Anthocyanins and Functional Compounds Change in a Third-Generation Snacks Prepared Using Extruded Blue Maize, Black Bean, and Chard: An Optimization.

The effect of extrusion cooking on bioactive compounds in third-generation snacks (TGSE) and microwave-expanded snacks (MWSE) prepared using black bean, blue maize, and chard (FBCS) was evaluated. FBCS was extruded at different moisture contents (MC; 22.2-35.7%), extrusion temperatures (ET; 102-142 °C), and screw speeds (SP; 96-171 rpm). Total anthocyanin content (TAC), contents of individual anthocyanins, viz., cyanidin-3-glucoside, malvidin-3-glucoside, pelargonidin-3-glucoside, pelargonidin-3-5-diglucoside, and delphinidin-3-glucoside chloride, total phenolic content (TPC), antioxidant activity (AA), and color parameters were determined. TAC and individual anthocyanin levels increased with the reduction in ET. ET and MC affected the chemical and color properties; increase in ET caused a significant reduction in TPC and AA. Microwave expansion reduced anthocyanin content and AA, and increased TPC. Extrusion under optimal conditions (29% MC, 111 rpm, and 120 °C) generated products with a high retention of functional compounds, with high TAC (41.81%) and TPC (28.23%). Experimental validation of optimized process parameters yielded an average error of 13.73% from the predicted contents of individual anthocyanins. Results suggest that the TGSE of FBCS obtained by combining extrusion and microwave expansion achieved significant retention of bioactive compounds having potential physiological benefits for humans.

In Vitro Antibacterial Activity of Hibiscus sabdariffa L. Phenolic Extract and Its In Situ Application on Shelf-Life of Beef Meat.

Compounds from spices and herbs extracts are being explored as natural antibacterial additives. A plant extract used in traditional folk medicine is Hibiscus sabdariffa L., also known as Roselle. Therefore, the potential use of a phenolic hibiscus extract as antibacterial or natural food preservative was analyzed in vitro and in situ. A phenolic extract was obtained from hibiscus calyces and fractionated, and then the fractions were tested against foodborne pathogen bacteria. Liquid-liquid extraction and solid-phase extraction were used to fractionate the hibiscus extract, and HPLC was employed to analyze the fractions' phenolic composition. Minimum bactericidal concentration (MBC) and minimal inhibitory concentration (MIC) were calculated for brute hibiscus phenolic extract, each of the fractions and pure commercial phenolic compounds. Bacteria tested were Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Listeria monocytogenes and Bacillus cereus. The fraction obtained after liquid-liquid extraction presented the best performance of MBC and MIC against the bacteria tested. Furthermore, a hibiscus ethanolic extract was employed as a natural preservative to extend the shelf-life of beef. Microbiological, color and sensory analyses were performed to the meat during the shelf-life test. The application of the phenolic hibiscus extract also showed an increase of the duration of the meat`s shelf life.

Functional Expression and One-Step Protein Purification of Manganese Peroxidase 1 (rMnP1) from Phanerochaete chrysosporium Using the E. coli-Expression System.

Manganese peroxidases (MnP) from the white-rot fungi Phanerochaete chrysosporium catalyse the oxidation of Mn2+ to Mn3+, a strong oxidizer able to oxidize a wide variety of organic compounds. Different approaches have been used to unravel the enzymatic properties and potential applications of MnP. However, these efforts have been hampered by the limited production of native MnP by fungi. Heterologous expression of MnP has been achieved in both eukaryotic and prokaryotic expression systems, although with limited production and many disadvantages in the process. Here we described a novel molecular approach for the expression and purification of manganese peroxidase isoform 1 (MnP1) from P. chrysosporium using an E. coli-expression system. The proposed strategy involved the codon optimization and chemical synthesis of the MnP1 gene for optimised expression in the E. coli T7 shuffle host. Recombinant MnP1 (rMnP1) was expressed as a fusion protein, which was recovered from solubilised inclusion bodies. rMnP1 was purified from the fusion protein using intein-based protein purification techniques and a one-step affinity chromatography. The designated strategy allowed production of an active enzyme able to oxidize guaiacol or Mn2+.