Multiplex PCR method for the detection of human norovirus, Salmonella spp., Shigella spp., and shiga toxin producing Escherichia coli in blackberry, coriander, lettuce and strawberry.

A multiplex PCR method was developed for the simultaneous detection of murine norovirus (MNV-1) as a surrogate for human norovirus (HuNoV) GI and GII, Salmonella spp., Shigella spp., and Shiga toxin producing Escherichia coli (STEC) in fresh produce. The toxicity of the glycine buffer on bacterial pathogens viability was evaluated. The growth of each of the three pathogens (previously stressed) was evaluated at 35 and 41.5 °C in modified buffered peptone water (mBPW) and trypticase soy broth (TSB), supplemented with vancomycin, novobiocin and brilliant green at two concentration levels. The selected conditions for simultaneous enrichment were: 41.5 °C/mBPW/supplemented with 8 ppm vancomycin, 0.6 ppm novobiocin and 0.2 ppm brilliant green. The pathogens and aerobic plate count (APC) growth was evaluated in the enrichment of lettuce, coriander, strawberry and blackberry under the best enrichment conditions. Starting from 1 to 10 CFU/mL, Salmonella reached from 7.63 to 8.91, Shigella 6.81 to 7.76 and STEC 7.43 to 9.27 log CFU/mL. The population reached for the APC was 5.11-6.56 log CFU/mL. Simultaneous detection by PCR was done using designed primers targeting invA, ipaH, stx1 and stx2 genes, and MNV-1. The detection sensitivity was 10-100 PFU for the MNV-1 and 1-10 CFU for each pathogenic bacteria. This protocol takes 6 h for MNV-1 and 24 h for Salmonella spp., Shigella spp., and STEC detection from the same food portion. In total, 200 samples were analyzed from retail markets from Queretaro, Mexico. Two strawberry samples were positive for HuNoV GI and one lettuce sample was positive for STEC. In conclusion, the method developed in this study is capable of detecting HuNoV GI and GII, Salmonella spp., Shigella spp and STEC from the same fresh produce sample.

Antimicrobial Effects of Basil, Summer Savory and Tarragon Lyophilized Extracts in Cold Storage Sausages.

The problem of functional foods with bioactive components of natural origin is current for the food industry. Plant extracts rich in polyphenols with antioxidant and antimicrobial activity are a promising source for use in improving the quality and characteristics of fresh meat and meat products. In this context, the purpose of the present study was to evaluate the physico-chemical, microbiological, sensory properties of sausages prepared with the addition of lyophilized extract of basil, thyme or tarragon. For the beginning, the total amount of polyphenols, the antioxidant and antimicrobial activity of the extracts obtained from three spices were evaluated. In the sausages previously infected with Staphylococcus aureus and Escherichia coli it was observed that there is a much larger number of colonies of microorganisms in the control sample compared to the other samples within 24 and 48 h. Moreover, following the addition of sausage extracts, no changes were found regarding their sensory acceptability.

Evaluation of fungal contamination and ochratoxin A detection in different types of coffee by HPLC-based method.

BACKGROUND: Mycotoxins are secondary fungal metabolites that are produced by some toxigenic fungi on foodstuffs which are poisoning and potentiate for human's health hazards. In coffee samples, ochratoxin A and fungal contamination were examined. METHODS: Immunoaffinity columns were used for treating of all 50 samples from four types of coffee, after that high-performance liquid chromatography was used for determining the amount of ochratoxin. For the identification of fungi, all coffee samples were cultured in appropriated media. RESULTS: The results showed that all samples were contaminated by ochratoxin A but only up to 50% of them had toxins higher than acceptable level as detected in black beans (47%), green beans (33.3%), torch (33.3%), and espresso (25%). Black coffee had a higher mean concentration of ochratoxin A than green coffee. CONCLUSION: Predominant fungi isolated from coffee samples were Aspergillus species. Finally, careful monitoring of mycotoxins in coffee samples is essential to improve the quality of this favorable beverage in future.

Sustained-release modeling of clove essential oil in brine to improve the shelf life of Iranian white cheese by bioactive electrospun zein.

