Coating effects of tea polyphenol and rosemary extract combined with chitosan on the storage quality of large yellow croaker (Pseudosciaena crocea)

The coating effects of tea polyphenol (TP) and rosemary extract (R) combined with chitosan (Ch) respectively on the quality of large yellow croaker (Pseudosciaena crocea) during refrigerated storage at (4 ± 1 °C) were evaluated. A solution of TP (0.2%, w/v) and R (0.2%, w/v) was used for dip pretreatment, and Ch (1.5%, w/v) was used for the coating. Microbiological (total viable count), physicochemical (pH, TVB-N, K value, PV, TBARS), and sensory attributes were periodically assessed over 20 days. The results indicated that the two dip pretreatments combined with chitosan coating could more effectively maintain the good quality and could extend the shelf life by 8-10 days compared with the control group during the refrigerated storage.     

Combined effects of chemical dip and/or carrageenan coating and/or controlled atmosphere on quality of fresh-cut banana

The combined effect of chemical dip and/or edible coating and/or controlled atmosphere (CA) on quality of fresh-cut banana was investigated. Banana slices were subject to a 3-min dip into a solution containing 1% (w/v) calcium chloride, 0.75% (w/v) ascorbic acid and 0.75% (w/v) cysteine and/or combined with a carrageenan coating and/or combined with controlled atmosphere (3% O₂ + 10% CO₂). Physico-chemical and microbiological qualities were evaluated during 5 days of storage at 5 °C. Dip combined with CA treatment prevented product weight loss and increase of polyphenol oxidase activity during the 5 days of storage. Colour, firmness, pH, tritatable acidity and total soluble solids values and total phenolic content presented the smallest changes. Microbial analysis showed that minimally processed bananas were within the acceptable limits during 5 days of storage at 5 °C.     

The detection of Atlantic cod (Gadus morhua) using loop mediated isothermal amplification in conjunction with a simplified DNA extraction process

Atlantic cod (Gadus morhua) is a commercially important species of white fish, and one of three species legally identifiable as cod in the UK. Mislabelling of G. morhua does occur, as does the substitution of G. morhua for less expensive species. Sensitive molecular tests based on PCR have been developed for this species, but they have limitations, including the need for expensive thermal cycling equipment, and complex DNA extraction procedures. A loop mediated isothermal amplification (LAMP) assay was designed for the G. morhua cytochrome b gene, which was capable of detecting 0.1% w/w G. morhua in a homogenised raw fish mix. The LAMP assay was also able to detect G. morhua DNA when a rapid sample preparation was used, involving heating 100 mg of fish in a 1 ml aliquot of water and testing the supernatant, showing a higher tolerance of amplification inhibitors than a PCR assay. The LAMP assay did not generate a positive result when challenged with a range of non-target species, including Gadus macrocephalus, and Gadus chalcogrammus, indicating a high level of specificity. Direct detection of a positive reaction using propidium iodide was also demonstrated.     

The potential of some spice essential oils in the control of A. parasiticus CFR 223 and aflatoxin production

Essential oils of sweet basil (Ocimum basilicum), cassia (Cinnamomum cassia), coriander (Coriandrum sativum) and bay leaf (Laurus nobilis) at 1–5% (v/v) concentration in palm kernel broth inoculated with spore suspension (10⁶/ml) of Aspergillus parasiticus CFR 223 were evaluated for their potential in the control of aflatoxigenic fungus A. parasiticus CFR 223 and aflatoxin production. Healthy sorghum grains (120/treatment) immersed in the oils and distributed in three petri dishes with wet cotton wool were also inoculated with spore suspension (10⁶/ml) of A. parasiticus CFR 223 and assayed for grain protection. Sweet basil oil at optimal protective dosage of 5% (v/v) was fungistatic on A. parasiticus CFR 223 and aflatoxins produced in vitro and on fungal development on sorghum grains (P ⩽ 0.05) with a residual effect that lasted for 32 days. In contrast, oils of cassia and bay leaf stimulated the mycelia growth of the fungus in vitro but reduced the aflatoxin concentration (B₁ + G₁) of the fungus by 97.92% and 55.21% respectively, while coriander oil did not have any effect on both the mycelia growth and aflatoxin content of the fungus. The combination of cassia and sweet basil oils at half their optimal protective dosages (2.5% v/v) completely inhibited the growth of the fungus. The feasibility of implementing the results of this study to control aflatoxins was examined by the addition of whole and ground dry basil leaves at 5% and 10% (w/w), respectively, to 10 g sorghum, groundnut, maize and melon seed after 35 days storage period. It was found that the addition of whole and ground basil leaves markedly reduced aflatoxin contamination; however, 10% (w/w) of whole leaves was more effective as the reduction in aflatoxin was between 89.05% and 91%.The findings showed that aflatoxins can be controlled by co-storing whole sweet basil leaves with aflatoxin infected foods. The economic value of the study lies in the simplified technique for control of aflatoxin contamination in agricultural products and the benefits derivable from the use of local resources.     

