Carbon dots synthesized from microorganisms and food by-products: active and smart food packaging applications.

Nanotechnology is rapidly becoming a commercial reality for application in food packaging. In particular, the incorporation of nanoparticles into packaging materials is being used to increase the shelf life and safety of foods. Carbon dots (C-dots) have a diverse range of potential applications in food packaging. They can be synthesized from environmentally friendly sources such as microorganisms, food by-products, and waste streams, or they may be generated in foods during normal processing operations, such as cooking. These processes often produce nitrogen- and sulfur-rich heteroatom-doped C-dots, which are beneficial for certain applications. The incorporation of C-dots into food packaging materials can improve their mechanical, barrier, and preservative properties. Indeed, C-dots have been used as antioxidant, antimicrobial, photoluminescent, and UV-light blocker additives in food packaging materials to reduce the chemical deterioration and inhibit the growth of pathogenic and spoilage microorganisms in foods. This article reviews recent progress on the synthesis of C-dots from microorganisms and food by-products of animal origin. It then highlights their potential application for the development of active and intelligent food packaging materials. Finally, a discussion of current challenges and future trends is given.

The potential of postbiotics as a novel approach in food packaging and biopreservation: a systematic review of the latest developments.

Metabolic by-products are part of the so-called postbiotics of probiotics and other beneficial microorganisms, particularly lactic acid bacteria, which have gained popularity as a feasible alternative to improving food quality and safety. Postbiotics in dry and liquid forms can be easily integrated into food formulations and packaging materials, exhibiting antimicrobial and antioxidant effects owing to the presence of multiple antimicrobials, such as organic acids, bacteriocins, exopolysaccharides and bioactive peptides. Postbiotics can thus control the growth of pathogens and spoilage microorganisms, thereby extending the shelf life of food products. Because of their ability to be easily manufactured without requiring extensive processing, postbiotics are regarded as a safer and more sustainable alternative to synthetic preservatives, which can have negative environmental consequences. Additionally, food manufacturers can readily adopt postbiotics in food formulations without significant modifications. This systematic review provides an in-depth analysis of studies on the use of postbiotics in the biopreservation and packaging of a wide range of food products. The review evaluates and discusses the types of microorganisms, postbiotics preparation and modification techniques, methods of usage in dairy products, meat, poultry, seafood, fruits, vegetables, bread, and egg, and their effects on food quality and safety.

Optimization and characterization of eco-friendly antimicrobial nanocellulose sheet prepared using carbon dots of white mulberry (Morus alba L.).

BACKGROUND: Carbon dots (C-dots) with antimicrobial activity were synthesized from the white mulberry extract with the aim of fabricating anti-listeria nanopaper using bacterial nanocellulose (BNC). Highly dispersed synthesized C-dots with a size smaller than 10 nm (approximately 4.9 nm) were impregnated into BNC by an ex situ coating method and then mechanical, morphological, UV-protectant and antibacterial activity were assessed. Randomized response surface methodology using a central composite design was applied to investigate the optimized concentration of C-dots in the BNC membrane. RESULTS: An optimized nanopaper including C-dots at a concentration of 530 g L-1 and an impregnation time of 14 h at 30 °C with significant antimicrobial activity on Listeria monocytogenes was designed. The addition of C-dots into BNC significantly increased ultimate tensile strength and decreased strain with respect to breaking BNC. A BNC sheet with high-efficient UV-blocking property was prepared using C-dots. CONCLUSION: Based on the results, the designed nanopaper shows a substantial capacity with respect to the fabrication of antimicrobial/UV-blocking sheets for food active packaging. © 2020 Society of Chemical Industry.

Postbiotics produced by lactic acid bacteria: The next frontier in food safety.

