Effect of Sous Vide Heat Treatment and Packaging Methods on the Microbiological Quality of Red Peppers (Capsicum annuum L.)

This study aimed to evaluate the effect of sous vide heat treatment and different packaging methods on the microbiological quality of red peppers (Capsicum annuum L.) during their refrigerated storage. Peppers of the Roberta variety were used in the study. The heat treatment of the peppers was carried out under vacuum conditions for all the packaging methods. ATM (unaltered gas atmosphere) and MAP (modified atmosphere packaging) products were repackaged under aseptic conditions into a suitable gaseous atmosphere after heat treatment and cooling into an unaltered atmosphere (ATM), and into a modified atmosphere (MAP: 30% CO2, 70% N2). The sous vide thermal treatment was performed in three variations: 30 min/60 °C, 15 min/70 °C, and 8 min/80 °C. The peppers were stored at 3 ± 1 °C until the bacterial count first exceeded 4 log CFU/g, but no longer than 24 days. The pH, TVC, Enterobacteriaceae count, and microscopic filamentous fungi count were determined in the products. A qualitative analysis of microbial isolates was also carried out using MALDI-TOF mass spectrometry. Sous vide heat treatment reduced the number of TVC (total viable count) (<2 to 2.35 log CFU/g), Enterobacteriaceae (<2 log CFU/g), and the number of microscopic filamentous fungi (<2 log CFU/g) compared with control (TVC 3.54–3.86 log CFU/g). The use of heat treatment combined with the packaging of culinary products effectively extends the shelf life of sous vide peppers, from 3 to 6 days for raw peppers to 15–24 days for sous vide peppers depending on the heat treatment and packaging method. All the packaging methods allowed the product to remain microbiologically safe (TVC below 4 log CFU/g) for 24 days for 30 min/60 °C and 15 min/70 °C treatments, and VAC packaging for 8 min/80 °C treatments. Bacterial identification by MALDI-TOF MS revealed that the predominant families were Pseudomonadaceae, Yersiniaceae, and Staphylococcaceae. Depending on the method of sous vide thermal treatment, it showed differences in the percentage of bacterial families in the culinary products. The proportions in the proportion of Gram+ and Gram- bacteria also changed. The use of sous vide processing in combination with appropriate packaging methods can significantly extend the shelf life of products obtained from peppers.