Influence of incorporating dried fruits on dairy drinks characteristics focusing on their antimicrobial effects.

Objective: The study was designed to show the effect of adding different levels of dried fruit extracts for 14 days on sensory and chemical parameters in dairy drinks. The survival of Pseudomonas aeruginosa and Bacillus cereus in artificially contaminated dairy drinks fortified with these extracts was also studied. Materials and Methods: The freshly watery extracts and nonaqueous extracts of dried fruits were prepared by rotary evaporators and solvents, respectively. The determination of the minimum inhibitory concentration of dried fruit extracts was achieved using the disc diffusion test. The sensory evaluation of samples was done, while the chemical parameters of the examined samples were determined by the calibrated analyzer. In addition, the degree of survival of P. aeruginosa and B. cereus in inoculated milk samples was also estimated. Results: In pasteurized and Rayeb milk samples, the water extract of carob and all alcoholic dried fruit extracts had a significant effect on compositional parameters in comparison to control samples. At day 14 of pasteurized milk storage, the watery (20.0%) and alcoholic (10.0%) extracts of carob significantly improved its sensory parameters. Conclusion: Based on the survival results, all utilized dried fruit extracts had a significant inhibitory effect on P. aeruginosa and B. cereus growth in the fortified milk samples at the end of storage. This trial of the survival of these new dairy drinks is the first investigation, particularly in the Middle East. Extracts of utilized dried fruits have prospective functions that enhance dairy drink characteristics.

Elimination of detached Listeria monocytogenes from the biofilm on stainless steel surfaces during milk and cheese processing using natural plant extracts.

Bacterial cells can form biofilm on food contact surfaces, becoming a source of food contamination with profound health implications. The current study aimed to determine some Egyptian medicinal plants antibacterial and antibiofilm effects against foodborne bacterial strains in milk plants. Results indicated that four ethanolic plant extracts, Cinnamon (Cinnamomum verum), Chamomile (Matricaria chamomilla), Marigold (Calendula officinalis), and Sage (Salvia officinalis), had antibacterial (12.0-26.5 mm of inhibition zone diameter) and antibiofilm (10-99%) activities against Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes and Salmonella Typhimurium. The tested extracts had minimum inhibitory concentration values between 0.14 and 2.50 mg/ml and minimum bactericidal concentration values between 0.14 and 12.50 mg/ml. L. monocytogenes was more sensitive for all tested ethanolic extracts; Sage and Cinnamon showed a bacteriocidal effect, while Chamomile and Marigold were bacteriostatic. The ethanolic extracts mixture from Chamomile, Sage, and Cinnamon was chosen for its antibiofilm activity against L. monocytogenes using L-optimal mixture design. Gas chromatography and mass spectrometry analysis showed that this mixture contained 12 chemical compounds, where 2-Propenal,3-phenyl- had the maximum area % (34.82%). At concentrations up to 500 µg/ml, it had no cytotoxicity in the normal Vero cell line, and the IC50 value was 671.76 ± 9.03 µg/ml. Also, this mixture showed the most significant antibacterial effect against detached L. monocytogenes cells from formed biofilm in stainless steel milk tanks. At the same time, white soft cheese fortified with this mixture was significantly accepted overall for the panelist (92.2 ± 2.7) than other cheese samples, including the control group.

Investigation of the influence of xanthan on mozzarella cheese characteristics focusing on its antimicrobial effect.

Objective: This study was designed to show the effect of adding different levels of microbial (lab-produced) and commercial xanthan (CX) for 30 days on the sensory, chemical, and microbiological parameters of mozzarella cheese (MC). Materials and Methods: The production of xanthan was done in Garcia-Ochoa's medium. The sensory evaluation of the examined MC was achieved through a tabulated scorecard. The Gerber method was used for the determination of MC fat%. The mean counts of staphylococci [colony forming unit (CFU)/gm], coliforms (most probable number/gm), fungi (CFU/gm), and mesophilic bacteria (CFU/gm) were estimated in different fortified cheeses. Also, mean counts of Escherichia coli O157 and Staphylococcus aureus in artificially contaminated MC were determined. Results: The microbial xanthan (MX) had a significant (p < 0.05) effect on the sensory parameters of the examined samples with its concentration (0.0007%) after 20 days of storage. The MX (0.0005%) and CX (0.0002%) had a significant effect on moisture, fat in dry matter, and protein percentage of MC throughout the storage period. The high meltability degree of MC was observed in samples with both types of xanthan (0.0002%) at the end of storage. Conclusion: Both types of xanthan at all concentrations had a significant reducing effect on E. coli O157 and S. aureus in all samples from 10 to 30 days of storage. Xanthan has accepted attentiveness and offers beneficial and safe characteristics that improve its adaptability in MC. In the Middle East, this survival trial of E. coli O157 and S. aureus in the MC supplemented by xanthan is considered a scarce exploratory investigation.

