Food Safety Doctoral Work

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    Synthesis and Antioxidant, Anticancer, and Antimicrobial Activities of Palmityl Ester Derivative of Carnosic Acid
    (North Dakota State University, 2013) Prasad, Asharani
    Carnosic acid (CA) along with carnosol (CAR) is the strongest phenolic diterpene antioxidants (PDAs) present in rosemary plant. However, CA has low antioxidant activity in emulsion-type food system due to its polar nature. The identification and characterization of the anticancer and antimicrobial properties of natural products and their semisynthetic derivative such as that of CA and CAR have received significant interest over the years. The goals of this research were to synthesize lipophilic palmityl derivative (PE) of CA and study its antioxidant activity in bulk and emulsified corn oil. Anticancer properties against CCRF-CEM, K-562 and P388D1 leukemia cell lines and antimicrobial activity against Staphylococcus auerus (S. auerus), Bacillus cereus (B. cereus), Salmonella enterica, and Escherichia coli (E. coli) O157:H7 bacteria were also tested. A four steps synthetic route was designed. In the first step CAR was converted into a benzyloxy protected benzyl ester of CA (yield 78%). Reduction of the benzyl ester to a primary alcohol (yield 63%) followed by esterification with palmitoyl chloride gave the palmityl ester derivative (yield 97%). Finally, double bond reduction followed by deprotection of benzyloxy group gave PE (yield 99%). Overall yield for the route was 47%. The modification of CA affected functionality. PE had improved antioxidant activity in emulsified corn oil compared to bulk corn oil than the CA. However, CA was more effective in bulk oil. Compounds with hydroxyl groups were found to have cytotoxicity against three cell lines CCRF-CEM, P388D1 and K-562. Among compounds tested, CAR was found to be the most potent anticancer agent against all three cell lines. The study also indicated structure dependent activities for the compounds that had hydroxy group at the C-20 position. CA and CAR had antimicrobial activity against S. auerus, B. cereus, Salmonella, and E. coli O157:H7. S. auerus, B. cereus were more sensitive to CA and CAR than Salmonella, and E. coli O157:H7. Other compounds, without hydroxyl groups, did not have antimicrobial activity. Study also indicated that antimicrobial activity varied depending on functional group present at C-20 position. Compound PE did improve antioxidant activity in emulsion but did not improve antimicrobial activity.
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    Ochratoxin A and Ochratoxigenic Fungi in Freshly Harvested and Stored Barley and Wheat
    (North Dakota State University, 2014) Kuruc, Julie
    Ochratoxin A (OTA) is a toxin produced both prior to harvest and during storage by Penicillium and Aspergillus species in a variety of commodities. Although several studies have been conducted in Europe and Canada examining the occurrence and concentration of OTA in cereal grains, data is lacking for the United States, where guidance levels and regulations do not exist. This study aims to fill in the knowledge gaps surrounding OTA and ochratoxigenic fungi in barley and durum and hard red spring wheat grown in the northwestern and Upper Great Plains regions of the United States. In total 2.7% (n = 37) of the 1370 samples taken over 2 consecutive years had detectable levels of OTA (0.15-9.11 ng/g) directly after harvest. The number of positive samples was significantly greater in 2012 compared to 2011. This difference may be due to weather conditions during the planting and growing seasons or simply natural variation between years. Stored barley and wheat (N = 262) had a higher prevalence (12.2%) and greater range (0.16-185.24 ng/g) of OTA compard to freshly harvested samples. Although 81.3% of the OTA-positive samples had been stored for ≥6 months, samples that had been stored for as short as 1 month also tested positive. These results underline the importance of proper storage conditions in minimizing OTA contamination. P. verrucosum was found to be the primary ochratoxigenic species in these samples. Of the 110 isolates tested, 64.7% were confirmed OTA producers. Samples containing >1 ng/g OTA had significantly more OTA-producing P. verrucosum strains than samples with undetectable OTA. Infestation rate did not correlate with OTA level. Additionally, OTA concentration did not correlate with otanpsPN, an OTA biosynthesis gene. This indicates that the concentration of P. verrucosum in a sample may increase the likelihood of contamination but is not a reliable indicator of OTA level.
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    Total Glucosinolate Preservation and Near Infrared Prediction in Rapeseed Meal
    (North Dakota State University, 2015) Kittelson, Jayd Marshal
    Glucosinolates (GLS) and their hydrolysis products are of great food and feed safety concern because they are responsible for both the beneficial and harmful properties of GLS-containing plants. Understanding GLS storage stability and total GLS concentration in Brassica oil meals is important to ensuring livestock health. The storage stability of GLS and potential of near infrared spectroscopy (NIRS) for screening the total GLS content of various Brassica meals obtained globally and over multiple growing seasons was evaluated. Decreases were observed in meal stored at 4 oC. GLS storage stability within stored Brassica meals was possible for 18 months and possibly longer providing the seed meals are protected from exposure to moisture conditions that promote endogenous myrosinase hydrolysis. NIRS spectra data from 400 to 2500 nm were recorded on various Brassica meal samples (186) at 2 nm intervals. A global calibration using the Brassica database was developed for both ground and unground meal samples with a modified partial least squares regression analysis of conventional laboratory analysis. The optimum NIR calibrations utilized the first derivative and standard normal variate data preprocessing. The ground NIRS calibration for total GLS resulted in a coefficient of determination (R2) and standard error of the calibration (SEC) and relative predictive determinant (RPD) of 0.96, 6.05, and 6.32, respectively, while the unground NIR calibration had a R2, SEC, and RPD of 0.93, 7.65, and 5.88, respectively. Finally, a sample set (20) with known GLS concentration (by HPLC) was split and one subset was analyzed via NIR “as is” and the other subset was analyzed by NIR after drying for 16 hours at 60 oC in a vacuum oven. The dried Brassica meal sample set had a slightly better residual (HPLC - NIR) standard deviation (4.57) and average residual (-0.74), compared to the “as is” moisture sample set standard deviation (5.00) and average residual (-1.26). The use of NIRS as a routine analytical method for total GLS in Brassica meals destined for animal feeds has great potential. In addition, the low cost of the NIR analysis may be attractive for manufacturers of Brassica meals.
