We investigated the effect of medium high hydrostatic pressure (<100 MPa) on acrylamide generation and the Maillard reaction using an equimolar asparagine-glucose aqueous solution adjusted to pH 9.0. The amounts of acrylamide and melanoidins generated and pH were determined after treatment at 70℃ and 60 or 90 MPa pressure or atmospheric pressure for up to 72 hours. Comparison of acrylamide and melanoidins contents revealed that pressure inhibited acrylamide generation in this solution. When added to the same solution, cysteine markedly inhibited acrylamide generation independent of pressure under the condition of 70℃ at 90 MPa or atmospheric pressure for 24 hours. Based on these results, under the same condition as the cysteine addition experiment, we examined the inhibitory effect of pressure and cysteine on acrylamide generation using a non-centrifugal cane sugar (NCS) solution at pH 5.5, which contains a relatively large amount of acrylamide. Adding cysteine to the NCS solution reduced its original amount of acrylamide and inhibited acrylamide generation during heat treatment. Pressurization of a cysteine-free NCS solution promoted acrylamide generation, but that of an NCS solution with high cysteine concentration promoted acrylamide decrease. These results suggest that acrylamide generation and the Maillard reaction during food processing might be regulated by medium high hydrostatic pressure and cysteine addition.

The stabilization effect of a biopolymer complex layer consisting of sodium caseinate (SC) and chitosan (CHI) formed via electrostatic interaction was investigated using an oil-in-water (O/W) emulsion containing palm oil droplets as the dispersed phase. O/W emulsions containing palm oil droplets with a narrow droplet diameter distribution were successfully prepared using two microchannel emulsification devices using SC as an emulsifier at 60℃. Surface modification of the palm oil droplets was conducted using different CHI/SC ratios. The surface charge of the droplets was negative and positive at CHI/SC ratios of less than 0.025 and more than 2.5, respectively. At an intermediate CHI/SC ratio between 0.025 and 2.5, the droplets formed large aggregates and became polydisperse. The adsorption of CHI on the surface of palm oil droplets at a high CHI/SC ratio was confirmed by fluorescent microscopy and ζ-potential measurement. Improved stability of the O/W emulsions with the CHI-SC complex layer was demonstrated during heating (60℃) and cooling (20℃) treatment, and long-term (7 months) storage at room temperature (20-25℃). Interestingly, separation of the large oil phase on the top of the emulsion samples and the formation of large crystals of palm oil were suppressed in the emulsion samples with the CHI-SC complex layer.

In the present study, we investigated effects of macroscopic 3D structures of soft foods such as nursing foods printed using a 3D food printer on the texture. First, 3D printing was performed using two types of soft foods with different hardness, and the modeling properties were evaluated. The results showed that the two types of soft foods did not become homogeneous and retained their original physical properties in the printed object and the printing direction had effect on the mechanical properties of printed object. Furthermore, 3D printings of fiber structure and layer structure were performed, and the texture of printed objects were evaluated. The results showed that the mechanical properties of fiber structure and layer structure could be reproduced even in the 3D printed soft foods. Additionally, fibrous texture and layered texture were expressed by these structures at a level which was significantly distinguishable by humans. The present findings suggested that macroscopic 3D structures printed using a 3D food printer could regulate the texture of soft foods.