Konstantinos Zaharioudakis

Following the trend of food waste valorization to produce innovative bio-based materials, this study proposes the conversion of brewer’s spent grain (BSG) into added value edible, high oxygen barrier, flexible, active packaging films via an extrusion molding compression method. Gelatin (Gel) was used as both a reinforcement and barrier agent and glycerol (Gl) as a plasticizer. Eugenol was nanoencapsulated on natural zeolite (EG@NZ), and pure clove powder (ClP) was used as an active agent to obtain BSG/Gel/Gl/xEG@NZ and BSG/Gel/Gl/xClP (x = 5, 10, and 15 %wt.) active films. Both BSG/Gel/Gl/xEG@NZ and BSG/Gel/Gl/xClP films show enhanced tensile, oxygen barrier, antioxidant, and antibacterial properties, and low toxicity and genotoxicity values. All BSG/Gel/Gl/xEG@NZ films presented a higher oxygen barrier, higher total phenolic content (TPC) values, higher antioxidant activity according to a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, higher inhibition zones against Staphylococcus aureus and Escherichia coli, and lower toxicity and genotoxicity than all BSG/Gel/Gl/xClP films. Thus, the superiority of the nanoencapsulated EG in NZ as compared to the physical encapsulated EG in ClP is proved. Briefly, BSG/Gel/Gl/15EG@NZ active film exhibited ~218% higher tensile strength, ~93% higher TPC value, and ~90% lower effective concentration for a 60% antioxidant activity value (EC₆₀) as compared to the pure BSG/Gel/Gl film. The zones against S. aureus and E. coli were 45 and 30 mm, respectively, and the oxygen barrier was zero. The use of this film extended the shelf life of fresh minced meat by two days and exhibited the high potential to be used as active packaging material.

Herein by following the trend of food waste valorization into innovative biobased materials the utilization of brewer's spent grain (BSG) into added value edible, high oxygen barrier, flexible active packaging films via extrusion molding compression method is presented. Gelatin (Gel) is used as both reinforcement and barrier agent and glycerol (Gl) as plasticizer. Eugenol nanoencapsulated on natural zeolite (EG@NZ) and pure clove powder (ClP) used as active agent to obtain BSG/Gel/Gl/xEG@NZ and BSG/Gel/Gl/xClP (x=5, 10, and 15 %wt.) active films. Both BSG/Gel/Gl/xEG@NZ and BSG/Gel/Gl/xClP films shown enhanced tensile, oxygen barrier, antioxidant, antibacterial properties and low toxicity and genotoxicity values. All BSG/Gel/Gl/xEG@NZ films presented higher oxygen barrier, higher total phenolic content (TPC) values, higher antioxidant activity according to 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, higher inhibition zones against Staphylococcus aureus and Escherichia coli and lower toxicity and genotoxicity than all BSG/Gel/Gl/xClP films proving the superiority of nanoencapsulated EG on NZ against physical encapsulated EG in ClP. Overall, BSG/Gel/Gl/15EG@NZactive film exhibited 218% higher tensile strength, 93% higher TPC value, 90% lower effective concentration for 60% antioxidant activity value (EC60) than pure BSG/Gel/Gl film and 45, 30 mm zone against S. Aureus and E. Coli correspondingly and zero oxygen barrier. This film succeeds in extending the shelf-life of fresh minced meat by two days and has high potential to be used as active packaging material.

In this study, aligned with the principles of the circular economy and sustainability, novel eugenol@natural zeolite (EG@NZ) and citral@natural zeolite (CT@NZ) nanohybrids were developed. These nanohybrids were successfully incorporated into a pork gelatin (Gel)/glycerol (Gl) composite matrix using an extrusion–compression molding method to produce innovative active packaging films: Gel/Gl/xEG@NZ (where x = 5, 10, and 15%wt.) and Gel/Gl/xCT@NZ (where x = 5 and 10%wt.). All films exhibited zero oxygen barrier properties. Release kinetic studies showed that both EG@NZ and CT@NZ nanohybrids adsorbed up to 58%wt. of their respective active compounds. However, EG@NZ exhibited a slow and nearly complete release of eugenol, whereas CT@NZ released approximately half of its citral content at a faster rate. Consequently, the obtained Gel/Gl/xEG@NZ films demonstrated significantly higher antioxidant activity as measured by the 2,2-diphenyl-1-picrylhydrazylradical (DPPH) assay and superior antibacterial effectiveness against Escherichia coli and Listeria monocytogenes compared to their CT-based counterparts. Overall, the Gel/Gl/xEG@NZ films show strong potential for applications as active pads for fresh pork ham slices, offering zero oxygen permeability, enhanced antioxidant and antibacterial properties, and effective control of total viable count (TVC) growth, maintaining a low and steady rate beyond the 10th day of a 26-day storage period.