Absolute quantification of genetically engineered traits with droplet digital PCR: Effect of DNA treatments and spiking with non-target DNA

Low level presence of unapproved genetically engineered (GE) materials in non-GE grains has been a challenge for grain importers and exporters and many countries also have regulatory requirements for use and cultivation of GE crops. Digital PCR has been used for absolute quantification of GE traits. The need for DNA pre-treatment for droplet digital PCR (ddPCR) has not been well assessed. The effect of non-shearing, QIAshredding and hydroshearing of genomic DNA (300 ng) on quantitative analysis of low concentrations of OXY235 canola, FP967 flax and DP305423 soybean samples was assessed using RainDance RainDrop™ Digital PCR system. 1000 ng DNA was also used for ddPCR to determine if pre-treatment is required for high DNA concentration. The measured percentage values were close to the expected 0.01, 0.1 and 1% values for non-sheared, QIAshredded and hydrosheared samples for three GE traits using 300 ng DNA. The ddPCR results were also similar to the expected 0.01, 0.1 and 1% values for non-sheared and QIAshredded samples for the three GE traits using 1000 ng DNA. The feasibility of absolute quantification of low levels of OXY235 canola, FP967 flax and DP305423 soybean samples spiked in non-GE barley and wheat samples was investigated using ddPCR. Successful quantification of OXY235 canola, FP967 flax and DP305423 soybean DNA samples spiked in barley and wheat DNA samples was achieved at 0.01, 0.1 and 1% levels. ddPCR carried out with DNA extracted from ground DP305423 soybean samples spiked in wheat and barley samples resulted in percentage values close to the expected 0.01, 0.1 and 1% values with some exceptions. The result shows the feasibility of using ddPCR for absolute quantification of low level presence of GE materials in other grain samples.     

Screening new gene markers for gluten detection in foods

In the present work, three DNA sequences encoding wheat proteins (α2-gliadin, agglutinin isolectin and thioredoxin h) were compared to trace gluten-containing cereals in food products. Quantitative real-time PCR methods using hydrolysis probes were successfully developed to target the three sequences for the detection of wheat DNA. The comparison of the three systems highlights the best sensitivity when tracing the α2-gliadin marker sequence, showing an absolute limit of detection (LOD) of 2 pg of wheat DNA and a relative LOD of 0.005% (50 mg/kg) of wheat in soybean, which corresponds to 4.5 mg/kg of gluten. All the systems reveal high specificity for detecting other gluten-containing cereals, such as barley and rye. Therefore, the developed real-time PCR systems can be used as non-immunological tools to confirm the presence of gluten-containing cereals in foods, towards the safety of celiac patients and wheat allergic individuals.     

