Alternative freezing: Effects on rehydration properties of freeze‐dried daikon (Raphanus sativusL.)

Abstract

Abstract Freeze‐drying of daikon was performed using four different freezing conditions: two processes at constant temperature (−20 and −30°C—conventional); and two alternative approaches (dynamic and variable by levels). Freezing rates were evaluated and all methods achieved commercial freezing requirements (10–50°C hr −1 ). The two modified processes presented similar freezing rates to the conventional operation; moreover, evidence was found to consider these two processes statistically equivalent. Then, freeze‐dried samples were rehydrated by immersion in distilled water, and rehydration kinetic curves were adjusted to semi‐empirical models; the Weibull model presented the best fit. Finally, rehydration quality parameters of the samples were evaluated. The dynamic freezing process showed the best rehydration quality, while the variable by levels showed the closest results to the conventional one. In conclusion, these results indicate a technologically attractive improvement as an alternative for traditional industrial processes. Practical Applications A new freezing methodology was proposed, which consists of changing the freezing operating conditions, considering the product temperature throughout the process. Such an operation provides high‐quality freeze‐dried products, regarding rehydration properties. The procedure can be used in the replacement of conventional freezing, resulting in better freeze‐dried products.