In this study aligned with the principles of the circular economy and sustainability, novel eugenol@natural zeolite (EG@NZ) and citral@natural zeolite (CT@NZ) nanohybrids were developed. These nanohybrids were successfully incorporated into a pork gelatin (Gel)/glycerol (Gl) composite matrix using an extrusion molding-compression method to develop produce innovative active packaging films: Gel/Gl/xEG@NZ (where x = 5, 10, and 15 %wt.) and Gel/Gl/xCT@NZ (where x = 5 and 10 %wt.). All films exhibited zero oxygen barrier properties. Release kinetic studies showed that both EG@NZ, and CT@NZ nanohybrids adsorbed up to 58 %wt. of their respective active compounds. However, EG@NZ exhibited a slow and nearly complete release of eugenol, whereas CT@NZ released approximately half of its citral content at a faster rate. Consequently, the obtained Gel/Gl/xEG@NZ films demonstrated significantly higher antioxidant activity as measured by the 2,2-Diphenyl-1-picrylhydrazylradical (DPPH) assay, and superior antibacterial effectiveness against Escherichia coli and Listeria monocytogenes compared to their CT-based counterparts. Overall, the Gel/Gl/xEG@NZ films show strong potential for applications as active pads for fresh pork ham slices, offering zero oxygen permeability, enhanced antioxidant and antibacterial properties and effective control of total viable count(TVC) growth, maintaining a low and steady rate beyond the 10th day of a 26-day storage period.

In the context of the circular economy, the valorization of bio-derived waste has become a priority across various production sectors, including food processing and packaging. Gelatin (Gel), a protein which can be recovered from meat industry byproducts, offers a sustainable solution in this regard. In this study, pork-derived gelatin was used to develop novel edible active packaging films, designed for meat products. Glycerol (Gl) was used as a plasticizer. Two types of montmorillonite-based nanohybrids were employed as both reinforcing agents and carriers of antioxidant/antibacterial compounds: eugenol-functionalized montmorillonite (EG@Mt) and citral-functionalized montmorillonite (CT@Mt). The active films were formulated as Gel/Gl/xEG@Mt and Gel/Gl/xCT@Mt, where x = 5, 10, or 15 wt.%. Controlled-release kinetics showed that EG@Mt released up to 95% of its adsorbed eugenol, whereas CT@Mt released up to 55% of its adsorbed citral. The films were evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay and tested for antibacterial activity against Escherichia coli and Listeria monocytogenes. Results demonstrated that the Gel/Gl/xEG@Mt films exhibited superior antioxidant and antibacterial performance compared to the Gel/Gl/xCT@Mt films. All formulations were impermeable to oxygen. Although the incorporation of EG and CT slightly reduced cell viability, values remained above 80%, indicating non-toxicity. In conclusion, the film containing 15 wt.% EG@Mt achieved an oxygen transmission rate of zero, an effective concentration (EC₆₀) of 9.9 mg/L to reach 60% antioxidant activity, and reduced E. coli and L. monocytogenes populations by at least 5.8 log CFU/mL (p < 0.05), bringing them below the detection limit. Moreover, it successfully extended the shelf life of fresh minced pork by two days.

Modern bioeconomy and sustainability demands lead food technology in the development of novel biobased edible food preservatives. Herein, the development and characterization of novel polysaccharide (xanthan gum and kappa-carrageenan)-based nanoemulgels (NGs) enhanced with essential oil derivatives; pure citral (CT); pure carvacrol (CV); and various CT:CV ratios (25:75, 50:50, and 75:25) are presented. The obtained NGs are applied as active edible coatings for extending the shelf life of Protected Designation of Origin (PDO) green table olives of Chalkidiki. The zeta potential demonstrated the high stability of the treatments, while light scattering measurement and scanning electron microscopy images confirmed the 50 indicated high antioxidant activity for all the tested samples. The fractional inhibitory concentration (FIC) confirmed the synergistic effect of NG with a CT:CV ratio at 50:50 against Staphylococcus aureus and at CT:CV ratios 25:75 and 75:25 against E. coli O157:H7. NG coatings with CT:CV ratios at 50:50 and at 25:75 effectively controlled the weight loss at 0.5%, maintained stable pH levels, and preserved the visual quality of green olives on day 21. The synergistic effect between CT and CV was confirmed as they reduced the spoilage microorganisms of yeasts and molds by 2-log [CFU/g] compared to the control and almost 1 log [CFU/g] difference from pure CT and CV-based NGs without affecting the growth of beneficial lactic acid bacteria crucial for fermentation. NGs with CT:CV ratios at 50:50 and at 25:75 demonstrated superior effectiveness in preventing discoloration and maintaining the main sensory attributes. Overall, shelf life extension was achieved in 21 compared to only 7 of the uncoated ones. Finally, this study demonstrates the potential of polysaccharide-based NGs in mixtures of CT and CV for the shelf life extension of fermented food products.