Inactivation of food poisoning bacteria and Geobacillus stearothermophilus spores by high pressure carbon dioxide treatment

Inactivation of the vegetative foodborne pathogens by high pressure carbon dioxide treatment (HPCT) was investigated. Pseudomonas aeruginosa IFO3445, Aeromonas hydrophila IFO13286, Salmonella enteritidis JCM3313, Salmonella typhimurium IID1000, Yersinia enterocolitica JCM1677, Escherichia coli O157:H7 ATCC35150, E. coli O157:H7 ATCC43889, Staphylococcus aureus FDA209P and Listeria monocytogenes 1/2a were used in this study. In all cases, HPCT at 35 °C, 10 MPa for 1 min reduced initial numbers by approximately 6 logs. In addition HPCT inactivation of 9 pathogenic strains of Bacillus cereus (mixture of spores and vegetative cells) was investigated. HPCT at 75 °C, 10 MPa for 120 min resulted in significant inactivation in all the strains. The effect of HPCT (30 MPa at 95 °C for up to 120 min) on the inactivation of Geobacillus stearothermophilus spores in the presence of sodium chloride (3% and 6% w/v), glucose (6% and 12% w/v) and ethanol (10% and 20% v/v) was also studied. Both sodium chloride and glucose had a protective effect and the level of inactivation was reduced. The effect was in proportion to the solute concentration. However, 10% and 20% ethanol did not significantly affect the level of inactivation.     

Comparison of two pre-enrichments broths for recovering Listeria spp. from salmon (Salmo salar) and salmon-trout (Oncorhynchus mykiss)

Low levels of occurrence of Listeria spp. in fresh salmon (Salmo_salar ) and salmon-trout (Oncorhynchus mykiss), may be related to the selectivity of the pre-enrichment broth recommended by ISO 11290-1. The purpose of this study was to compare the abilities of Fraser base (without supplements) and 0.1% (w/v) peptone water for recovering Listeria spp. from the fresh fish samples.Fifty-six fish were swabbed and the swabs placed in Fraser base and in 0.1% (w/v) peptone water. Samples were analysed 4–6 h later following the ISO 11290-1 protocol. A total of fifteen Listeria spp. positive samples were found. Three and twelve samples were found to contain respectively, L. monocytogenes and L. innocua. The Fraser base did not detect any of the three L. monocytogenes positive samples. Only two Listeria spp. positive samples were simultaneously recovered by the two broths.     

Inactivation of foodborne pathogens on gala apples by application of antimicrobial waxes

There is a need for effective postharvest controls capable of inactivating bacterial foodborne pathogens, which can be applied to the organic and conventional apple industries. This study evaluated the efficacy of natural antimicrobials (essential oils or cultured dextrose) when incorporated into carnauba wax and applied to apples. Organic Gala apples were spot inoculated with a five strains/serovars cocktail (∼9 Log CFU/mL) of Listeria monocytogenes, Shiga-toxigenic E. coli O157:H7, or Salmonella. Inoculated apples were coated with organic carnauba wax containing a 1% and 2% (v/v) mixture of essential oils (EOs) in equal proportions (oregano, clove bud, cinnamon bark, and coriander seed) or commercially cultured dextrose at 0.5% (w/v). Apples coated with carnauba wax only and uncoated apples were used as control treatments. Apples were stored at 20 °C and sampled for up to 40 days. Five treatments with three biological replicates and three samples per replicate were used for each treatment (n = 9). A sensory discrimination test was used to identify differences between waxed apples for treatments with the greatest efficacy. Carnauba wax containing 2% EOs was the most effective treatment for inactivating target foodborne pathogens inoculated on apples for 40 days. This treatment showed 4.05, 1.38 and 2.81 Log CFU/apple reduction in L. monocytogenes, E. coli O157:H7, and Salmonella, respectively, compared to uncoated apples. Carnauba wax containing 2% EOs showed significantly (P ≤ 0.001) lower populations of L. monocytogenes and Salmonella compared with 1% EOs, 0.5% cultured dextrose, or wax-only control. In contrast, there were no significant differences (P > 0.05) for E. coli O157:H7. Sensory evaluation showed that panelists could detect differences for apples treated with wax containing 2% EOs, but not for 1% EOs compared to wax-only control. This study provides information to the organic and conventional apple industry about the efficacy of antimicrobial waxes to inactivate bacterial foodborne pathogens.     

