Investigation on the Microbial Diversity of Fresh-Cut Lettuce during Processing and Storage Using High Throughput Sequencing and Their Relationship with Quality

Abstract

Microbial community distribution in vegetables can affect their quality. This study analyzed the distribution of the microbial community at various stages during processing and storage with the microbial diversity analysis, and evaluated the correlation between the dominant bacteria and sensory quality of lettuce using correspondence analysis with multiple regression analysis. Results showed that the process of washing, cutting, then disinfection and dewatering could change the community distribution and dominant bacteria in lettuce, and maintain better texture, morphology, aroma, color qualities of lettuce. The total number of colonies and relative abundance of Xanthomonas in fresh-cut lettuce decreased, while Afipia and Ralstonia increased during processing and pre-storage (storage for 6 h, 12 h and 1 d). After storage for 3 d, the total number of colonies in lettuce increased (more than 5 log CFU/g), especially the relative abundance of Pseudomonas, which led to the obvious deterioration of the sensory quality of lettuce. Throughout the process, the number of Bacillus cereus, Staphylococcus aureus, and E. coli was less than 100 CFU/g and 3 MPN/g. The number of typical pathogenic bacteria, Salmonella, Listeria monocytogenes and E. coli O157:H7, was below the detection limit. Overall, the prevention and control of psychrotrophic Pseudomonas in lettuce was still necessary. These results will provide useful information for the fresh-cut lettuce industry.

Microbial communities and metabolite profiles during the fermentation of Chinese Dongbei suancai with Chinese baijiu as supplementary material

“…It is worth noting that more bacterial genera were detected as biomarkers on the second day of fermentation. Some bacterial genera, such as Pseudomonas , Azospirillun , Acinetobacter , and so on, were the main bacteria present in fresh‐cut vegetables 22 . This indicated that, although the abundances of the bacteria introduced by the environment were low, these bacterial genera had significant effects on the flora diversity in the early stage of fermentation.…”

“…Some bacterial genera, such as Pseudomonas, Azospirillun, Acinetobacter, and so on, were the main bacteria present in fresh-cut vegetables. 22 This indicated that, although the abundances of the bacteria introduced by the environment were low, these bacterial genera had significant effects on the flora diversity in the early stage of fermentation. Lactococcus and Weissella were the biomarkers in the middle stage of fermentation, whereas Lactobacillus was the major biomarker in the later stage of fermentation.…”

Identification and Characterization of Antibiotic-Resistant, Gram-Negative Bacteria Isolated from Korean Fresh Produce and Agricultural Environment

“…At the genus level, Pseudomonas (30.2%) was the most prevalent genus, followed by Acinetobacter (14.4%), Pantoea (13.4%), and Enterobacter (9.4%). A previous study showed that Pseudomonas was the predominant Gram-negative bacteria present in the processing of endive lettuce and the low-temperature storage of fresh-cut lettuce [ 2 ]. In another study that investigated lettuce samples in Korea using culture-independent 16S rRNA gene amplicon metagenome analysis, Gram-positive Bacillus and Exiguobacterium , and Gram-negative Pseudomonas were the dominant genera observed in lettuce [ 5 ].…”

“…Fresh produce and fruits are known to harbor naturally occurring microorganisms with high diversity belonging to a great variety of microbial lineages [ 1 , 2 ]. Their consumption has increased over the last years and they are mostly eaten raw, which increases the risk of exposure to human pathogens such as Salmonella , Listeria monocytogenes , and Shiga-toxin-producing Escherichia ( E. ) coli , and/or opportunistic pathogens such as Klebsiella , Enterobacter , and Citrobacter [ 3 , 4 , 5 , 6 ].…”

Effects of Various Flavors of Baijiu on the Microbial Communities, Metabolic Pathways, and Flavor Structures of Dongbei Suancai

“…The diversity of bacteria in Suancai was different due to environmental factors and fermentation mode. The predominant bacterial genera found in fresh-cut vegetables were Pseudomonas, Acinetobacter and others [14], and their relative abundance gradually decreased during fermentation. Besides, Leuconostoc (as heterofermentative LAB) was active in the early fermentation stage.…”