Research On Shelf Life Prediction Of Milk Powder Considering Packaging Mass Transfer

Whole milk powder is a product with high-fat content and rich nutrition.The portable and economical flexible packaging milk powder has broad market demand.However,whole milk powder is prone to be more hygroscopic and oxidized than ordinary milk powder,so it is difficult to predict the shelf life.Besides,if the model only considers one single indicator,it will lead to a large error.Therefore,it is of great significance to carry out systematic research on the flexible packaged whole milk powder shelf life based on comprehensive indicators,and to carry out packaging design.In this paper,whole milk powder is taken as the research object,and its moisture absorption and oxidation characteristics are analyzed experimentally.The storage experiments are designed to determine product’s moisture absorption and oxidation thresholds respectively.In the meantime,the permeability of packaging materials was evaluated.Based on the previous research,the packaging shelf life prediction model was established,and the accuracy of the model was verified through accelerated tests.The main research contents and research results include:(1)A moisture-proof shelf life prediction model of permeable packaged whole milk powder was established.The isothermal hygroscopicity model was used to characterize the hygroscopic properties of whole milk powder,and the critical moisture content of the product was determined based on the sensory evaluation indicators.The influence of temperature on the moisture permeability of packaging materials and the hygroscopic characteristics of the product was considered.And then the shelf life prediction of whole milk powder based on the influence of temperature and humidity was established.The validity of the model was verified by accelerated test at RH 70 % and 37 ℃.The results show that the moisture-proof packaging shelf life prediction model of based on the moisture absorption model of m GDW(Modified Generalised DArcy and Watt model)can effectively characterize the moisture absorption characteristics of whole milk powder,and fully consider the effect of temperature.The deviation between the predicted value of shelf life and the accelerated test results is less than 6 %,which indicates that the established model has high accuracy.(2)Research on lipid oxidation characteristics of whole milk powder.The storage test of whole milk powder was carried out under non-permeable brown bottle and three temperature conditions,and the changes of packaging headspace oxygen,peroxide value,sensory evaluation and other indicators were measured.The correlation of indicators was analyzed in order to determine the most suitable oxidation indicators to characterize the oxidation process of milk powder.The results show that the headspace oxygen consumption can be selected as the key indicator for later shelf life prediction.Based on further experimental analysis,oxygen consumption threshold and average oxygen consumption rate were used as two indicators to characterize the oxidation characteristics of milk powder.(3)A anti-oxidative shelf life prediction model of permeable packaged whole milk powder was established.Evaluate the oxygen permeability of packaging materials at a specific temperature.And then a dynamic model of packaging headspace oxygen is proposed,which integrates the oxygen permeability of packaging materials and product oxidation characteristics.On this basis,the total oxygen consumption model of milk powder was established,which can be used to predict the shelf life.The model was verified by accelerated test at RH 50 % and 45 ℃.The results show that the experimental data are consistent with the predicted data(relative deviation is less than 4 %),and the established model has high accuracy.The orthogonal test range analysis method determined that the oxygen permeability of packaging materials has the most significant effect on anti-oxidative packaging shelf life.(4)A moisture-proof and anti-oxidative shelf life prediction model of permeable packaged whole milk powder was established.Whole milk powder with different water activity were prepared and stored in non-permeable brown bottles to determine the respective average oxygen consumption rates.Empirical models were used to characterize the mathematical relationship between the water activity and average oxygen consumption rates.Considering the influence of water vapor and oxygen permeability of packaging materials on the shelf life of milk powder,a comprehensive-quality shelf life model was established.The model was validated by accelerated tests at RH 70 % and 45 °C.The results show that the quadratic regression model can better characterize the relationship between the average oxidation rate and water activity of whole milk powder;the experimental data are consistent with the predicted data(relative deviation is less than 8 %).The shelf life prediction model established in this paper can provide theoretical support for the packaging design of whole milk powder.