Flavor and flavor chemistry differences among milks processed by high-temperature,short-time pasteurization or ultra-pasteurization

Typical high-temperature, short-time (HTST) pasteurization encompasses a lower heat treatment and shorter refrigerated shelf life compared with ultra-pasteurization (UP) achieved by direct steam injection (DSI-UP) or indirect heat (IND-UP). A greater understanding of the effect of different heat treatments on flavor and flavor chemistry of milk is required to characterize, understand, and identify the sources of flavors. The objective of this study was to determine the differences in the flavor and volatile compound profiles of milk subjected to HTST, DSI-UP, or IND-UP using sensory and instrumental techniques. Raw skim and raw standardized 2% fat milks (50 L each) were processed in triplicate and pasteurized at 78°C for 15 s (HTST) or 140°C for 2.3 s by DSI-UP or IND-UP. Milks were cooled and stored at 4°C, then analyzed at d 0, 3, 7, and 14. Sensory attributes were determined using a trained panel, and aroma active compounds were evaluated by solid-phase micro-extraction or stir bar sorptive extraction followed by gas chromatography-mass spectrometry, gas chromatography-olfactometry, and gas chromatography-triple quad mass spectrometry. The UP milks had distinct cooked and sulfur flavors compared with HTST milks. The HTST milks had less diversity in aroma active compounds compared with UP milks. Flavor intensity of all milks decreased by d 14 of storage. Aroma active compound profiles were affected by heat treatment and storage time in both skim and 2% milk. High-impact aroma active compounds were hydrogen sulfide, dimethyl trisulfide, and methional in DSI-UP and 2 and 3-methylbutanal, furfural, 2-heptanone, 2-acetyl-1-pyrroline, 2-aminoacetophenone, benzaldehyde, and dimethyl sulfide in IND-UP. These results provide a foundation knowledge of the effect of heat treatments on flavor development and differences in sensory quality of UP milks.     

超高温巴氏杀菌对全蛋液功能性质和理化性质的影响

该文首先比较超高温巴氏杀菌、传统巴氏杀菌对全蛋液中3种不同病原微生物的灭活效果,然后通过分析全蛋液起泡性、泡沫稳定性、乳化性、乳化稳定性、溶解度、巯基含量、表面疏水性质、十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE),比较超高温巴氏杀菌、传统巴氏杀菌全蛋液在冷藏(4℃)过程中功能性质和理化性质的变化趋势。结果表明,超高温巴氏杀菌相对于传统巴氏杀菌更为有效地灭活全蛋液中的大肠杆菌、沙门氏菌、金黄色葡萄球菌。超高温巴氏杀菌与传统巴氏杀菌全蛋液的起泡性、泡沫稳定性均显著高于未杀菌,但二者之间没有显著差异,冷藏1周后,三者起泡性均显著下降,而泡沫稳定性呈上升趋势,但是随着冷藏时间延长至6周,三者均未呈现显著变化。超高温巴氏杀菌全蛋液乳化性及乳化稳定性为先增加后降低,在整个储藏过程中,两者间均无显著性差异。不同杀菌方式对全蛋液中蛋白质溶解度、游离巯基影响不显著。超高温巴氏杀菌对全蛋液功能性质和理化特性影响与传统巴氏杀菌没有显著差异,为其在全蛋液工业生产的应用提供理论依据。