Antimicrobial activity of eugenol and carvacrol against Salmonella enterica and E. coli O157:H7 in falafel paste at different storage temperatures.

The objectives of the current study were: i) to investigate the antimicrobial activity of 0.125, 0.250 and 0.50 % (7.54, 15.08 and 30.17 mmol/Kg of eugenol) and (8.15, 16.31, and 33.61 mmol/Kg of carvacrol) against S. enterica and E. coli O157:H7 in falafel paste (FP) stored at 4, 10 or 25 °C for 10 d; and ii) to study the sensory properties of fried falafel treated with eugenol and carvacrol. S. enterica grew well in untreated falafel (control) samples at 10 and 25 °C, while E. coli O157:H7 grew only at 25 °C. However, numbers of S. enterica and E. coli O157:H7 in FP stored at 4 °C were reduced by 1.4-1.6 log CFU/g after 10 d. The antimicrobial agents were more effective at 25 °C against S. enterica, but were better at 4 and 10 °C against E. coli O157:H7. Addition of 0.125-0.5 % eugenol or carvacrol reduced the S. enterica numbers to undetectable level by direct plating (2 log CFU/g) by 2-10 d at 25 °C. FP samples treated with 0.5 % eugenol or 0.25-0.5 % carvacrol were negative for S. enterica cells by enrichment (1 CFU/5 g) by 10 d at 25 °C. In contrast, viable E. coli O157:H7 were not detected by direct plating when FP was treated with 0.25-0.5 % carvacrol or 0.5 % eugenol and stored at 4 °C by 2 d. Addition of eugenol or carvacrol did not affect the color, texture, and appearance of fried falafel but decreased the flavor and overall acceptability scores compared to untreated falafel. Using eugenol and carvacrol as natural antimicrobials have the potential to enhance the safety of FP by reducing the threat from foodborne pathogens.

Survival and growth behavior of common foodborne pathogens in falafel paste under different storage temperatures.

Falafel is a popular breakfast food in the Middle East that has been recently involved in several outbreaks of foodborne illnesses. The aim of the study was to explore the growth behavior of Salmonella enterica, Escherichia coli O157:H7, Shigella sonnie, Shigella flexneri, Listeria monocytogenes and Staphylococcus aureus in falafel paste (FP) under different storage temperatures (4, 10, or 24 °C) for 14 days. FP (pH = 6.2, aw = 0.96) was inoculated with 5.0 to 6.0 log CFU/g of each of the pathogens separately. Salmonella spp. significantly declined by 1.5 log at 4 °C but grew significantly by ca. 2 and 4 log at 10 and 24 °C, respectively after 14 days. E. coli O157:H7 significantly increased (4.5 log) in FP when stored under 24 °C and survived at a level of ~105 CFU/g at 10 °C. Comparatively, Sh. sonnie and Sh. flexneri showed a better survival pattern in FP stored under 4 °C and grew (˃ 3 log) after 5 days at 10 and 24 °C. L. monocytogenes was capable of growing by 1.9 and 4.3 log after 14 d days and by 3.9 log after 3 days at 4, 10, or 24 °C, respectively. No significant decline in S. aureus counts at 4 and 10 °C occurred, however, it increased significantly to ˃ 7 log CFU/g at 24 °C. Total mesophilic count and yeast and mold count reached to spoilage levels (˃107 CFU/g) in un-inoculated FP after 1 and 3 days of storage at 24 and 10 °C, respectively. FP could support the growth of common foodborne pathogens and hence it is recommended to utilize natural antimicrobials in FP and keep the product under refrigeration (4 °C) to preclude the growth of vegetative foodborne pathogens.

Evaluation of food quality and safety parameters and food safety knowledge and practices of food handlers at fast foods restaurants at universities in Jordan during COVID-19.

