Development Of Blueberry Anthocyan In Intelligent Label And Its Application In Fresh Meat Packaging

During transportation and storage,meat food is inevitably contaminated by microorganisms in the environment or carried by itself,which spoilage and produce volatile basic nitrogen,which leads to changes in the pH of the food packaging.Therefore,pH indicators can be used as functional materials for preparing smart labels,and the freshness of meat products can be observed by detecting pH changes in packaging.Blueberry has high nutritional value,and the anthocyanins extracted from it can show different colors in different pH environments,which is a natural pH indicator.Blueberry anthocyanin is stable and easy to extract,it is a kind of flavonoids with good antioxidant and bacteriostatic properties.In this paper,blueberry anthocyanin was used as indicator to prepare indicator film by adding degradable polymer material,which was used to indicate the freshness of beef.The main research contents are as follows:(1)Measure the sensory evaluation,TVB-N,pH value,TBARS value and TVC of frozen beef at 4°C within 0~10 days to evaluate the freshness of beef.The results showed that with the increase of storage time,the sensory evaluation value of beef decreased,both the chemical index value and the microbial index value gradually increased.The freshness grade of beef was comprehensively divided by various indexes,0~4d was fresh meat,4~7d was secondary fresh meat,and 7d later was spoiled meat.It laid the foundation for the freshness detection of smart labels and the classification of beef freshness grade by electronic nose.(2)Preparation and properties of blueberry anthocyanin indicator film.Using corn starch(CS),carboxymethyl cellulose(CMC)as film forming matrix and glycerol as plasticizer,different amounts of blueberry anthocyanins(BA)were added respectively to prepare CS/CMC composite film and CS/CMC-BA3%/6%/12%/18% indicator film by casting method.During the change of pH from 1 to 13,the color of blueberry anthocyanin aqueous solution has a colorimetric response,The color changed from red to purple,then to blue and green,and finally to brown.The absorbance and wavelength also changed continuously with the change of structure.According to the physical properties of the indicator film,with the increase of BA content,the tensile strength and water vapor permeability of the indicator film increased gradually,the elongation at break decreased,and the moisture content increased first and then decreased.The oxidation resistance of the films were obviously improved by adding BA,and the DPPH radical scavenging rate increased with the increase of BA content.DSC analysis showed that the addition of BA can improve the thermal stability of anthocyanin raw materials and CS/CMC composite film.The more BA content,the better the thermal stability.Fourier transform infrared spectroscopy and scanning electron microscope analysis showed that the compatibility of components were good,and after adding BA,the films surface were more compact and smooth.The sensitivity of CS/CMC-BA3% film was the highest in the response test of ammonia gas,and the sensitivity reached 66.09% at 21 min.With the increase of BA content,the sensitivity of the indicator membrane decreased.(3)Preparation and application of smart labels.Four kinds of indicator films were used to detect the beef freshness.The results showed that the color change of CS/CMC-BA3% film was continuous and obvious,and the indicator effect was the best.Therefore,using the CS/CMC-BA3% indicator film to prepare smart labels,consumers can judge beef quality information against the colorimetric card.Compared with the electronic nose detection method,the smart label had more advantages and convenience in practicability.The smart label can be used as a rapid nondestructive testing method to indicate the freshness of meat products.