## 4 Biocontrol Methods
### Postbiotics  
Thus, the use of postbiotics, i.e., metabolites of LAB, has been proposed as an alternative. Postbiotics are compounds produced by probiotic bacteria, such as peptides, vitamins, and fatty acids, with health benefits, including anti-inflammatory, antioxidant, antihypertensive, and anti-obesity effects [109]. Encapsulation of postbiotics in films increased their solubility in water and the opacity of the films without altering their mechanical properties. The incorporation of postbiotics or bacteriocin-rich extract demonstrated significant antibacterial activity [110]. [PERSON] et al. (2018) [111] used cellulose paper with chitosan-ZnO nanocomposite and nisin (500-1000 ug/mL), obtaining a strong inhibition of _L. monocytogenes_. After 14 days of storage at 4 \({}^{\circ}\)C, nisin films completely inactivated _L. monocytogenes_ on the surface of white cheese [112]. Hurdle technology is used to achieve cumulative antimicrobial effects in foods, improving food safety by reducing the intensity of treatments and preserving product quality [113]. LAB easily adapt to various processing and storage conditions, such as refrigeration, low pH, and salting, which makes them useful in this technology. Their ability to produce antimicrobial substances allows them to be an important element in food safety [88]. Bacteriocins are ribosomally produced peptides by LAB, resistant to heat and acids, with antimicrobial activity against pathogenic bacteria in food products by creating pores in the cell membrane and inhibiting DNA replication and protein synthesis [114]. Bacteriocins are effective antimicrobial compounds capable of inhibiting pathogenic bacteria, such as _L. monocytogenes_, through various mechanisms, such as changing the permeability of the cell membrane, inhibiting cell wall synthesis, and interfering with metabolic processes [61]. Depending on the gene sequence and amino acid composition, bacteriocins are classified into four classes: class I (lantibiotics) below 5 kDa, heat stable, with lanthionine; class II (unmodified peptides) below 10 kDa, heat stable, without lanthionine; class III (large and thermolabile peptides) proteins above 30 kDa, heat sensitive; and class IV (cyclic peptides), bacteriolysins [24]. A notable example of a heat-stable bacteriocin is nisin, a lantibiotic produced by _L. lactis_, approved for use as a food additive (E234), generally recognized as safe for human consumption (GRAS) by the World Health Organization and the FDA, and used in over 50 countries. It acts by interfering with bacterial cell wall biosynthesis, being effective against pathogens such as _L. monocytogenes_ and _Staphylococcus aureus_, and is used in various food products such as processed cheeses [115]. Nisin forms pores in the membrane of pathogenic cells, thereby blocking cell wall synthesis and inhibiting bacterial growth. However, the use of nisin, a natural antibacterial agent, is limited in dairy products with neutral pH, such as whole milk or fresh cheese. The effectiveness of nisin decreases in environments with pH above 6, and in queso fresco, nisin did not effectively inhibit the growth of _L. monocytogenes_[116]. Also, the presence of divalent cations such as calcium and magnesium and the fat composition of dairy products influence the activity of nisin, reducing its potency, especially in the case of homogenized milk. This phenomenon is explained by the absorption of nisin by the homogenized fat globules, which decreases the antibacterial efficiency. Under these conditions, more studies are needed to determine the impact of factors such as pH, fat content, and divalent cations on the activity of nisin in other dairy products [9]. An important aspect of the application of probiotics and bacteriocins in the food industry is the protection of these compounds from harsh processing conditions [117]. For example, nisin is widely used in various food products such as meat, dairy, and aquatic products due to its antibacterial efficacy against Gram-positive bacteria, including _L. monocytogenes_.