Effects of Treatment, Alone or in Combination, with Bacteriocin AS-48 and High Hydrostatic Pressure on the Microbial Load and Bacterial Diversity in a Vegetable Cream Subjected or Not to Temperature Abuse

A commercial refrigerated vegetable cream containing pumpkin and carrots as main ingredients was stored under refrigeration for 30 days without treatment (controls), supplemented with bacteriocin AS-48, treated by high hydrostatic pressure (HHP, 600 MPa, 8 min, 55ºC) or a combination of bacteriocin and HHP. At day 2, half of the samples were incubated for 24 h at room temperature (simulating a temperature abuse event) and then refrigerated again. Total viable counts and bacterial diversity were determined. Bacteriocin did reduce viable counts, but HHP treatment (singly or in combination with bacteriocin) was the most effective. Viable counts increased in controls during temperature abuse, but not in samples treated with bacteriocin, HHP or both. The initial microbiota of control samples was composed mainly by Pseudomonadota (74.50%), followed by Bacillota (21.19%) and Actinobacteriota (3.69%). Bacillota became the predominant group during refrigerated storage (87.21 to 99.48%). After simulation of a 24-h temperature abuse event, control samples had lower relative abundances of Bacillota during storage and higher relative abundances of Pseudomonadota, Bacteroidota and Actinobacteriota. All treated samples (irrespective of the type of treat-ment) showed a lower relative abundance of Bacillota during storage compared to untreated controls without temperature abuse. Genus Bacillus was the predominant group in the control samples during storage and, although in lower abundance, it was also detected in samples treated with high pressure, bacteriocin or their combination. Acinetobacter was associated with temperature abuse.