The quality and the safety of the foods that are served at fast foods restaurants and their effect on the consumer health could become a matter of concern during COVID-19. Therefore, the objectives of this study were i) to evaluate the quality and safety of raw foods, suitability and availability of manufacturing places, physical facilities, drinking water and waste management system, and processing conditions, and ii) to assess the knowledge, attitudes, practices regarding food safety and hygienic practices among food handlers at fast foods restaurants in the different universities in Jordan during COVID-19. The study was conducted in 12 fast foods restaurants of 3 different universities in Jordan which are located in different places in Jordan. A desirable practice was given a score of one while no score will be allotted for an undesirable practice through using a standard questionnaire for all the food establishments. This was used to compare with the maximum score obtainable for that relevant operation and the percentage scores was calculated for each operation. Analysis of Variance (ANOVA) of the data was performed to study the significant differences at P ≤ 0.05 in all the evaluated properties among the food establishments in the different universities. The results showed that low percentage scores were obtained with 68%, 75%, 32% and 56% for the production area, waste management, product evaluation (chemical, microbial) and food safety program application, respectively. Also, it was found that there were insignificant differences at P ≤ 0.05 among different food serving establishments in different universities in all the safety properties. This means that all the food establishments in all the universities suffer from the same problems with the same degree. As a conclusion, more work should be done to produce safe food in the different food establishments that were studied in the different universities.

The Role of Communication and Commitment in COVID-19 Knowledge, Attitudes, and Behaviors Among University Students in Jordan: Interaction and Analysis.

INTRODUCTION: Several fields, such as public health, economy, and science, have been adversely affected by the COVID-19 pandemic. The objectives of the present study were to investigate knowledge, attitudes, communication, commitment, and behavioral practices of Jordan university students; and using structural equation modelling (SEM) to investigate the relationship among COVID-19 knowledge, attitude, communication, commitment and behavioral practices of students. METHODS: In this cross-sectional study, the primary data were collected from 1,095 students comprising 298 males (27.21%) and 797 females (72.79%) from three major universities in Jordan using an online-based questionnaire. RESULTS: It was found that scores of knowledge, attitudes, communication, commitment, and behavioral practices of students about COVID-19 were 81.4, 79.3, 70.0, 72.6, and 67.4%, respectively. The results also showed that significant association the variables of knowledge and attitudes as well as the commitment and communication are partial mediators in this relationship. Further, a clear positive relationship was observed between the communication, commitment, and behavioral practices of students. CONCLUSIONS: This study confirms the importance of communication and commitment to generate proactive behavioral practices.

Survival of Salmonella enterica and Listeria monocytogenes in date palm paste and syrup at different storage temperatures.

This study aimed to investigate the behavior of Salmonella enterica and Listeria monocytogenes in processed date paste and syrup at different temperatures. Commercial products were inoculated with approximately 6 log CFU/mL of S. enterica or L. monocytogenes and stored at 4, 10, and 24°C for 90 days. S. enterica was able to survive in date products until the end of storage at 4°C. At this temperature, numbers decreased by 2.1 log CFU/g in date paste and by 3.4 log CFU/g in date syrup; however, at 10°C, cells were reduced >4.2 log CFU/g and were undetectable by direct plating in date paste or by enrichment (complete elimination) in syrup. Further, at 24°C, complete elimination of S. enterica was achieved in date paste and syrup by 30 and 7 days, respectively. L. monocytogenes numbers decreased by 1.4, 4.4, and >4.6 log CFU/g in date paste stored at 4, 10, and 24°C for 90 days, respectively. In date syrup, numbers of L. monocytogenes decreased to undetectable levels by 50, 14, and 4 days at 4, 10, and 24°C, respectively, by direct plating and complete elimination was observed at 10 and 24°C by 50 and 30 days of storage, respectively. The initial pH values of date paste and syrup were 4.7 and 4.8, respectively, and remained stable until the end of storage except for L. monocytogenes-inoculated syrup. PRACTICAL APPLICATION: Salmonella enterica and Listeria monocytogenes can easily survive in date paste and syrup particularly at refrigerator temperature, which explains the necessity of preventing the contamination of date products with foodborne pathogens.

Immunomodulatory Properties of Human Breast Milk: MicroRNA Contents and Potential Epigenetic Effects.