In this study, the sustained-release of clove essential oil (CEO) loaded into the structure of electrospun zein was used as a biopreservative to extend the shelf life of Iranian white cheese. CEO was loaded at levels of 5, 7.5, and 10% w/w in the structure of electrospun nanofibers. In this study, a concentration of 35% w/v zein was used to produce electrospun fibers, and in the field emission scanning electron microscope (FESEM) it was observed that by increasing the loading of CEO from 5 to 10% w/w in the fiber structure, their diameter decreased from 517.96 ± 41.57 nm to 457.88 ± 32.45 nm. Although increasing the level of CEO reduced the diameter of the electrospun nanofibers, Young's modulus, tensile strength, and a higher level of CEO increased elongation at break of the films. The results of mechanical properties showed that by increasing the amount of CEO application in the structure of electrospun zein nanofibers from 5 to 10% w/w tensile strength from 8.18 ± 0.62 to 4.43 ± 0.86 MPa, and Young's modulus from 38.25 ± 2.81 to 27.25 ± 3.48 MPa decreased. Successful encapsulation of CEO in designed structures and the absence of adverse bonds between the encapsulant material (zein) and the core (CEO) were confirmed by the Fourier-transform infrared spectroscopy (FTIR) test. The in vitro sustained-release of the CEO in 8% w/v brine during 45 days of storage at 4 °C was modeled. The Fickian diffusion was the dominant release mechanism of the CEO and the Peppas-Sahlin model was the best model describing the essential oil release behavior. The electrospun films containing CEO were well able to suppress the growth of Listeria monocytogenes and Escherichia coli O157: H7 in samples of Iranian white cheese kept in 8% brine for 45 days at 4 °C. The samples treated with the electrospun film containing 7.5% w/w of CEO had the highest acceptability among different treatments.

Towards a Bioactive Food Packaging: Poly(Lactic Acid) Surface Functionalized by Chitosan Coating Embedding Clove and Argan Oils.

Here we introduce a new method aiming the immobilization of bioactive principles onto polymeric substrates, combining a surface activation and emulsion entrapment approach. Natural products with antimicrobial/antioxidant properties (essential oil from Syzygium aromaticum-clove and vegetal oil from Argania spinosa L-argan) were stabilized in emulsions with chitosan, a natural biodegradable polymer that has antimicrobial activity. The emulsions were laid on poly(lactic acid) (PLA), a synthetic biodegradable plastic from renewable resources, which was previously activated by plasma treatment. Bioactive materials were obtained, with low permeability for oxygen, high radical scavenging activity and strong inhibition of growth for Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli bacteria. Clove oil was better dispersed in a more stable emulsion (no separation after six months) compared with argan oil. This leads to a compact and finely structured coating, with better overall properties. While both clove and argan oils are highly hydrophobic, the coatings showed increased hydrophilicity, especially for argan, due to preferential interactions with different functional groups in chitosan. The PLA films coated with oil-loaded chitosan showed promising results in retarding the food spoilage of meat, and especially cheese. Argan, and in particular, clove oil offered good UV protection, suitable for sterilization purposes. Therefore, using the emulsion stabilization of bioactive principles and immobilization onto plasma activated polymeric surfaces we obtained a bioactive material that combines the physical properties and the biodegradability of PLA with the antibacterial activity of chitosan and the antioxidant function of vegetal oils. This prevents microbial growth and food oxidation and could open new perspectives in the field of food packaging materials.

Rosa spp. Extracts as a Factor That Limits the Growth of Staphylococcus spp. Bacteria, a Food Contaminant.