There are many critical challenges in the use of primary and secondary cultures and their biological compounds in food commodities. An alternative is the application of postbiotics from the starter and protective lactic acid bacteria (LAB). The concept of postbiotics is relatively new and there is still not a recognized definition for this term. The word "postbiotics" is currently used to refer to bioactive compounds, which did not fit to the traditional definitions of probiotics, prebiotics, and paraprobiotics. Therefore, the postbiotics may be presently defined as bioactive soluble factors (products or metabolic byproducts), produced by some food-grade microorganisms during the growth and fermentation in complex microbiological culture (in this case named cell-free supernatant), food, or gut, which exert some benefits to the food or the consumer. Many LAB are considered probiotic and their postbiotic compounds present similar or additional health benefits to the consumer; however, this review aimed to address the most recent applications of the postbiotics with food safety purposes. The potential applications of postbiotics in food biopreservation, food packaging, and biofilm control were reviewed. The current uses of postbiotics in the reduction and biodegradation of some food safety-related chemical contaminants (e.g., biogenic amines) were considered. We also discussed the safety aspects, the obstacles, and future perspectives of using postbiotics in the food industry. This work will open up new insights for food applications of postbiotics prepared from LAB.

Bacterial nanocellulose-based nanopaper activated by ß-cyclodextrin/ Salvia officinalis essential oil complexes for shelf life extension of shrimp.

Active bacterial nanocellulose (BNC) nanopapers containing Salvia officinalis essential oil (SEO) in free form and encapsulated with ß-cyclodextrin (ßCD) were prepared, and their effect on the shelf life extension of shrimp was investigated. The GC-MS analysis of the SEO indicated the presence of various active compounds such as Thujone (21.53 %), Ledol (12.51 %) and Eucalyptol (11.28 %) in the essential oil composition. The cytotoxicity of the SEO and SEO-ßCD complexes in the L929 cell line was quite low. FTIR analysis revealed new interactions in the nanopapers containing SEO-ßCD complexes. Microscopic images showed that SEO-ßCD complexation improved the surface morphology of the BNC nanopapers, whereas free SEO had a negative effect. X-ray diffraction patterns of the nanopapers showed higher crystallinity of the SEO-ßCD containing nanopapers than that of the SEO-incorporated nanopapers. Moreover, the addition of the SEO-ßCD complex improved the thermal properties of the BNC nanopaper. Water contact angle analysis showed higher hydrophobicity of the samples containing free SEO than that of the other samples. Both SEO-ßCD and free SEO increased the elongation at break and decreased the tensile strength of the nanopaper. The prepared active films showed a greater antimicrobial effect on L. monocytogenes than on E. coli. The results showed a higher antioxidant capacity of the free SEO-containing nanopapers (58-78 %). The desirable effects of the active nanopapers on shrimp preservation were demonstrated by the results obtained for the microbial load, pH, and volatile nitrogen content of the product. The results demonstrate the potential of the prepared BNC active nanopapers for use in active antioxidant/antimicrobial food packaging.

Beyond probiotics: Exploring the potential of postbiotics and parabiotics in veterinary medicine.

Postbiotics and parabiotics (PP) are emerging fields of study in animal nutrition, preventive veterinary medicine, and animal production. Postbiotics are bioactive compounds produced by beneficial microorganisms during the fermentation of a substrate, while parabiotics are inactivated beneficial microbial cells, either intact or broken. Unlike probiotics, which are live microorganisms, PP are produced from a fermentation process without live cells and show significant advantages in promoting animal health owing to their distinctive stability, safety, and functional diversity. PP have numerous beneficial effects on animal health, such as enhancing growth performance, improving the immune system and microbiota of the gastrointestinal tract, aiding ulcer healing, and preventing pathogenic microorganisms from colonizing in the skin. Moreover, PP have been identified as a potential alternative to traditional antibiotics in veterinary medicine due to their ability to improve animal health without the risk of antimicrobial resistance. This review comprehensively explores the current research and applications of PP in veterinary medicine. We aimed to thoroughly examine the mechanisms of action, benefits, and potential applications of PP in various species, emphasizing their use specifically in livestock and poultry. Additionally, we discuss the various routes of administration to animals, including feed, drinking water, and topical use. This review also presents in-depth information on the methodology behind the preparation of PP, outlining the criteria employed to select appropriate microorganisms, and highlighting the challenges commonly associated with PP utilization in veterinary medicine.