Infants who are exclusively breastfed in the first six months of age receive adequate nutrients, achieving optimal immune protection and growth. In addition to the known nutritional components of human breast milk (HBM), i.e., water, carbohydrates, fats and proteins, it is also a rich source of microRNAs, which impact epigenetic mechanisms. This comprehensive work presents an up-to-date overview of the immunomodulatory constituents of HBM, highlighting its content of circulating microRNAs. The epigenetic effects of HBM are discussed, especially those regulated by miRNAs. HBM contains more than 1400 microRNAs. The majority of these microRNAs originate from the lactating gland and are based on the remodeling of cells in the gland during breastfeeding. These miRNAs can affect epigenetic patterns by several mechanisms, including DNA methylation, histone modifications and RNA regulation, which could ultimately result in alterations in gene expressions. Therefore, the unique microRNA profile of HBM, including exosomal microRNAs, is implicated in the regulation of the genes responsible for a variety of immunological and physiological functions, such as FTO, INS, IGF1, NRF2, GLUT1 and FOXP3 genes. Hence, studying the HBM miRNA composition is important for improving the nutritional approaches for pregnancy and infant's early life and preventing diseases that could occur in the future. Interestingly, the composition of miRNAs in HBM is affected by multiple factors, including diet, environmental and genetic factors.

Novel Gluten-Free Cinnamon Rolls by Substituting Wheat Flour with Resistant Starch, Lupine and Flaxseed Flour.

Celiac disease (CD) is an immunological mediated disorder that occurs to genetically susceptible individuals who suffer from gluten consumption. Therefore, the most effective treatment of CD is a life-long gluten-free diet. This study aimed to produce a nutritious gluten-free cinnamon roll, where resistant starch and lupine flour were used instead of wheat flour, in addition to 10% flaxseed flour and a fixed amount of hydrocolloid (1% xanthan gum). Eight different gluten-free cinnamon roll treatments (T1-T8) were produced with different ratios of resistant starch and lupine flour according to the following percentages (85:5, 80:10, 75:15, 70:20, 65:25, 60:30, 55:35 and 50:40, respectively). The proximate analysis, physical properties, color measurements and sensory evaluation of all cinnamon roll treatments and flours were determined. It was found that lupine and flaxseed flours in all different treatments had significantly (p ≤ 0.05) higher levels of ash, protein, lipid and crude fiber compared to wheat flour treatment (control treatment). However, carbohydrate levels were significantly (p ≤ 0.05) higher in control treatment compared with treatments 3-8. Gluten-free cinnamon rolls had significantly (p ≤ 0.05) higher levels of unsaturated fatty acids (oleic acid, linoleic acid and linolenic acid) than control. Further, there were significant differences in lightness (L*), redness (a*) and yellowness (b*) color values between the gluten-free and control treatments. The control cinnamon roll significantly (p ≤ 0.05) had the highest level of lightness and the lowest level of redness. The sensory evaluation obtained by consumer evaluation indicated that control cinnamon rolls significantly (p ≤ 0.05) received the highest score in overall impression, overall flavor, hardness and aftertaste. However, treatment 5 significantly (p ≤ 0.05) received the highest score in all the sensory scores in comparison with other gluten-free treatments. It is possible to develop a quality gluten-free cinnamon roll with respect to nutritional value manifested in higher levels of protein, fibers, unsaturated acids and prebiotics with acceptable sensory attributes.

Use of citric acid and garlic extract to inhibit Salmonella enterica and Listeria monocytogenes in hummus.

