4D printing: a new approach for food printing; effect of various stimuli on 4D printed food properties. A comprehensive review

4D printing is an additive manufacturing technique and is an extension of 3D printing. 4D food printing is a newly developed area in 4D printing, and it is in the stage of infancy. 4D food printing has gained much attention from the academic and industrial sectors. Compared to other fields of 4D printing, the number of literature reviews available for 4D food printing is scanty. The current article gives an overview of 4D printing with an emphasis on 4D food printing. This review address the effect of various stimuli on the properties such as color, flavor, texture, and shape of 4D printed food samples. Besides, it also covers 4D design development, food printing ink, and various methods used in 4D food printing. Most 4D food printing focuses on microwave treatment or the influence of pH as a stimulating agent in printed food objects. The food properties like color, taste, aroma, texture and the shape of 4D printed food changed under stimuli. Starch, soy protein isolate, potato purees, buckwheat dough, etc., are food materials yet to be explored in 4D printing. The printing ink used in 4D printing consists of a stimulus-responsive material, bringing spontaneous changes in 3D printed structure. Anthocyanine, vanillin powder, and curcumin area few stimulus-responsive materials used in 4D food printing, which will change color in response to pH. The use of multiple stimulus-responsive materials and different stimulating agents like light can be explored.