Valorization of Larix decidua Mill. bark by functionalizing bioextract onto chitosan films for sustainable active food packaging

The present study explored the use of chitosan films functionalized with antioxidants extracted from Larix decidua Mill. bark for active packaging. The pristine chitosan and extract-incorporated chitosan films were evaluated for their structural, physico-mechanical, thermal, viscoelastic and antioxidant properties using advanced characterization techniques. The infrared spectroscopy revealed hydrogen bonding between the extract polyphenolic antioxidants and chitosan, whereas the surface microscopy studies indicated good compatibility between them. The addition of bark extract caused a significant increase in color parameters and solubility with reduction in swelling and elongation at break of the films. The thermal analysis indicated a drop in thermal stability of chitosan films modified with the extract. The dynamic mechanical analysis confirmed the extract-polymer interactions and the viscoelastic nature of the films. The incorporation of bark extract caused remarkable enhancement in the antioxidant activity of chitosan films. Overall, larch bark extract-functionalized chitosan films demonstrated promising potential for food packaging.

Deciphering optimal biostimulation strategy of supplementing anthocyanin-abundant plant extracts for bioelectricity extraction in microbial fuel cells

BACKGROUND

Microbial fuel cells (MFCs) are effective biofuel devices that use indigenous microbes to directly convert chemical energy from organics oxidation into bioelectric energy. To maximize energy-converting efficiency for bioelectricity generation in MFCs, redox mediators (RMs) (e.g., extracts obtained from plant resource-Camellia green tea) have been explored for optimal stimulation upon electron transfer (ET) capabilities. Anthocyanins are natural antioxidants widely used in food science and medicinal industry. This first-attempt study revealed optimal strategies to augment extracts of anthocyanin-rich herbs (Lycium ruthenicum Murr., Clitoria ternatea Linn. and Vaccinium Spp.) as biofuel sources of catalytic RMs for stimulating bioenergy extraction in MFCs.

RESULTS

This work showed that extracts of anthocyanin-rich herbs were promising electroactive RMs. The maximal power density of MFCs supplemented with extract of L. ruthenicum Murr. was achieved, suggesting that extract of L. ruthenicum Murr. would be the most electrochemically appropriate RMs. Compared to C. ternatea Linn. and Vaccinium Spp., L. ruthenicum Murr. evidently owned the most significant redox-mediating capability to stimulate bioenergy extraction likely due to significantly high contents of polyphenols (e.g., anthocyanin). Evidently, increases in adenosine triphosphate (ATP) content directly responded to supplementation of anthocyanin-rich herbal extracts. It strongly suggested that the electron-shuttling characteristics of RMs upon electroactive microorganisms could effectively promote the electron transfer capability to maximize bioenergy extraction in MFCs.

CONCLUSION

Anthocyanin as the main water-soluble vacuolar pigments in plant products were very electroactive for not only excellent antioxidant activities, but also promising electron-shuttling capabilities for renewable biofuel applications. This work also suggested the electron-shuttling mechanism of RMs that could possibly promote electron transport phenomena through microbial cell membrane, further influencing the electron transport chain for efficient bioenergy generation.

Exploring optimal supplement strategy of medicinal herbs and tea extracts for bioelectricity generation in microbial fuel cells

This first-attempt study used extracts of appropriate antioxidant abundant Camellia and non-Camellia tea and medicinal herbs as model ESs to stably intensify bioelectricity generation performance in microbial fuel cells (MFCs). As electron shuttles (ESs) could stimulate electron transport phenomena by significant reduction of electron transfer resistance, the efficiency of power generation for energy extraction in microbial fuel cells (MFCs) could be appreciably augmented. Using environmentally friendly natural bioresource as green bioresource of ESs is the most promising to sustainable practicability. As comparison of power-density profiles indicated, supplement of Camellia tea extracts would be the most appropriate, then followed non-Camellia Chrysanthemum tea and medicinal herbs. Antioxidant activities, total phenolic contents and power stimulating activities were all electrochemically associated. In particular, the extract of unfermented Camellia tea (i.e., green tea) was the most promising ESs to augment bioenergy extraction compared to other refreshing medicinal herb extracts.

An improved method for extraction of nutraceutically important polyphenolics from Berberis jaeschkeana C.K. Schneid. fruits

Berberis jaeschkeana fruits, source of nutraceutically important polyphenolics were investigated. A total of 32 experimental run were conducted under Plackett-Burman and central composite design. Microwave power, methanol and HCl concentration significantly (p<0.05) affect extraction of polyphenols under linear, quadratic and interactive effect. The model showed good fitness with significant (p<0.05) model F-value and a non-significant lack of fit. Under optimum microwave assisted extraction (MAE) condition the total phenolics, flavonoids, tannins and antioxidant activity were in closed context with predicted values. As compared to ultrasonic (UAE) and maceration extraction (ME), MAE showed significantly (p<0.05) higher recovery of TP, TF and FRAP antioxidant activity. HPLC-DAD analysis detects a total of 10 polyphenolic compounds under MAE as compared to 9 under UAE and ME. Designing of MAE conditions showed promising results for polyphenolic antioxidants extraction as revealed by higher yield with lesser time and solvent consumption, which can contribute in green extraction technology and its application in nutraceutical industry.

Application of direct-injection detector integrated with the multi-pumping flow system to chemiluminescence determination of the total polyphenol index

In this work, we present a novel chemiluminescence (CL) method based on direct-injection detector (DID) integrated with the multi-pumping flow system (MPFS) to chemiluminescence determination of the total polyphenol index. In this flow system, the sample and the reagents are injected directly into the cone-shaped detection cell placed in front of the photomultiplier window. Such construction of the detection chamber allows for fast measurement of the CL signal in stopped-flow conditions immediately after mixing the reagents. The proposed DID-CL-MPFS method is based on the chemiluminescence of nanocolloidal manganese(IV)-hexametaphosphate-ethanol system. The application of ethanol as a sensitizer, eliminated the use of carcinogenic formaldehyde. Under the optimized experimental conditions, the chemiluminescence intensities are proportional to the concentration of gallic acid in the range from 5 to 350 ng mL(-1). The DID-CL-MPFS method offers a number of advantages, including low limit of detection (0.80 ng mL(-1)), high precision (RSD = 3.3%) and high sample throughput (144 samples h(-1)) as well as low consumption of reagents, energy and low waste generation. The proposed method has been successfully applied to determine the total polyphenol index (expressed as gallic acid equivalent) in a variety of plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices).

A study on the selection of chemiluminescence system for the flow injection determination of the total polyphenol index of plant-derived foods

Different chemiluminescence systems based on luminol, permanganate, manganese(IV) and cerium(IV) reagents were compared regarding their sensitivity and selectivity to determine plant polyphenols. Among the seventeen systems tested, Mn(IV)-formaldehyde-hexametaphosphate was considered to be the most suitable for polyphenols detection. The developed flow injection method (FI-CL) based on enhancing effect of polyphenols on Mn(IV) chemiluminescence is characterised by low detection limit of gallic acid (0.02μgL(-1)) and high precision (RSD=1.7%). The calibration graph was linear from 0.1 to 100μgL(-1). The selectivity studies revealed that the FI-CL method ensures accurate determination of the total polyphenols content in food samples. The method was successfully applied to analysis of a variety of plant-derived foods (wine, tea, cereal coffee, fruit and vegetable juices, herbs and spices). The proposed method is superior to conventional spectrophotometric assays due to its higher sample throughput (195samplesh(-1)), simplicity, sensitivity and, above all, higher selectivity.