Lloyd M A, Hess S J, Drake M A
Department of Food, Bioprocessing and Nutritional Sciences, Southeast Dairy Food Research Center, North Carolina State University, Raleigh 27694, USA.
J Dairy Sci. 2009 Jun;92(6):2409-22. doi: 10.3168/jds.2008-1714.
The US industry standard for shelf-life of whole milk powder (WMP) is 6 to 9 mo, although previous research has demonstrated flavor changes by 3 mo at ambient storage. This study evaluated the influence of packaging atmosphere, storage temperature, and storage time on WMP shelf-life using sensory and instrumental techniques. Two commercial batches of WMP were repackaged in plastic laminate pouches with air or nitrogen and stored at 2 degrees C or 23 degrees C for 1 yr. Descriptive analysis was conducted using a 10-member trained panel; volatile analysis was performed using solid-phase microextraction with gas chromatography-mass spectrometry. Consumer acceptance (n = 75) was conducted every 3 mo with reconstituted WMP and white and milk chocolate made from each treatment. Data were analyzed using ANOVA with Fisher's LSD, Pearson correlation analysis, and principal component analysis. Air-stored WMP had higher peroxide values, lipid oxidation volatiles, and grassy and painty flavors than nitrogen-flushed WMP. Storage temperature did not affect levels of straight chain lipid oxidation volatiles; 23 degrees C storage resulted in higher cooked and milkfat flavors and lower levels of grassy flavor compared with 2 degrees C storage. Consumer acceptance was negatively correlated with lipid oxidation volatiles and painty flavor. Nitrogen flushing prevented the development of painty flavor in WMP stored up to 1 yr at either temperature, resulting in chocolate with high consumer acceptance. Nitrogen flushing can be applied to extend the shelf life of WMP for use in chocolate; storage temperature also plays a role, but to a lesser extent.
全脂奶粉（WMP）的美国行业保质期标准为6至9个月，尽管先前的研究表明，在常温储存下3个月时就会出现风味变化。本研究使用感官和仪器技术评估了包装气氛、储存温度和储存时间对WMP保质期的影响。将两批市售WMP重新包装在带有空气或氮气的塑料复合袋中，并在2℃或23℃下储存1年。使用由10名经过培训的小组成员进行描述性分析；使用固相微萃取结合气相色谱-质谱法进行挥发性分析。每3个月对由每种处理方法制成的复原WMP以及白巧克力和牛奶巧克力进行消费者接受度调查（n = 75）。使用方差分析、Fisher最小显著差数法、Pearson相关分析和主成分分析对数据进行分析。与充氮WMP相比，空气储存的WMP具有更高的过氧化物值、脂质氧化挥发物以及青草味和油漆味。储存温度不影响直链脂质氧化挥发物的水平；与2℃储存相比，23℃储存会产生更高的熟味和乳脂味，且青草味水平更低。消费者接受度与脂质氧化挥发物和油漆味呈负相关。在任一温度下，充氮都可防止储存长达1年的WMP产生油漆味，从而使巧克力具有较高的消费者接受度。充氮可用于延长用于巧克力生产的WMP的保质期；储存温度也有作用，但程度较小。
