Effects of cryoprotectant on 3D printability of frozen shrimp surimi based on principal component analysis

Shrimp surimi is a food material suitable for 3D printing, due mainly to that the sol can form an elastic gel with a certain viscosity and fluidity. Nevertheless, the shrimp surimi is usually frozen and stored before 3D printing. However, freezing and storage can easily denature the protein of shrimp surimi, leading to 3D printability. Fortunately, cryoprotectants can be used to effectively prevent the freezing denaturation of protein. Therefore, this study aims to investigate the effects of cryoprotectants on the rheological and textural properties, as well as 3D printability of shrimp surimi. The relationships between them were also established using principal component analysis (PCA). Five treatments were divided for the shrimp surimi used in the experiment. The first treatment was the control treatment (CK) without cryoprotectant, and the rest four treatments were added with commercial cryoprotectants, including 4% sucrose + 4% sorbitol + 0.3% polyphosphate (SSP), 8% trehalose (TH), 0.3% polyphosphate (PP), and 8% trehalose + 0.3% polyphosphate (TP). Shrimp surimi in five treatments was frozen to -20 ℃ and then stored at -18 ℃. Samples were taken at regular intervals to analyze 3D printing accuracy and stability, rheological and textural properties. The results showed as follows. The 3D printing lines of shrimp surimi were rough after frozen storage in the CT treatment, leading to deposition and collapse in the products concurrently with the worst appearance. However, the appearance of 3D printing products was improved to some extent after frozen storage in the treatments added with cryoprotectants. More importantly, the 3D printing lines after the TP treatment were fine and smooth, while the product presented no obvious deposition and collapse, indicating the best appearance. Since shrimp surimi was a kind of pseudoplastic fluid, there was a shear-thinning phenomenon under high-speed shear stress. Particularly, all treatments reduced the accuracy and stability of 3D printing, viscosity constant, the connection strength among rheological units, hardness, springiness, adhesion, and water holding capacity for the shrimp surimi, as the frozen storage days increased. The accuracy and stability of 3D printing of shrimp surimi significantly increased (P<0.05) in four treatments adding cryoprotectants, compared with the CT treatment. At the same time, the decreasing trend of rheological and textural parameters became slow significantly (P<0.05), as the frozen storage days increased. Correspondingly, the best 3D printing accuracy and stability were achieved in the TP treatment. However, the rheological and textural parameters of TP treated products were not the largest or the smallest, but suitable for 3D printing. Therefore, the food raw materials were necessary to behave suitable rheological and textural parameters for post processing. In addition, PCA showed that the accuracy and stability of 3D printing were positively correlated with the viscosity constant, the connection strength among rheological units, springiness, hardness, adhesion, and water holding capacity of shrimp surimi. The 3D printability of shrimp surimi was also positively correlated with these indicators. Consequently, TP (8% trehalose + 0.3% polyphosphate) treatment performed the best inhibition effect on the frozen denaturation of myofibrillar protein in shrimp surimi. The shrimp surimi still displayed better 3D printability after 30 d of frozen storage, where the 3D printing accuracy and stability were 96.64% and 97.61%, respectively. The finding can provide a strong theoretical reference to ensure the supply of raw materials for the 3D printing of shrimp surimi.