Postbiotics-enriched flaxseed mucilage coating: A solution to improving postharvest quality and shelf life of strawberry.

This research aimed to assess the effects of flaxseed mucilage (Mu) coatings supplemented with postbiotics (P) obtained from Lactobacillus acidophilus LA-5 on various physical, biochemical, and microbial characteristics of strawberry fruits. Strawberry fruits were immersed for 2 min in Mu2.5 (2.5 % mucilage in distilled water), Mu5 (5 % mucilage in distilled water), P-Mu2.5 (2.5 % mucilage in undiluted postbiotics) and P-Mu5 (5 % mucilage in undiluted postbiotics) solutions and were stored at 4 °C and 85 RH for 12 days. All coatings were effective in reducing fungal count compared to the uncoated control fruits. Mu5 coating exhibited the highest efficacy, reducing fungal count by 2.85 log10 CFU/g, followed by Mu2.5 (1.47 log10 CFU/g reduction) and P-Mu2.5 groups (0.90 log10 CFU/g reduction). The fruits coated with edible coatings showed significant delays in the change of weight loss, pH, and total soluble solids as compared to the uncoated fruits. The coating containing postbiotics i.e., P-Mu5 also showed a significant increase in the total phenolic contents, total flavonoid content, antioxidant capacity, and total anthocyanin content at the end of storage relative to the uncoated fruits. Thus, Mu and P-Mu coatings may be a useful approach to maintaining the postharvest quality of strawberry fruits during cold storage.

Anti-Listeria activity of postbiotics of Lactiplantibacillus sakei in beef fillet using aerosolization technique.

In recent years, the use of probiotics and their metabolites, known as postbiotics as natural preservatives has received increasing attention in the food industry. This study aimed to prepare and characterize postbiotics of Lactiplantibacillus sakei and to investigate its application as an anti-Listeria solution on beef fillets using an aerosolization technique. The functional groups, including organic acids, polysaccharides and other minor metabolites, were identified by Fourier transform infrared (FTIR) in the postbiotics. The 2, 2'-diphenyl-1-picrylhydrazyl radical scavenging activity of the postbiotics was reported as 0.82 mg mL-1. The antimicrobial test using the agar well diffusion method revealed a zone of inhibition of 27.00 ± 1.20 mm. Application of an aerosolized postbiotics solution resulted in a significant reduction in Listeria monocytogenes counts on beef fillets, reaching 3.30 log10 CFU g-1 over a 15-day storage period at 4.00 ± 1.00 ˚C. The results of this study revealed that the postbiotics of L. sakei was an effective antimicrobial additive for controlling foodborne pathogens in beef fillets and aerosolization is a promising method for developing an antimicrobial coating on meat to enhance meat safety.

Development and characterization of active packaging system based on zein nanofibers mat incorporated with geraniol-loaded nanoliposomes.

In recent years, development of biopolymeric nanofibers as an active biodegradable packaging system has attracted specific attention. The objective of this research was to develop zein-based electrospun nanofibers (NFs) incorporated with geraniol-loaded nanoliposomes (G-loaded NLPs). Geraniol was encapsulated into NLPs with an efficiency of 79.23%. The particle size and zeta potential of G-loaded NLPs were 121.50 nm and -38.30 mV, respectively. The successful loading of geraniol in the NLPs was approved by Fourier transform infrared (FT-IR) spectroscopy. The liposomal vesicles showed spherical shapes. G-loaded NLPs were added in the zein-based electrospun NFs at three different concentrations (0.25, 0.5, and 1%w/v). All NFs samples exhibited fibrillar structure. The increase of NLPs concentration enhanced the thermal stability of the NFs. However, the crystalline structure of zein NFs did not change by the addition of G-loaded NLPs. The highest surface hydrophobicity was related to the NFs containing 1% G-loaded NLPs. The mechanical parameters of NFs depend on the concentration of NLPs. The NFs incorporated with G-loaded NLPs showed inhibition activity against four foodborne pathogenic bacteria (Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella typhimurium) with an inhibition zone of 4.5-22 mm. Moreover, the α-diphenyl-ß-picrylhydrazyl (DPPH) scavenging activity of NFs samples was located at the range of 20%-48%. These findings represent the Efficiency of the G-loaded NLPs for use as bioactive compound in the zein-based NFs as an active packaging material.

