High pressure processing during drying of fermented sausages can enhance safety and reduce time required to produce a dry fermented product

Abstract

Dry fermented sausages (DFS) rely on a combination of ingredients, fermentation, and drying for pathogen control. However, this might not always provide the mandated 5-log Escherichia coli O157:H7 reduction. High-pressure processing (HPP) has been successfully used to inactivate pathogens in ready-to-eat (RTE) foods, however, different food ingredients and physicochemical properties of foods protect pathogens against high-pressure (HP) inactivation. The present study examined the effectiveness of using HPP during the drying of fermented sausages to achieve the highest inactivation of E. coli O157:H7 and its recovery during storage at 4 °C. Sausages containing a five-strain cocktail of E. coli O157:H7 at 107 CFU/g were manufactured and subjected to HPP at 600 MPa for 3 min after fermentation and at different times during drying. Changes in inoculated E. coli O157:H7 and added starter culture bacteria counts and physicochemical properties of the sausages at differing time points in drying subjected to HPP were compared to their respective controls. A 1.6-log CFU/g inactivation of E. coli O157:H7 was observed in sausages that had a aw and MPr of 0.95 and 2.22, respectively, following fermentation and maturation and prior to drying (day 5). However, pressure treatment of these sausages enhanced E. coli O157:H7 inactivation by 4.8-log CFU/g, resulting in an overall 6.4-log inactivation. After 7 days of drying, when the aw and MPr of the sausages fell to 0.85 and 1.35, respectively, E. coli O157:H7 inactivation due to HPP was only 2.2 logs. E. coli O157:H7 inactivation due to HPP was further reduced as the sausages continued to dry. High-pressure treatment did not significantly affect the starter culture bacterial population. Examination of HP treated sausages stored at 4 °C revealed that E. coli O157:H7 could be recovered a week into storage, but the numbers were not significantly (P = 0.0742) different from those in sausages right after HP treatment. E. coli O157:H7 was not recovered from any pressure-treated sausage thereafter in weeks 2, 3, and 4 of storage at 4 °C. These results suggest that HPP could be successfully used in conjunction with fermentation and drying to reduce the time required to achieve a 5-log E. coli O157:H7 inactivation and is most effective when HP treatments are applied prior to the fermented sausages reaching a aw of ≤0.90 or MPr in the range of 1.9–2.3.