Effect of natural cross-linkers and drying methods on physicochemical and thermal properties of dried porcine plasma protein

Porcine plasma protein (PPP) is a good source of protein from a slaughterhouse by-product; however, modification of PPP is still needed to improve its properties. The effect of various natural cross-linkers (rutin; RT, caffeic acid; CA and genipin; GP) and different drying methods (freeze drying: FD and spray drying: SD) on the properties of PPP were investigated. Cross-linking with RT, CA and GP could markedly affect the color of the modified PPP. The freeze-dried modified PPP with RT exhibited the lowest free amino group contents while using CA and GP exhibited the lowest sulfhydryl group contents. The spray-dried modified PPP with RT had lower free amino group contents than CA and GP. Modification of PPP changed the molecular weight and FT-IR spectra of both freeze-dried and spray-dried samples. The scanning electron microscope images showed that all spray-dried modified PPP samples exhibited shrinkage with a spherical shape whereas freeze-dried modified PPP exhibited a rough, grainy surface. The freeze-dried modified PPP with GP improved the thermal properties of PPP. Thus, RT, CA and GP can be considered as alternative natural cross-linkers. Moreover, the drying method reflected the properties of dried PPP for final food application.