Optimization of Preparation Process and Quality Evaluation of Purple Sweet Potato Preserves Fermented by Lactobacillus plantarum

The present study aimed to enhance the quality of purple sweet potato preserves by fermentation with Lactobacillus plantarum. Researchers conducted single-factor and orthogonal experiments to obtain the fermented purple sweet potato preserved fruit (FPSF). Then, they compared the differences in color, total acid, soluble sugar, texture, water distribution, and tissue structure between the FPSF and the unfermented purple sweet potato preserved fruit (UPSF) directly soaked in sugar under the same conditions. The results revealed the optimal production process of FPSF was as follows: fermentation with 2% L. plantarum for 24 h, solid-liquid ratio of 1:8 (g/g), microwave sugar-soaking at 560 W for 25 min in a 40% (g/g) sugar solution, soaking in sugar at room temperature for 8 h, and drying at 60 °C for 140 min. Findings indicated FPSF had a bright color, a sweet and sour taste, and a crisp texture. Compared with UPSF, its total acid content increased by 1.13 times, and texture indexes such as hardness and chewiness nearly doubled. The water fluidity of FPSF was weaker than that of UPSF. The proportion of the peak area of T₂₂ (immobile water) increased to 91.17%. The degree of surface water aggregation decreased significantly, and the tissue structure became more complete and more compact. The overall sensory comprehensive score of FPSF was approximately 16.77% higher than that of UPSF. The findings of this study furnish a theoretical basis for the development of diversified preserved fruit products and the modification of the tissue structure of fruits and vegetables.