Due to their richness of bioactive substances, rose hips are a valuable raw material for obtaining extracts with potential antimicrobial activity. The aim of the study was to determine the antagonistic potential of whole pseudo-fruit and flesh extracts of three Rosa sp. varieties against Staphylococcus spp. bacteria isolated as food contaminants. The biological material in this study consisted of seven strains of bacteria from the genus Staphylococcus. Two strains-Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis DSMZ 3270-were used as reference strains. The other five strains were food-derived isolates-S. epidermidis A5, S. xylosus M5, S. haemolyticus M6, S. capitis KR6, and S. warneri KR2A. The material was the pseudo-fruits of Rosa canina, Rosa pomifera Karpatia, and Rosa rugosa. The polyphenols were extracted from the fleshy part and the whole pseudo-fruit for all rose varieties. The tested preparations differed significantly in their polyphenol composition. The sum of polyphenols ranged from 28 862 to 35 358 mg/100 g of lyophilisate. The main groups of polyphenols found in the preparations were flavanols and ellagitannins. All of the tested extracts inhibited the growth of staphylococci at a concentration of 500 mg/mL. Rosa rugosa fruit extract showed the strongest antimicrobial properties among the studied extracts. For all the strains, the growth inhibition had a diameter of 20.3-29.0 mm. Moreover, six out of the seven tested strains showed the highest inhibition with the use of this extract. The MIC of rose extracts was in the range of 3.125-500 mg/mL and was strictly dependent on the bacterial species, the species of the rose, and the part of the fruit from which the extract was obtained. Correlations were assessed between the main groups of polyphenols in the extracts and their inhibition of bacterial growth. In the case of pseudo-fruit extracts, the inhibitory effect on bacterial growth positively correlated with the content of ellagitannins, and this effect was observed for almost all the tested strains. The results presented herein follow the current trend of minimising the use of chemical preservatives in food; from this point of view, rose extracts are very promising.

Novel Prosopis juliflora leaf ethanolic extract as natural antimicrobial agent against food spoiling microorganisms.

Fresh produces spoilage is a worldwide concern that accompany the global increase in food demand. Adverse human health and environmental effects of commercial spoilage control agents are major public concern. In this study, Prosopis juliflora leaves and fruit extracts had their antimicrobial activities evaluated against the growth of selected bacteria and yeast, and against mycelial growth and conidial germination of selected mycotoxins-producing fungi. P. juliflora water-soluble leaf ethanolic (PJ-WS-LE) extract with its novel extraction method showed the strongest antibacterial activity. Antimicrobial tests showed total inhibition of Botrytis cinerea, Alternaria alternata, Bacillus subtilis, Staphylococcus aureus and Candida albicans with MICs ranging between 0.125 and 1 mg/ml. Percent inhibition of mycelial growth (PIMG) of the extract was also determined against seven other fungal strains with highest value against Geotrichum candidum (66.2%). Even the least affected fungal strain showed alterations in their hyphae and spores exposed to PJ-WS-LE extract when observed using scanning electron microscope (SEM), alterations include exfoliated flakes, pores, vacuolation and applanation. Small-scale fruit bioassays controlled experiment showed high efficacy of the extract in protecting inoculated cherry tomato samples from B. cinerea and A. alternata infections. In conclusion, PJ-WS-LE extract is a feasible, natural antifungal agent that can replace common anti-spoiling chemicals.

Integrated proteomics and metabolomics analysis of tea leaves fermented by Aspergillus niger, Aspergillus tamarii and Aspergillus fumigatus.

Post-fermented Pu-erh tea (PFPT) is a microbially-fermented tea with distinct sensory qualities and multiple health benefits. Aspergillus are the dominant fungi in the fermentation and the main contributors to the characteristics of PFPT, so their underlying functions warrant detailed study. Here, tea leaves were fermented by Aspergillus niger, Aspergillus tamarii and Aspergillus fumigatus, and resulting samples (designated as Asn, Ast and Asf, respectively) were analyzed by proteomic and metabolomic methods. Changes to the composition of flavonoids, glycerophospholipids, organo-oxygen compounds and fatty acids resulting from Aspergillus fermentation were observed. Carbohydrate-active enzymes, e.g., endoglucanases and cellulases, for degradation of cellulose, starch, lignin, pectin, xylan and xyloglucan were identified. Glycoside hydrolase, glycosyltransferases, tannase, laccases, vanillyl-alcohol oxidases and benzoquinone reductase were identified and hypothesized to catalyze hydrolysis, oxidation, polymerization and degradation of phenolic compounds. Together, functions of Aspergillius were demonstrated as production of enzymes to change concentrations and compositions of metabolites in tea leaves.

The effect of different ultraviolet-C light doses on microbial reduction and the components of camel milk.

