Study on Setting Method of Best-Before Date for Plum Jam

<p>　Low-sugar content plum jams were stored at 24℃ which is equivalent to room temperature, and a microorganism test, physicochemical test and sensory evaluation test of the jam were performed to set the Best-before date. In addition, we preserved jams at high temperatures of 34℃ and 44℃, which were assumed to be accelerated tests. We then derived the Arrhenius equation from the results of physicochemical tests and sensory evaluation tests, and investigated a method for predicting the Best-before date. As a result, the following findings were obtained. (1) The microbial test confirmed that the jam was not spoiled by microorganisms. Therefore, it was found that the microbial test results do not serve as an index for setting the Best-before date when the sterilization treatment is performed properly. (2) The results of sugar content, pH, and water activity measured as physical and chemical tests did not change significantly at any temperature during storage, but the color value (color difference) changed depending on the storage period and temperature. (3) The comprehensive evaluation point of the sensory evaluation test decreased linearly at any storage temperature, and the higher the temperature, the more remarkable the evaluation score decreased. (4) It was clarified that the color difference, which was observed to change during storage, and the comprehensive evaluation point of the sensory evaluation test were indexes for setting the Best-before date. The Best-before date of the plum jam was calculated based on the results, and the color difference was 140.2 days, and the sensory evaluation score was 87.3 days. Since the period obtained from the latter was shorter, this was adopted and further multiplied by the safety factor to determine the Best-before date of the plum jam as 69 days. (5) The color difference showed a change corresponding to the first-order reaction, but it was not possible to predict the time-varying equation only by the Arrhenius equation. On the other hand, the change in the comprehensive evaluation point of the sensory evaluation test corresponded to the 0th-order reaction. The Best-before date estimated by the Arrhenius equation, which was derived from the time-varying equation of the comprehensive evaluation point of the sensory evaluation test at each storage temperature, was close to the measured value.</p>