Preparation of an intelligent pH film based on biodegradable polymers and roselle anthocyanins for monitoring pork freshness

Freshness monitoring technology of fish products in intelligent packaging

Fish products are one of the preferred products in modern healthy diets, because they contain unqualified proteins, polyunsaturated fatty acids and a variety of vitamins and minerals. However, because of their vulnerability to deterioration, methods to maintain their freshness have attracted wide attention. Intelligent packaging can effectively monitor the quality and safety of fish products, provide warning, and has a great market and development potential. Therefore, this paper reviews the research progress of intelligent packaging technology used to monitor the freshness of fish products. The quality attributes of freshness of fish products are summarized. The classification, principle and latest application progress of three advanced technologies, indicator, sensor and radio frequency identification (RFID), are summarized. In addition, the advantages and disadvantages of the intelligent packaging technology for monitoring the freshness of products are discussed, and the current research results are summarized and prospected.

Biodegradation Pattern of Glycopolymer Based on D-Mannose Oligomer and Hydroxypropyl Acrylate

Glycopolymers are polymers with sugar moieties which display biodegradable and/or biocompatible character. They have emerged as an environmentally-friendly solution to classical synthetic polymers and have attracted significant research interest in the past years. Herein, we present the synthesis of a D-mannose based glycopolymer with biodegradable features. The glycopolymer was synthesized by radical copolymerization between a D-mannose oligomer bearing polymerizable double bonds and 2-hydroxypropyl acrylate, in a weight ratio of 1:2. The copolymerization kinetics was investigated by differential scanning calorimetry (DSC) and the activation energy of the process was comparatively assessed by Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods. The obtained glycopolymer displayed good thermal behavior, fact proven by thermogravimetrical (TG) analysis and it was submitted to biodegradation inside a bioreactor fed with water from the Bega River as the source of microbial inoculum. The glycopolymer sample degraded by approximately 60% in just 23 days. The biodegradation pattern of the glycopolymer was successfully fitted against a modified sigmoidal exponential function. The kinetic model coefficients and its accuracy were calculated using Matlab and the correlation coefficient is more than promising. The changes inside glycopolymer structure after biodegradation were studied using TG and FTIR analyses, which revealed that the sugar moiety is firstly attacked by the microbial consortia as nutrient source for proliferation.

Development of an easy-to-use colorimetric pH label with starch and carrot anthocyanins for milk shelf life assessment

An intelligent freshness indicator was developed by immobilizing anthocyanins of black carrot (ABC) within the starch matrix (total anthocyanins content of 10 mg/100 mL) to monitor freshness/spoilage of milk. The microstructural, spectral, swelling and solubility properties as well as color stability (as a function of time, temperature and light) of the indicator at different pHs were characterized. The incorporation of ABC did not change the swelling index and water solubility. The prepared label showed visible color changes as a function of pH and excellent color stability after one month storage at different conditions. The total color difference (TCD) value of the indicator corresponded to the pH, acidity, and microbial growth of the pasteurized milk. The Pearson correlation coefficient showed a high correlation between TCD and pH (R = -0.979), while a high and positive correlation between TCD and acidity as well as TMC (R = 0.983 and 0.968, respectively) was observed. The developed label can discriminate fresh milk form the milk entered into the initial (TCD: 7.8 after 24 h) and final (TCD: 34.8 after 48 h) steps of spoilage. The fabricated label opens a new perspective to use anthocyanins-incorporated biopolymers in the milk intelligent packaging as a simple and easy-to-use freshness indicator.

Preparation, Characterization and Application of a Low Water-Sensitive Artemisia sphaerocephala Krasch. Gum Intelligent Film Incorporated with Anionic Cellulose Nanofiber as a Reinforcing Component

A low-water-sensitive Artemisia sphaerocephala Krasch. gum (ASKG) based intelligent film was developed. Red cabbage extracts (RCE) was selected as a natural pH-sensitive indicator, and anionic cellulose nanofiber (ACNF) was added as a hydrophobic and locking host. The zeta potential, rheology, Fourier-transform infrared spectroscopy, X-ray diffractometry, and release results indicated that the RCE was locked by the ACNF via electrostatic interactions, moreover, broke the original complicated network and ordered arrangement of polymer molecules in the developed intelligent films. RCE addition decreased the tensile strength, oxygen, and water vapor barrier properties and light transmission of the developed intelligent films, while increasing the elongation at break. The films could respond to buffer solutions and NH₃ through different color changes. The developed intelligent film was hydrophobic, which could precisely detect the freshwater shrimp freshness in real time via color changes, which indicated that the films have potential in intelligent packaging and gas-sensing label fields.