As a result of increasing interest in non-thermal technologies as a possible alternative or complementary to milk pasteurization processing, the objectives of this study were to determine the effects of different ultraviolet-C light doses on the viability of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium and chemical changes to camel milk components. Pasteurized and inoculated camel milk samples were ultraviolet-C treated in a continuous flow system. The viability of E. coli O157:H7 and S. Typhimurium was evaluated with both in vivo imaging system and traditional plate count agar method. Samples subjected to the 4.15, 8.30, and 12.45 mJ/cm2 of ultraviolet-C treatment resulted in 1.9, 3.3, and 3.9-log reductions in E. coli O157:H7 and 0.9, 3, and 3.9-log reductions in S. Typhimurium, respectively. The measurement of secondary lipid peroxidation products (or ThioBarbituric Acid Reactive Substance values) showed no significant (P > 0.05) differences between the raw and ultraviolet-C treated milk samples. Additionally, no changes (P > 0.05) in the protein profiles of αs1-casein, α-lactalbumin, and lactoferrin were observed between both samples. Compared to the untreated raw milk, c9t11 conjugated linoleic acid decreased (P < 0.01) while t10c12 conjugated linoleic acid increased (P < 0.01) in the ultraviolet-C treated milk. Furthermore, three new volatile compounds were identified in the ultraviolet-C treated milk compared to the control. In conclusion, milk treated with the ultraviolet-C light at a dose of 12.45 mJ/cm2 did not meet the Food and Drug Administration (FDA) requirements for the 5-log pathogen reduction. The ultraviolet-C treatment, on the other hand, had minimal effects on camel milk components.

Improving the storage stability of tomato paste by the addition of encapsulated olive leaf phenolics and experimental growth modeling of A. flavus.

It is necessary to apply some preservatives for tomato paste since in the harvest season, a high load of tomatoes need to be processed as they are among highly perishable products. Application of antimicrobial extracts or essential oils, as natural preservatives, in their raw forms might reduce their efficiency when they are exposed to environmental conditions. However, microencapsulation is a well-known method to solve this problem. Our main goal was to restrict fungal growth rate in stored tomato paste and increase its storage stability by incorporating encapsulated olive leaf phenolic-rich extract. Total Soluble Solids (TSS), consistency, pH, color indices and diametrical growth rate of Aspergillus flavus were measured for different samples. The treatments designed in terms of considering two levels of non-encapsulated olive phenolics extract with 500 and 1000 ppm (NE500 and NE1000), the same levels with encapsulated extract; i.e., 500 and 1000 ppm (ME500 and ME1000), and similar levels of the common preservative of sodium benzoate with 500 and 1000 ppm (B500 and B1000). Antifungal properties of NE samples were higher than ME ones during storage although ME samples could maintain diametrical growth rate of the fungus more stable than NE ones. NE samples justified lower maximum growth rate than ME samples while ME samples could extend lag phase of microbial growth compared with NE one and delay their internal deteriorative reactions. Among Baranyi, modified Baranyi, Modified Gompertz, and Logistic models, Modified Gompertz model represented the best model and could fit the growth factors of A. flavus on tomato paste with higher R2 index as well as lower RMSE and SSE indices. Based on the results obtained, it could be concluded that usage of encapsulated olive leaf extract in tomato paste is an effective, natural and sustainable approach to improve the shelf life of tomato paste since this natural compound could perform as favourable as preservatives; also it could maintain physicochemical as well as microbial properties of tomato paste for a long term. Thus, it is strongly recommended that application of encapsulated olive leaf extract to be considered seriously by the tomato paste industry as it can effectively reduce the mold and fungal contaminations which are very common and prevalent in the plants. The future work in this regard should focus on sensory evaluations when incorporating encapsulated olive leaf extract into tomato paste.

Metabolic extract of the endophytic fungus Flavodon flavus isolated from Justicia brandegeana in the control of Alicyclobacillus acidoterrestris in commercial orange juice.

