## 6 Challenges in Using LAB and Their Metabolites as a Clean Label Approach  
Although antimicrobial compounds produced by LAB are promising alternatives to replace chemical preservatives used in the food industry, there are some challenges in their use as clean label ingredients. The efficacy of this biopsyervation approach is intricately associated with LAB viability and activity. Diverse aspects, including pH, temperature, and environment, can influence LAB performance. Additionally, incorporating LAB into food products can influence flavor profiles. For example, over-acidification due to high concentrations of organic acids may be considered a defect in food products for individuals [17]. Another limitation is that the antimicrobial activity of bacterioxins can be prejudiced when coming into contact with lipids and proteins, since they are sensitive to lipolytic and proteolytic enzymes [105,106]. Thus, new systems such as nanotechnology emerge to help address these challenges. Using nanoencapsulation becomes an innovative alternative for bacterioxins to enhance their stability when applied to food and contribute to the controlled release of organic acids [106].  
The extraction and purification processes for bacterioxins and other LAB antimicrobial metabolites can drive up production costs. Using bacteriocin-producing bacteria can overcome challenges associated with the cost and sensitivity of purified bacterioxins to proteolytic enzymes. Applying this strategy will also contribute to continuously producing the antimicrobial compound in the food matrix [107]. Fermented products derived from bacteriocin production is another strategy for dairy preservation, without the need to initiate a new fermentation process in the dairy product itself. However, this approach presents challenges related to preservation potential, as fluctuations in the concentration and activity of bacterioxins in these fermented products may occur [17].  
Only a few bacterioxins (nisin, pediocin, and micocin(r)) are approved by the Food and Drug Administration for food preservation [108]. Nevertheless, many other bacterioxins are currently being developed for use in food [81]. Another concern about using bacterioxins as food preservatives is the possible development of resistance by pathogens to bacterioxins. It represents a threat to food preservation and safety, specifically in products fermented by LAB. However, it is necessary to research and understand pathogens' resistance mechanisms towards these antimicrobial molecules and identify innovative strategies to counteract this issue [61].  
The challenges related to using EPS from LAB as a clean label preservative for the food industry include the low yields obtained and the variability between the different bacterial strains that produce it, making it difficult to achieve a consistent production of the antimicrobial compound [17]. Furthermore, understanding the relationship between the structure and function of EPS in foods has posed a challenge [18].  
Therefore, the main challenges are related to the efficiency and costs of natural preservatives compared to synthetic preservatives. Achieving the same shelf life at a low cost and keeping food products safe and attractive is crucial to developing clean label products. Thus, it is necessary to determine the appropriate concentration for the incorporation of antimicrobial compounds from LAB so that they are effective and do not compromise food products' nutritional and technological characteristics.