Utilization of spray-dried raspberry powder as a natural additive to improve oxidative stability, microbial quality and overcome the perception of discoloration in vacuum-packed ground beef during chilled storage.

The present study was conducted to determine the effects of spray-dried raspberry powder (SDRP) (CONTROL, 1.0%, 2.0%, and 3.0%) as a natural antioxidant, antimicrobial, and colorant on physicochemical properties, lipid oxidation, discoloration, and microbial quality of vacuum-packed (VP) ground beef during chilled storage at 2 ± 0.5 °C for 18 days. By incorporating SDRP into VP ground beef pH, lipid oxidation (TBARS), lightness, and hue angle (h°) values decreased (P < .01), while redness (a*) and chroma (C*) values improved (P < .01). SDRP treatments had higher redness, more stable color, and lower pH and TBARS values during storage in a dose-dependent manner (P < .05), demonstrating that SDRP had a preventive effect on lipid oxidation and discoloration. The combination of vacuum packaging with SDRP generally resulted in lower bacterial growth during storage. These results demonstrated that 2% or 3% SDRP treatment has promising potential as an effective strategy to achieve oxidative and microbial stability and overcome discoloration in VP fresh meats.

From Secretion in Pichia pastoris to Application in Apple Juice Processing: Exo-Polygalacturonase from Sporothrix schenckii 1099-18.

BACKGROUND: Polygalacturonases are a group of enzymes under pectinolytic enzymes related to enzymes that hydrolyse pectic substances. Polygalacturonases have been used in various industrial applications such as fruit juice clarification, retting of plant fibers, wastewater treatment drinks fermentation, and oil extraction. OBJECTIVES: The study was evaluated at the heterologous expression, purification, biochemical characterization, computational modeling, and performance in apple juice clarification of a new exo-polygalacturonase from Sporothrix schenckii 1099-18 (SsExo-PG) in Pichia pastoris. METHODS: Recombinant DNA technology was used in this study. Two different pPIC9K plasmids were constructed with native signal sequence-ssexo-pg and alpha signal sequence-ssexo-pg separately. Protein expression and purification performed after plasmids transformed into the Pichia pastoris. Biochemical and structural analyses were performed by using pure SsExo-PG. RESULTS: The purification of SsExo-PG was achieved using a Ni-NTA chromatography system. The enzyme was found to have a molecular mass of approximately 52 kDa. SsExo-PG presented as stable at a wide range of temperature and pH values, and to be more storage stable than other commercial pectinolytic enzyme mixtures. Structural analysis revealed that the catalytic residues of SsExo- PG are somewhat similar to other Exo-PGs. The KM and kcat values for the degradation of polygalacturonic acid (PGA) by the purified enzyme were found to be 0.5868 µM and 179 s-1, respectively. Cu2+ was found to enhance SsExo-PG activity while Ag2+ and Fe2+ almost completely inhibited enzyme activity. The enzyme reduced turbidity up to 80% thus enhanced the clarification of apple juice. SsExo-PG showed promising performance when compared with other commercial pectinolytic enzyme mixtures. CONCLUSION: The clarification potential of SsExo-PG was revealed by comparing it with commercial pectinolytic enzymes. The following parameters of the process of apple juice clarification processes showed that SsExo-PG is highly stable and has a novel performance.

Oxidative stress related changes in the brain of hypercholesterolemic rabbits.

In recent years, there has been increasing evidence that cholesterol plays a role in the pathology of Alzheimer disease. Since hypercholesterolemia was reported to increase the levels of reactive oxygen species and Alzheimer disease has clearly involved an oxidative component, it is possible that hypercholesterolemia is via increased oxidant production facilitating the disease development of the neurodegenerative disease. Therefore, we tested in an established model of enhanced cholesterol feed in rabbits the effects of serum cholesterol increase on oxidative stress parameters as well in serum as in the brain. In addition to that we tested the effects of vitamin E on the cholesterol-induced oxidative stress. Since Alzheimer disease is largely connected with increased protein oxidation whereas cholesterol is rather connected with lipid peroxidation processes, we tested both protein carbonyl levels and the formation of malondialdehyde, a marker of lipid peroxidation. We could clearly demonstrate an increase in serum malondialdehyde due to high cholesterol feeding, which is accompanied by an increase in protein oxidation parameters in the brain, especially in the hippocampus. Therefore, we suggest that specific neuropathological changes occur during the feeding of hypercholesterolemic diet.