# Bacterial Diversity and Dominant Spoilage Microorganisms in Fresh-Cut Broccoli
## 1 Introduction  
Broccoli is a health-promoting vegetable known for its rich content of bioactive components, such as vitamins, antioxidant substances, and anticarcinogenic precursors. It is cultivated worldwide due to high consumer popularity [1]. Studies show that glucosionolates have recently attracted great research interest because of their potential health benefits in cardiovascular diseases such as hypertension, atherosclerosis and cholesterol reduction [2, 3]. Fresh-cut vegetables refer to those processed by washing, sorting, peeling, and slicing, and the most popular ones among them are cruciferous vegetables such as broccoli, cauliflower and cabbage [4]. Fresh-cut fruits and vegetables, which originated in the United States in the 1950s, have received much attention due to their nutrition, convenience and flavor [5]. While fresh-cut vegetables are rich in essential nutrients, they are susceptible to external biological, chemical, and physical processes, which may create a variety of safety issues. During the process of fresh-cut produce, cutting is an essential procedure that unavoidably produces wounding stress, which may cause fresh-cut broccoli to be infected by microorganisms [6]. Moreover, the mechanical damage caused by primary processing, such as peeling, cutting, and slicing, leads to the release of intracellular products in broken cells and tissues, enhancing the risk of bacterial contamination compared with vegetables without processing. Although fresh-cut fruits and vegetables will be contaminated by a variety of microorganisms during the process of picking and transportation, it is noteasy to determine the quality of vegetables solely on the total bacterial count at the end of storage, because not all bacteria are capable of proliferating on vegetables behaving as spoilage bacteria.  
In addition to enzymolysis of nutrients, spoilage of fruits and vegetables can be caused by the activity of a wide variety of microorganisms. Thus, a great number of studies have focused on identifying the bacteria responsible for vegetable spoilage. Most of the microorganisms causing fruits and vegetables to spoil are aerobic bacteria or molds, while a few are anaerobic microorganisms [7]. Multiple bacteria have been identified as spoilage microorganisms in fruits and vegetables, including _Pseudomonas_[8], _Bacillus_[9], and _Erwinia_[10]. Because vegetables are easily infected by bacteria in soil, the number of microbial colonies is high even in the primary stage and the common ones belonged to _Pseudomonas_ and _Bacillus_, as reported in [11]. The total number of colonies in some vegetables can even reach up to a high level, which may be caused by mechanical damage and environmental pollution in the process of picking and processing [12].  
To investigate the microorganisms in the process of broccoli becoming putrid, the culture-dependent method, relying on separation and identification methods, is considered to be a wide and conventional isolation technique, which lays a solid foundation for the study of microorganisms in foods. In addition, culture-independent molecular techniques can also be used to fully estimate microbial communities [13; 14; 15; 16].  
The objective of this study was to evaluate the effect of cutting types and storage on bacterial diversity of fresh-cut broccoli with culture-dependent methods and to conduct the spoilage potential analyses of dominant spoilage microorganisms. Many studies have investigated the contamination processes of specific bacteria, but the overall microbial diversity of rotten vegetables is still unclear. In order to keep vegetables fresh and prolong their shelf life, it is important to determine which kinds of microorganisms will actually deteriorate vegetables. The findings could provide information to food scientists and food industries in controlling microbial contamination and extending the shelf life of foods.