Preparation Of Two Anthocyanins Active And Smart Packaging Films And Their Application In Hairtail Meat

Anthocyanins are natural pigments with wide sources,high p H sensitivity and various biological activities,and are widely used in the development of active and smart food packaging.However,the mechanism of the effect of anthocyanins structural differences on the same film matrix is not yet clear,and the application of anthocyanins-based active and smart packaging in hairtail meat remains to be explored.In this study,the structure and properties of purple potato and roselle anthocyanins were determined,and active and smart packaging films based on chitosan/polyvinyl alcohol/Zn O NPs/anthocyanins were prepared by solution casting method.The effect mechanism of purple potato and roselle anthocyanins on the same film matrix was explored,and the fresh-keeping effect and freshness monitoring of chitosan/polyvinyl alcohol/Zn O NPs/anthocyanins as active and smart packaging on refrigerated hairtail were explored.The main research contents are as follows:（1）Extraction,preparation and property analysis of anthocyaninsUsing purple potato and roselle as raw materials,anthocyanins were extracted by solvent extraction method,and their structures and properties were determined and analyzed to explore the differences in structure and properties of the two anthocyanins.The results showed that the results of the two anthocyanins were significantly different:roselle contained delphinidin and cyanidin,and purple potato anthocyanins contained cyanidin and peonidin with a large amount of acylated glycosides.Both purple potato and roselle anthocyanins are sensitive to p H.From acidic to alkaline environment,the color change of purple potato anthocyanins solution is red-pink-purple-blue-green-yellow,and the color change of roselle anthocyanins solution is presented in turn red-dark blue-dark green.The large amount of acylated glycosides contained in purple potato anthocyanins made its stability（temperature,light and hydrogen peroxide）and antioxidant activity（DPPH and ABTS free radical scavenging rate）higher than those of roselle anthocyanins.（2）Preparation,characterization and property analysis of active and smart packagingBiodegradable active and smart packaging films were prepared by solution casting method,in which chitosan/polyvinyl alcohol was used as film matrix,and nano-zinc oxide and purple potato or roselle anthocyanins were loaded as active functional components.The results of FT-IR and XRD spectra showed that the two anthocyanins and nano-zinc oxide were successfully immobilized in the film matrix through hydrogen bonding.The SEM results show that the surface of the film is smooth and uniform,and the addition of low-content anthocyanins can improve the agglomeration caused by nano-zinc oxide,and make the cross-section of the film smooth and continuous.The increase of anthocyanins concentration will enhance the mechanical resistance of chitosan/polyvinyl alcohol film（TS increased from 7.19 MPa to 20.68MPa）,and reduce its flexibility（EB decreased from 69.50%to 16.00%）and moisture content,and significantly improved the UV-visible light blocking properties of the film（240 mg/100 m L of anthocyanins film UV blocking rate is close to 100%）and antioxidant properties.Nano-zinc oxide can significantly enhance the antibacterial properties of the films（p<0.05）.The p H response results show that CPZ-PPE II film and CPZ-RE II film have better color rendering effect than other film samples as p H indicator labels,and there are fewer groups with limited p H color rendering,which are more suitable for real-time monitoring of food freshness.（3）Active and smart packaging is used for the preservation and freshness model construction of hairtailChitosan/polyvinyl alcohol/nano-zinc oxide/purple potato anthocyanins films were used as active and smart packaging and applied in the research on preservation and freshness monitoring of hairtail.The experimental results show that the purple potato anthocyanin-based film（CPZ-PPE II）inhibits the growth and reproduction of microorganisms and delays the oxidation of proteins and lipids by preventing the entry of external oxygen and microorganisms,and releasing the loaded nano-zinc oxide and anthocyanins,thus showing a trend of significantly delaying the rise of indicators（TVC,p H,TVB-N,TBA）.The experimental results of color difference and sensory evaluation showed that the quality of hairtail was ranked as follows:CPZ-PPEⅡ>CP>control group,and it was found that CPZ-PPEⅡfilm can prolong the shelf life of refrigerated hairtail by 3-6 days.In addition,combined with the classification results of hairtail freshness level,the color change results of smart labels are roughly divided into the following four stages:fresh（day 0,purple）,sub-fresh（day 1-4,lavender）,spoiled（day6-9,blue-grey）and complete spoiled（day 12-15,green）.Using the traditional freshness index TVB-N value and theΔE of smart labels to build a freshness prediction model:TVB-N=0.10683*ΔE^{^2.15919},R2=0.93422.The TVB-N value of hairtail can be predicted by measuring theΔE of the film,thus reflecting the degree of corruption of hairtail.