Recently, the consumption of hummus has become popular in the United States, European countries, and Canada, and unfortunately, several foodborne outbreaks and recalls have been reported due to its contamination with Listeria monocytogenes and Salmonella enterica. The current study aimed to investigate the inhibitory activity of 0.5, 1.0, and 1.5% citric acid (CA) and 1.0, 2.0 and 3.0% garlic extract (GE) toward S. enterica and L. monocytogenes in hummus stored at 4, 10 and 24 °C. L. monocytogenes grew well in untreated (control) hummus samples at all tested temperatures, whereas S. enterica grew only at 10 and 24 °C. CA at 0.5 to 1.5% reduced L. monocytogenes numbers by 3.0-3.3 log CFU/g at 4 °C, 1.7-3.9 log CFU/g at 10 °C, and 0.9-1.4 log CFU/g at 24 °C. Numbers of S. enterica were reduced by 0.6-1.7, 4.1-4.9 and <1.5 log CFU/g, at 4, 10 and 24 °C, respectively, compared to the control during 10 d storage. GE at 1.0-3.0% also reduced numbers of L. monocytogenes at 10 d by 0.7-3.0, and 1.3-3.6 log CFU/g at 4 and 10 °C, respectively, and numbers of S. enterica by 0.7-1.2, 1.8-2.6 and 0.5-1.6 log CFU/g, at 4, 10 and 24 °C, respectively, compared to the control. Chromatographic analysis of GE revealed the presence of four organosulfur compounds including diallyl disulfide, diallyl trisulfide, 2-vinyl-(4H)-1,3-dithiin and 3-vinyl-(4H)-1,2-dithiin where the latter was the predominant compound with a level of 22.9 mg/g which significantly contributed to the inhibitory effect of GE. CA and GE are adequate natural antimicrobials in hummus to reduce L. monocytogenes and S. enterica numbers and enhance product safety.

Development and Characterization of Nutritious Gluten-Free Doughnuts with Lupin and Inulin Flours.

Celiac disease is an immune-mediated disease caused by ingestion of gluten-containing products. The main aim of this study was to develop novel gluten-free doughnuts with high nutritional value using inulin and lupin flour. Five different doughnuts were formulated. Lupin flour was used to replace the potato starch-corn flour composite at levels of 15, 30, 45, 60 and 75% in gluten-free doughnut formulations (AF), (BF), (CF), (DF) and (EF), respectively. Inulin was added to all blends at a level of 6%. Doughnuts made with 100% wheat flour (C1) and 100% corn flour-potato starch blend (C2) served as the controls. The results indicated that the moisture, ash, fat, protein and crude fibre contents of the doughnuts were increased significantly (p < 0.05) with increasing levels of lupin flour. The rheological properties showed that the dough development time increased significantly (p < 0.05) with increasing lupin flour in the formulation with higher water absorption. The consumer acceptability sensory results varied among the different treatments. However, the AF, CF, and EF doughnuts had the highest value for flavour, texture and crust colour, respectively. Different levels of lupin flour can be used in gluten-free doughnuts production to improve their quality and to enhance their nutritional value in the presence of inulin at a 6% level. These results may have significant implications for the development of novel, healthier food products for gluten-sensitive consumers.

Effect of gamma irradiation against microbial spoilage of hummus preserved under refrigerated storage.

The current study aimed to evaluate the preservation of hummus packed in laminated pouches to extend its shelf life for a period of 35 d using a combined treatment of gamma irradiation and refrigerated storage. The effects of different irradiation doses (0, 0.1, 1.5 and 2.5 kGy) and refrigeration (4 °C) against microbial spoilage were investigated. Microbial criteria of total mesophilic aerobic counts, lactic acid bacterial counts, and yeasts and molds decreased significantly (P ≤ 0.05) in a dose dependent manner. Furthermore, dose of 2.5 kGy decreased the lactic acid bacteria counts to undetectable levels for the first 10 d of storage. Although microbial load increased during 35 d of refrigerated storage, samples treated with doses of 1.5 and 2.5 kGy showed a good microbial quality that complies with microbial limits set by national and international authorities for ready to eat foods. Furthermore, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis and coliform bacteria were not detected in the irradiated samples as well as in the controls. It was observed that a dose ≥1.5 kGy combined with refrigerated storage at 4 °C could be used to extend the shelf life of hummus samples in laminated pouches up to 35 d.

Microbial safety of oily, low water activity food products: A review.

