The optimal storage conditions for walnut milk packaged in PET containers were determined by storing the products under different light and temperature conditions and then measuring their stability using a Turbiscan Lab stability analyzer. A single-factor experiment, an orthogonal experiment, and a validation experiment were then performed to elucidate the influences of the storage temperature and duration and the illumination intensity on the stability of the packaged liquids and to determine the optimal combination of storage conditions. The selection of the different factor levels and the possible mechanisms underlying the effects of the factor combination were also explained. The smallest stability index value (i.e., the optimal state of preservation for the packaged walnut milk) was achieved for storage under ambient temperature and an illumination intensity of 30 lx for 10 days after production. The degrees of influence of the selected factors decreased in the order of temperature>duration>illumination intensity, which may be explained by the following mechanism: Under these conditions, walnut milk stored in a PET container exists as a heterogeneous liquid system. Consequently, the instability caused by the thermodynamic effect of molecular fusion and the kinetic effect of gravity stratification results in mutual constraints among the various influencing factors. However, the influences on the stability of a packaged liquid are dependent on specific processing techniques, such as emulsification. Therefore, differences may exist between the results of this study and the optimal storage conditions of walnut milk obtained using different production techniques.
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