Production of whey protein aggregates with controlled end-use properties

摘要 – 通过控制终产品的特性生产乳清蛋白凝聚物。本文研究了逆流喷雾干燥对乳清蛋白结构和发泡性的影响。在其他工艺参数不变的条件下, 分别采用两种不同的内外气流温度 (170/85 ◦C 或 260/138 ◦C)。由于采用不同的处理工艺, 分别经过中温和高温热处理后的两种乳清蛋白 (WP-P85 和 WP-P138) 性质不同于未处理的乳清蛋白 (WP-L)。正如我们期望的, 与 WP-P85 蛋白粉相比, WP-P138 蛋白粉的水分含量低、不含乳糖,颗粒内部的孔隙度较大、颗粒孔壁薄。比较了未处理乳清蛋白稀释液和两种喷雾干燥的乳清粉 (WP-P85和WP-P138)分散液的构象稳定性。与未处理的乳清蛋白和 WP-P85 乳清蛋白不同, WP-P138 粉中乳清蛋的色氨酸发射波长向红的一段移动, 在 420 nm 出现了一个新的荧光化合物。此外, 与未处理的乳清蛋白相比, 喷雾干燥的乳清呈现较高比例的以共价键结合形成的凝聚物 (WP-P138为11%, WP-P85为 5%), 但是再次加热后其构象稳定性下降 (WP-P138约下降 50%,[br/]WP-P85约下降 30%)。最后, 将气体经过一个多孔的喷洒器鼓入含有蛋白质溶液的柱子里,通过一个在线摄像机自动截获泡沫形成的图像, 实验证明在最高气流温度下喷雾干燥获得的WP-P138 溶液比 WP-P85 和 WP-L 溶液具有较大的发泡性。

We studied the structural behaviour and foaming properties of whey proteins under the effects of spray-drying in a co-current configuration. We used two different inlet/outlet air temperatures (170/85 degrees C or 260/138 degrees C, respectively), the other operating conditions being unchanged. Using different characterisation techniques, we showed that both whey proteins (WP-P-85 and WP-P-138) which were submitted to hydro-thermal treatments under mild and high air processing conditions behaved differently from untreated proteins (WP-L). As expected, WP-P-138 powder exhibited lower moisture and free lactose contents, a higher particle internal porosity, and a thinner particle wall thickness than the WP-P-85 powder. The conformational stability of whey proteins, obtained by dilution of untreated whey proteins (WP-L) and dispersions of the two spray-dried powders (WP-P-85 and WP-P-138), were compared. Whey proteins in the WP-P-138 powder showed a red- shift in the tryptophan emission wavelength, the appearance of a newly created fluorescent compound at 420 nm, contrary to untreated and WP-P85 whey proteins. In addition, we observed formation of a higher proportion of covalently-bound aggregates (11% in WP-P-138, instead of 5% in WP-P-85) and a decrease in conformational stability against re-heating (similar to 50% s in WP-P-138, instead of similar to 30% in WP-P-85) compared with untreated WP-L solution. Finally, combination of continuous measurements of foam volume (by an on-line video camera) and liquid (by conductivity) entrained in a column foam during its formation by air injection, in parallel with automatic acquisition of video-foam images during the destabilisation step, showed that solution of WP-P-138 spray-dried powder, obtained using the highest air temperature conditions, has higher foaming properties than WP-P-85 and WP-L solutions.