Comparison of the effect of hydrofluidization and immersion freezing on the qualitative features of a model plant material

One of the most promising food freezing methods in terms of high heat transfer coefficients and resulting in reduced freezing times is a hydrofluidization method that potentially offers a higher quality of small food products compared to other well-established methods. For this reason, this work aimed to assess the effect of hydrofluidization freezing on the quality characteristics of the model plant material. Namely, the raw material in the form of apple cubes was used for the hydrofluidization freezing process in a 50% glycerol solution and a 40% ethanol solution and then compared to immersion freezing in the same media and chamber freezing. In the test carried out, the hydrofluidization method was characterized by an average heat transfer coefficient of 1055 W/(m ² K) and 835 W/(m ² K) for the glycerol and ethanol solutions, respectively, which resulted in a 40% reduction in freezing time compared to the immersion freezing in the corresponding solution. Then color, drip loss, texture parameters, the content of phenolic compounds, vitamin C, and polyphenol oxidase activity were evaluated for all three methods. As a result, the obtained product was characterized by a lower drip loss and a significantly better color after thawing. However, no substantial advantages of this method were found, compared to the immersion method, regarding the content of phenolic compounds, vitamin C, and the activity of polyphenol oxidase.