Intelligent colorimetric pH sensoring packaging films based on sugarcane wax/agar integrated with butterfly pea flower extract for optical tracking of shrimp freshness

A novel pH colorimetric film was prepared from various sugarcane wax (SW) concentrations (1, 1.5 and 2% w/v) on agar matrix (Agr) combined with butterfly pea flower (BF) extract for monitoring the shrimp freshness. A combination of BF anthocyanins with SW as lipid (hydrophobic) showed different changes in color under acidic conditions (pH 2-6) with slight changes under alkalinity (pH 7-12), which matched the visual color changes of two different ammonia vapors (50 and 100 mmol/l). FTIR, XRD spectra, and SEM micrographs revealed that SW was effectively fixed into the Agr-BF network during the film-forming process. The different homogenized SW films enhanced the physical and mechanical properties without significant differences in elongation and water vapor permeability. Remarkably, SW films displayed complete protection against UV-vis light (0%) and valuable reduction in visible light. This study presents SW colorimetric films as promising natural derivatives for smart packaging in tracking food freshness.

Biochemical characterization of the endo-α-N-acetylgalactosaminidase pool of the human gut symbiont Tyzzerella nexilis

Three large (2084-, 984-, and 2104-amino acids) endo-α-N-acetylgalactosaminidase candidate genes from the commensal human gut bacterium Tyzzerella nexilis were successfully cloned and subsequently expressed in Escherichia coli. Activity tests of the purified proteins revealed that two of the candidate genes (Tn0153 and Tn2105) were able to hydrolyze the disaccharide unit from Galβ1-3GalNAc-α-pNP. The biochemical characterization revealed optimum pH conditions of 4.0 for both enzymes and temperature optima of 50 °C. The addition of 2-mercaptoethanol, Triton X-100 and urea had only minor effects on the activity of the enzymes, and the addition of imidazole and sodium dodecyl sulfate led to a significant reduction of the enzymes' activities. A mutational study identified and confirmed the role of the catalytically significant amino acids. The present study describes the first functional characterization of members of the GH101 family from this human gut symbiont.

Exploring the Potential of High-Voltage Electric Field Cold Plasma (HVCP) Using a Dielectric Barrier Discharge (DBD) as a Plasma Source on the Quality Parameters of Carrot Juice

The main aim of the current investigation was to contemplate the impact of high-voltage electric field cold plasma (HVCP) on different quality characteristics (enzymes, microbial activities, coloring pigments, ascorbic acid, polyphenolic compounds, °Brix, acidity, and color index) of carrot juice in correlation with thermal processing. A carrot juice (250 mL) sample sealed in pre-sterilized food-grade bottles, which placed between two dielectric quartz plates for HVCP treatment. The gap between the plates was 30 mm, and a stable and uniform plasma dielectric barrier discharge (DBD) generated for 3 and 4 min at 60, 70, and 80 kV. Air was used as a working gas during the DBD-based plasma treatment. The observed rise in temperature was 2-5 °C during the HVCP treatment. A water bath was used to carry out thermal treatment (100 °C for 5 min). The maximum inactivation of enzymes and microorganisms was achieved with thermal treatment and then with HVCP treatment at 70 kV for 4 min. However, maximum retention of coloring compounds, ascorbic acid, total phenols, flavonoids, and tannins was found following HVCP (70 kV for 4 min) treatment compared to thermal treatment. The °Brix, pH, and acidity remained unchanged irrespective of treatments. These findings suggest that HVCP treatment at 70 kV for 4 min may be a good alternative to thermal treatment, and it may successfully be applied in carrot juice production, resulting in reduced enzymes, lower microbial activity, and improved bioactive compounds. The prospects of overcoming the existing conventional physical and chemical methods for sterilization make it a novel and more economical technique to maintain food's natural nourishment, composition, appearance, structure, and freshness.

1,3-Di(2-dipyridyl)propan-1,3-dione – a new fluorogenic labeling reagent for milk oligosaccharides

We herein demonstrate the use of 1,3-di(2-dipyridyl)propan-1,3-dione (DPPD) as a fluorogenic label for oligosaccharides. A number of milk-derived oligosaccharide standards were successfully labeled with this reagent, with the advantage of greatly simplified sample preparation compared to other commonly used fluorescent tags. DPPD shows a selectivity for oligosaccharides which do not possess a 2-acetamido-2-deoxy-hexose moiety at the reducing terminus, potentially aiding in the identification of complex mixtures of carbohydrates. The use of DPPD for the structural determination of oligosaccharides through exoglycosidase treatment, quantitative analysis of reactions, and in the synthesis of labeled oligosaccharides was also explored. This reagent has, in addition to the analysis of individual and mixed oligosaccharides, potential applications in the study of glycosidases and glycosyltransferases and as such represents a valuable addition to the tools available to the glycoscientist.