Storage Impact on the Physicochemical and Microbiological Stability of Apricot, Cherry, Raspberry, and Strawberry Jams.

Fruits, such as apricots, cherries, raspberries, and strawberries, are very often processed into jams to extend their shelf life. Jams are highly appreciated by consumers, and their storage conditions are important for preserving their quality. This study investigates the impact of storage on the microbiological quality and physicochemical parameters of five commercial fruit (apricot, sour cherry, white cherry, raspberry, and strawberry) jams. The pH, titratable acidity, moisture, sugar content, viscosity, and color were evaluated immediately after opening the jam containers and during storage at 2-4 °C and 20 °C. The total number of mesophilic aerobic germs (TMAG) and the total number of yeasts and molds (TYM) were also determined. The samples were analyzed during storage at 14, 42, and 56 days after opening the jam jars. The pH of the fruit jam samples varied from 2.91 (strawberry jam) to 3.47 (sour cherry jam) and decreased during storage, while the titratable acidity (TA) ranged from 0.46 (cherry and raspberry jams) to 0.52% malic acid (apricot jam) and increased during storage, regardless of the storage temperature. The moisture content was between 15.78% (apricot jam) and 21.82% (raspberry jam), and decreased in all the jam samples during storage. The sugar content (30.40-44.59 g per 100 g of jam) was typical for low-sweetened jams and increased during storage. Also, the viscosity of the fruit jam samples increased during storage (more in the samples stored at room temperature). Under the storage conditions, all the jam samples lost their specific color. Immediately after opening the jam jars, no yeasts or molds were found in the apricot and sour cherry jam samples. The highest number of yeasts and molds was detected in the white cherry jam samples (4.25 log10 CFU/g). The TYM increased during storage, as did the TMAG. The time-temperature interaction factor influenced the physicochemical and microbiological properties of the jam samples.