The Application of (+)-Catechin and Polydatin as Functional Additives for Biodegradable Polyesters

Plant polyphenols are a huge group of compounds with a wide spectrum of applications. Substances from this group have been used in polymer materials such as stabilizers, dyes, indicators, fungicides, and bactericides, especially in new generation packaging materials. The aim of this study is to obtain environmentally friendly materials based on the biodegradable aliphatic polyesters, polylactide (PLA) and polyhydroxyalkanoate (PHA), with plant functional additives, (+)-catechin and polydatin. These natural polyphenols (polydatin and (+)-catechin) have not been used so far in polymer materials (especially in biodegradable polyesters) as stabilizers, dyes, and indicators of aging. The application of polydatin and (+)-catechin as multifunctional additives for biodegradable polymers is a scientific novelty. This paper presents the following analyses of polyester materials: SEM microscopy, wide angle x-ray diffraction, mechanical properties, thermal analysis, surface free energy analysis, and determination of change of color after controlled UV exposure, thermal oxidation and weathering. Both PLA and PHA polyesters were characterized by higher resistance to oxidation and greater resistance to degradation under the influence of UV radiation. In addition, (+)-catechin was used simultaneously as a dye and an indicator of the aging time of polymeric materials. In contrast, polydatin did not dye polymers, but was a very good indicator of their lifetime, changing color under the influence of various external factors. Both polyphenols can be successfully used as natural additives for pro-ecological polyesters.

Zirconium doping level modulation combined with chalconylthiourea organic frameworks induced enhancement of luminescence applied to cell imaging

Derivatives of a zirconium metal–organic framework as the center polymer material with a chalconylthiourea polymer (CT) were applied to cell imaging.

Prospect of Polysaccharide-Based Materials as Advanced Food Packaging

The use of polysaccharide-based materials presents an eco-friendly technological solution, by reducing dependence on fossil resources while reducing a product's carbon footprint, when compared to conventional plastic packaging materials. This review discusses the potential of polysaccharides as a raw material to produce multifunctional materials for food packaging applications. The covered areas include the recent innovations and properties of the polysaccharide-based materials. Emphasis is given to hemicelluloses, marine polysaccharides, and bacterial exopolysaccharides and their potential application in the latest trends of food packaging materials, including edible coatings, intelligent films, and thermo-insulated aerogel packaging.

Preparation and pH Controlled Release of Fe3O4/Anthocyanin Magnetic Biocomposites

Anthocyanins are a class of antioxidants extracted from plants, with a variety of biochemical and pharmacological properties. However, the wide and effective applications of anthocyanins have been limited by their relatively low stability and bioavailability. In order to expand the application of anthocyanins, Fe3O4/anthocyanin magnetic biocomposite was fabricated for the storage and release of anthocyanin in this work. The magnetic biocomposite of Fe3O4 magnetic nanoparticle-loaded anthocyanin was prepared through physical intermolecular adsorption or covalent cross-linking. Scanning electron microscopy (SEM), Dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and thermal analysis were used to characterize the biocomposite. In addition, the anthocyanin releasing experiments were performed. The optimized condition for the Fe3O4/anthocyanin magnetic biocomposite preparation was determined to be at 60 °C for 20 h in weak alkaline solution. The smooth surface of biocomposite from SEM suggested that anthocyanin was coated on the surface of the Fe3O4 particles successfully. The average size of the Fe3O4/anthocyanin magnetic biocomposite was about 222 nm. Under acidic conditions, the magnetic biocomposite solids could be repeatable released anthocyanin, with the same chemical structure as the anthocyanin before compounding. Therefore, anthocyanin can be effectively adsorbed and released by this magnetic biocomposite. Overall, this work shows that Fe3O4/anthocyanin magnetic biocomposite has great potential for future applications as a drug storage and delivery nanoplatform that is adaptable to medical, food and sensing.