Oily, low water activity (OL aw) products including tahini (sesame seed paste), halva (tahini halva), peanut butter, and chocolate, have been recently linked to numerous foodborne illness outbreaks and recalls. This review discusses the ingredients used and processing of OL aw products with a view to provide greater understanding of the routes of their contamination with foodborne pathogens and factors influencing pathogen persistence in these foods. Adequate heat treatment during processing may eliminate bacterial pathogens from OL aw foods; however, post-processing contamination commonly occurs. Once these products are contaminated, their high fat and sugar content can enhance pathogen survival for long periods. The physiological basis and survival mechanisms used by pathogens in these products are comprehensively discussed here. Foodborne outbreaks and recalls linked to OL aw foods are summarized and it was observed that serotypes of Salmonella enterica were the predominant pathogens causing illnesses. Further, intervention strategies available to control foodborne pathogens such as thermal inactivation, use of natural antimicrobials, irradiation and hydrostatic pressure are assessed for their usefulness to achieve pathogen control and enhance the safety of OL aw foods. Sanitation, hygienic design of manufacturing facilities, good hygienic practices, and environmental monitoring of OL aw food industries were also discussed.

Factors affecting the viability of Staphylococcus aureus and production of enterotoxin during processing and storage of white-brined cheese.

Staphylococcus aureus is a major foodborne pathogen that causes severe disease in humans. It is commonly found in milk and dairy products, particularly in fresh brined cheese. Our aim was to investigate the behavior of Staph. aureus and enterotoxin production during the storage of white-brined cheese prepared with or without a starter culture and stored in a 10 or 15% NaCl brine at 10°C and 25°C for 28 d. NaCl concentration, water activity, pH, and number of Staph. aureus and lactic acid bacteria were determined in cheese and brine. Only 1 of 4 Staph. aureus strains (ATCC 439) was positive for enterotoxin production, and its production was detected in unsalted UHT milk, but not in salted milk or in any of the cheese treatments held at 37°C for 1, 3, or 7 d. Staphylococcus aureus grew in the cheese stored in both brines at 10°C and 25°C, regardless of the presence of a starter culture, although the latter significantly reduced Staph. aureus growth in cheese or its brine at 10°C. Staphylococcus aureus numbers were increased by 2.26 and 0.47 log10 cfu/g in cheese stored in 10 and 15% NaCl brine, respectively, in the presence of starter culture, and by 2.78 and 2.96 log10 cfu/g, respectively, in the absence of starter culture at 10°C. Nonetheless, the pathogen grew, but at a lower number in the brines. The salt concentration of cheese stored in 10% brine remained at approximately 5% during storage; however, in 15% brine, the salt concentration increased to almost 8% (wt/wt) by 28 d. The addition of a starter culture, high salt concentration, low temperature, and pH (∼5.2) had inhibitory effects on the growth of Staph. aureus. Moreover, lactic acid bacterial numbers increased considerably in cheese and brine by d 28. The use of starter cultures, salt (15%), and low storage temperature (10°C) reduced the growth of Staph. aureus, and salt may have prevented enterotoxin production in white-brined cheese.

Inactivation of Salmonella spp. in tahini using plant essential oil extracts.

Tahini is a popular food product in the Middle East region and is used as a major ingredient in several ready-to-eat food products. Tahini and its products have been linked to foodborne illness outbreaks and product recalls worldwide as a result of Salmonella spp. contamination. The objectives of the current study were to investigate: i) the effectiveness of 10 plant essential oil extracts on the viability of Salmonella spp. using disc diffusion ii) the antimicrobial activity of the most effective oils against Salmonella spp. in commercial or 10% w/v hydrated tahini (tahini-based product model) stored at 37, 25 and 10 °C for 28 d and iii) the effect of the addition of essential oil extracts on the sensory acceptability of tahini and hydrated tahini. Among the tested essential oils, thyme (TO) and cinnamon oil (CO) showed the highest antimicrobial activity against tested Salmonella spp. at 37 and 10 °C using a disc diffusion assay method. In tahini, the addition of 2.0% CO reduced the numbers of Salmonella spp. by 2.87, 2.64 or 2.35 log10 CFU/ml at 37, 25 or 10 °C, respectively, by 28 d. However, the antimicrobial activity of CO was more pronounced at all storage temperatures in hydrated tahini where no viable cells were detected after 3 d storage at 25 and 37 °C, or after 7 d at 10 °C. However, at 25 and 37 °C, the antimicrobial activity of CO was more evident since no viable cells were detected after 14 d when 0.5% was used. The numbers of Salmonella spp. were reduced by 3.29, 3.03 or 2.17 log10 CFU/ml at 37, 25 or 10 °C, respectively, after 28 d when 2.0% TO was added to tahini. Salmonella spp. were not detected in the hydrated tahini treated with 2.0% TO after 28 d at 37 °C or 25 °C, while at 10 °C, the numbers of Salmonella spp. were not significantly reduced after 28 d in hydrated tahini compared to the initial numbers at zero time. Therefore, the addition of TO and CO could be used to preclude the post process contamination of tahini with foodborne pathogens, yet, the addition of TO and CO to tahini reduced its consumer acceptability compared untreated tahini.

