# Bacterial Diversity and Dominant Spoilage Microorganisms in Fresh-Cut Broccoli
## 4 Discussion  
The cutting types had great impacts on the amounts of microorganisms in broccoli but had little impact on the species of microorganisms. The amounts of microorganisms gradually increased and conformed to the S-shaped curve of microbial growth. During storage, the total number of colonies of broccoli treated with different cutting types had the same trend, but the average count of bacteria in broccoli subjected to different cutting types showed a significant difference. The processed fruits and vegetables were more perishable than the raw products from which they were prepared. Cutting of fruits and vegetables might cause mechanical damage, outflow of nutrients, and provide favorable living conditions for microorganisms to grow and multiply. In addition, it increased the chance of contamination of fruits and vegetables and resulted in the microbial spoilage of fruits through the transfer of microflora on the outer surfaces to the interior tissue, where microorganisms had access to nutrient-laden juice. On the other hand, fresh-cut fruits and vegetables lost the barrier and protection of the epidermis, and the surface exposed to the air increased, resulting in the disorder of the original physiological function and the destruction of the self-protection system, so that the resistance of the body decreased, resulting in more microorganisms invading the internal tissues of fruits and vegetables from the wound. The larger the specific surface area formed by cutting treatment, the more serious the microbial infection was, and the worse the storage of fresh-cut products. The resistance of fresh-cut fruits and vegetables to microbial infection in the environment gradually decreased. However, even in the early storage, the amounts of microorganisms can also be large. There were three main ways fresh-cut fruits and vegetables were shown to be infected by microorganisms before and during storage. Firstly, fresh-cut fruits and vegetables were easily infected by microorganisms living in manure, fertilizer, soil and irrigation water sources during planting or harvest. The microorganisms contained were usually bacteria, molds, yeasts, and actinomycetes [30]. Secondly, in the process of cutting, the main pollution sources of fresh-cut fruits and vegetables were usually from cutting equipment or the environment [31]. Moreover, the cross contamination of microbial communities between fruits and vegetables could accelerate their decay and deterioration. Thirdly, fresh-cut fruits and vegetables were easily infected by microorganisms during storage. The resistance of harvested fruits and vegetables to microbial infection in the environment gradually decreased, and the number of microorganisms on the surface of fruits and vegetables increased. From this study, the phylogenetic relationships of the 97 bacterial isolates were determined in comparison to type strains with the neighbor-joining method. Among them, _Pseudomonas_ spp. were the most predominant and might have the greatest impact on food quality. The physiological properties of _Pseudomonas_ spp. were adapted to the environment of vegetables. At the end of storage, the relative abundance of other flora decreased gradually. The main reason was that the growth of dominant bacteria was too fast, which inhibited the growth of other microorganisms. _Pseudomonas_ spp. are aerobic,Gram-negative bacteria, and are widely distributed in nature. Different from enzymatic browning of vegetables, _Pseudomonas_ spp. mainly cause the tissue of fresh-cut vegetables to become rotten and proved to result in a rapid browning reaction on the surface of fresh-cut vegetables [32]. _Pseudomonas_ spp. can utilize organic compounds, oxidize glucose and maltose to produce acid, resulting in the decline of food quality. In addition, _Pseudomonas_ spp. can also produce catalase and oxidase, and hydrolyze or lipolyze frozen food, so as to make it corrupt.