Anti-proliferation activities of Oryza sativa L. anthocyanins-Hohenbuehelia serotina polysaccharides complex after in vitro gastrointestinal digestion

In order to improve the bioavailability of Oryza sativa L. anthocyanins, we fabricated Oryza sativa L. anthocyanins-Hohenbuehelia serotina polysaccharides (OSA-HSP) complex and investigated its anti-proliferation activities taking into account its changes along simulated gastrointestinal digestion in vitro. Results showed that OSA mainly composed by delphinidin, cyanidin, petunidin, malvidin and their derivatives was combined with HSP through electrostatic interaction. OSA-HSP complex belonged to non-crystalline substance, and had compact and laminar structural characteristics. Under simulated gastrointestinal digestion, OSA-HSP complex significantly prevented the degradation of anthocyanins, and presented sustain release effect. However, the anti-proliferation activities of OSA-HSP complex digested by different gastrointestinal process were remarkably changed, especially after small intestinal digestion. HeLa cells treated with OSA-HSP complex exhibited pro-apoptosis characteristics by triggering endogenous mitochondrial apoptosis pathway through activating the expressions of Bax, cytochrome c and Caspase-3 as well as inhibiting the expression of Bcl-2. These findings provided new insight to improve the bioavailability of anthocyanins in functional foods and tumor therapy.

pH-responsive pectin-based multifunctional films incorporated with curcumin and sulfur nanoparticles

pH-responsive pectin-based functional films have been prepared by incorporating curcumin and sulfur nanoparticles (SNP). FTIR and SEM results indicated that curcumin and SNP were uniformly dispersed in the pectin to form a well-developed composite film. Addition of curcumin and SNP significantly influenced the surface color and UV-blocking properties of the composite films. The composite films showed a higher water contact angle and thermal stability compared with the neat pectin film, however, the mechanical and water vapor barrier properties did not change significantly. The composite film exhibited antibacterial activity against E. coli and L. monocytogenes, and strong antioxidant activity. When applied to shrimp packaging, the film showed a pH-responsive highly distinctive color change from yellow to orange as the quality of the shrimp changed.

Development of bacterial cellulose/chitin multi-nanofibers based smart films containing natural active microspheres and nanoparticles formed in situ

Nanofiber-based materials have recently gained increasing attention in food packaging, drug delivery, and biomedical applications. In this study, a multi-nanofibers composite film was developed based on bacterial cellulose nanofiber (BCNF)/chitin nanofiber (CNF) hybridization. The nanofibers were responsible for the formation of well-dispersed curcumin (Cur) micro/nanoparticles in the nanocomposite films. The release of Cur from the films were affected by CNF and the sizes of Cur particles formed in situ. The Cur particles reduced tensile strength and increased water vapor permeability of BCNF film. However, CNF improved the mechanical strength and barrier property of the Cur/BCNF/CNF composite film. Moreover, the multi-nanofibers composite film showed excellent dynamic antioxidant capacity and antibacterial activity, as well as was capable to monitor pH change and trace amount of boric acid. Results of this study suggested that the Cur/BCNF/CNF composite film can be used as a smart and active food packaging material.

A novel pH-sensing indicator based on bacterial cellulose nanofibers and black carrot anthocyanins for monitoring fish freshness

A novel intelligent pH-sensing indicator based on bacterial nanocellulose (BC) and black carrot anthocyanins (CA) was developed and characterized to monitor the freshness/spoilage of rainbow trout and common carp fillet during the storage at 4 °C. The indicator displayed wide color differences from red to gray over the 2-11 pH range, which was clearly discerned by the naked eye. The fabricated pH-sensing indicator showed distinguishable color changes during fresh (deep carmine color), best to eat (charm pink color), and spoiled (jelly bean blue and khaki colors) stages of both fish fillets. Moreover, a strong and positive correlation was obtained between the total color differences values of the indicator and bacterial count (R = 0.952 and 0.991) and total volatile basic nitrogen (R = 0.815 and 0.92) in rainbow trout and common carp samples. The results of this work demonstrated a significant correspondence of fish shelf life and color changes of a nanocellulose-based pH-sensing indicator.