The Use of Malic and Acetic Acids in Washing Solution to Control Salmonella spp. on Chicken Breast.

Salmonella is a persisting contaminant in poultry products that may pose a potential risk to consumers. Thus, developing decontamination strategies to eliminate or reduce this pathogen in chicken is crucial. The objective of the current study was to investigate the antimicrobial activity of malic acid (MA) and acetic acid (AA) or their combination against Salmonella on chicken breast at 4 °C for 10 days. The effect of storage temperature (4 and 21 °C) on Salmonella inactivation was also investigated for up to 21 days. Five serovars of Salmonella were inoculated in a model Mueller-Hinton (MH) broth system to a level of about 7 log10 CFU/mL and the broth was treated with 5 mg/mL of each of MA, AA or their combination. AA was more effective than MA in the model system at 21 °C, where it resulted in total elimination of Salmonella, but MA was more effective in eliminating Salmonella at 4 °C. However, the combined MA and AA solutions were more effective than either MA or AA alone. When applying washing solutions containing 5 mg/mL of either of MA, AA, or their combination to chicken breast inoculated with about 5 log10 CFU/g, the MA+AA washing solution was the most effective. It resulted in complete elimination of Salmonella from chicken breast and rendered a significant reduction in mesophilic aerobic bacteria and lactic acid bacteria numbers. PRACTICAL APPLICATION: This study indicates that the use of a washing solution containing MA and AA could improve the safety and extend the shelf life of raw chicken by substantially reducing Salmonella and contaminating microflora on the product.

Control of Salmonella enterica and Listeria monocytogenes in hummus using allyl isothiocyanate.

Hummus (chickpea dip) is a ready-to-eat product which has been implicated in several foodborne outbreaks and food recalls. This study aimed to screen the antimicrobial activity of allyl isothiocyanate (AITC) against 5 strains of each of Salmonella enterica and Listeria monocytogenes using a disc diffusion method. Additionally, the antimicrobial activity of 0.1-1.5% (v/w) AITC against both pathogens and aerobic bacteria in hummus was also investigated. The inhibition zones of AITC were 8.5-15 and 7.0-8.5 mm against the S. enterica and L. monocytogenes strains, respectively, at 37 °C. S. enterica numbers were reduced by >6 log10 CFU/g in hummus containing ≥0.5% AITC by 3 days at both 4 and 10 °C. While 0.1-0.25% AITC reduced S. enterica by 2.5-5.1 log10 CFU/g at 4 °C or by 4.7-6.0 log10 CFU/g at 10 °C by 10 days. Similarly, L. monocytogenes numbers decreased by >6 log10 CFU/g in hummus with ≥0.5% or ≥1.0% AITC at 4 or 10 °C, respectively, by 3 days. Further, 0.25% AITC significantly reduced L. monocytogenes in hummus by 2.7 and 4.3 log10 CFU/g at 4 and 10 °C, respectively. Moreover, 0.1% AITC reduced L. monocytogenes by 1.8 log10 CFU/g in hummus at 10 °C and inhibited the growth at 4 °C for up to 10 days. The aerobic bacterial count also significantly decreased in un-inoculated hummus treated with 1.0-1.5% AITC at both 4 and 10 °C, while a concentration of 0.25-0.5% AITC inhibited their growth at 4 °C. AITC can be used to reduce the risk of salmonellosis or listeriosis in hummus and extend its shelf-life.