In this work, the antibacterial activity of a crude extract of the endophytic fungus Flavodon flavus (JB257), isolated from leaves of Justicia brandegeana, was evaluated against both the vegetative and sporulated forms of Alicyclobacillus acidoterrestris. The microdilution technique was performed in order to determine the antibacterial activity of the crude extract alone as well as in combination with the bacteriocin, nisin. The minimum inhibitory concentration (MIC) of the crude extract and nisin alone against A. acidoterrestris vegetative forms were 250 µg/mL and 31.5 µg/mL, respectively, while the minimum bactericidal concentrations (MBC) were 1000 µg/mL and 62.5 µg/mL,respectively. For A. acidoterrestris spores, treatment with the crude extract at a concentration of 500 µg/mL caused a 47% reduction in growth, while nisin at 62.5 µg/mL could reduce 100% of the growth. The in vitro evaluation of the crude extract combined with nisin against A. acidoterrestris by the Checkerboard method showed a synergistic interaction between the two compounds. In addition, greater selectivity towards bacterial cells over host cells, a human hepatocyte cell line, was achieved when the crude extract was combined with nisin, Using scanning electron microscopy, interferences in the cell membrane of A. acidoterrestris could be observed after treatment with the crude extract. The results presented in this study indicate that the crude extract of the endophyte F. flavus has biotechnological potential in the food industry, especially for the treatment of orange juices through the control of A. acidoterrestris.

MacConkey broth purple provides an efficient MPN estimation method for Shigatoxigenic Escherichia coli.

MacConkey broth purple provides a more efficient method for Most Probable Number estimation for Shigatoxigenic Escherichia coli (E.coli) than the process of bacterial enrichment in buffered peptone water followed by detection on MacConkey agar, since it is a single-step process that gives comparable results in plant extracts.

Nitroso-hemoglobin-ginger conjugates effects on bacterial growth and color stability in a minced beef model.

This study aims to enhance the color and microbiological qualities of a raw beef using natural ingredients. Nitroso-hemoglobin (NO-Hb) integrated with vitamin C (VC), calcium lactate, and ginger complexation were used as natural inhibitors against the growth of aerobic and pathogenic bacteria, namely (Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Salmonella. NO-Hb inhibited E. coli, S. aureus, and Salmonella, and enhanced the color stability more than nitrite in the minced beef model. After the multiexponential analysis of relaxation decays, the water component (T2b) was analyzed using the low-field NMR. The results indicated that, at the 7th d of cold-storage the third component (T2) was detected. Significant correlations were observed between T21 and T22 relaxation times and water-holding capacity in minced beef, implying that the LF-NMR measurements could be an efficient method for the determination and prediction of beef freshness. NO-Hb- ginger mixture, as a novel ingredient, could be used instead of nitrite in terms of meat safety.

Inactivation of microbes on fruit surfaces using photodynamic therapy and its influence on the postharvest shelf-life of fruits.

In this study, the disinfection effect of curcumin-mediated photodynamic therapy on the contact surfaces of fresh fruit was investigated. Our results showed that the optimum concentration of curcumin and the energy density required were 0.5 µM and 7.2 J/cm2, respectively. Photodynamic therapy showed an excellent disinfection rate for the fresh fruits with a reduction of more than 80% in the total bacteria and coliform counts. The photodynamic therapy inhibited species that belonged to the categories of gram-negative and facultative anaerobic bacteria, except for two species of the Trichoderma fungus. Importantly, photodynamic therapy prolonged the shelf-life of grapes for two days at room temperature. Therefore, photodynamic therapy should be commercialized as a high efficiency and non-thermal sterilization technology for use in the food industry.

Research Note: Microbial inactivation of raw chicken meat by supercritical carbon dioxide treatment alone and in combination with fresh culinary herbs.

The objective of the present study was to assess the potential synergistic effect between supercritical carbon dioxide (SC-CO2) and fresh culinary herbs (Coriandrum sativum and Rosmarinus officinalis) on the microbial inactivation of raw chicken meat. The microbiological inactivation was performed on Escherichia coli and natural flora (total mesophilic bacteria, yeasts, and molds). High pressure treatments were carried out at 40°C, 80 or 140 bar from 15 to 45 min. Microbial inactivation had a strong dependence on treatment time, achieving 1.4 log CFU/g reduction of E. coli after 15 min, and up to 5 log after 45 min, while a pressure increase from 80 up to 140 bar was not significant on the microbial inactivation. Mesophilic microorganisms were strongly reduced (>2.6 log CFU/g) after 45 min, and yeasts and molds were below the detection limits of the technique (<100 CFU/g) in most cases. The combination of fresh herbs together with SC-CO2 treatment did not significantly increase the inactivation of either E. coli or natural flora, which was similar to the SC-CO2 alone. The synergistic effect was obtained on the inactivation of E. coli using a proper concentration of coriander essential oil (EO) (0.5% v/w), while rosemary EO did not show a significant effect. Color analysis after the treatment showed an increment of lightness (L*), and a decrease of redness (a*) on the surface of the sample, making the product visually similar to cooked meat. Texture analysis demonstrated the modification of the texture parameters as a function of the process pressure making the meat more similar to the cooked one.