Coated composite paper with nano-chitosan/cinnamon essential oil-nanoemulsion containing grafted CNC@ZnO nanohybrid; synthesis, characterization and inhibitory activity on Escherichia coli biofilm developed on grey zucchini.

This investigation aims to highlight the applicability of a potent eco-friendly developed composite film to combat the Escherichia coli biofilm formed in a model food system. ZnO nanoparticles (NPs) synthesized using green methods were anchored on the surface of cellulose nanocrystals (CNCs). Subsequently, nano-chitosan (NCh) solutions were used to disperse the synthesized nanoparticles and cinnamon essential oil (CEO). These solutions, containing various concentrations of CNC@ZnO NPs and CEO, were sequentially coated onto cellulosic papers to inhibit Escherichia coli biofilms on grey zucchini slices. Six films were developed, and Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, biodegradation, and mechanical properties were assessed. The film containing 5 % nano-emulsified CEO + 3 % dispersed CNC@ZnO nano-hybrid in an NCh solution was selected for further testing since it exhibited the largest zone of inhibition (34.32 mm) against E. coli and the highest anti-biofilm activity on biofilms developed on glass surfaces. The efficacy of the film against biofilms on zucchini surfaces was temperature-dependent. During 60 h, the selected film resulted in log reductions of approximately 4.5 logs, 2.85 logs, and 1.57 logs at 10 °C, 25 °C, and 37 °C, respectively. Applying the selected film onto zucchini surfaces containing biofilm structures leads to the disappearance of the distinctive three-dimensional biofilm framework. This innovative anti-biofilm film offers considerable potential in combatting biofilm issues on food surfaces. The film also preserved the sensory quality of zucchini evaluated for up to 60 days.

A systematic review and meta-analysis of the use of plant essential oils and extracts in the development of antimicrobial edible films for dairy application.

The purpose of this review was to assess the use of plant essential oils and extracts (PEOE) in the development of antimicrobial edible films for dairy application through a systematic review and meta-analysis. All studies published in multiple databases were explored via PRISMA protocol on November 1, 2022. According to the results, the interquartile range of pathogen reduction potential of essential oil (EO) in dairy products, irrespective of EO, film and product type, was 0.10 - 4.70 log CFU g-1 per % concentration. The findings from 38 articles indicate that among all EOs or their compounds, Zataria multiflora Boiss in protein film, thyme in protein film, Z. multiflora Boiss EO in protein film, Trans-cinnamaldehyde in carbohydrate film and lemongrass EO in protein film had extraordinary pathogen reduction potential on important foodborne pathogens. In the case of plant extract, fish gelatin film with Lepidium sativum extract, whey protein isolate film loaded with oregano EO and carboxymethyl cellulose film with clove EOs had the highest antimicrobial effect on mesophilic bacteria (9.50 log CFU g-1 per % concentration), yeast-mold (2.63 log CFU g-1 per % concentration) and mesophilic/ psychrophilic counts (> 9.06 log CFU g-1 per % concentration), respectively. Listeria monocytogenes is the primary species of interest; whereas, mesophiles and mold-yeast populations were the most investigated microbiota/mycobiota in cheese with PEOE-incorporated film. In light of these findings, the choice of PEOE at appropriate concentrations with the selection of appropriate edible film may improve the safety, sensory, and shelf life of dairy products.

Food freshness monitoring using poly(vinyl alcohol) and anthocyanins doped zeolitic imidazolate framework-8 multilayer films with bacterial nanocellulose beneath as support.