Emergence of Antibiotic Resistance in Listeria monocytogenes Isolated from Food Products: A Comprehensive Review.

Listeria monocytogenes is an opportunistic pathogen that has been involved in several deadly illness outbreaks. Future outbreaks may be more difficult to manage because of the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products. The present review summarizes the available evidence on the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products and the possible ways this resistance has developed. Furthermore, the resistance of food L. monocytogenes isolates to antibiotics currently used in the treatment of human listeriosis such as penicillin, ampicillin, tetracycline, and gentamicin, has been documented. Acquisition of movable genetic elements is considered the major mechanism of antibiotic resistance development in L. monocytogenes. Efflux pumps have also been linked with resistance of L. monocytogenes to some antibiotics including fluoroquinolones. Some L. monocytogenes strains isolated from food products are intrinsically resistant to several antibiotics. However, factors in food processing chains and environments (from farm to table) including extensive or sub-inhibitory antibiotics use, horizontal gene transfer, exposure to environmental stresses, biofilm formation, and presence of persister cells play crucial roles in the development of antibiotic resistance by L. monocytogenes.

Inhibition of Shigella sonnei and Shigella flexneri in Hummus Using Citric Acid and Garlic Extract.

Hummus (chickpea dip) is a ready-to-eat product that may pose a significant risk to human if pathogens are present. Several organisms including Shigella spp. have been isolated from hummus. However, studies on the survival and inhibition of Shigella spp. in food are scarce. This study investigated the growth pattern of Sh. sonnei and Sh. flexneri in hummus at different temperatures (4, 10, and 24 °C). Additionally, the inhibitory activity of different concentrations of citric acid (CA) (0.5%, 1.0%, and 2.0%) and garlic extract (GE) (1.0%, 2.0%, and 3.0%) against Sh. sonnei and Sh. flexneri inoculated into hummus and stored at 4 and 10 °C was investigated. Both Shigella spp. survived well at 4 °C, while both grew to >7.0 log10 after 4 d at 10 °C or 1 d at 24 °C. At 4 °C, CA at 0.5% and 1.0% resulted in a slight reduction in the count (approximately 1.0 log10 ); a complete elimination of Sh. sonnei was attained by using 2.0% CA. However, approximately 3.0 log10 reduction in Sh. sonnei was obtained at 10 °C. For Sh. flexneri, CA at 0.5% and 1.0% resulted in a bacteriostatic inhibition. GE at 1.0% and 2.0% resulted in approximately 1.0 to 2.0 log10 reduction in Sh. sonnei count at 4 °C, while at 3.0% GE, approximately 4.0 and 3.0 log10 reductions were obtained at 4 and 10 °C, respectively. In comparison, the 2.0% and 3.0% GE resulted in a bacteriostatic effect against Sh. flexneri at 4 and 10 °C.

Feasibility of Using Gamma Irradiation for Inactivation of Starvation-, Heat-, and Cold-Stressed Salmonella in Tahini.

Salmonella continues to be the leading cause of acute gastroenteritis and recently has been involved in infections related to edible seeds and their products, including tahini. This study investigated the (i) effectiveness of using gamma irradiation to inactivate starvation- and heat- or cold-stressed Salmonella in tahini, (ii) effect of storage on the sensitivity of stressed Salmonella to irradiation, and (iii) effect of irradiation on the chemical and physical characteristics of tahini. Tahini samples were inoculated with a cocktail of unstressed or stressed (starvation and heat or cold stress) Salmonella isolates and then exposed after storage at 21°C for 0, 7, and 30 days to gamma irradiation for up to 2.0 kGy. Additionally, the effect of irradiation on the color, peroxide, p-anisidine, and acid values of tahini were assessed. The initial level of unstressed and starvation- and heat-stressed Salmonella in tahini decreased by ca. 4.6 log CFU/g after exposure to 2.0 kGy, while cold-stressed cultures decreased by 4.5 log after exposure to 0.6 kGy. Irradiation doses of 1.0 kGy after 7 days of storage or 0.75 kGy after 30 days of storage decreased the populations of the unstressed and starvation- and heatstressed Salmonella by ca. 3.4 or 2.6 log, respectively. The D10-value of the unstressed Salmonella was 0.43 kGy. Starvation and heat stresses showed no significant effect (P > 0.05) on the calculated D10-value, whereas cold stress significantly (P < 0.05) decreased the D10-value to 0.14 kGy. Preirradiation storage for 7 and 30 days significantly decreased the D10-value to 0.31 and 0.28 kGy, respectively. An irradiation dose of 2.0 kGy did not significantly affect the color, peroxide, p-anisidine, and acid values of tahini when compared with nonirradiated samples. Therefore, this study lays the foundation for using irradiation as an effective means for minimizing the risk of Salmonella in tahini without compromising its quality.