A comparative study on the antifungal effect of potassium sorbate, chitosan, and nano-chitosan against Rhodotorula mucilaginosa and Candida albicans in skim milk acid-coagulated (Karish) cheese.

Background and Aim: Yeasts are common contaminants in the cheese industry, which frequently arise from raw milk, the surrounding environment, and equipment, resulting in economic losses in addition to health hazards. This study aimed to compare the antifungal effect of chitosan and nano-chitosan as natural preservatives with a commonly used chemical preservative (potassium sorbate) against Rhodotorula mucilaginosa and Candida albicans. Materials and Methods: Laboratory Karish cheese was manufactured with the addition of potassium sorbate, chitosan, nano-chitosan, and their combinations at different concentrations. The survival of R. mucilaginosa and C. albicans was monitored in different treatments (CR, PR1, PR2, CR1, CR2, NR1, NR2, MR, CC, PC1, PC2, CC1, CC2, NC1, NC2, MC) during storage in a refrigerator with continuous measurement of pH. The impact of using these antifungal agents on the organoleptic parameters of Karish cheese during storage was also evaluated. Results: There was a significant decrease in the count of yeasts in all treatments from the 3rd day of storage, while the mixture of 0.1% potassium sorbate (MR) and 2% chitosan (MC) improved the antifungal effect of chitosan with a lower potassium sorbate concentration and showed the best antifungal effects against both R. mucilaginosa and C. albicans. This combination reduced the yeast count from 8.92 and 9.57 log10 colony-forming unit (CFU)/g in MR and MC treatments, respectively, until it became undetectable on the 9th day of storage, which was earlier than for all other treatments. It was noted that the addition of chitosan nanoparticles (ChNPs) at either 0.25% (NR1 and NC1) or 0.5% (NR2 and NC2) during the manufacturing of Karish cheese significantly lowered the counts of R. mucilaginosa and C. albicans compared with chitosan with a higher molecular weight, but significantly lower than potassium sorbate until 6th day of storage as all treatments of chitosan nanoparticles became significantly higher than potassium sorbate treatments. After 9 days of storage, NR2 and NC2 treatments showed the most significant decreases in count (3.78 and 4.93 log10 CFU/g, respectively), indicating better stability of ChNPs. At the end of the storage period, PR2, PC2, CR2, and CC2 showed significantly high pH values among the groups of 4.8, 5.0, 4.8, and 5.1, respectively. The overall acceptability was significantly higher in treated Karish cheese samples than in the control group, especially at the end of the storage period. Conclusion: Potassium sorbate, chitosan, and ChNPs are effective antifungal preservatives against R. mucilaginosa and C. albicans. In addition, the combination of chitosan with potassium sorbate showed synergistic antifungal activity. These additives also preserve the sensorial criteria longer than for cheese without preservatives.

Characterization of multidrug-resistant potential pathogens isolated from milk and some dairy products in Egypt.

Objective: This study aimed to explore the incidence and antimicrobial resistance (AMR) of Escherichia coli, Staphylococcus aureus, and Bacillus cereus in raw milk and some Egyptian dairy products, namely Kariesh cheese and rice with milk. Material and Methods: 112 samples (70 raw milk, 30 Kariesh cheese, and 12 rice with milk) were randomly collected from different districts in Cairo and Giza, Egypt. The samples were examined for E. coli, S. aureus, and B. cereus presence. The susceptibility of the obtained isolates was tested against 11 antimicrobials using the disk diffusion method, and further, the presence of AMR genes was examined. Results: The incidences of E. coli, S. aureus, and B. cereus were 69.64%, 12.5%, and 16.7% in the examined samples, respectively. The antibiogram indicated that E. coli isolates (n = 60) were resistant to gentamycin (73.33%), ampicillin (AM, 53.3%), and cefotaxime (CTX, 16.66%). Multidrug-resistant (MDR) E. coli strains (n = 5) were tested for ß-lactams resistance genes. blaTEM was detected in all isolates, and two of them additionally carried blaCTX-M. Staphylococcus aureus isolates (n = 10) were resistant to AM (100%), followed by tetracycline (TE), CTX, and gentamycin (60% each). All MDR S. aureus strains (n = 4) carried blaZ and tetK, and three of them additionally carried aac(6')-aph (2''). Bacillus cereus isolates (n = 30) showed resistance to AM (100%), amoxicillin (20%), and TE (6.66%). bla and tetA genes were detected in all MDR B. cereus isolates (n = 6). Conclusion: Our findings denote the high incidence of potential health hazards in raw milk and some of its products and the existence of AMR bacteria, including MDR strains, which can cause human illnesses that are difficult to treat.

