Research On Fabrication N And Application Of A Freshness Indicator For Beef

The quality and shelflife of foods are closely related to storage conditions.Nowadays consumers estimate food quality mainly through the shelflife,simple but not detailed and accurate enough sometimes.As a type of intelligent packaging,indicators can provide various information of the packaging food,depending on its structure and function.Beef is the second largest consumed meat in China due to its abundant nutritions.Raw beef contains a lot of protein and water,which are easily got contaminated by microorganisms and result in spoilage.This article aims to fabricate a freshness indicator which can indicate the freshness quality of beef(fresh,less fresh,spoilage).Three aspects are mainly studied:firstly,classifying the beef into three levels according to its freshness during storage;secondly,selecting the best indicator formula and optimize the fabrication method of the indicator;thirdly,validating the accuracy of the indicator used under dynamic temperature and differ weight of the beef,and the application conditions of the indicator.The main results of this paper are as follows:1.According to the changes of sensory index,TVB-N content,CO2 content and total count of bacteria,the beef stored at 4℃ and 20℃ was categorized into three freshness levels.The experimental results show that the beef refrigerated at 4℃ within 4 days is classified as "fresh",4-7 days is "less fresh" and more than 7 days is "spoilage".Beef stored at 20℃within 9 hours is "fresh”,9-18 hours is "less fresh" and more than 18 hours is "spoilage".2.Based on the freshness of beef,select an appropriate indicator formula from five different formulas with color changes matching up with the changes of freshness of beef.Through single factor experiments,relationships between the color changing time and the amount of hydroxypropyl methyl cellulose,the amount of indicator,the initial pH value were investigated.The interaction between hydroxypropyl methyl cellulose,indicator dosage and initial pH value were studied by response surface experiment using color changing time as the response value.The optimized indicator formula is:using 1.25 ml/50 ml bromocresol green as the indicator,the dosage of hydroxypropyl methyl cellulose is 8.37 g/L,and the initial pH value of the solution is 4.00.Using this recipe,the freshness indicator has higher accuracy both in 4℃ and 20℃.Using the optimized indicator formula,the indicator was validated the accuracy used under dynamic storaging temperature,different weight levels of the beef,and different storaging humidity and temperatures.The results show that the indicator can be used under dynamic temperature accurately.When the beef was weighed between 100 g to 500 g,the indicatorcan indicate the freshness of the beef accurately.The color of indicator is stable when stored under different humidity and temperatures.