Effect of acidic electrolyzed water-induced bacterial inhibition and injury in live clam (Venerupis philippinarum) and mussel (Mytilus edulis).

The effect of acidic electrolyzed water (AEW) on inactivating Escherichia coli O104:H4, Listeria monocytogenes, Aeromonas hydrophila, Vibrio parahaemolyticus and Campylobacter jejuni in laboratory contaminated live clam (Venerupis philippinarum) and mussel (Mytilus edulis) was investigated. The initial levels of bacterial contamination were: in clam 4.9 to 5.7log10CFU/g, and in mussel 5.1 to 5.5log10CFU/g. Two types of AEW were used for treatment time intervals of 1 and 2h: strong (SAEW) with an available chlorine concentration (ACC) of 20mg/L, pH=3.1, and an oxidation-reduction potential (ORP) of 1150mV, and weak (WAEW) at ACC of 10mg/L, pH=3.55 and ORP of 950mV. SAEW and WAEW exhibited significant inhibitory activity against inoculated bacteria in both shellfish species with significant differences compared to saline solutions treatments (1-2% NaCl) and untreated controls (0h). SAEW showed the largest inhibitory activity, the extent of reduction (log10CFU/g) ranged from 1.4-1.7 for E. coli O104:H4; 1.0-1.6 for L. monocytogenes; 1.3-1.6 for A. hydrophila; 1.0-1.5 for V. parahaemolyticus; and 1.5-2.2 for C. jejuni in both types of shellfish. In comparison, significantly (P<0.05) lower inhibitory effect of WAEW was achieved compared to SAEW, where the extent of reduction (log10CFU/g) ranged from 0.7-1.1 for E. coli O104:H4; 0.6-0.9 for L. monocytogenes; 0.6-1.3 for A. hydrophila; 0.7-1.3 for V. parahaemolyticus; and 0.8-1.9 for C. jejuni in both types of shellfish. Among all bacterial strains examined in this study, AEW induced less bacterial injury (~0.1-1.0log10CFU/g) and more inactivation effect. This study revealed that AEW (10-20mg/L ACC) could be used to reduce bacterial contamination in live clam and mussel, which may help control possible unhygienic practices during production and processing of shellfish without apparent changes in the quality of the shellfish.

Discrimination between Bacillus and Alicyclobacillus isolates in apple juice by Fourier transform infrared spectroscopy and multivariate analysis.

Alicyclobacillus is a causative agent of spoilage in pasteurized and heat-treated apple juice products. Differentiating between this genus and the closely related Bacillus is crucially important. In this study, Fourier transform infrared spectroscopy (FT-IR) was used to identify and discriminate between 4 Alicyclobacillus strains and 4 Bacillus isolates inoculated individually into apple juice. Loading plots over the range of 1350 and 1700 cm(-1) reflected the most distinctive biochemical features of Bacillus and Alicyclobacillus. Multivariate statistical methods (for example, principal component analysis and soft independent modeling of class analogy) were used to analyze the spectral data. Distinctive separation of spectral samples was observed. This study demonstrates that FT-IR spectroscopy in combination with multivariate analysis could serve as a rapid and effective tool for fruit juice industry to differentiate between Bacillus and Alicyclobacillus and to distinguish between species belonging to these 2 genera.