Modification of proteins with polyethylene glycol (PEGylation) contributes to improve the stability of the proteins. However, homogeneous liquid-phase reactions generally give a mixture of multiple PEGylated isomers with different stability and functions. Ion exchange chromatography (IEC) can potentially be applied to separate these isomers on the basis of the mechanistic model of IEC elaborated with respect to non-modified proteins. To clarify this point, PEGylated proteins on the IEC column with the linear salt gradient elution were analyzed on the basis of the model with mono-PEGylated bovine serum albumin (BSA) and random-PEGylated lysozyme as model samples. The model predicted that the number of binding sites of PEGylated proteins on the resin of IEC was the same as that of the non-modified ones. Furthermore, solid-phase PEGylation reaction and separation with IEC were simultaneously controlled by selecting the salt concentration in the mobile phase on the basis of the model. The number of isomers of PEGylated lysozyme could be reduced by the solid-phase PEGylation and the isoform of interest could be purified on the same IEC column. A recycle-type solid-phase continuous reaction and separation operation was designed, and successfully perfomed at high yields.

A highly heat-resistant spore-forming mesophilic bacterium was isolated from dried sardine meal (DSM, Iriko) and identified it as Bacillus amyloliquefaciens. The thermal death characteristics of the bacterial spores were evaluated in a laboratory test. To kill such spores contaminated in DSM, we examined the efficiency of a recently developed ultrahigh-temperature and extremely short-time (UHT-est) processor, which was designed for sterilization of powdered food materials. In the processor, such powders were injected into wet heat steam and processed at temperatures of 140, 150 and 160℃ for 0.16 s and then were instantly cooled down to about 60 to 70℃ at an abrupt pressure drop upon passing through a special nozzle. It was found that the survivors obtained after practical operation of the UHT-est processor at those high temperatures were much less than those estimated from D and z values obtained in the laboratory test. After the treatment under even more severe heating conditions, the DSM color was found to change only slightly. It is suggested that the UHT-est processor effectively kills spores present in DSM, seemingly keeping acceptable quality.

Rice crackers have been used to test masticatory ability, for mastication training, and investigate the dynamics of mastication in humans. However, no study has examined the relationship between the change in rice cracker structure during mastication and their physical properties in the food bolus, so the aim of this study is to investigate this relationship. In this study, artificial food boluses of 10 different rice crackers, each with a different texture and perceived ease of swallowing, were prepared using a bead mill. At each mastication stage (5-20 s), the permeation of saliva into the artificial food bolus and the status of particle shape were visualized by X-ray computed tomography, and physical properties were measured with a texture analyzer. By freeze-drying, it was possible to visualize inner structure of the artificial food bolus that stopped the enzymatic reaction and saliva absorption during each mastication stage. There were three types of artificial food bolus and positive correlation between swallowability and cohesiveness. Our results showed that rice crackers are easy to swallow if they are softened by quick permeation of saliva in the late stage of mastication, or remain until the late stage of mastication as pieces covered with digested starch.

To develop new foods from plant-based protein, we prepared a soybean-based meat analogue. Soybean flour, sodium alginate, soybean-based fiber, and plant oil were used to produce a gel by cross-linking with calcium ion after freezing. The resulting gel was frozen again and thawed, followed by infiltration of soy protein solution to form a layered-porous structure. Effects of freezing on the formation of the structure and that of the presence of fibers on the texture were evaluated, showing the properties similar to animal meat one. Sensory evaluation also showed that the texture was significantly preferable to that of conventional soy-based meat analogue and was closer to animal meat. These results suggest that the proposed method would be promising for realizing soy-based meat substitutes with a texture closer to animal meat.