*3.3. Five Days-Fermented Whey Presents Dose-Dependent Antibacterial Activities and Is E*ff*ective Against Several Bacterial Species*

Based on the results in Figure 1 and Table 1, whey fermented for 120 h was selected to further analyze antibacterial activities towards thirteen pathogenic and spoilage strains, and results are presented in Figure 2. Results show that growth inhibition was induced in all strains, either being Gram-negative or Gram-positive species, corroborating a broad range of antibacterial activity. Subsequently, 120 h whey samples were evaluated against *L. monocytogenes* and assessed at three different dilutions (Table 2) and compared to milk and non-fermented whey. Results show there was a dose-dependent effect in 120 h fermented whey, whereas neither milk nor unfermented whey exhibited an antibacterial effect (*p* < 0.05) (Table 2).


**Figure 2.** Inhibition halos of different bacteria exposed to 120 h fermented whey. Chlorine was used as a positive control. Results are the average of three replicates ± standard deviation. Note: NI = No inhibition observed.

**Table 2.** Halos of inhibition of *L. monocytogenes* growth exposed to 120 h fermented whey, milk, or non-fermented whey diluted in water.


Note: \*\* Corresponding lactic acid concentrations (g·L<sup>−</sup>1): <sup>+</sup> 4.59; \* 9.19; # 18.38, respectively.

*3.4. Industrial Whey Is an E*ff*ective Disinfecting Agent When Applied to Lettuce, with Better or Similar Results When Compared Chlorine*

Because we aimed to test our 120 h fermented whey in a more realistic manner, we set out to determine its efficacy as a lettuce disinfectant, testing quality indices such as texture and color, including its evaluation by a sensory panel, and also assessing its microbiological quality.
