Research On 3D Printing And Thermally-induced Gelation Of Silver Carp Surimi System

At present,China’s freshwater surimi products have the limitations of small production scale and insufficient variety of types,and the development of its further processing has on the agenda.The endogenous protease content of freshwater surimi is much higher than that of marine fish which is susceptible to denaturation during the freezing process.Therefore,freshwater surimi is prone to gel deterioration and reduced elasticity during the processing,appropriate exogenous substances such as starch and protein need to be added to improve its quality,or the heat-induced gelation process needs to be explored to reduce costs on the one hand and improve the gelation characteristics of freshwater surimi on the other.3D printing technology is a new technology based on the principle of additive manufacturing and is developing rapidly in China’s food processing industry.Unlike traditional production techniques,3D food printing technology has the advantages of high efficiency,energy saving and environmental protection,and personalised customisation.The printing material is the core of 3D food printing technology.Extrusion-based 3D printing technology requires food materials with certain rheological properties,gel strength and viscosity,and the surimi system meets this condition.The thesis investigated the effect of different exogenous additives on the printing quality and accuracy of silver carp surimi to improve the suitability of the material for 3D printing,and further studied the effect of the additives on the gelation system of minced fish to explore the formulation composition that could improve the gelation characteristics and develop nutrition-fortified 3D printed food products.The research also focused on the heat-induced gelation process of 3D printed surimi products,and proposed to develop a media-free heating technology suitable for 3D printing surimi products combined with insect protein to promote gel formation and improve gel characteristics.The effect of different Na Cl contents(0,0.5,1.0,1.5,2.0%)on the printing effect of silver carp surimi was initially investigated.By observing the 3D printing pictures and evaluating the print quality,the best Na Cl content was selected to be 2%,with significantly less filament breakage,smoother filament production and surface collapse improved.Based on this formulation,different levels of potato starch(0,3,6,9 and 12%)were added to investigate the effect on the 3D printing characteristics of surimi and the effect on the colour difference,moisture distribution,water holding capacity,gel strength and textural properties of the surimi products after heating.The results showed that the addition of starch allowed the surimi to print more smoothly,with certain fluidity and easy extrusion.Especially with the addition of 3% potato starch,the surimi resulted in higher print stability and accuracy and a significant increase in water holding capacity,chewiness,gel strength,hardness and adhesion(p<0.05),with water holding capacity of69.3%,gel strength of 2287.97 g·mm.The final selection of 3% potato starch was the best ratio.The insect protein powder was added to the surimi mixture to analyse the printing and gelation characteristics with a view to developing nutritionally enhanced 3D printed surimi products.The addition of insect protein powder enriched the amino acid content of the surimi,with a significant increase in the majority of amino acids.At the same time,the rheological properties again proved that the combination of surimi and insect protein is a suitable food material for 3D printing,with G’ and G’’ increasing with the content of insect protein powder,and G’ being much larger than G’’,and the material embodying shear thinning properties with some viscoelasticity.In addition,the combination of insect protein powder resulted in a significant decrease in the brightness,whiteness,water holding capacity,gel strength and hardness of the surimi mixture(p<0.05).This may be related to the different cross-linking mechanisms between mealworm proteins and meat proteins.It is urgently needed to improve the thermally induced gelation process of surimi by using a novel thermally induced gelation technology instead of traditional water bath heating method,which has problems of long processing time,high water consumption and unfriendliness to the environment.By comparing the color difference,water distribution,water holding capacity,gel strength,textural properties and microstructure of 3D printed surimi insect protein mixture under three thermally induced gelation processes,i.e.two-stage water bath heating method(WB-WB),a single microwave heating method(MW)and a combined heating method(WB-MW),the results showed that microwave as an alternative technology to the second stage of water bath heating in the gel deterioration stage enhanced the ability of proteins to bind to less mobile water,improved gel juiciness and increased gel water holding capacity.In terms of gel strength,hardness and chewiness,the WB-MW and MW groups were significantly higher than the WB-WB group,with the gel strength of the WB-MW group reaching to 4484.33 g·mm.However,there was no significant difference in the colour difference values of the surimi products under three different heat-induced gelation processes(p>0.05).Stronger threedimensional network structure of the surimi gels formed by WB-MW,with a flat surface and more uniform pore size and arrangement.