Antimicrobial activity of Citrus spp. and Anethum graveolens components against Candida metapsilosis in ranch sauce.

In this paper, a study was carried out to test the inhibitory effect of a natural food compound (NFC), based on flavonoids (naringenin, hesperetin, tangeritin, luteolin, apigenin and kaempferol) from citrus and dill, in ranch sauce. A strain of C. metapsilosis, isolated from a spoiled sample of ranch sauce, was used as target pathogen microorganism. The inhibitory effect of NFC was compared with a common mixture of chemical preservatives used in this type of sauces: potassium sorbate and sodium benzoate (S/B). An in vitro test was performed by the microtiter plate assay at 10, 25 and 37 °C for 24 h in modified Tryptic Soy Broth. An additive antimicrobial effect had been observed in the combination of acetic acid and NFC. The results of the microtiter assay were validated in a challenge test in ranch sauce at 5, 25 and 37 °C for 10 weeks. NFC showed partial fungicidal effect against C. metapsilosis, reducing two logarithmic units at 5 °C for 10 weeks. At 5 °C, the traditional doses of S/B used in ranch sauce decreased viable cells to non-detectable counts from the second week of the experiment. At 25 and 37 °C, the use of S/B mixture or the use of NFC showed the same fungicidal effect. The incorporation of NFC, alone or in combination with acetic acid, opens the possibility of formulating clean label sauces with good protection against the development of the acid resistant yeast C. metapsilosis.

Inactivation of Alicyclobacillus acidoterrestris spores by high pressure CO2 in apple cream.

Alicyclobacillus acidoterrestris (A. acidoterrestris) is a bacillus-type spore former that causes significant alterations in fruit products. It is highly resistant to typical pasteurization regimes; thus, this work explored the use of high-pressure CO2 (HPCD) for its deactivation in apple cream. The assays were conducted in a high-pressure apparatus where the cream was placed in an agitated vessel and the CO2 passed over under different operating conditions for distinct periods of time. The HPCD was able to deactivate the A. acidoterrestris spores in the apple cream by four orders of magnitude at 30 °C and 10 MPa. On the other hand, the lethal effect of HPCD was independent of the thermal effect since the application of dry heat without CO2 at the same temperature did not cause any A. acidoterrestris deactivation. The important variables in terms of improving the method were the flow regime and the way to put in contact the HPCD and the cream. Finally, the HPCD treatment did not affect the most important sensorial and rheological properties of the cream; although there was a slight reduction in the vitamin C content due to thermal degradation.

Antimicrobial activity of clove and cinnamon essential oils against Listeria monocytogenes in pasteurized milk.

The antimicrobial activity of essential oils (EOs) of cinnamon bark, cinnamon leaf, and clove against Listeria monocytogenes Scott A were studied in semiskimmed milk incubated at 7 degrees C for 14 days and at 35 degrees C for 24 h. The MIC was 500 ppm for cinnamon bark EO and 3,000 ppm for the cinnamon leaf and clove EOs. These effective concentrations increased to 1,000 ppm for cinnamon bark EO, 3,500 ppm for clove EO, and 4,000 ppm for cinnamon leaf EO when the semiskimmed milk was incubated at 35 degrees C for 24 h. Partial inhibitory concentrations and partial bactericidal concentrations were obtained for all the assayed EOs. The MBC was 3,000 ppm for the cinnamon bark EO, 10,500 ppm for clove EO, and 11,000 ppm for cinnamon leaf EO. The incubation temperature did not affect the MBC of the EOs but slightly increased the MIC at 35 degrees C. The increased activity at the lower temperature could be attributed to the increased membrane fluidity and to the membrane-perturbing action of EOs. The influence of the fat content of milk on the antimicrobial activity of EOs was tested in whole and skimmed milk. In milk samples with higher fat content, the antimicrobial activity of the EOs was reduced. These results indicate the possibility of using these three EOs in milk beverages as natural antimicrobials, especially because milk beverages flavored with cinnamon and clove are consumed worldwide and have been increasing in popularity in recent years.