An in-depth analysis of commercial, shock, and acoustic-extra-freezing techniques in fruit preservation

The development of innovative freezing technologies is becoming increasingly important in the food sector to ensure product quality while minimizing nutrient loss and structural degradation. Conventional methods like commercial and shock freezing have known limitations, particularly regarding cell integrity and sensory characteristics. In response, new approaches such as Acoustic Extra Freezing (AEF)—a commercial device that uses “acoustic” elastic waves to influence the crystallization process—are being explored as potential alternatives. This study aims to evaluate the impact of the novel AEF technology on the preservation quality of plant-based products, specifically blueberries and grapes. The core objective is to compare AEF with conventional commercial freezing and industrial shock freezing in terms of texture, color, and sensory performance—both after freezing and subsequent thawing. Blueberries and grapes were subjected to three freezing techniques: standard commercial freezing, shock freezing, and AEF (Acoustic Extra Freezing). Thawing was conducted using three methods: traditional refrigeration, water bath thawing, and the integrated thawing function of the AEF device. Sensory analyses, texture measurements, and microscopic evaluations were conducted to assess cell integrity and visual appearance post-treatment. Fresh fruit samples clearly exhibited superior quality across all parameters (texture, color, and sensory). Among frozen variants, shock freezing preserved sensory and structural properties best. The AEF method, despite its theoretical advantage of producing more uniform ice crystals, did not outperform conventional techniques. In fact, fruits treated with AEF showed more pronounced structural degradation and color migration in the microscopic analysis. Sensory evaluation also revealed off-flavors and texture softening in AEF-treated samples, particularly after thawing with the same system. While the AEF technology represents an innovative approach to acoustic-assisted freezing, the current findings suggest that it requires substantial optimization before practical application. The discrepancy between theoretical expectations (e.g., finer ice crystal formation) and experimental outcomes highlights the need for systematic refinement of process parameters. Future studies should focus on optimizing energy input, pulse modulation, and thawing protocols to unlock the full potential of this promising non-thermal preservation technique for high-quality fruit products.