoctoral grant (BOU204-220/2020 UdL) and the Serra Húnter contract awarded to Pilar Col´ as-Med`a for supporting this work. This work also received support from the PT national funds (FCT/ MECI, Fundaç˜ao para a Ciˆ encia e Tecnologia and Minist´erio da Educaç˜ ao, Ciˆ encia e Inovaç˜ ao) through the project UID/50006 – Laborat´ orio Associado para a Química Verde - Tecnologias e Processos Limpos. This study was also funded by the PRR – Plano de Recuperaç˜ ao e Resiliˆ encia and by the NextGenerationEU funds at Universidade de Aveiro, through the scope of the Agenda for Business Innovation “Plataforma de Valorizaç˜ao, Industrializaç˜ ao e Inovaç˜ ao comercial para o AgroAlimentar (VIIAFOOD)” (Project no. 37 AAC n. ◦ application C644929456-00000040).