# Evaluation of the Temperature and Time in Centrifugation-Assisted Freeze Concentration
## 1 Introduction  
Freeze concentration (FC) or cryoconcentration is an attractive nonthermal technology applied to several liquid foods, and sub-zero temperatures are used, instead of thermal technologies such as evaporation that are usually performed at temperatures above 70 \({}^{\circ}\)C. Compared to conventional evaporation processes, FC is a method that allows the preservation of the organoleptic and nutritional properties of liquid food products [1]. FC is a method for recovering a food solute from a solution based on the separation of pure ice crystals from a freeze-concentrated aqueous phase [2]. Four FC techniques are used: (i) suspension freeze concentration [3]; (ii) progressive freeze concentration [4]; (iii) falling-film freeze concentration [5; 6; 7]; and (iv) block freeze concentration (BFC) [8; 9]. The industrial future of FC is mostly associated with developments in the configuration of BFC rather than conventional freeze concentration systems or suspension crystallization, given the simpler separation step of BFC [10]. Another advantage of one-step block freeze concentration systems is their simplicity in terms of both the construction and operation of the systems [11]. In BFC, a food-liquid solution is completely frozen, the whole frozen solution is thawed, and then, the concentrated fraction is separated from the ice fraction by gravitational thawing. Other techniques may or may not be used in the last stage to improve the separation efficiency, and the ice block acts as a solid casing through which the concentrated fraction passes [4]. The technical viability of the block freeze concentration method has been demonstrated by several researchers [12; 13; 14; 15; 16; 17]. Considering these conditions, [PERSON], [PERSON] and [PERSON] [10; 11; 18; 19] suggested that the advancement of the freeze concentration technique is associated with the development of the characteristics or mechanisms of solute recovery occluded in the ice. These mechanisms are simple and economical in terms of their application; thus, these mechanisms serve as alternatives that allow us to make the process more efficient. Many studies have focused on centrifugation and vacuuming as techniques to assist in freezing concentration. Centrifugation is an effective assisted technique to remove the concentrated solution from the ice matrix in a one-stage freeze concentration. The force of gravity is largely replaced by a greater driving force applied by centrifugal force. The higher concentration yield by freezing using centrifugation is attributed to the ice matrix acting as a porous solid through which the concentrated solution is filtered through ice drainage channels, which is enhanced by the centrifugal force applied [13; 20; 21; 22]. Some authors have studied how the choice of the parameters for the assisted technique can help achieve more efficient freeze concentration. For example, [PERSON] [23] investigated the initial concentration of sucrose and the centrifugation speed. [PERSON] [24] reported that centrifugation enhances the separation of the concentrated solution of frozen fruit juices (blueberry and pineapple). However, there are no scientific reports in which parameters, such as the temperature and centrifugation time, have been studied in detail to obtain a highly efficient FC concentration process. Furthermore, although research has shown the advantages of applying machine learning techniques to food technology [25; 26], the authors did not find any previous reference to the use of these techniques for predicting the effects of the parameters in the centrifugation-assisted freeze concentration process. In this paper, we study the influence of temperature and time parameters on the centrifugation process as an assisted technique. This study is focused on the case in which the centrifugation process is applied to the freezing concentration of blueberry juice. In the first stage, we collected experimental data to evaluate the effects of the temperature and centrifugation time.