No abstract

Autofocusing, as a simple and safe technique, was used to fractionate casein hydrolysate based on the amphoteric nature of its peptides. The antibacterial activity of casein hydrolysate and its autofocusing fractions (A1-10) was examined against Escherichia coli and Bacillus subtilis. The basic fraction A9 exhibited the highest activity with minimum inhibitory concentration (MIC) of 150 μg/mL, whereas casein hydrolysate showed MIC values ranging from 2000 to 8000 μg/mL. The antibacterial peptides in A9 were purified by using a series of size exclusion and reversed phase chromatographies. Three peptides exhibited the most potent antibacterial activity with MIC values ranging from 12.5 to 100 μg/mL. These peptides were generated from α(s2)-casein, α(s1)-casein, and κ-casein and identified as K165 KISQRYQKFALPQYLKTVYQHQK188, I6KHQGLPQEV15, and T136EAVESTVATL146, respectively. Therefore, the results revealed that casein hydrolysate had potent antibacterial peptides that could be isolated by autofocusing technique.

No abstract

No abstract

Pseudomonas spp are considered the most common milk-associated psychotropic bacteria, leading to milk deterioration during storage so, our study aimed to study the growth behavior of Pseudomonas aeruginosa in milk after employing chitosan nanoparticles (CsNP 50, 25 and15 mg/100ml) and selenium nanoparticles (SeNP 0.5, 0.3 and 0.1mg/100ml) as a trial to control the bacterial growth in milk during five days of cooling storage. Our study relies on using ion gelation method and green synthesis for conversion chitosan and selenium to nanosized particles, respectively, we subsequently confirmed their size and shape using SEM and TEM. Depending on using Pseudomonas selective agar medium supplemented by glycerol for monitoring the bacterial growth along the cooling storage. Our findings reported that, both synthesized nanoparticles exhibit antibacterial activity in a dose dependent manner. Moreover, the uniform aggregated with average size 60 ± 5 nm CsNP50 could inhibit the P. aeruginosa survival growth to mean average 2.62 ± 1.18 log10cfu/ml in the fifth day of milk cooling storage, also it was noted that the hexagonal particles with average size 20 ± 5nm SeNP0.5 could inhibit 2.49 ± 11 log10cfu/ml in comparison to, the control P. aeruginosa milk group exhibited growth survival 7.24 ± 2.57 log10cfu/ml under the same conditions. As conclusion, in order to improve milk safety, we suggest employing chitosan and selenium nanoparticles.

The aim of work is to evaluate antibacterial activities of egg white hydrolysates against Escherichia coli, Staphylococcus aureus and Bacillus subtilus. Also, the effect of the highest antibacterial hydrolysate on shelf life of soft cheese was evaluated. The Egg white hydrolysis was conducted in 1 mol/l HCl solution (pH 1.5 ,2, 2.5, 3, 3.5, 4, 4.5) at temperature of 37°C for 48hours using pepsin enzyme (2% enzyme/substrate (E/S) ratio). Results revealed that raw egg hydrolysate (REWH) hydrolyzed at pH 1.5 after 12hours was the most potent antibacterial hydrolysate. This hydrolysate extended the shelf life of soft cheese to 28 days. In addition, this hydrolysate showed a significant inhibitory effect on total bacterial count and yeast & mold count. Escherichia coli was the most sensitive organism to this hydrolysate. Accordingly, REWH obtained at pH 1.5 is considered as the most efficient natural preservative to be applied in food system.

No abstract