Combination of procedure for ultra rapid extraction (PURE) and loop-mediated isothermal amplification (LAMP) for rapid detection of Mycoplasma bovis in milk.

Polymerase chain reaction (PCR) is typically used for the early detection of mycoplasma in bovine milk; it requires 3 days to obtain results because of the necessary enrichment process. A more rapid, simple, and accurate detection method is required to directly detect the Mycoplasma bovis (M. bovis) gene in milk. In this study, we assess the utility of combining the following two methods to achieve this goal: the loop-mediated isothermal amplification (LAMP), which is more sensitive than PCR, and the procedure for ultra rapid extraction (PURE), which adsorbs and filters components that inhibit DNA amplification/detection. LAMP was examined using DNA extracts obtained by four methods. This showed that PURE had the highest sensitivity and specificity and that the combination of PURE and LAMP was able to detect M. bovis in milk. We then showed that the detection limit of M. bovis was 102 colony-forming units per milliliter of milk using the PURE-LAMP. Finally, the respective sensitivities of the PURE-LAMP and PCR were 57% and 86% for bulk tank milk, 89% and 74% for mature milk, 85% and 92% for colostrum/transitional milk, and 97% and 95% for mastitis milk. The specificity was 100% for all milk samples in both LAMP and PCR. We conclude that PCR was suitable for detecting mycoplasma in bulk tank milk and that the PURE-LAMP could detect mycoplasma within 2 hr and was also effective for mature and mastitis milk.

Spray drying and storage of probiotic-enriched almond milk: probiotic survival and physicochemical properties.

BACKGROUND: The combination of the nutritional profile of almond milk with the benefits of probiotic bacteria is an interesting development to meet the demand for sustainable and health-promoting food. Almond milk inoculated with probiotic Lactobacillus plantarum (ATCC8014) was spray dried and the almond, its milk, and powders were characterized physicochemically. Samples were characterized in terms of bacterial survival before and after atomization. Bacterial viability and total fatty acid changes were studied during 8 months' storage at 4 and 22 °C. RESULTS: Results showed adequate physicochemical properties and an optimal bacterial survival rate, maintaining almost the same values before and after the spray-drying operation. A decrease was observed in the cell viability for samples stored at 4 °C. However, the cell count was maintained above the minimum level suggested (107 living cells) to allow potential probiotic functionality for 8 months. On the other hand, the count cell of powders stored at 22 °C was below the minimum level required after 6 months. The fatty acids profile was not significantly (P > 0.05) affected by storage time and temperature. CONCLUSION: A new almond-based-product with probiotics was developed to meet consumer demands. Almond nutrients were recovered from almond milk powder and were found to be a good source of K and high in Mg and in monounsaturated fat. The viability of bacteria was assured during 8 months of storage at 4 °C and up to 6 months for samples stored at 22 °C. © 2020 Society of Chemical Industry.

A novel fungal beta-propeller phytase from nematophagous Arthrobotrys oligospora: characterization and potential application in phosphorus and mineral release for feed processing.