Multilayer intelligent freshness labels based on bacterial nanocellulose (BNC), poly(vinyl alcohol) (PVA), and anthocyanins doped zeolitic imidazolate framework-8 (A-ZIF-8) nanocrystals were developed in this study. First, optical, structural, thermal, and surface characterizations of A-ZIF-8 nanocrystals were performed, and the successful incorporation of anthocyanins into ZIF-8 nanocrystals was demonstrated. Next, A-ZIF-8 was added into PVA, and multilayer films were fabricated by spin-coating PVA/A-ZIF-8 layers onto BNC. The effect of the number of deposition cycles on the barrier, mechanical, thermal, morphological, and colorimetric properties of multilayer labels was investigated. The ammonia sensing, mechanical, and barrier properties of the films were shown to be tuned by the number of the PVA/A-ZIF-8 layers on the BNC. Among the developed films, BNC-2PVA/A-ZIF-8 films with the best colorimetric sensitivity toward volatile ammonia were used to monitor the freshness of skinless chicken breasts. The changes in the ΔE and a* values of BNC-2PVA/A-ZIF-8 film demonstrated a good correlation with the microbial and TVB-N levels in samples over 10 days of storage at 4 °C.

The prevalence and concentration of ochratoxin A in meat and edible offal: A global systematic review and meta-analysis.

The prevalence of ochratoxin A (OTA) in meat, edible offal, and meat products (MOP) was assessed through systematic review and meta-analysis. Four electronic databases were used to gather data from 1975 to September 15, 2022. Seventy-five articles comprising 8585 samples were identified and analyzed. The studies included in the analysis were conducted at a global level, with a predominant focus on Europe [72% (54/75)], Asia [13.33% (10/75)], Africa [13.33% (10/75)], and North America [1.33% (1/75)]. The overall prevalence of OTA in MOP was 39%. The highest and lowest prevalence percentages were recorded in Iraq (77%) and the USA (3%), respectively. Concerning food type, OTA prevalence was highest in the poultry gizzard (66%) and lowest in the cow liver (2%). The overall concentration of OTA in the MOP was 1.789 µg/kg. Poultry kidneys had the highest concentration of OTA (0.880-22.984 µg/kg), while pork had the lowest concentration (0.127-0.824 µg/kg). Conspicuous amounts of OTA contamination have been reported in fermented sausages. The lowest OTA concentration was found in Belgium (0.220 µg/kg) and the highest in Denmark (60.527µg/kg). These results can help food authorities minimize and control OTA in the MOP.

Cellulose/Salep-based intelligent aerogel with red grape anthocyanins: Preparation, characterization and application in beef packaging.

The purpose of this study was to prepare a porous intelligent aerogel for food packaging applications, in particular for monitoring minced beef freshness, using cellulose extracted from grape stalk, Salep as a copolymer, and red grape anthocyanins as a pH-sensitive pigment. Aerogels based on cellulose 1% (w/v) and Salep 1% (w/v) at ratios of 1:3, 3:1, and 1:1 were prepared by lyophilization. Aerogel with high porosity, low density, and higher mean pore size was chosen for preparing intelligent colorimetric aerogel (ICA) with the addition of 0.44 mg/100 mL of anthocyanins. Based on the color parameters, the stability of ICA was satisfactory when exposed to both light and dark conditions, as well as when stored at either 4 or 25 °C. Additionally, X-ray diffraction and thermogravimetric analyses indicated that an amorphous aerogel was formed, with a thermal decomposition temperature of 320 °C. The color of the ICA changed from purple on the first and 3rd days of packaging to blue-gray on the 6th day. As the spoilage process continued, the color of the indicator became dark brown. Taken together, ICA showed a quick response to minced beef spoilage with the ability to differentiate between fresh and spoiled meat during storage at 4 °C.

Carbon dots from sour whey to develop a novel antimicrobial packaging for fiordilatte cheese.