Quantitative identification of plant genera in food products using PCR and Pyrosequencing® technology

The ability to extract, amplify, identify and quantify fruit DNA from commercially available jams and yogurts was investigated. Efficient methods for extracting DNA from jams and yogurts were developed based on a modified CTAB protocol. DNA sequence alignment of plant chloroplast rbcL sequences allowed the development of a 104 bp PCR reaction capable of characterising plant genera present in fruit products using DNA amplification and direct sequencing to reveal single nucleotide polymorphisms (SNPs). The rbcL single nucleotide polymorphism approach was made quantitative by combining PCR analysis with Pyrosequencing^® technology. This enabled the detection of rhubarb yogurt in raspberry yogurt with a detection limit of 2% w/w based on the use of commercially available samples. The method represents a new quantitative approach for determining the identity of plant genera in products.     

A survey on the microbiological and chemical composition of buffalo milk in China

One hundred and twelve samples of raw buffalo milk were collected at four locations in China, and their microbiological and chemical composition was analyzed. Average levels of major components were: fat 7.59% (v/v), crude protein 4.86% (w/w), lactose 4.74% (w/w), total solids 18.44% (w/w), ash 0.85% (w/w), and pH 6.65. The crude protein, fat, total solids and ash contents of milk from multi-crossbreed buffalo were higher than those of river buffalo’s, but lower than those of crossbreed F₁ and F₂ buffalo’s. Microbiological enumeration revealed counts of total mesophilic aerobic bacteria of 5.59 log cfu/ml, bacterial endospores 2.31, lactic acid bacteria 4.62, fungi 1.79, coliforms 2.42, Escherichia coli 1.53, and Staphylococcus aureus 1.68. Listeria spp. were below detection level in all of the samples. The microbiological quality of buffalo milk was judged marginal and indicates the need for improved hygienic standards.     

Resistances to UV-C irradiation of Salmonella Typhimurium and Staphylococcus aureus in wet and dried suspensions on surface with egg residues

To clarify the effects of food sediments on ultraviolet-C (254 nm) sanitation in food-related environments, we examined the resistance of pathogenic bacteria (Salmonella Typhimurium and Staphylococcus aureus) cells, in wet and dried suspensions adhered with 1.5-15% w/v egg albumen, 1.5-15% yolk or 3.0-30% whole egg solutions, against UV-C irradiation. Bacterial suspensions (0.1 ml of 8 log CFU/ml) were put on 47 mmφ glass dishes and dried at room temperature (20-24 °C) for 180 min in a bio safety cabinet with ventilation. Viable S. Typhimurium and S. aureus cells in distilled water decreased during the drying period from 7.2 to 3.2 and from 8.0 to 6.5 log CFU/dish, respectively,. On the other hand, the bacteria cells were protected from drying by egg compounds, even by the lowest concentration. The UV-C treatment (0.16 mW/cm² for 10 min) showed a clear bactericidal effect in the absence of egg compounds. However, the bactericidal effect was inhibited by 15% yolk and 30% whole egg. Results in this study suggested that the small food sediment protect bacteria on the surfaces from dryness and UV-C irradiation and it might introduce cross contamination.     

Multiplex qualitative PCR assay for identification of genetically modified canola events and real-time event-specific PCR assay for quantification of the GT73 canola event

Genetically modified (GM) canola is the most widely grown oilseed crop in Canada. At this time, commercially produced GM canola cultivars in Canada have the events GT73/RT73 and Ms8xRf3. Commercial seed sale of canola cultivars containing the GM events such as OXY235 and T45 has been discontinued. Adventitious presence of GM seeds and grains in non-GM grains is a concern for international grain trade, and development of effective detection methods is important. A multiplex qualitative PCR procedure was established for the detection of the GM canola events OXY235, Ms8xRf3, T45 and GT73. The presence of the GM canola events was also successfully detected in ground spiked wheat and barley grain samples prepared at 0.1%, 0.5% and 1.0% levels (w/w). The GT73 real-time PCR assay was successfully used to quantify DNA extracted from spiked ground canola samples consisting of 5%, 1%, 0.5% and 0.1% GT73 (w/w).     

