High-sensitivity intelligent packaging films harnessing rose anthocyanins and hydrophilic silica aerogel for visual food freshness monitoring

The enhancement of the sensitivity for anthocyanin-based indicator films in food freshness monitoring in real time is important for application.In this study,hydrophilic silica aerogel(SiO2 NA)was incorporated into corn starch(CS)/chitosan(CH)/rose anthocyanins(RACNs)-encapsulated potato amylopectin nanoparticles(APNPs)composite film to increase the sensitivity for shrimp freshness detection.The microstructure of films revealed that the gas absorption capacity was improved by amorphous SiO2 NA via hydrogen interactions.The pore size(1.74–5.60 times),pore volume(3.92–5.60 times),and specific surface area(2.21–2.34 times)of films increased with the addition of SiO2 NA.The sensing of NH3 and pH and the reversibility of films were also reinforced.Meanwhile,the pH-responsive films containing SiO2 NA changed visibly in color from purple–red to orange–gray and finally to gray,enabling effective monitoring of shrimp freshness during storage at 4°C.Thus,anthocyanin-based indicator films with improved sensitivity by adding SiO2 NA were successfully designed for monitoring shrimp freshness.

Anthocyanins/chitosan films doped by nano zinc oxide for active and intelligent packaging:comparison of anthocyanins source from purple tomato or black wolfberry

The multifunctional films was prepared by blending chitosan and nano-ZnO with purple tomato anthocyanins or black wolfberry anthocyanins.The properties of films functioned by anthocyanins source and nano-ZnO content were studied.It was found purple tomato anthocyanins showed more significant color change against pH than black wolfberry anthocyanins.The nano-ZnO were widely dispersed in matrix and enhanced the compatibility of anthocyanins with chitosan.However,the anthocyanins source influenced the properties of the films more slightly than nano-ZnO addition.The tensile strength,antioxidant and antibacterial effects of the chitosan films dramatically increased after cooperated by nano-ZnO and anthocyanins,which also enhanced with increase of nano-ZnO content,whereas the elongation at break of the composite films decreased.Especially,the anthocyanin and nano-ZnO promoted the antibacterial activity of films synergistically.Composite films made from black wolfberry anthocyanins exhibited higher mechanical performance than those made from purple tomato anthocyanins but weaker antibacterial effects.The purple tomato anthocyanins/chitosan and nano-ZnO/purple tomato anthocyanins/chitosan films effectively reflected pork spoilage,changing their colors from dark green to brown,indicating the potential for applications in active and intelligent food packaging.

Electrospun gelatin/chitosan nanofibers containing curcumin for multifunctional food packaging

Recently,food grade nanofiber-based materials have received growing attentions in food packaging.In this work,novel active and intelligent packaging nanofibers based on gelatin/chitosan with curcumin(GA/CS/CUR)were developed via electrospinning technique.Effects of the incorporation of CUR content(0.1%-0.3%,m/m)on the microstructure and functional properties of the electrospun nanofibers were investigated.Morphological studies using scanning electron microscopy indicated that loading CUR can affect the average diameter of nanofiber mats,which remained around 160-180 nm.The addition of an appropriate level CUR(0.2%,m/m)led to a stronger intermolecular interaction,and thus enhanced the thermal stability and tensile strength of the obtained nanofibers.Meanwhile,the incorporation of CUR significantly improved antioxidant activity and the antimicrobial activity of GA/CS/CUR nanofibers.Moreover,the sensitivity of nanofibers to ammonia results indicated that GA/CS nanofibers containing 0.2%CUR(GA/CS/CURⅡ)presented high sensitivity of colorimetric behavior to ammonia(within 3 min).These results suggest GA/CS/CURⅡnanofibers has great potential as a multifunctional packaging to protect and monitor the freshness of proteinrich animal foods,such as meat and seafood.

