原生态与人工添加二十二碳六烯酸羊乳制品贮藏期脂肪酸稳定性比较

Fatty Acid Stability of Goat Milk Products Naturally and Artificially Enriched with Docosahexaenoic Acid during Storage

通过饲喂奶山羊富含二十二碳六烯酸(docosahexaenoic acid,DHA)的微藻粉,获得原生态DHA羊乳(DHA含量为30 mg/100 g原料乳),然后将其制作成超高温瞬时灭菌(ultra-high temperature instantaneous sterilization,UHT)乳及全脂乳粉,同时设立人工添加富含DHA微胶囊粉的UHT乳及全脂乳粉作为对照组,在常温(25℃)和高温(37℃)下进行为期28 d的贮藏实验,研究原生态与人工添加DHA羊乳制品贮藏期脂肪酸稳定性。结果表明,与人工添加组相比,贮藏期间原生态UHT乳及全脂乳粉的DHA含量下降速率明显减缓,在UHT乳中,人工添加组乳制品DHA含量降低率在37℃下最高达(40.92±3.52)%(贮藏第28天),此时原生态组DHA降低率为(36.70±4.84)%。贮藏期间,原生态与人工添加DHA的UHT乳及全脂乳粉中多不饱和脂肪酸相对含量总体均下降,且与人工添加DHA的乳制品相比,原生态组中多不饱和脂肪酸相对含量更高,更易氧化生成碳链更短的脂肪酸。此外,随着贮藏期的延长,原生态DHA乳制品组中的油脂氧化指标过氧化值和酸价上升速率明显低于人工添加DHA乳制品组。综上,本实验可为制备富含DHA的天然奶制品提供理论参考。

Goat milk naturally enriched with docosahexaenoic acid(DHA),containing 30 mg of DHA per 100 g of sample,was obtained by dietary supplementation of DHA-enriched microalgae powder and used to produce ultra-high temperature(UHT)sterilized milk and whole milk powder.UHT-sterilized milk and whole milk powder artificially added with microencapsulated DHA-enriched algae oil powder were also prepared and used as controls.All samples were stored for up to 28 days at 25 or 37℃to evaluate the stability of fatty acids in goat milk products naturally and artificially enriched with DHA during storage.The results showed that compared to the samples artificially enriched with DHA,the decrease of DHA in UHT-sterilized milk and milk powder naturally enriched with DHA during storage was significantly slowed.At 37℃,the maximum percentage decrease of the DHA content in UHT-sterilized milk artificially enriched with DHA was(40.92±3.52)%compared to(36.70±4.84)%for its natural counterpart.For all samples,the content of polyunsaturated fatty acids decreased over storage time.In addition,polyunsaturated fatty acids were more abundant and more prone to oxidation forming fatty acids with shorter carbon chains in the milk samples naturally enriched with DHA relative to their artificial counterparts.Moreover,the lipid oxidation indexes peroxide value(POV)and acid value(AV)increased with storage time more slowly in the natural enrichment groups compared to the artificial addition groups.The results of this study provide a theoretical reference for the preparation of dairy products naturally rich in DHA.