Effect of pH and Mexican Oregano (Lippia berlandieri Schauer) Essential Oil Added to Carboxymethyl Cellulose and Starch Edible Films on Listeria monocytogenes and Staphylococcus aureus

Table 1

Listeria monocytogenes and Staphylococcus aureus Fermi model biological parameters values at different concentrations of Mexican oregano (Lippia berlandieri Schauer) essential oil and pH values added to CMC and starch edible films.

Microorganism	Film	pH	% EO	(min)		Fit R^2adj
L. monocytogenes	CMC	5	0.00	—	—	—
		5	0.25	7.59 ± 1.94^a	0.23 ± 0.07^a	0.992
		5	0.50
		5	0.75
		5	1.00
		6	0.00	—	—	—
		6	0.25	46.65 ± 8.37^b	11.61 ± 2.09^b	0.995
		6	0.50
		6	0.75
		6	1.00
		7	0.00	—	—	—
		7	0.25	—	—	—
		7	0.50	188.18 ± 9.58^c	58.09 ± 5.52^d	0.886
		7	0.75	70.42 ± 9.25^d	17.83 ± 4.23^b	0.992
		7	1.00
	Starch	5	0.00	—	—	—
		5	0.25	56.27 ± 7.28^b	21.56 ± 4.76^c	0.894
		5	0.50	7.59 ± 1.94^a	0.23 ± 0.07^a	0.992
		5	0.75
		5	1.00
		6	0.00	—	—	—
		6	0.25	—	—	—
		6	0.50	243.33 ± 12.45^e	74.32 ± 8.65^a	0.917
		6	0.75	38.48 ± 5.78^b	10.93 ± 2.78^b	0.979
		6	1.00
		7	0.00	—	—	—
		7	0.25	—	—	—
		7	0.50	—	—	—
		7	0.75	57.41 ± 7.34^b	45.38 + 9.78^d	0.833
		7	1.00
S. aureus	CMC	5	0.00	—	—	—
		5	0.25	9.24 ± 2.01^a	1.29 ± 0.01^a	0.909
		5	0.50
		5	0.75
		5	1.00
		6	0.00	—	—	—
		6	0.25	68.62 ± 8.41^b	16.30 ± 4.05^b	0.996
		6	0.50
		6	0.75
		6	1.00
		7	0.00	—	—	—
		7	0.25	—	—	—
		7	0.50	—	—	—
		7	0.75	78.60 ± 9.14^b	15.11 ± 3.48^b	0.982
		7	1.00
	Starch	5	0.00	—	—	—
		5	0.25	—	—	—
		5	0.50	—	—	—
		5	0.75	95.31 ± 11.41^c	56.72 ± 7.81^c	0.851
		5	1.00	9.24 ± 2.01^a	1.29 ± 0.01^a	0.909
		6	0.00	—	—	—
		6	0.25	—	—	—
		6	0.50	—	—	—
		6	0.75	163.52 ± 19.67^d	71.16 ± 7.87^d	0.902
		6	1.00	50.05 ± 8.45^b	25.82 ± 6.39^b	0.964
		7	0.00	—	—	—
		7	0.25	—	—	—
		7	0.50	—	—	—
		7	0.75	173.59 ± 14.33^d	64.75 ± 7.25^c,d	0.853
		7	1.00	72.86 ± 9.14^b	19.41 ± 4.81^b	0.982

⁺ is the time needed to reduce 50% of microbial population; is the slope of the curve around . —, Growth. Inhibition. Means followed by a different superscript letter within a column for each concentration are significantly different ().