Preparation Of Antibacterial And Mildew Modified Polyethylene Film And Its Application On Maintaining Quality Of Dried Tofu During The Storage

Fresh dried tofu contains abundant protein,including vitamins,fats and other nutrients,which is the most important provider of plant protein on the table.With the improvement of the level of consumption,consumer demands for food quality and safety are also on the rise.How to achieve the shelf life of fresh dried tofu products at normal temperature and ensure the safety of food and the health of consumers is the pursuit of fresh dried tofu products industry.Due to the abundant nutritional content of dried tofu products,microorganisms multiply in large quantities as long as the environment is suitable.Moreover,it is easily contaminated by microorganisms during processing and storage,resulting in spoilage,affecting its sensory quality and shelf life.In particular,the sales of fresh dried tofu products in bulk are extremely susceptible to secondary pollution during transportation and sales.The unpackaged dried tofu products’shelf life is short and it’s difficult to transport and storage,which greatly limits the scope of its sales,seriously affected the further development of soybean products industry.This article takes into account the food safety and fresh dried tofu products at room temperature perishable spoilage problem,using household flavor:white sugar,salt,vinegar as a preservative solution,calcium propionate（CP）and disodium edetate（Na₂-EDTA）as antibacterial agent,poly（vinylidene fluoride）resin（FM）as antifungal agent and low density polyethylene（LDPE）as substrate to study antifungal and antimicrobial film,to study its preservation on fresh dried tofu at room temperature.The main conclusions are as follows:（1）Living seasoning with bactericidal effect sugar,salt and vinegar are used to prepare preservative liquid,and the fresh fragrant dried tofu is packed by the polyamide（Polyamide,PA）film with better barrier properties.The results showed that the preservation effect of fresh dried tofu treated by different fresh storage solutions was better than that of the blank group by changing the sugar,salt and vinegar.The optimum combination of fresh-keeping liquid and orthogonal test was obtained optimal ratio.The result showed that the best preservation solutions are 1g/L sugar,7 g/L salt,3 g/L vinegar as a mixed preservation solution,the best boiling water sterilization is 0.5min.（2）Low-density polyethylene（LDPE）was used as base material,and 2.5%calcium propionate and 4%EF antibacterial antifungal resin were used as modifier to modify the film to prepare calcium propionate modified CP-EF antibacterial.The results of SEM showed that there was no obvious change in the surface smoothness and crystallinity of the film,and no porosity and agglomeration appeared.In this case,the mechanical strength of the film is the best,the transverse tensile strength increased49.07%,the longitudinal tensile strength increased 32.36%,the membrane barrier properties,antibacterial properties and thermal stability properties also increased.But the light transmittance of the film was gradually reduced from 85.96%to 72.45%,and the haze gradually increased from 3.01%to 7.91%because of the addition of modifier.Adding this ratio of additives,the film’s comprehensive performance is the best.（3）The fresh-keeping liquid and calcium propionate modified CP-EF antiseptic film were used to study the fresh-keeping packaging of fresh dried tofu.At normal temperature,the texture,sensory,protein content,water content,odor change,acidity and alkalinity and microbial indexes were observed and measured.The excellent order of fresh-keeping parameters of fresh dried tofu is:fresh-keeping liquid+modified film treated fresh dried tofu>calcium propionate modified CP-EF antibacterial mildew proof film packed with fresh dried tofu>blank LDPE film packed fresh dried tofu,and the decrease trend of the content of dried protein,moisture content and pH value of the test group was obviously smaller than that of the blank control.The activity of microorganism in dried beans dried with fresh liquid and modified membrane was obviously inhibited,which reduced the acid substance produced in the dried tofu and slowed down the decrease of the pH value of the dried tofu.The test results of the electronic nose also fitted the results of the sensory evaluation,and the combination of the preservative liquid and the modified film were all better than the preservative or modified film.The results showed that the fresh-keeping liquid and calcium propionate modified antibacterial and anti mould film had synergistic antiseptic effect and good preservation effect.