Nutrition & Food Science

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    Regulation Mechanism of ssDNA Aptamer in Nanozymes and Application of Nanozyme-Based Aptasensors in Food Safety
    (MDPI, 2022-02-14) Wang, Lijun; Zhou, Hong; Hu, Haixia; Wang, Qin; Chen, Xianggui
    Food safety issues are a worldwide concern. Pathogens, toxins, pesticides, veterinary drugs, heavy metals, and illegal additives are frequently reported to contaminate food and pose a serious threat to human health. Conventional detection methods have difficulties fulfilling the requirements for food development in a modern society. Therefore, novel rapid detection methods are urgently needed for on-site and rapid screening of massive food samples. Due to the extraordinary properties of nanozymes and aptamers, biosensors composed of both of them provide considerable advantages in analytical performances, including sensitivity, specificity, repeatability, and accuracy. They are considered a promising complementary detection method on top of conventional ones for the rapid and accurate detection of food contaminants. In recent years, we have witnessed a flourishing of analytical strategies based on aptamers and nanozymes for the detection of food contaminants, especially novel detection models based on the regulation by single-stranded DNA (ssDNA) of nanozyme activity. However, the applications of nanozyme-based aptasensors in food safety are seldom reviewed. Thus, this paper aims to provide a comprehensive review on nanozyme-based aptasensors in food safety, which are arranged according to the different interaction modes of ssDNA and nanozymes: aptasensors based on nanozyme activity either inhibited or enhanced by ssDNA, nanozymes as signal tags, and other methods. Before introducing the nanozyme-based aptasensors, the regulation by ssDNA of nanozyme activity via diverse factors is discussed systematically for precisely tailoring nanozyme activity in biosensors. Furthermore, current challenges are emphasized, and future perspectives are discussed.
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    MICROBIOLOGICAL ASSESSMENT OF ORGANIC PRODUCE PRE- AND POST- HARVEST ON MARYLAND FARMS AND IMPACT OF GROWING AND HANDLING METHODS ON EPIPHYTIC BACTERIA
    (2014) XU, Aixia; Buchanan, Robert L; Micallef, Shirley A; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Although the consumption of organic produce has dramatically increased in recent years and many outbreaks continue to occur, the microbiological safety of organic produce has not been fully assessed. This study generated microbiological data to evaluate organic produce safety and also assessed the impact of growing methods (ground cover effects) and handling methods (washing practices) in organic lettuce systems. The study evaluated microbiological safety of pre- and post-harvest fresh produce samples from small organic farms in Maryland, the effect of mulching on survival of indicator bacteria and the impact of post-harvest washing method on microbiological safety and epiphytic bacterial communities. Results indicate that (1) washed post-harvest produce had higher risks than unwashed and pre-harvest organic produce as measured by indicator bacteria E. coli, total coliforms, APC, yeast and mold; (2) different mulches affected the microbial levels differently; (3) different washing methods altered the bacterial communities both immediately and following 5 days of storage. This study presents data that could be used to assess food safety risks of organic produce associated with their cultivation and on-farm handling practices.
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    Isolation and characterization of antimicrobial resistant Staphylococcus aureus in retail ground meats
    (2010) Li, Yi; Meng, Jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Staphylococcus aureus is commonly present in humans and animals. It can cause a variety of suppurative infections, food intoxication and toxic shock syndrome. Antimicrobial resistant S. aureus, especially methicillin-resistant S. aureus (MRSA), have emerged and are a major public health concern. There is an increasing risk of food production animals serving as a reservoir and transmitting S. aureus and MRSA in community environments. Due to the increased food safety risk posed by MRSA in addition to its multidrug resistance, we were interested in determining the prevalence of S. aureus and MRSA in retail meat and investing the multidrug resistance of the S. aureus isolates. A survey study was conducted, involving 480 retail ground meat samples (231 ground pork and 249 ground beef) collected in the Washington DC area from March 2009 to March 2010. Approximately 42.08% (n = 202) of the samples were identified as S. aureus positive and one MRSA isolate was recovered from a ground beef sample. Antimicrobial resistance testing showed 53.34% of recovered S. aureus isolates exhibited different levels of antimicrobial resistance to CLI, CHL, GEN, LEVO, CIP, SYN and TGC. The MRSA isolate was resistant to 8 of 22 antimicrobials tested. PFGE fingerprinting identified the MRSA isolate as USA300 subtype, which also carried genes of virulence factors PVL and protein A. Our findings indicated that antimicrobial resistant S. aureus strains were common in retail ground beef and port, and that MRSA could also be present in such products that could potentially serve as a reservoir.
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    Detection of norovirus and indicator organisms on fresh produce
    (2005-12-06) Williams, Karen Elizabeth; Meng, Jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Food borne illness is a major problem around the world. Recently, more food borne outbreaks involve produce as the vehicle and viruses as the source of contamination. Norovirus is a common food borne viral pathogen. Genetic diversity among the viruses has made detection difficult. Due to the difficulties in detection, the norovirus is an ideal candidate for having an indicator organism. FRNA bacteriophages share several similarities with enteric viruses and would be an ideal candidate. In this study, we evaluated reverse transcriptase polymerase chain reaction (RT-PCR) detection of norovirus and evaluated using FRNA bacteriophages, E. coli, and Enterococcus as indicator organisms for the virus on produce. Of the five RT-PCR methods tested, only two worked with both controls. Of the 180 produce samples tested, 37.2% were positive for FRNA bacteriophage, 17.2% were positive for Enterococcus, and 0% were positive for E. coli. We conclude that RT-PCR is not an efficient method for screening norovirus on produce and including FRNA bacteriophages as indicator organisms for viruses may help decrease outbreaks.