Nowadays bioeconomy and sustainability trend drive food technology in the development of novel biobased edible food preservatives to enhance food shelf-life and safety. This study explored the development, characterization, and application of novel polysaccharide-based nanogels enhanced with essential oil derivatives carvacrol and citral, investigating their potential synergistic effects as active edible coatings for extending the shelf life of Chalkidiki PDO green table olives. Nanogels were formulated using xanthan gum and kappa-carrageenan and tested in various ratios (25:75, 50:50, 75:25). Physicochemical characterization of nanogels was done via zeta potential dynamic light scattering measurements and scanning electron microscopy images, while preliminary tests demonstrated high antioxidant activity. Antimicrobial assessments revealed significant bactericidal effects, with FIC results confirming a synergistic effect of NGCTCV 50:50 against Staphylococcus aureus and NGCTCV 25:75 and 75:25 against. The nanogel coatings were applied to Chalkidiki green table olives and evaluated over a 21-day storage period. The NGCTCV 50:50 and 25:75 coatings effectively reduced weight loss, maintained stable pH levels, and preserved visual quality, while inhibiting spoilage microorganisms without affecting beneficial lactic acid bacteria crucial for fermentation. Lab colorimetry confirmed the ability of these nanogels to prevent discoloration, maintaining the olives' characteristic green color. Sensory analysis indicated that NGCTCV 50:50 and 25:75 outperformed both individual nanogels and uncoated samples, effectively extending shelf life by over 14 days. Finally, this study demonstrates the potential of polysaccharide-based nanogels, particularly in the 50:50 and 25:75 ratios, for improving the shelf life of perishable food products, with promising applications in fermented food preservation.

Carvacrol is well documented for its antibacterial and antioxidant effects. However, its high volatility has directed researchers toward nanoencapsulation technology according to bioeconomy and sustainability trends. This study examined and compared free carvacrol (FC), carvacrol microemulsion (MC), carvacrol microemulsion busted with chitosan (MMC), and carvacrol nanoemulsions (NC) as active coatings on extending minced pork meat shelf life at 4 ± 1 °C for 9 days, focusing on microbiological, physiochemical, and sensory characteristics. The research involved pre-characterizing droplet sizes, evaluating antioxidants, and determining antibacterial efficacy. The results demonstrated that NC with a 21 nm droplet size exhibited the highest antioxidant and antibacterial activity. All coatings succeeded in extending the preservation of fresh minced pork meat in comparison to the free carvacrol sample (FC). The NC coating showed the highest extension of minced pork meat preservation and maintained meat freshness for 9 days, with a lower TBARs of 0.736 mg MDA/Kg, and effectively reduced mesophilic, lactic acid, and psychotrophic bacterial counts more significantly by 1.2, 2, and 1.3 log, respectively, as compared to FC. Sensory assessments confirmed the acceptability of NC and MCC coatings. Overall, the carvacrol-based nanoemulsion can be considered a novel antioxidant and antimicrobial active coating due to its demonstrated higher efficacy in all the examined tests performed.

Carvacrol is well-documented for its antibacterial and antioxidant effects. However, its high volatility has directed researchers towards nanoencapsulation technology according to bioeconomy and sustainability trends. This study examined and compared carvacrol microemulsion (MC), carvacrol microemulsion busted with chitosan (MMC) and carvacrol nanoemulsions as active coatings on extending minced pork meat shelf-life at 4±1 oC for 9 days, focusing on microbiological, physiochemical, and sensory characteristics. The research involved pre-characterizing droplet sizes, evaluating antioxidant, and determining antibacterial efficacy. The results demonstrated that NC with a 21 nm droplet size exhibited the highest antioxidant and antibacterial activity. All coatings succeed to extend the preservation of fresh minced pork meat in comparison to free carvacrol sample (FC). NC coating showed the highest extension of minced pork meat preservation and maintained meat freshness for 9 days, with a lower TBARs of 0.736 mg MDA/Kg, and effectively reduced mesophilic, lactic acid, and psychrotrophic bacterial counts more significantly 1.2, 2, and 1.3 log respectively as compared to FC. Sensory assessments confirmed the acceptability of NC and MCC coatings. Overall, the carvacrol based nanoemulsion can be considered as novel antioxidant and antimicrobial active coating due to its demonstrated higher efficacy in all the examined tests performed.