Industrial Waste Whey as a Low-Cost, Efficient, and Environmentally Safe Disinfectant, with Potential Applications for Minimally Processed Foodstuff

Being a fast and reliable way to access healthy products, fresh-cut fruit and vegetables are becoming a rapidly rising sector of the horticultural industry with a concomitant high consumer demand. Fresh-cut processing usually involves sanitizing steps, with chlorine washing being the general choice. Due to the health harming effects of chlorine, there has been an increasing demand for alternative disinfecting agents. Under this context, fermented cheese whey has shown potential as a natural sanitizing agent but has been poorly tested in fresh-cut produce. Furthermore, it also continues to pose an environmental problem because it still contains a high organic load.

Here we aimed at developing a low-cost, scalable fermentation protocol to produce a disinfectant from dairy waste that has very little organic content and high levels of lactic acid. Fermentation was achieved with industrial whey from ewe, goat, and cow´s milk, using a specific mesophilic-lactic acid bacteria starter mix over a more prolonged fermentation of 120 h, which yielded the highest lactic acid production and the lowest lactose content. Antibacterial activity was observed against Listeria monocytogenes, Salmonella enterica, and Escherichia coli O157:H7, plus a total of thirteen other food pathogenic and spoilage strains, and antibacterial activities were determined to be highest after 120 h.

We further validated this whey’s application as a disinfectant in shredded lettuce and compared its efficacy to that of chlorine, evaluating microbial quality, texture, color, and sensory perception, pH, and O2 and CO2 determinations. Results showed that not only was microbial quality better when using our whey solution (p < 0.05), but also the quality indicators for whey were statistically similar to those treated with chlorine. Hence, our work validates the use of an industrial waste whey as a low-cost, efficient, and environmentally safe disinfectant, with potential applications for minimally processed foodstuffs as an alternative to chlorine.