Inactivation of stressed Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes in hummus using low dose gamma irradiation.

Hummus is a popular dip in the Middle East region prepared by mixing the boiled chickpeas with tahini and other ingredients, and because its consumption has increased world-wide some notoriety has developed following an increase in the incidence of hummus-related illness outbreaks and recalls. The objectives of the current research were (i) to study the efficiency of low dose gamma irradiation to inhibit Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in hummus, and (ii) to assess the effect of environmental stresses namely cold, heat, and desiccation on the resistance of these pathogens to gamma irradiation. The samples of hummus were prepared and then individually inoculated with approximately 7.0 log CFU/g of unstressed or cold-, heat-, or desiccated-stressed cocktail cultures of each of E. coli O157:H7, S. enterica, and L. monocytogenes. The inoculated samples were then exposed to gamma irradiation at doses of 0.1 to 0.6 kGy. The numbers of unstressed E. coli O157:H7, S. enterica, and L. monocytogenes were decreased by 0.6-3.9, 0.7-2.9, and 1.0-3.0 log CFU/g, respectively, by irradiation treatment. The resistance of E. coli O157:H7 to gamma irradiation was not affected by desiccation, heat, and cold stresses. However, the pre-exposure of S. enterica and L. monocytogenes cells to these stresses reduced their resistance toward gamma irradiation. PRACTICAL APPLICATION: Gamma irradiation is a non-thermal treatment that can be used in food processing to ensure food safety and quality. The current study proved that low levels (≤0.6 kGy) of gamma irradiation can effectively decrease the risk of unstressed and cold-, heat-, or desiccation-stressed Salmonella enterica, Listeria monocytogenes, or Escherichia coli O157:H7 in hummus.

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.

Survival and growth of Listeria monocytogenes and Staphylococcus aureus in ready-to-eat Mediterranean vegetable salads: Impact of storage temperature and food matrix.

This study aimed to evaluate the survival or growth behavior of L. monocytogenes and S. aureus in ready-to-eat vegetable salads including Arabic salad (tomato-cucumber salad) with or without 0.5% (w/w) salt and 1% (v/w) lemon juice, tahini salad, coleslaw salad, toum sauce salad (aioli) stored at 4, 10, and 24 °C for 5 d. L. monocytogenes showed greater growth or survival in all types of salads at all temperatures tested. L. monocytogenes grew in Arabic salad without additives at 10 °C and tahini salad at 4 and 10 °C. L. monocytogenes survived all preparation and storage conditions used in the current study and its numbers were detectable in all types of salads tested, and with a maximum reduction of 3.0 log CFU/g, except for toum sauce salad at 24 °C, the cells were not detected using enrichment broth. In addition, S. aureus survived in Arabic salad with or without additives and in tahini salad with a maximum reduction of 2.3 log CFU/g. However, S. aureus numbers sharply decreased in coleslaw and toum sauce salad and at 5 d they reached undetectable levels (≥2 log CFU/g) in coleslaw at 24 °C and in toum sauce at 10 and 24 °C. Addition of lemon juice and salt to Arabic salad significantly reduced the numbers of both pathogens.

The potential application of probiotics and prebiotics for the prevention and treatment of COVID-19.

COVID-19 is a pandemic disease caused by the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This new viral infection was first identified in China in December 2019, and it has subsequently spread globally. The lack of a vaccine or curative treatment for COVID-19 necessitates a focus on other strategies to prevent and treat the infection. Probiotics consist of single or mixed cultures of live microorganisms that can beneficially affect the host by maintaining the intestinal or lung microbiota that play a major role in human health. At present, good scientific evidence exists to support the ability of probiotics to boost human immunity, thereby preventing colonization by pathogens and reducing the incidence and severity of infections. Herein, we present clinical studies of the use of probiotic supplementation to prevent or treat respiratory tract infections. These data lead to promising benefits of probiotics in reducing the risk of COVID-19. Further studies should be conducted to assess the ability of probiotics to combat COVID-19.

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.

A Novel cooked extruded lentils analog: physical and chemical properties.

Developing an extruded lentil analog is our aim. Lentil analog with six formulations were produced using a pilot-scale single (SS) and twin screw (TS) extruders. Texture analysis of lentil analogs prepared for consumption revealed that the products formulated with 60:40 and 70:30 soy: wheat ratios exhibited a significantly higher hardness, adhesiveness and lower springiness as compared to all other treatments. Differential Scanning Calorimeter (DSC) results indicated that all starches in dry blend are completely 100 % gelatinized by extrusion for all treatments at 100 °C. The maximum peak of viscosity for TS was formed after 5.58 min. from the run at 89.9 °C for the best treatment. However, this lentil analog product can provide a high quality lentil which can be used as a substitute for regular lentils.

Physicochemical and sensory characteristics of no-bake wheat-soy snack bars.

BACKGROUND: Health and wellness is a trend observed throughout ready-to-eat cereals, cereal health bars. Therefore, the main objectives of this research were to produce a low cost, acceptable, nutritious and healthy wheat- and soy-based bar under no-bake conditions. Also, the physical, chemical, microbial, acceptability and the nutritional value of this product were studied. Six different bars were produced: a wheat bar (WB), a wheat bar with coating (WBC), a wheat and soy bar with coating (WSBC), a soy bar with coating (SBC), a wheat bar with 3% glycerin (WB3%), and a wheat bar with 6% glycerine (WB6%). RESULTS: WB and WBC had the highest water activities while WSBC had the lowest. The three bars with coating had higher L and lower b values, which indicates that they were lighter and not as highly yellow coloured as the wheat samples. WSBC had the lowest value for hardness while the SBC and WBC had the highest. SBC received the highest scores for overall acceptability, appearance, sweetness, flavour and texture while WSBC received the second highest score in all categories. CONCLUSION: It appears that consumers prefer the soy varieties to the wheat bars. These types of bars can aid in feeding the general population, which is becoming increasingly concerned with nutrition and convenience.