Phytases are widely utilized in feed industry to increase the utilization of phosphorus, minerals, and amino acids for improvement of animal and human nutrition. At present, all known ß-propeller phytases (BPP) have been generated from bacteria, particularly Bacillus. In this work we report for the first time a new fungal-derived BPP phytase. We identified a phytase highly differentially expressed only in the parasitic stage of a nematophagous fungus, Arhtrobotrys oliogospora, during the development of the 3D traps. We found that this phytase was homologous to the known bacterial BPP phytase, thus we referred the new phytase to Aophytase. The heterologous expression of codon-optimized Aophytase gene in Pichia pastoris was successfully investigated to yield recombinant Aophytase (r-Aophytase) with high specific enzyme activity of 74.71 U/mg, much higher than those of recombinant BPP phytases derived bacteria. The kinetic parameters of the r-Aophytase, the optimum pH and temperature, as well as the effects of surfactant, EDTA and different ions on its enzyme activity were further investigated. The potential utilization of r-Aophytase in feed processing was finally explored. We found that the optimal pH value was about 7.5, and the optimal temperature was 50 °C.; r-Aophytase significantly increased the release of inorganic phosphorus from soybean meal, and improved the release of soluble minerals from the durum wheat flour and finger millet flour. The findings indicate its potential utilization in the feed processing to ameliorate nutritional value of cereals and animal feed in the future.

Heat sensitization of hepatitis A virus and Tulane virus using grape seed extract, gingerol and curcumin.

Human noroviruses (HNoV) and hepatitis A virus (HAV) are predominantly linked to foodborne outbreaks worldwide. As cell-culture systems to propagate HNoV in laboratories are not easily available, Tulane virus (TV) is used as a cultivable HNoV surrogate to determine inactivation. Heat-sensitization of HAV and TV by "generally recognized as safe'' (GRAS) substances can potentially reduce their time-temperature inactivation parameters during processing to ensure food safety. Curcumin, gingerol (from ginger), and grape seed extract (GSE) reportedly have anti-inflammatory, immune-modulating and antiviral properties. The objective of this study was to determine and compare the D-values and z-values of HAV and TV at 52-68 °C with or without curcumin (0.015 mg/ml), gingerol (0.1 mg/ml), or GSE (1 mg/ml) in 2-ml glass vials. HAV at ~7 log PFU/ml and TV at ~6 log PFU/ml were diluted in phosphate buffered saline (PBS) and added to two sets of six 2-mL sterile glass vials. One set served as the control and the second set had the three extracts individually added for thermal treatments in a circulating water bath for 0-10 min. The D-values for TV in PBS ranged from 4.55 ± 0.28 to 1.08 ± 0.16 min, and for HAV in PBS ranged from to 9.21 ± 0.24 to 0.67 ± 0.19 min at 52-68 °C. Decreased D-values (52-58 °C) for TV with curcumin ranging from 4.32 ± 0.25 to 0.62 ± 0.17 min, gingerol from 4.09 ± 0.18 to 0.72 ± 0.09 min and GSE from 3.82 ± 0.18 to 0.80 ± 0.07 min, with similar trends for HAV were observed. The linear model showed significant differences (p < 0.05) between the D-values of HAV and TV with and without plant extracts for most tested temperatures. This suggests that GRAS substances can potentially lower temperature and time regimens needed to inactivate HAV and TV.

Synergistic antimicrobial activity of oregano and thyme thymol essential oils against Leuconostoc citreum in a laboratory medium and tomato juice.

This study was done to identify combinations of essential oils (EOs) that elicit synergistic antimicrobial effects against Leuconostoc citreum, a spoilage bacterium in vegetable and fruit juices. Twenty-four EOs were tested for antimicrobial activity against L. citreum using an agar well diffusion assay. Ten EOs showed relatively strong antimicrobial activity. Among those, cinnamon bark, oregano, and thyme thymol EOs showed the strongest activity (minimal inhibitory concentration = 1.25 µL/mL). It was confirmed that a combination of oregano and thyme thymol EOs had a synergistic antimicrobial activity (fractional inhibitory concentration index = 0.3750) using a checkerboard assay. This combination also had a synergistic antimicrobial activity against L. citreum in tomato juice. An initial population of L. citreum in tomato juice (5.3 log CFU/mL) increased to ≥ 8.6 log CFU/mL within 48 h at 15 °C and 24 h at 25 °C. Populations reached 6.8-7.2 log CFU/mL in tomato juice containing either 0.156 mL/mL oregano or thyme thymol. However, in the presence of both EOs (0.156 µL/mL in total), populations of L. citreum were significantly lower (5.7-6.5 log CFU/mL) (P ≤ 0.05). Findings will be useful when developing non-thermal food preservation technologies to increase the shelf-life of juices and other foods not containing synthetic preservatives.