In this study, monodispersed and quasi-spherical C-Dots with an average size of 7.2 nm were successfully synthesized from sour whey solution by a hydrothermal method (200 °C for 9 h) for fiordilatte cheese packaging. C-Dots (2500 and 5000 mgL-1) were added to the cheese through an alginate-based coating or directly to the cheese brine. No significant changes in TM4 cell viability were observed at concentrations lower than 10,000 mgL-1. Microbiological and sensory properties of cheese coated and uncoated with C-Dots indicate a substantial preserving effect of the C-Dots. The uncoated control fiordilatte exhibited unacceptable levels of microbial proliferation within 3.5 days. Conversely, the coated cheese remained within acceptable limits, effectively doubling its shelf life compared to the control, primarily due to the coating protection rather than the addition of C-Dots. When compared to the control fiordilatte, the addition of C-Dots in the brine at 5000 mgL-1 resulted in an extension of over 10 days in cheese shelf life. Considering the significance of the sustainable approach in C-Dots synthesis and the exceptional use of C-Dots in the food industry, these findings hold great potential in terms of research and industrial applications.

Essential oil-loaded starch/cellulose aerogel: Preparation, characterization and application in cheese packaging.

Novel antimicrobial emitting aerogels based on starch/cellulose/Thymus daenensis Celak essential oil (SC-TDEO) were developed and optimized for antimicrobial packaging of Koopeh cheese. An aerogel formulation containing cellulose (1 %; extracted from sunflower stalks) and starch (5 %) in a 1:1 ratio was selected for in vitro antimicrobial assay and subsequent cheese application. The minimum inhibitory dose (MID) of TDEO in the vapor phase against Escherichia coli O157:H7 was determined by loading various concentrations of TDEO onto the aerogel, and an MID of 256 µL/Lheadspace was recorded. Aerogels containing TDEO at 25 × MID and 50 × MID were then developed and used for cheese packaging. During a 21-day storage period, cheeses treated with SC-TDEO50 MID aerogel exhibited a significant 3-log reduction in psychrophile counts and a 1-log reduction in yeast-mold counts. Moreover, significant changes in the population of E. coli O157:H7 were observed in cheese samples. After 7 and 14 days of storage with SC-TDEO25 MID and SC-TDEO50 MID aerogels, the initial bacterial count became undetectable, respectively. Sensory evaluations indicated that the samples treated with SC-TDEO25 MID and SC-TDEO50 aerogels received higher scores compared to the control group. These findings demonstrate the potential of the fabricated aerogel to develop antimicrobial packaging suitable for cheese applications.

Application of antimicrobial coating based on carboxymethyl cellulose and natamycin in active packaging of cheese.

The effects of carboxymethyl cellulose (CMC)-natamycin (N; 0.05 and 0.5%) coating on the quality of high-moisture mozzarella cheese (HMMC) were examined. The cheeses were immersed in the coating solutions and then kept at 7 °C for 8 days and microbial specifications (i.e., total mesophilic count, total psychrophilic count, lactic acid bacteria, and yeast-mold), pH, weight loss, and sensory properties were examined. The results of the agar spot diffusion assay represented inhibitory effects of CMC-N coating solution on Aspergillus flavus, A. fumigatus, A. niger, Penicillium citrinum, and Candida albicans. In HMMC, the natamycin-free CMC coating caused a significant decrease (p < 0.05) in all microbial groups, while the addition of natamycin to the coating only reduced the count of mold and yeast. As a result, the coating with natamycin at 0.05 and 0.5% represented a 0.6 and 0.9 log cycle reduction in yeast-mold populations, respectively. Based on the total mesophilic count, the control samples reached the 7 log CFU/g on day 4, indicating a 4-day shelf life of HMMC, while in HMMC coated with and without natamycin this limit was achieved on the 8th day of storage, which indicates that the coatings have doubled the HMMC shelf life.

Application of Cheese Whey Containing Postbiotics of Lactobacillus acidophilus LA5 and Bifidobacterium animalis BB12 as a Preserving Liquid in High-Moisture Mozzarella.

