Category Archives: Alicyclobacillus

Research – Inactivation of Alicyclobacillus acidoterrestris in apple juice using pulsed light

Posted on May 21, 2024 by | Leave a comment

Science Direct

We aimed to investigate the effect of pulsed light (PL) on inactivating Alicyclobacillus acidoterrestris in apple juice, the mechanism behind the inactivation, and the resultant effects on the quality of the juice. Our results showed that PL had a good inactivation effect on both spores and vegetative cells of A. acidoterrestris in apple juice, with a reduction of 3.5 ± 0.1 and 2.1 ± 0.1 log CFU/mL, respectively, following 3 s of treatment. This effect was better when lower concentrations of apple juice and lower liquid layer depths were used. Transmission electron microscopy (TEM) showed that the morphology and structure of A. acidoterrestris spores did not change significantly before and after treatment. When we compared the dipicolinic acid (DPA) release rate and death rate of the spores, we hypothesized that PL might have damaged the cortical proteins on A. acidoterrestris that are associated with the resistance of the spores, thus leading to their death. However, TEM revealed that the cell membranes of vegetative cells of A. acidoterrestris were intact and smooth before the treatment, but significantly wrinkled afterward. Raman spectroscopy revealed that the main targets of PL on A. acidoterrestris vegetative cells were: amide I on the proteins, nucleic acids [adenine(A) and guanine (G), in particular] and DNA (O–P–O‾ stretching) structures, and lipids (C–H2 deformation). The PL treatment increased the sugar content significantly, while having little to no effect on the other basic physicochemical parameters of apple juice.

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Posted in Alicyclobacillus, Bacterial Spores, Food Microbiology Research, Food Technology, Pulsed Light, Research, Technology

Research – Fruit Juice Spoilage by Alicyclobacillus: Detection and Control Methods—A Comprehensive Review

Posted on March 8, 2022 by | Leave a comment

MDPI

Fruit juices have an important place in humans’ healthy diet. They are considered to be shelf stable products due to their low pH that prevents the growth of most bacteria. However thermo-acidophilic endospore forming bacteria of the genus Alicyclobacillus have the potential to cause spoilage of commercially pasteurized fruit juices. The flat sour type spoilage, with absence of gas production but presence of chemical taint compounds (mostly guaiacol) and the ability of Alicyclobacillus spores to survive after pasteurization and germinate under favorable conditions make them a major concern for the fruit juice industry worldwide. Their special characteristics and presence in the fruit juice industry has resulted in the development of many isolation and identification methods based on cell detection (plating methods, ELISA, flow cytometry), nucleic acid analysis (PCR, RAPD-PCR, ERIC-PCR, DGGE-PCR, RT-PCR, RFLP-PCR, IMS-PCR, qPCR, and 16S rRNA sequencing) and measurement of their metabolites (HPLC, GC, GC-MS, GC-O, GC-SPME, Electronic nose, and FTIR). Early detection is a big challenge that can reduce economic loss in the industry while the development of control methods targeting the inactivation of Alicyclobacillus is of paramount importance as well. This review includes a discussion of the various chemical (oxidants, natural compounds of microbial, animal and plant origin), physical (thermal pasteurization), and non-thermal (High Hydrostatic Pressure, High Pressure Homogenization, ultrasound, microwaves, UV-C light, irradiation, ohmic heating and Pulse Electric Field) treatments to control Alicyclobacillus growth in order to ensure the quality and the extended shelf life of fruit juices.

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Posted in Alicyclobacillus, Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Research

Research – Bacterial Spore Inactivation in Orange Juice and Orange Peel by Ultraviolet-C Light

Posted on April 15, 2021 by | Leave a comment

MDPI

Spore-forming bacteria are a great concern for fruit juice processors as they can resist the thermal pasteurization and the high hydrostatic pressure treatments that fruit juices receive during their processing, thus reducing their microbiological quality and safety. In this context, our objective was to evaluate the efficacy of Ultraviolet-C (UV-C) light at 254 nm on reducing bacterial spores of Alicyclobacillus acidoterrestris, Bacillus coagulans and Bacillus cereus at two stages of orange juice production. To simulate fruit disinfection before processing, the orange peel was artificially inoculated with each of the bacterial spores and submitted to UV-C light (97.8–100.1 W/m2) with treatment times between 3 s and 10 min. The obtained product, the orange juice, was also tested by exposing the artificially inoculated juice to UV-C light (100.9–107.9 W/m2) between 5 and 60 min. A three-minute treatment (18.0 kJ/m2) reduced spore numbers on orange peel around 2 log units, while more than 45 min (278.8 kJ/m2) were needed to achieve the same reduction in orange juice for all evaluated bacterial spores. As raw fruits are the main source of bacterial spores in fruit juices, reducing bacterial spores on fruit peels could help fruit juice processors to enhance the microbiological quality and safety of fruit juices. View Full-Text