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    Detection and Molecular Typing of Methicillin-Susceptible Staphylococcus Aureus (MSSA) and Methicillin-Resistant Staphylococcus Aureus (MRSA)
    (North Dakota State University, 2015) Velasco, Valeria
    Methicillin-resistant (MRSA) and multidrug-resistant (MDR) Staphylococcus aureus, and the serotype (ST) 398 have been associated with human and livestock infections, being also detected in retail meat. The aim of this study was to determine the prevalence and molecular types of S. aureus strains from animals, retail raw meat, deli meat, and humans, determining the genetic similarity between the strains. A two-step selective enrichment followed by selective plating were used to isolate S. aureus from animals (n=167), retail raw meat (n=145), and deli meat (n=46). In addition, S. aureus from healthy people (n=550) was isolated by culture method. Positive isolates and MRSA isolates from clinical cases (n=108) were subjected to multiplex PCR (16S rRNA, mecA, and PVL genes), molecular typing and antimicrobial susceptibility testing. In addition, a real-time PCR assay was developed in order to decrease the time of detection of target genes of S. aureus in animal and meat samples, comparing the results with the standard culture/PCR method. The prevalence of S. aureus was 34.7% in animals, 47.6% in meat, and 13.0% in deli meat. The mecA gene was detected in S. aureus isolated from five pork meat samples and exhibited penicillin resistance. The ST398 was found in sheep, pigs, and pork meat. The S. aureus nasal carriage in healthy people was 7.6%. A total of 105 MRSA strains (97.2%) from clinical cases harbored the mecA gene and 11 (10.2%) the PVL gene. The rate of MDR was 70% in humans. A genetic similarity between strains from animals and meat, and from humans and meat was observed. Total agreement between the culture/PCR method and real-time PCR for detection of S. aureus was 68.9 to 97.8% (k=0.68-0.88), and the mecA gene, 86.7 to 98.7% (k=0-0.49). Therefore, the real-time PCR assay may be recommended as a rapid method for the detection of S. aureus, with confirmation of MRSA using the standard culture method. The presence of emerging S. aureus strains in the meat production chain and the genetic similarity between strains of different origin, suggests the contamination of meat, and a potential risk of transmission to humans.
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    Survey of Claviceps purpurea and Fusarium Toxins in Spring Wheat and Fungicide Efficacy on Ergot Sclerotia, Alkaloid Content, and Saprophytic Fusarium Associated Toxins
    (North Dakota State University, 2022) Alaoufi, Shatha Hamad
    Fusarium head blight (FHB) and ergot of the claviceps purpurea (Fr.) Tul. have adverse effects on grain quality and human and animal health. Each year, Hard Red Spring (HRS) wheat samples are collected at harvest to survey the end use quality. HRS-wheat survey samples (n= 207) were obtained from four growing states (ND, SD, MN, and MT) during 2019 and 2020. Grading and non-grading factors and the presence of Deoxynivalenol (DON) and ergot alkaloids (EAs) were determined, naturally occurring mycotoxins produced by Fusarium species and C. purpurea, respectively. Chromatography-Mass Spectrometry (GC-MS) was utilized for DON content and Reveal Q+Max test for total EAs. The mean DON contents during the 2019 and 2020 growing seasons were 1.5 ppm and 0.6 ppm, respectively. The mean for total EAs contents in 2019 and 2020 were 81.5 ppb and 180.5 ppb, respectively. Both toxins showed location had significant (P≤0.05) effect on variations within one individual year. Deoxynivalenol and EAs shared positive and significant correlations with total defects (0.257, P<0.001) and (0.162, P<0.05), respectively. In the field experiment, four fungicides (Sphaerex, Miravis Ace, Quilt, and Priaxor) were applied on a confidential HRS wheat cytoplasmic male sterile (CMS-HRS wheat) line. After separating the ergot sclerotia samples from other contents, they were evaluated for naturally occurring saprophytic Fusarium toxins and EAs. The mean value for DON content in Miravis Ace (0.07 ppm) sample was significantly (P≤0.05) less than the mean value for the non-treated control and Priaxor samples (0.24 and 0.21ppm, respectively). Ergot body weight was significantly (P≤0.05) higher for the non-treated control compared to other treatments. Among fungicides, ergot body weight was significantly lower in Miravis Ace samples (39.57 g) compared to Quilt (55.83 g), Priaxor (55.04 g), and Sphaerex (54.82 g) treated samples. Total EAs in Priaxor (244,840 ppb) samples was significantly (P≤0.05) less than the mean values found in Sphaerex and Quilt samples (359,485 ppb and 352,375 ppb, respectively). Priaxor could be a potential fungicide to control ergot body weight and total EAs production. Future studies are needed to test more fungicides’ effectiveness to reduce ergot body and total EAs production.