EFFECTS OF AEROSOL OT ON THE PHASE SEPARATION TEMPERATURES OF METHANOL/HYDROCARBON/WATER BLENDS

Methanol-gasoline blends have been under consideration for use as transportation fuels to help extend the current fuel supply. The use of these blends is limited, in part, because low temperatures and/or the presence of dissolved water can lead to phase separation. In this work, the effects 1 to 5 % w/v of a model twin-tailed surfactant, Aerosol OT (sulfosuccinic acid, bis[2-ethylhexyl] ester, [577-11-7]), on the phase separation temperature of a simulated gasoline-methanol fuel mixture doped with 0.1, 0.2, and 0.3% v/v dissolved water was studied. The Aerosol OT did lower the phase separation temperature substantially though not as much as straight chain surfactants examined in earlier work.     

Detection of gluten-containing cereals in flours and “gluten-free” bakery products by polymerase chain reaction

A polymerase chain reaction-based method for the detection of gluten-containing cereals in flours and “gluten-free” bakery products was optimized and its intralaboratory validation was carried out. The optimized method involved DNA isolation by chaotropic solid-phase extraction and PCR with primers of Dahinden et al. [Dahinden I., von Büren M., Lüthy J., 2001. A quantitative competitive PCR system to detect contamination of wheat, barley and rye in gluten-free food for coeliac patients. European Food Research and Technology 212, 228–233]. Using purified DNA, intrinsic detection limit of 42 ± 12 pg was determined, which corresponds to 10° genome copies. By the analysis of a panel of 26 European wheat cultivars and flours from six non-gluten-containing plants, which are commonly used for the production of gluten-free bakery products, inclusivity of 100% and exclusivity of 100% were determined. By the analysis of model samples of soya flour and cakes, detection limit of 0.1% (w/w) of fine wheat flour was determined, which is suitable for the analysis of “gluten-free” food products, as it is approximately equivalent to the limit of 10 mg per 100 g for gluten stated by Codex Alimentarius. The method was successfully applied to four samples of flours and 13 brands of biscuits designated “gluten-free”, out of which two flours and one brand of biscuits were found positive for gluten-containing cereals. The method proved to be suitable for routine use, it was relatively straightforward and could be completed in one working day.     

EFFECTS OF AEROSOL OT ON THE PHASE SEPARATION TEMPERATURES OF METHANOL/HYDROCARBON/WATER BLENDS

ABSTRACT

Methanol-gasoline blends have been under consideration for use as transportation fuels to help extend the current fuel supply. The use of these blends is limited, in part, because low temperatures and/or the presence of dissolved water can lead to phase separation. In this work, the effects 1 to 5 % w/v of a model twin-tailed surfactant, Aerosol OT (sulfosuccinic acid, bis[2-ethylhexyl] ester, [577-11-7]), on the phase separation temperature of a simulated gasoline-methanol fuel mixture doped with 0.1, 0.2, and 0.3% v/v dissolved water was studied. The Aerosol OT did lower the phase separation temperature substantially though not as much as straight chain surfactants examined in earlier work.     

Efficacy of Fir and Qysoom essential oils,alone and in combination,in controlling Listeria monocytogenes in vitro and in RTE meat products model

Listeria monocytogenes, frequently associated with ready-to-eat meat products (RTE-MP), is the causal agent of listeriosis, the virulent foodborne disease. Accordingly, this work aimed to study the effectiveness of essential oils (EOs) of different plants to control growth of L. monocytogenes in RTE-MP model. EOs antilisteric activities were screened by disk diffusion method. Then, efficacy of EOs (1% v/w) with strong inhibition activities were further examined in meat luncheon model, against 2 levels of L. monocytogenes strains cocktail (3 and 6 log CFU/g) coupled with storage at 4 °C for 14 days. The EOs of Fir and Qysoom showed to have the highest significant (p < 0.05) antilisteric activity. In the food model, L. monocytogenes populations in control samples increased by 4 log cycles after 14 days of storage at 4 °C. At the end of storage, for samples with low contamination; Fir, Qysoom, and EOs mixture had approximately 6.37, 6.04, and 5.53 log CFU/g of L. monocytogenes respectively, compared to 6.90 log of control. Whereas in the samples with high contamination level, populations reached to 8.43, 8.88 and 6.75 log CFU/g for Fir, Qysoom, and EOs mixture respectively, compared to 9.90 log of the control. The application of 1% EOs (v/w) to RTE-MP surfaces significantly showed to reduce (p < 0.05) the L. monocytogenes populations growth rate as compared to control in the 2 levels treatments after 14 days of storage at 4 °C. Accordingly, our results suggest that these EOs could be used as natural bio-preservatives in many food products produced in Jordan and worldwide, particularly in RTE-MP.     

