Impact of Physicochemical Modifications in Casein Promoted by UV-C on the Peptide Profile of Gastric Digestion and the Transepithelial Transport of Peptides.

Caseins are the main proteins in milk, and their structure and spatial conformation are responsible for their slow digestion rate. The release of bioactive and ß-casomorphin peptides from casein digestion may induce allergic responses during consumption. Spectroscopic techniques were used to observe the structural changes in casein conformation induced by Ultraviolet light irradiation (UV-C). Raman spectroscopy results showed more pronounced peaks at 618 and 640 cm-1 for phenylalanine and tyrosine moieties of the photolyzed micellar casein, respectively, suggesting changes in the micelle structure. The decrease in the intensity of Raman signals for tryptophan and tyrosine corroborates to the UV-C-induced modifications of the micelle structure. Particle size distribution showed a decrease in the average micelle size after 15 min of UV-C exposure, while low-temperature, long-time (LTLT) pasteurization led to the formation of large aggregates, as observed by atomic force microscopy. UV-C did not impact the formation or transport of peptides, as observed by using the Caco-2 cell as a model for peptide absorption. However, the absence of the opioid peptide SRYPSY from κ-casein and only 20% of the concentration of opioid peptide RYLGY were noted. This work demonstrated that UV-C can be utilized to induce the physicochemical modification of dairy products, promoting a higher digestion rate and reducing allergenicity.

In vivo functional and health benefits of a prebiotic soursop whey beverage processed by high-intensity ultrasound: Study with healthy Wistar rats.

New technologies for food processing have been used to enhance the beneficial effects of foods. This study aimed to evaluate the effects of a prebiotic soursop whey beverage processed by high-intensity ultrasound (HIUS) on healthy rats. Whey beverages were processed by HIUS (20KHz, 520 W of nominal power, <53 °C, 20.3 W of acoustic power, energy density of 2.9 kJ.cm-3 and 9.5 min to process 100 mL) and high-temperature short-time (HTST, 75 °C for 15 s) before being supplemented to Wistar rats by gavage for 15 days. Antioxidant, antidiabetic, anti-hypertensive, and anticancer activities, lipid peroxidation, bioactive peptides, and microstructure of the beverages were analyzed. In addition, the body mass, food, and water intake, systolic blood pressure, biochemical and oxidative stress parameters were measured. The sonicated beverage induced satiety, decreased glutathione peroxidase activity, total triglycerides, very-low-density lipoprotein cholesterol, and alanine aminotransferase. These findings suggest that ultrasound technology can provide in vivo health and functional benefits.

Evaluation of the antimicrobial activity of chitosan and its quaternized derivative on E. coli and S. aureus growth

Abstract Chitosan is largely known for its activity against a wide range of microorganisms, in which the most acceptable antimicrobial mechanism is found to include the presence of charged groups in the polymer backbone and their ionic interactions with bacteria wall constituents. This interaction suggests the occurrence of a hydrolysis of the peptidoglycans in the microorganism wall, provoking the leakage of intracellular electrolytes, leading the microorganism to death. The charges present in chitosan chains are generated by protonation of amino groups when in acid medium or they may be introduced via structural modification. This latter can be achieved by a methylation reaction resulting in a quaternized derivative with a higher polymeric charge density. Since the charges in this derivative are permanents, it is expected a most efficient antimicrobial activity. Hence, in the present study, commercial chitosan underwent quaternization processes and both (mother polymer and derivative) were evaluated, in gel form, against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), as model bacteria. The results, as acquired from turbidity measurements, differ between materials with an expressive reduction on the Gram-positive microorganism (S. aureus) growth, while E. coli (Gram-negative) strain was less sensitive to both polymers. Additionally, the antibacterial effectiveness of chitosan was strongly dependent on the concentration, what is discussed in terms of spatial polymer conformation.