Intelligent pH-sensitive indicator based on starch-cellulose and alizarin dye to track freshness of rainbow trout fillet

A novel pH-sensitive indicator was prepared by incorporation of alizarin in a starch-cellulose paper to monitor the freshness of rainbow trout fillet. Water solubility of the fabricated indicator reduced by incorporation of alizarin, while the percentage of swelling didn't change. FTIR certified that alizarin was properly incorporated which was revealed by the formation of intermolecular hydrogen bonding in the cellulose-starch matrix. SEM and ultraviolet-visible spectrum results also demonstrated that alizarin had good compatibility with the components of the indicator. The alizarin-starch-cellulose indicator (ASC) had greater color efficiency from yellow to purple at pH 2-11 and greater color stability after two months of storage at 4 °C. It can be concluded that the color changes of ASC, from orange to reddish brown, were entirely corresponded with TVB-N contents of fish, which presents a satisfactory capability of developed indicator to identify the initiation of spoilage in the refrigerated fish fillet.

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.

Development of active and intelligent films based on cassava starch and Chinese bayberry (Myrica rubra Sieb. et Zucc.) anthocyanins

Chinese bayberry (Myrica rubra Sieb. et Zucc.) fruit is a functional food rich in anthocyanins. In this study, anthocyanin-rich bayberry extract (BBE) was added into cassava starch to develop food packaging films with antioxidant and pH-sensitive properties. Results showed the main anthocyanin in BBE was cyanidin-3-O-glucoside (95.6%). The addition of 1 wt% of BBE into the film matrix resulted in a dense and compact internal microstructure, which greatly improved the water vapor permeability and tensile strength of the film. However, the addition of 2, 3 and 4 wt% of BBE into film matrix produced heterogeneous inner microstructures due to the formation of agglomerated BBE. The intermolecular interactions between BBE and the starch film matrix were through hydrogen binding. As compared with the starch film, starch–BBE films exhibited higher thicknesses, tensile strength, UV-vis light barrier and antioxidant properties. Moreover, starch–BBE films presented significant color changes when exposed to hydrogen chloride and ammonia gases. The pH-sensitive starch–BBE films were able to monitor the freshness of pork. Our results suggested that starch–BBE films could be used as smart and active packaging materials in the food industry.

In this study, anthocyanin-rich Chinese bayberry extract (BBE) was added into cassava starch to develop food packaging films with antioxidant and pH-sensitive properties.

Ethylene-vinyl Alcohol Copolymer-Montmorillonite Multilayer Barrier Film Coated with Mulberry Anthocyanin for Freshness Monitoring

Colorimetric films incorporated with anthocyanins as an indicator for freshness monitoring have aroused growing interest recently. However, the application of the films is limited by the easily oxidizable nature of anthocyanins. In this work, we developed a novel colorimetric film with a barrier by coating mulberry anthocyanin (MBA) on the internal side of an ethylene-vinyl alcohol copolymer-montmorillonite (EVOH-MMT) multilayer film. A facile layer-by-layer (LBL) assembly was employed under a parallel electric field to build the EVOH-MMT multilayer structure, in which the exfoliated MMT nanosheets were well-oriented and assembled on the EVOH matrix to form a tightly stacked layer between two EVOH layers. The interlayer of MMT significantly enhanced the barrier and mechanical properties of the films (below 40 layers). The interactions between EVOH and MMT and between EVOH and MBA were confirmed to be intermolecular hydrogen bonds. The colorimetric response of (EVOH-MMT)₄₀-MBA₃ to volatile ammonia and pH was sensitive, and the color change could be easily distinguished by the naked eye. The successful application of (EVOH-MMT)₄₀-MBA₃ to shrimp-freshness monitoring confirms its high potential for the freshness monitoring of packaged food.