Table 1. Clear zone sizes (mm; mean±SD) formed by antimicrobial hydrogels (1×1 cm) absorbed 0.1% grapefruit seed extract (GSE) or 0.1% citrus extract (CE) for 30, 60, 120, and 240 min against Listeria monocytogenes.

Hydrogel	Control	0.1% GSE				0.1% CE
		30 min	60 min	120 min	240 min	30 min	60 min	120 min	240 min
1	0.0	2.14±0.7aA	2.40±0.5aA	2.57±0.5aA	-*	3.00±0.5aA	3.29±1.0aA	3.63±0.7aA	2.80±0.8aA
2	0.0	0.83±0.3cB	1.06±0.2bcB	1.19±0.3bB	1.94±0.6aA	0.82±0.3aB	0.91±0.3aB	0.98±0.3aB	0.96±0.1aB
3	0.0	0.23±0.1aC	0.23±0.1aC	0.23±0.1aC	0.16±0.1aB	0.11±0.1cC	0.28±0.2bC	0.45±0.1aC	0.43±0.1aC
4	0.0	0.2±0.2bC	0.35±0.2abC	0.42±0.3aC	0.23±0.1bB	0.09±0.0cC	0.53±0.2abBC	0.71±0.3aBC	0.44±0.3bC

^* Hydrogel was dissolved thoroughly.

^a–c Different letters in a same row indicate significant differences between means at p<0.05.

^A–C Different letters in a same column indicate significant differences between means at p<0.05.

Hydrogel 1, 5% alginate+1% chitosan+0.2% CaCl₂+40% glycerol; Hydrogel 2, 1% κ-carrageenan+1% chitosan; Hydrogel 3, 2% κ-carrageenan+1% CaCl₂; Hydrogel 4, 2% κ-carrageenan+3% CaCl₂.