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Posted in Alicyclobacillus, Bacillus, Bacillus cereus, Bacillus coagulans, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, UV Microbiology

Research – Assessment of spoilage potential posed by Alicyclobacillus spp. in plant-based dairy beverages mixed with fruit juices during storage

Posted on October 19, 2020 by | Leave a comment

Journal of Food Protection

The scope of the present study was to assess the spoilage potential of different Alicyclobacillus spp. in commercial pasteurized (ambient-stable) plant-based dairy beverages mixed with fruit juices at different inoculation levels and storage temperatures. Different products (Coconut and Berry‒CB; Almond, Mango, and Passionfruit‒AMP; Oat, Strawberry, and Banana‒OSB) were inoculated with 10 or 2×103 spores/mL of either Alicyclobacillus acidoterrestris or A. fastidiosus or A. acidocaldarius strain composites, while non‒inoculated samples served as controls. Samples inoculated with A. acidoterrestris and A. fastidiosus were stored at 30°C and 45°C, while in case of A. acidocaldarius storage took place at 50°C for 240 days. Gas composition, Alicyclobacillus spp. populations, total viable counts, pH, aw, color, and guaiacol off-taste were monitored. CB and AMP supported growth of A. acidoterrestris and A. fastidiosus, reaching populations of 4.0‒5.0 log CFU/mL. In OSB, populations of the latter species remained close to the initial inoculation levels during storage at 30°C, while at 45°C, the populations declined <1 CFU/mL. A. acidocaldarius growth was supported only in CB samples, reaching ca. 3.0 log CFU/mL at 50°C, regardless of initial inoculum size. Total color change was increased during storage, however the instrumentally recorded color changes were not macroscopically visible. Spoilage in terms of guaiacol off-taste, was identified only in CB and AMP samples inoculated with A. acidoterrestris after 60 days at 30°C and 45°C. Considering that these products are becoming increasingly popular and the scarcity of existing literature related to their spoilage by Alicyclobacillus spp., the contribution of the findings and data of present study are critical for assessing the significance of Alicyclobacillus spp. as a potential spoilage hazard in these products and thus, to assist in the design and implementation of effective mitigation strategies by the beverage industry.

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Posted in Alicyclobacillus, food contamination, Food Hygiene, Food Inspections, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Poisoning, Food Safety, Food Safety Alert, Research

Research – Biofilm‐forming ability of Alicyclobacillus spp. isolates from orange juice concentrate processing plant

Posted on March 31, 2018 by | Leave a comment

Wiley Online

Abstract

The objective of this study was to evaluate the biofilm‐forming ability of Alicyclobacillus spp. isolates. Biofilm formation was evaluated under a stainless steel surface using orange juice as a culture medium at different temperatures (28 and 45  °C, 30 and 45  °C, and 45 and 60  °C) and contact times (24, 72, and 120 hr). The degree of hydrophobicity and the survival time of the different isolates on the abiotic surface were also investigated. Five Alicyclobacillus spp. isolates from the orange juice industry and a reference strain of Alicyclobacillus acidoterrestris 0244T were used. The biofilm formation of Alicyclobacillus was observed from 24 hr of contact in at least one temperature tested, as a function of the different incubation times and temperatures. Alicyclobacillus spp. presented variations in the degree of hydrophobicity. Surprisingly, two biofilm‐forming isolates (CCT 7230 and CCT 7346) were hydrophilic, with hydrophobicity index <20%, therefore, they are not necessarily related to cell hydrophobicity and adherence of Alicyclobacillus to the stainless steel surface. This study demonstrated that Alicycclobacillus spp. isolates from the industry can survive the processing conditions and form biofilms on contact surfaces.

Practical applications

Alicyclobacillus spp. may be present in the orange juice industry and form biofilms. In addition, it is known that the equipment is exposed to a wide temperature range for different periods of time and that poorly sanitized stainless steel equipment and surface can provide substrates for the formation of biofilms by Alicyclobacillus spp. Therefore, it is of the most importance to understand how these factors influence the adhesion and formation of Alicyclobacillus spp. in the processing of orange juice.

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Posted in Alicyclobacillus, Research, Uncategorized