Effect of sage extract on the survival of Staphylococcus aureus in Portuguese alheira sausage

Different methods for extraction of sage (Salvia officinalis) have been investigated by this research group. Hydroethanolic solid-liquid extracts presented the highest inhibitory capacity against pathogens. Alheira is a non-ready-to-eat sausage produced in Northern Portugal, which has in the past shown moderate prevalence of S. aureus. Thus, the aim of this study was to evaluate the antimicrobial effect of sage extract against S. aureus in alheira sausages exerted during the stage of maturation.

Lyophilised extract of sage aerial parts was obtained using ethanol 80% and distilled water as solvents, and kept at 15ºC for one week until use. Alheira batter was produced and added with 0.0%, 0.5%, 1.0% or 1.5% of sage (w/w), and stuffed in natural casings to reach an individual weight of ~85 g. They were then individually inoculated with a S. aureus ATCC 6538 culture to reach ~5 log CFU/g, while a non-inoculated control was kept. Sausages were hung in a chamber at 10 ºC/85% RH for 10 days. Water activity (aw), pH and S. aureus counts were determined every two days.

During maturation of inoculated and non-inoculated samples, aw in time followed an exponential decay model, dropping from 0.9913 to 0.9780, while pH dropped from 5.95 to 5.50. The inoculated S. aureus population decreased according to a downward concave Weibull model in 1.00, 1.12 and 1.23 log CFU/g, when alheira was formulated with 0.5, 1.0 and 1.5% sage extract, respectively. Oppositely, in the control treatment (0%), S. aureus counts did not change significantly (p>0.05) throughout maturation.

This work demonstrated that sage extract has a beneficial effect in controlling S. aureus in alheira. Individual phenolic compounds quantified for this extract also support this result, which is very relevant to artisanal producers since this frequently-found pathogen is mostly introduced to the batter through inadequate manipulation when mixing and stuffing.