High-moisture mozzarella cheese (HMMC) is a highly perishable cheese with a short shelf life. In this study, the effects of UF cheese whey containing postbiotics from Lactobacillus acidophilus LA-5 (P-LA-5), Bifidobacterium animalis BB-12 (P-BB-12), and their combination on the microbial (i.e., psychrophiles, mesophiles, lactic acid bacteria, and mold-yeast population) and sensory properties of HMMC were investigated. Postbiotics were prepared in a cheese whey model medium as a novel growth media and used as a preserving liquid in HMMC. The results demonstrate that postbiotics reduced the growth of all microorganisms (1.5-2 log CFU/g reduction) and P-LA5 and P-BB12 had the highest antibacterial performance on mesophiles and psychrophiles, respectively. Mold and yeast had the highest susceptibility to the postbiotics. Postbiotics showed a significant effect on maintaining the microbial quality of HMMC during storage, proposing postbiotics as a new preserving liquid for HMMC.

Application of bacterial nanocellulose decorated with zeolitic imidazolate framework (ZIF-L) as a platform for food freshness monitoring.

Recently, the food freshness indicator (FFI) has garnered great interest from consumers and food producers. A novel FFI based on bacterial nanocellulose (BNC)/zeolitic imidazolate framework-L (ZIF-L) and grape anthocyanins was developed and characterized using field emission scanning electron microscopy, Fourier-transform infrared, X-ray diffraction, water contact angle, and BET techniques. The results confirmed that the BNC fibrils were decorated by in situ growth of ZIF-L, with a 3D flower-shaped structure and randomly multiple sharp-edged petals, and hydroxyl and oxygenated heterocycle aromatic ring functional groups on its surface. The reversibility, color stability performance, and moisture sorption of FFI were studied and its applicability in a two-layer arrangement as a visual freshness monitoring of shrimp and minced beef was evaluated. The FFI was able to distinguish (ΔE > 5) the fresh, medium fresh, and spoiled minced meat and shrimp visually during 10 and 4 days of storage at 4 °C, respectively. Also, monitoring of food chemical and microbiological parameters approved the correlation of food spoilage with the color parameters of FFI. These results confirmed the function of ZIF-L in the fabrication of highly pH-sensitive food intelligent packaging material.

Potential application of postbiotics metabolites from bioprotective culture to fabricate bacterial nanocellulose based antimicrobial packaging material.

Postbiotics (P) of FreshQ, a food protective culture, was prepared and used to develop an antimicrobial membrane by bacterial nanocellulose (BNC). Postbiotics were prepared in de Man, Rogosa and Sharpe medium and freeze-dried. The chemical composition was investigated by GC-MS and the antibacterial activity of postbiotics on different bacterial and fungal strains was investigated. Finally, postbiotics were included in wet and lyophilized BNC by ex-situ method, and their antibacterial activity and FTIR specifications were studied. The GC-MS analysis of postbiotics revealed the presence of fatty acids, alkanes, aldehydes, hydrocarbones fatty acid esters, propionic acid, and certain antibacterial and antifungal compounds such as 2,4-Di-tert-butyl phenol and dotriacontane. Postbiotics revealed antibacterial activity on all investigated strains in a concentration-dependent manner and as the concentation decreased, there was a significant reduction in antimicrobial effects. The zone of inhibition for all bacterial pathogens exceeded 20 mm, then they were classified as "extremely sensitive microorganisms" to the postbiotics at 50 % concentration, while fungal strains revealed a lower zone of inhibition (<17 mm). The order of antimicrobial susceptibility was as follows: Listeria monocytogenes > Staphylococcus aureus > Escherichia coli > Salmonella Typhimurium > Aspergillus flavus > Penicillium citrinum. We also recognized that P-BNC in wet form has significant antimicrobial activity than lyophilized form due to the high adsorption capacity and open 3D structure of BNC in wet form. The fabricated material can serve as an antimicrobial membrane for food applications.