Study On The Photooxidation Characteristics And Packaging Shelf Life Of UHT Pure Milk

UHT(Ultra High Temperature treatment)pure milk,as a kind of dairy product with long shelf life,has become the mainstream milk product in the current market.However,UHT pure milk has complex components,various packaging forms,and complex quality deterioration and its influencing factors.The quality change mechanism and packaging shelf life prediction of different products have become the focus of the industry.Therefore,the evaluation of packaging shelf life based on the initial formula,storage and transportation conditions and packaging of UHT pure milk has important engineering value for scientific prediction of product packaging shelf life and guidance of new product packaging design.This project takes UHT pure milk as the research object,tests and analyzes the photooxidation characteristics of UHT pure milk,determines the characteristic indicators of product quality,and synthetically determines the deterioration threshold of product characteristic indicators based on the combined effect of storage conditions,packaging,product formula and other factors on milk quality.Based on the characteristic flavor and total dissolved oxygen consumption,the prediction model of quality deterioration and packaging shelf life of UHT pure milk was established.The main research contents and research results include:(1)Study on photooxidation deterioration characteristics of UHT pure milk.The test was carried out under the condition of ensuring sufficient oxygen and photooxidation reaction in the packaging.The sensory evaluation and quality index determination were combined to analyze and determine the correlation between the total dissolved oxygen consumption,volatile substances and other indicators and the change of milk quality.A multi-factor accelerated test was carried out based on the initial formula,storage and transportation conditions,packaging and other factors.It was found that temperature,light intensity,oxygen and fat content could significantly affect the deterioration reaction rate of UHT pure milk,and lead to significant differences in quality change.When the dissolved oxygen content and fat content are low,milk quality changes slowly.(2)Establishment of shelf life prediction model of UHT pure milk packaging based on characteristic flavor.The storage tests of three different formulas based on storage temperature,light flux and initial content of unsaturated fatty acids were carried out to determine and analyze the flavor differentiation characteristics of milk,and to clarify the necessity of comprehensive evaluation of multiple flavor senses of UHT pure milk.Orthogonal partial least squares discriminant analysis was used to determine that cardboard,oil,powder,and bitter were the most effective flavor characteristics for consumer sensory evaluation.Headspace solid-phase microextraction(HS-SPME-GC-MS)technology was used to calibrate the content of characteristic flavor substances,and the correlation between characteristic flavor substances of different formulations and comprehensive evaluation was established.The shelf life prediction model of UHT pure milk based on the comprehensive effects of temperature,light intensity and initial characteristic formula of products was established.Experimental results were used to verify the effectiveness of the model.(3)Establishment of shelf life prediction model of UHT pure milk packaging based on total dissolved oxygen consumption.The effects of temperature and light flux per unit volume of milk on the changes of dissolved oxygen concentration and headspace oxygen pressure were measured and analyzed.The relationship between dissolved oxygen concentration and headspace oxygen pressure and time was characterized by first-order kinetic model.A correlation model combining the oxygen dissolution mechanism of packaging headspace with the principle of poor product quality was established to predict the total dissolved oxygen consumption of headspace-non-permeable packaging products.On this basis,the calculation method of total dissolved oxygen consumption in the product was further established,the total dissolved oxygen consumption threshold based on shelf life evaluation was obtained,and the shelf life prediction model of UHT pure milk packaging based on total dissolved oxygen consumption control was established.The accuracy of the model prediction was verified by experiment.