Development,Characterization and Application of a Three-Layer Intelligent pH-Sensing Indicator Based on Bromocresol Green(BCG)for Monitoring Fish Freshness

As a novel food quality monitoring technology,intelligent freshness indicator has received wide attention in recent years.However,its poor safety and stability are the main problems hindering its practical application.Hence a new pH-sensing indicator based on bromocresol green(BCG)was developed in this study for nondestructive and real-time monitoring the freshness of marine fishes.The indicator was designed with a three-layer structure,using the polytetrafluoroethylene(PTFE)membrane with high hydrophobicity and air permeability as the inner layer to isolate the moisture in the package,BCG-coated filter paper as the colorchanging layer to indicate the freshness of fish,and a transparent unidirectional permeable(TUP)membrane with moisture resistance as the out layer to isolate the moisture in the environment.This contributed to weaken the influence of humidity and prevent dye migration,so as to improve the accuracy and safety of the indicator.Therefore,a highly sensitive and distinguished color variation response to trimethylamine(TMA)standard solution with different concentrations was observed on the indicator.Additionally,the indicator showed a high color stability at different storage temperatures up to 14 days with total color differences(ΔE)less than 5.0.The indicator presented visible color variations from yellow to green then eventually to blue when applied to monitor the freshness of sea bass and salmon stored at 4℃,implying that fish was spoiled.Meanwhile,indicatorsΔE value was significantly positively correlated with total volatile basic nitrogen(TVB-N)and total viable count(TVC)in sea bass and salmon samples.Thus,the pH-sensing indicator can be applied as a cost-effective and promising intelligent indicator for monitoring fish freshness.

Carbon dots enhanced gelatin/chitosan bio-nanocomposite packaging film for perishable foods

Carbon dots(CDs)with intriguing fluorescent property,good biocompatibility,high stability,easy interaction with substrates,are burgeoning carbon nanoparticles with large potential in various applications.Incorporating CDs into the polymer matrix is becoming a popular strategy to endow the complex with new functions.Herein,the green-synthesized CDs was integrated into the mixture of gelatin(derived from waste fish scale)and chitosan,and a multifunctional bio-nanocomposite(defined as Gelatin/Chitosan/CDs)film was developed,which showed the excellent antibacterial,antioxidant,pH-sensitivity,UV shielding,and blue-emission properties.The effects of different concentrations of CDs on the physical,mechanical,structural,and functional activity of bio-nanocomposite film were tested.Compared with the Gelatin/Chitosan film,the Gelatin/Chitosan/CDs film with an optimum addition of 20%CDs showed the enhanced antibacterial,antioxidant as well as UV shielding activities.More importantly,it was used as an effective packaging material for fish meat preservation,reducing the loss of nutritional quality consumption,extending the shelf life of food.Besides,the bio-nanocomposite films also possessed the anti-counterfeiting and pH-responsive properties due to the strong fluorescent emission of CDs,and had the great potential in developing the intelligent packaging materials.Our work shed new light on the new application of CDs and the synthesis of bio-nanocomposite film in food industry.

A biopolymer-based pH indicator film for visually monitoring beef and fish spoilage

Food safety is a worldwide public concern that has recently gained increased attention due to the emerging outbreaks of foodborne diseases.Therefore,there is a pressing need to make simple,cost-effective,and environmentally friendly methods for detecting food spoilage and to mitigate the impact of possible outbreaks.The aim of this study is to develop a biodegradable indicator film which was made by combining cellulose-nanofiber/chitosan dyed with methyl red synthesis(CCM)as a pH indicator film and followed by a single layer coating of polylactic acid(PLA)on its surface,named PLA/CCM film.The microstructural properties of PLA/CCM films were studied using scanning electron microscopy(SEM)and results showed that PLA effectively adhered to the surface of CCM film.The microbial response to PLA/CCM film was determined via a bacterial plating method.It was found that the contact of film with the microbes caused a substantial color change in the film.The coating of PLA upon the CCM film decreased the percentage of the water vapor transmission rate(WVTR).The color of the film vividly altered from slightly red to yellow in response to a pH change in the range of 4-8.The PLA/CCM film was applied to monitor the spoilage of beef and fish at room temperature(23℃)and revealed the onset of food spoilage by displaying the color change from red to yellow after 1 day.The total viable counts(TVC)of microorganisms and pH of the tested beef sample were determined,and the results revealed that both TVC and pH increased concurrently after beef spoilage.