Applicability of a novel reference molecule suitable for event-specific detections of maize NK603 based on both 5′ and 3′ flanking sequences

Plasmid molecule based reference material (RM) has been shown to be a good alternative as the calibrator for genetically modified organisms (GMOs) identification and quantification, while most of the currently developed plasmid RM can only be used for one specific target detection. In this study, a flexible plasmid RM pNK containing three DNA fragments, i.e. 5′ and 3′ event-specific sequences of maize NK603 and endogenous gene zSSIIb, was developed. We have proved that pNK is suitable for using as a calibrator in both 5′ and 3′ event-specific detection of maize NK603, compared with that of genuine genomic DNA. The limit of detection (LOD) was 10 copies of pNK DNA in conventional PCR assays. The absolute LOD and limit of quantification (LOQ) in quantitative PCR assays were 5 and 25 copies. The standard curves targeting to zSSIIb, 5′ and 3′ event-specific sequences based on pNK DNA showed high reaction efficiency and good linearity. Also, low bias and variations were obtained in practical samples quantification using pNK as the calibrator. These results demonstrated that the developed pNK is flexible and suitable for identification and quantification of maize NK603, as a preferable substitute of RM from the plant raw material.     

Comparing the effectiveness of chitosan and nanochitosan coatings on the quality of refrigerated silver carp fillets

The coating effects of chitosan and chitosan nanoparticles on the quality of silver carp (Hypophthalmicthys molitrix) fillets during refrigerated storage at 4 °C were compared. Solutions of Chitosan (2%, w/v) and nanochitosan (2%, w/v) were used for the coating. The control and the coated fish samples were analyzed periodically for microbiological (total mesophilic and psychrotrophic count), physicochemical (pH, TVB-N, TBARS), and sensory attributes. The results indicated that both chitosan and nanochitosan coating were effective for the preservation of silver carp fillets during refrigerated storage. However, nanochitosan exhibited higher antimicrobial activity than chitosan during the storage period. Furthermore, nanochitosan showed a stronger ability to inhibit the TVB-N content than chitosan. Therefore, to extend the shelf life and delay the deterioration of fresh silver carp fillets during refrigerated storage, nanochitosan coating is more effective.     

Use of a commercial mixture of volatile compounds from the fungus Muscodor to inhibit Salmonella in ground turkey and beef

Additional interventions to reduce the risk of Salmonella in ground meat products are needed in the industry. Fungi in the genus Muscodor produce an array of volatile compounds with antimicrobial activity. A commercial mixture of these volatile compounds (all considered to be GRAS), in proportions similar to that produced by the fungus, was assessed for its inhibitory activity against Salmonella in vitro. The minimal inhibitory concentration of the volatiles mixture for growth of Salmonella enterica in Mueller-Hinton broth was 0.5% (v/v). Exposure to the vapor phase of the volatile compounds similarly inhibited visible growth of Salmonella on agar (up to 6 cm zone of inhibition). Addition of the volatiles mixture (0.25%–1.0% v/w) inhibited Salmonella by 1.5 and 2.8 log₁₀ CFU in ground turkey (85% or 93% lean, respectively) and 2.2 and 1.7 log₁₀ CFU in ground beef (73% or 93% lean, respectively) during a 5 day period at 8 °C. Addition of the volatiles also inhibited growth of normal microflora on ground turkey at 8 °C by approximately 5.3 log₁₀ CFU. These findings indicate this mixture of volatile compounds retards growth of spoilage organisms and Salmonella in ground meat.