The effect of two dehydration technologies, spray-drying and freeze-drying, on the viability of 12 lactic acid bacteria (LAB) were compared. All LAB cultures had been previously isolated from porcine blood and were candidates to be used as biopreservatives in order to maintain the quality of porcine blood until further processing to obtain added-value blood derivatives is carried out. The residual viability and the reductions in microbial counts in dried LAB samples at 20 °C and 5 °C during 60-day storage were determined. Cellular damage due to freeze-drying was observed immediately after drying whereas cellular damage due to spray-drying did not become evident until the subsequent phase of storage. For most of the strains, the faster decrease in viability of spray-dried as compared to freeze-dried cultures was compensated by the higher percentage of viable cells obtained after dehydration, leading to comparable survival rates at the end of the storage period. Dehydration resulted in a good alternative to freezing at 80 °C for preservation purposes. Spray-drying has been shown to be as suitable as freeze-drying for preserving LAB strains during a 2-month storage period. Results suggest the possibility of achieving a good formulation system for the LAB strains with a high number of viable cells to be used for the industrial development of bioprotective cultures.

No abstract

The proteolytic activity of plasmin on soluble caprine beta-casein (CN) was studied in 50 mM Tris.HCI buffer, pH 8.0, at 37 degrees C. Electrophoretic studies showed that hydrolysis of this protein results in an electrophoretic pattern that is similar to the pattern obtained from plasmin hydrolysis of bovine beta-CN (gamma-CN and complementary N-terminal fragments), suggesting that plasmin probably attacks the same regions that are susceptible to cleavage in bovine beta-CN. As determined by SDS-PAGE, the gamma-like components of caprine milk consisted of two fragments with relative molecular mass of 9200 and two with relative molecular mass of 21,400 that could differ in the level of phosphorylation. Apparently, the high molecular mass components are homologous to bovine beta-CN (f 29-209) (gamma 1-CN), and the low molecular mass components are homologous to bovine beta-CN (f 106-209) and beta-CN (f 108-209) (gamma 2- and gamma 3-CN). Complementary N-terminal fragments had values for molecular masses in the range 13,600 to 8500 and urea-PAGE patterns that were more complex than those obtained in bovine casein because of the different phosphorylation levels in caprine beta-CN. These fragments were also present in the hydrolysate of whole caprine casein that had been treated with plasmin.

The properties of gels obtained from porcine blood plasma were studied under different pH conditions. Gels from liquid and spray-dried plasma were prepared and analyzed for water holding capacity (WHC), texture, and microstructure at pH 7.4, 6, 5.5 and 4.5. The denaturation extent of proteins was also determined by differential scanning calorimetry (DSC). All properties studied were dependent on pH. The WHC and consistency of gels decreased when pH decreased. These results correlated with microstructural changes observed by SEM. Spray drying affected the consistency of gels. The penetration force of the gel from dehydrated plasma was always lower than that prepared from liquid plasma where the pH was the same, but neither the WHC nor the microstructure of gels were affected.

No abstract