# Marination as a Hurdle to Microbial Pathogens and Spoilers in Poultry Meat Products: A Brief Review
## 1 Introduction
### Food Loss and Spoilage Bacteria  
Despite the increasing breakthroughs in food science over the years, meat spoilage remains a global problem due to the complexity of factors involving physical, chemical, and biological events which lead to meat deterioration [15; 16]. Due to its high-water activity, low acidity, high nutritive content ideal for microbial growth, presence of autolytic enzymes, and high amounts of fat and lipids benefiting oxidation and spoilage, meat presents itself as a highly perishable food that quickly spoils [17]. The slaughter process will promote oxidative lipid and protein deterioration, also inducing enzymatic autolytic spoilage. As a consequence of these oxidative biochemical reactions, the produced free radicals will develop the off-flavour in the product. Additionally, meat-handling processes such as cutting and mincing induce spoilage reactions [18]. Microorganisms present in meat microbiota will also play a crucial part in meat spoilage, especially those with proteolytic activity since after depleting glucose and exhausting lactate, bacteria will have to catabolise amino acids. In bacterial terms, the initial meat microbiome is filled with spoilage organisms such as _Acinetobacter_, lactic acid bacteria (LAB), Gram-positive spore formers (_Clostridium_), Gram-positive bacilli (_Broclothrix_), _Enterobacteriaceae_ (e.g., _Escherichia_), Gram-negative bacilli (_Pseudomonas_), Gram-positive cocci (e.g., _Enterococcus_, _Staphylococcus_, and _Streptococcus_) [19]. _Pseudomonas_ spp. is known for its chief role in meat spoilage under aerobic conditions, often accounting for the vast majority of the spoilage microbiome, by out-competing other bacteria [20; 21]. If the meat is stored at refrigeration temperatures, then, _Broclothrix thermosphata_ will reign supreme. This facultative anaer, a close relative to the psychrotrophicListeria monocytogenes, will quickly outgrow its competitors while breaking down the meat in order to produce various metabolites associated with off-odours [22]. After exhausting all the available carbon sources, _Pseudomonas_ spp. will catabolise amino acids, leading to a foul and putrid odour. The metabolic activities of _Pseudomonas fluorescence_ and _Pseudomonas aeruginosa_ also lead to characteristic meat discolouration patterns, such as the yellow-greenish colour provided by pyoverdine, a siderophore employed as an iron chelator [23], or even the blueish colour given by two particular pigment genes associated with the tryptophan pathway of certain _P. fluorescence_ strains [24]. Nonetheless, the early predominance and rapid growth of _Pseudomonas_ species lead to oxygen depletion, allowing facultative anaerobes to thrive (e.g., _Acinetobacter_ and _Enterobacteriaceae_). In oxygen-deprived environments, such as the ones provided by vacuum-packaged products, LAB, _Enterobacteriaceae_ family members, and _Clostridium_ species are the major contributors to meat degradation. Lactic acid bacteria lead to the formation of slime and a reduction in the pH value due to lactic acid production [25]. Together with _Clostridium_ spp., LAB produce gases leading to the \"blown packaging\" effect [26]. Additionally, the hydrogen sulphide produced by some members of the _Enterobacteriaceae_ family leads to the sulfuric odours experienced during meat spoilage [15]. The spoilage of meat leads to significant economic hindrances. In Europe, it is estimated that annually, nearly 24% of all meat products end up wasted across the food chain, with the prime stages responsible for this waste being distribution and retail (9%) and the consumer itself (11%) [27]. In the US, 41 k tonnes of meat products were spoiled at the retail level, while 330 k tonnes were lost in the hands of the consumer throughout 2019 [28]. To this extent, reducing food spoilage would align with the second and twelfth sustainable development goals set by the United Nations, which aim at reducing hunger and achieving responsible production and consumption while ensuring food security worldwide [29].