# Microbial Growth Dynamics in Minced Meat Enriched with Plant Powders
## 4 Discussion
[8] found that rhubarb petioles in raw meat samples and tomato, rhubarb petioles, and their combination in cooked meat samples had microbial growth inhibitory effects comparable to the effects of NaCl+NaNO\({}_{2}\). However, in the present study, the combination of Apple+BCber was effective only when it was supplemented with 1% onion. The combination of Apple+Tom was effective when 1% rhubarb petioles or 1% garlic was added to the meat samples. Onion and garlic are often used in recipes for meat products. Many studies have found that various plant extracts (for example garlic _Allium sativum_ L.), which are rich in sulphur compounds and phenolic substances have good antimicrobial properties against different microorganisms including pathogens [11; 12]. Onion is one of the oldest cultivated plants with nutritious, antioxidant, and antimicrobial properties. The strong antibacterial activity of onion (_Allium cpa_ L.) extracts against _Staphylococcus aureus_ was found in the in vitro study of [PERSON] [20]. Another study [21] found that onion had an inhibitory effect on bacterial growth, but this varied depending on the type of onion, its extraction concentration, and the bacteria tested. The results of the present study indicate that plant powders processed under hygienic conditions have initially very low microbial counts, and, therefore, can be used for the enrichment of meat or other food products without irradiation. However, microbiological analyses of plant materials are necessary before their use in other foods because the high microbiological quality of plant powders cannot be assumed. The results of this study demonstrate that rhubarb petioles and selected blends of berries and fruits have an inhibitory effect on microbial growth in meat samples. A similar finding was made by [PERSON] et al. [22], who demonstrated that beef patties containing berry pomace extracts had lower bacterial counts than the control. Additionally, it was found that the black chokeberry was the most promising preservative among the pomace extracts of other berries for samples under refrigerated conditions [22]. In the current study, very low total microbial counts were found in the cooked samples compared to the raw samples. Such a result was expected because effective heat treatment should destroy most of the initial content of microbes in meat products. The number of microorganisms was expected to grow slowly under refrigerated storage of cooked meat samples in screw-cap jars that were sterile prior to use. Many studies [23; 24; 25] on _L. monocytogenes_ have highlighted the need to change RTE food recipes to ensure food microbial safety including the inhibition of the growth of _L. monocytogenes_. Regulation (EC) No 2073/2005 on microbiological criteria for foodstuffs lays down the rules according to which the Food Business Operator (FBO) must comply and specifies microbiological criteria for _L. monocytogenes_ in RTE foods. Applying the numeric _L. monocytogenes_ criterion to RTE food products, food business operators need to demonstrate, to the satisfaction of the competent authority, that the product will not exceed the limit of 100 cfu/g throughout its shelf-life [2]. According to the technical guidance document of the European Union Reference Laboratory for _L. monocytogenes_, the growth potential below the criterion 0.5 log\({}_{10}\) cfu/g determines whether the RTE food is able to support the growth of _L. monocytogenes_ or not [18]. In the current study, all samples supported _L. monocytogenes_ growth. The highest growth potential of _L. monocytogenes_ was in the meat samples with onion (\(\delta\) = 7.92 log cfu/g) followed by garlic and meat samples without additives, and the lowest growth potential (\(\delta\) = 2.74 log cfu/g) was in the samples enriched with 2% rhubarb petioles. This is in good agreement with the results of our previous studies, where rhubarb has been found to be one of the most effective plant materials against the growth of microorganisms.