Microbiological safety and quality survey of some dairy confectioneries with cream filling and topping.

Background: Dairy confectionaries are recently categorized as an important part of different consumers' diets with increasing demand for cream-based cakes "Tourta" and gateau which are used as celebrating food for almost all occasions and celebrations. Aim: The study was designed for evaluating general quality and safety of such products. Methods: 100 cream-based (for topping and filing) samples; 50 cakes "Tourta" and 50 gateau, were purchased separately from several pastry shops covering international, national, and local brands in Great Cairo, Egypt, and subjected to microbiological analysis. Results: Results showed that international brands were the best for gateau samples while national brands were the best quality for cake samples. Regardless of the brand, the general hygienic quality of the cake product "Tourta" was lower on an average total colony, coliforms, yeast, and mold counts as compared with the gateau product. Although coliforms were found in 100% of the examined samples with the highest mean value of 33 × 102 ± 7.0 × 102 CFU/g in local gateau samples, Escherichia coli and Salmonella spp. could not be detected in these samples. Staphylococcus aureus was isolated from 8% of the total examined samples with the highest incidence of (22.2%) and a mean count of 38 × 10 ± 6.0 × 10 CFU/g in local brand gateau samples. Bacillus cereus was extensively isolated with the highest incidence in cake samples (32%) and mean counts higher than 103 in all of the examined samples. Bacillus cereus strains have harbored more than one toxigenic gene. In this aspect, nhe gene was the most predominant one as it was detected in 100% of the examined isolates, followed by cytK gene in 80%, whilehbl and ces genes could not be found. According to the Egyptian Standard specifications for cake (ES: 4037/2020), a higher acceptability degree was reported for the international brand gateau and cake "Tourta" samples. The incidence of using any preservative as an inhibitory substance was also analyzed generally using the Bacillus subtilis disk assay technique, but all samples were negative using this technique indicating the need for a more advanced technique for its detection such as using high-performance liquid chromatography. Conclusion: Finally, it was concluded that; more attention is needed to cream-based cakes' quality and safety, with essential modification required in the standards of cakes in Egypt.

MILK AS A SUBSTITUTE FOR SERUM IN DIAGNOSIS OF TOXOPLASMOSIS IN GOATS.

The present study determined the milk value rather than serum in diagnosis of toxoplasmosis in goats using ELISA and Modified Agglutination Test (MAT). ELISA proved to be more specific and sensitive (92% & 85%), than MAT (90% & 80%) in diagnosis of Anti-T. gondii Antibodies (ATAb) in group of microscopically proved T gondii aborted goats respectively. There was a direct relationship between.the mean ELISA O.D. value and the level of Ab-titer in MAT positive sera. The overall prevalence of infection in 600 serum samples from grazing goats was 22% and 20% after examination using ELISA and IAT respectively. It was lower after examination of their milk (20%) and (18%) by both techniques respectively. ATAb were significant high in serum (P < 0.05) during January, February and March, decreased significantly in April (P < 0.05) till August, then significant increased (P < 0.05) from September to December using ELISA. In time where ATAb were present by different levels among the whole year in serum, it didn't diagnose in milk from June to September. The infection was high in Egyptian Baladi breed in serum and milk (30% and 27%), while the Barki breed was the lowest one (13.33% and 12%) respectively. High rate of infection (30% in serum and 27% in milk) was recorded in goats > 2 years old, while no ATAb could be detected in goats less than one year old. The highest prevalence of infection (39.28% in serum and 37.14% in milk) was in Qalyoubia, the lowest one (11.25% & 9.58%) was in Giza governorate. The prevalence of infection was high after examination of serum and milk of goats with previous history of abortion in comparison with the other goats.