ABSTRACT
Essential oils (EOs) extracted by hydrodistillation from leaf parts of Algerian Eucalyptus globulus, Myrtus communis and Satureja hortensis were analyzed by gas chromatography/mass spectrometry (GC/MS). The main components of EOs obtained were γ-terpinene (94.48%), 1,8-cineole (46.98%) and carvacrol (46.10%), respectively, for E. globulus, M. communis and S. hortensis. The in vitro antimicrobial activity of the EOs was evaluated against Staphylococcus aureus CECT 4459 and Escherichia coli O157:H7 CECT 4267 using the agar diffusion technique. Results revealed that E. globulus and S. hortensis EOs had more antibacterial effects than that from M. communis. Minimal inhibitory concentrations (MIC) showed a range of 0.05-0.22% (volume by volume [v/v]). Sensitivity of gram-positive S. aureus was much higher than that of gram-negative E. coli. Plant EOs were added to minced beef (two-fold MIC value) at 0.10-0.44%, experimentally inoculated with the same pathogens at a level of 5 × 10(5) colony forming units (cfu)/g and stored at 5 ± 2 °C. Results showed that the EOs of E. globulus and S. hortensis had remarkable antibacterial properties, higher than that of M. communis, against S. aureus and E. coli. Indeed, a reduction of 5.8 log cfu/g (70.74% of reduction) was recorded after 7 days of storage for S. hortensis against E. coli. However, regarding S. aureus, both S. hortensis and E. globulus caused a highly significant (p < 0.05) decrease of microbial counts, most evident after 5 days of storage; S. aureus numbers were 3.50 and 2.50 cfu/g, respectively, corresponding to a reduction of 2.20 and 3.20 log cfu/g (38.60 and 56.14% of reduction) after 1 week of storage. Sensory evaluation revealed that the aroma of minced beef meat treated with EOs was acceptable by panelists at the levels used.
Subject(s)
Escherichia coli O157/drug effects , Eucalyptus/chemistry , Meat/microbiology , Myrtus/chemistry , Oils, Volatile/pharmacology , Satureja/chemistry , Staphylococcus aureus/drug effects , Algeria , Animals , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Cattle , Cyclohexane Monoterpenes , Cyclohexanols/analysis , Cyclohexanols/pharmacology , Cymenes , Eucalyptol , Food Handling , Food Preservatives/chemistry , Food Preservatives/pharmacology , Humans , Hydrogen-Ion Concentration , Meat/analysis , Medicine, African Traditional , Microbial Sensitivity Tests , Monoterpenes/analysis , Monoterpenes/pharmacology , Odorants , Oils, Volatile/chemistry , Plant Leaves/chemistryABSTRACT
This research was aimed at evaluating the inhibition of oxidative changes of beef patties packaged in modified atmosphere (70% O(2)+20% CO(2)+10% N(2)) by natural antioxidants: ascorbic acid (500 ppm), taurine (50 mM), carnosine (50 mM), rosemary powder (1000 ppm) and their combinations with the first. Beef patties stored at 2±1°C for 20 days were evaluated for colour (L*, a*, b*, C* and H*), TBARS, metmyoglobin formation (% of total myoglobin), psychrotrophic microbial counts and sensory odour and discolouration. Rosemary, either alone or with ascorbic acid, was highly effective in inhibiting both metmyoglobin formation and lipid oxidation; sensory analysis was in agreement with these results. Ascorbic acid, ascorbic acid+taurine and ascorbic acid+carnosine treatments showed a limited inhibitory effect of myoglobin oxidation, while carnosine and carnosine+ascorbic acid were effective in inhibiting lipid oxidation. Taurine alone failed to exert any antioxidant effect. Principal components analysis confirmed these results.
ABSTRACT
The use of atmospheres with low concentrations of CO (0.1 to 1%), in combination with O(2) (24%), high CO(2) (50%) and N(2) (25 to 25.9%), for preserving chilled beef steaks was investigated. The atmosphere used as reference contained 70% O(2)+20% CO(2)+10% N(2). Bacterial counts showed that all atmospheres containing CO greatly reduced total aerobic population numbers, including Brochothrix thermosphacta. Lactic acid bacteria, however, were not affected. CO concentrations of 0.5-0.75% were able to extend shelf life by 5-10 days at 1±1°C, as demonstrated by delayed metmyoglobin formation (less than 40% of total myoglobin after 29 days of storage), stabilisation of red colour (no change of CIE a* and hue angle after 23 days), maintenance of fresh meat odour (no variation of sensory score after 24 days) and significant (P<0.01) slowing of oxidative reactions (TBARS).
