Cryoprotectant is a substance used to protect biological tissue from freezing injury. However, there was few research paper on application of cryoprotectant in food stuff although its benefits was approved from the biological cell tissues. The objective of this study was to investigate the effect of the sugar addition as a cryoprotectant on the properties of frozen soybean sprouts. Before freezing process, the samples were blanched at 100°C for 1 min to observe the influence of blanching treatment. The blanched or non-blanched soybean sprouts was immersed in sugar solution as cryoprotectant, and continuously, the samples were frozen at -18°C for 24 h. Their physicochemical properties such as drip loss, hardness, color and cellular tissue were analyzed after thawing in running water. In our study, the drip loss of blanched sample without sugar was 43%, and comparatively, blanched one with sugar was 20% which was the lowest value among all samples. There was no significant difference of hardness between sample with sugar and without sugar. From our results, it was supposed that sugar can protect the soybean sprouts during freezing process regardless blanching process.

Soybean peptide (SP) exhibited low intestinal absorption at oral administration due to its fragile structure under gastric digestion. Therefore, we have attempted to encapsulate peptide by cross-linkage interaction between positive charged chitosan (CS) or chitosan oligosaccharide (CSO) and negative charged peptide. The CS (or CSO) with SP nanoparticles were prepared by using ultrasonification technique. The objective of this study was to find the optimal processing method by changing concentration, pH, and homogenizing conditions. We measured physicochemical properties such as particle size, zeta-potential, encapsulation efficiency (EE%), release rate (RR) and antioxidant ability of samples. The results showed that the optimal processing method was using 0.5% (w/v) CSO (diluted by pH 3 Acetic acid buffer) mixed with 0.5% (w/v) SP (diluted by pH 6 buffer) by 9:1 ratio. Afterwards, using high-speed mixer at 12,000 rpm for 3 min, and then passed 2 times through an ultrasonicator (50% power, 3 min). In this way for processing, the particle sizes of CSO/SP nanoparticles were approximately 300 nm, zeta-potential were approximately 45 mV. In addition, the EE% and RR of CS/SP nanoparticles was higher than the CSO/SP nanoparticles. The increase in antioxidant ability of SP was attributed to the affected by CS/CSO microcapsules. In conclusion, this research can befoundation for the manufacturing process of CS/SP nanoparticles, and it was expected that the future application of this nanoparticle in food matrix.