The late blowing defect of hard cheeses: Behaviour of cells and spores of Clostridium tyrobutyricum throughout the cheese manufacturing and ripening

Abstract

21The late blowing defect still represents a problem for hard cheeses. Thus, the behaviour of the 22 cheese spoiling bacterium C. tyrobutyricum was studied throughout the cheesemaking and ripening and then were no longer cultivable. However, 2 x 10 2 spores appeared at the end of this stage, likely 28 triggered by the exponential growth phase, and were present until 6-month ripening. In cheese, C. 29tyrobutyricum UC7086 proved to convert free arginine to citrulline and then to ornithine, and to 30 produce γ-aminobutyric acid by glutamate transamination rather than by decarboxylation.

A fluorescence in situ staining method for investigating spores and vegetative cells of Clostridia by confocal laser scanning microscopy and structured illuminated microscopy

“…5d). Similar behaviour was observed for C. tyrobutyricum during the vat processing of hard cheese, where the curd cooking step involves heating conditions close to those tested in the simple experimental system used here (D'Incecco et al, 2018). In the prior study, electron microscopy was adopted in order to achieve higher resolution and to detect initial signs of either cell sporulation or spore germination.…”

“…Due to their small size, Clostridium spores are often observed by conventional electron microscopy, either in scanning or transmission mode, that has a high resolution (D'Incecco et al, 2015(D'Incecco et al, , 2018Bassi et al, 2009;El Jaam et al, 2017;Trunet et al, 2017). A disadvantage of this technique is that it requires specific skills, since sample preparation procedures for specimen fixation have to be used This approach, however, involves dead vegetative cells and spores thus no in vivo studies can be performed.…”

Antimicrobial activity of resveratrol-derived monomers and dimers against foodborne pathogens

“…Cell suspensions of L. monocytogenes Scott A (3 × 10 9 cells/mL) in PBS (0.1 M, pH 7.2, control) or exposed to DMSO (control), chlorhexidine (10 or 100 µg/mL) and Lux105 (10 or 100 µg/mL) were investigated at the ultrastructural level by TEM 46 . After 30 min incubation at 37 °C, cell suspensions were centrifuged at 10,000 × g for 10 min, and the pellets were fixed at 4 °C for 2 h with a solution containing 2% glutaraldehyde and 2% paraformaldehyde in 0.1 M sodium cacodylate solution buffered at pH 7.2 (Agar Scientific, Stansted, UK).…”

Microfiltration and ultra-high-pressure homogenization for extending the shelf-storage stability of UHT milk

“…Ultrastructure of the milk samples submitted to different homogenization treatments, HOM-1 and HOM-2, as well as the control raw milk, was investigated adopting the conditions described by D'Incecco, Pellegrino, Hogenboom, Cocconcelli, & Bassi, (2018). Briefly, a 0.5 mL aliquot of sample was mixed with 2 mL of low-temperature gelling agarose (2% w/v in water, melted at 35-40°C) (VWR, Milan, Italy).…”