桑葚渣多酚提取物冻干粉的制备及稳定性分析

Preparation and Stability of Freeze-Dried Polyphenol Extracted from Mulberry Juice Processing Residues

桑葚渣是一种潜在的多酚类食品功能成分,但其氧化和热降解稳定性低,限制了其实际应用。本研究以副产物桑葚渣为原料,制备一种醇溶液提取物,添加冻干保护剂得到7种不同的桑葚渣多酚提取物冻干粉(P1~P7)。结果表明,添加不同冻干保护剂后的桑葚渣多酚提取物冻干粉的总酚含量(单独添加麦芽糊精组除外)及抗氧化活性均有所提高,但单体花色苷含量(表观)均显著降低(P<0.05),保护剂的包裹影响了花色苷的提取率,P5的保护效果较好,其次为P4、P7(麦芽糊精包埋组)。25℃贮藏1个月后未添加保护剂组的总酚含量、总花色苷含量、抗氧化活性较初始分别下降了19.27%、18.16%、11.41%,麦芽糊精和乳清蛋白粉提高了其贮藏稳定性,且活性成分含量更高,抗氧化活性更强。未添加保护剂组的矢车菊素-3-葡萄糖苷及矢车菊素-3-芸香糖苷含量分别为(11.63±0.13)、(4.14±0.05)mg/g,较初始分别下降了26.72%、16.53%,P4、P7两种主要的花色苷单体的含量没有明显下降,稳定性较好。随着体外消化的进行,各组花色苷含量呈下降趋势,且微胶囊包埋组(P3、P6、P2)中花色苷保留率较高,提高了桑葚渣多酚提取物的消化稳定性。

Mulberry juice processing residues are a potential source of polyphenols to be used as functional ingredients in foods,but their low stability to oxidation and thermal degradation limits their practical application.In this study,a 70%ethanol extract was prepared from mulberry pomace,a by-product of mulberry juice processing,and freeze-dried with and without cryoprotectants(maltodextrin and/or whey protein,and fermented litchi residues)to obtain seven different powders(P1-P7).Results showed that the total polyphenol content and antioxidant activity of the freeze-dried polyphenol extracts with each cryoprotectant except maltodextrin increased compared with the control group without cryoprotectant,while the(apparent)content of monomeric anthocyanins significantly decreased(P<0.05).The cryoprotectants affected the extraction efficiency of anthocyanins by encapsulating them,and fermented litchi residues(P5)showed the strongest effect,followed by the mixtures of the freeze-dried extract and maltodextrin at ratios 1:2(P4)and 1:4(P7).The contents of total phenols and total anthocyanins,and antioxidant activity in the control group decreased by 19.27%,18.16%and 11.41%,respectively,after being stored at 25℃for one month.Maltodextrin and whey protein improved the storage stability of the extract,increasing the content of bioactive components and enhancing the antioxidant activity.In the control group,the contents of cyanidin-3-glucoside and cyanidin-3-rutinoside were(11.63±0.13)and(4.14±0.05)mg/g,respectively,which decreased by 26.72%and 16.53%compared with those before storage,respectively.However,the contents of the two main monomeric anthocyanins in the mixtures of the freeze-dried extract and maltodextrin at ratios 1:2(P4)and 1:4(P7)did not decrease significantly,indicating their good stability.During in vitro digestion,anthocyanin contents in each group decreased,and the retention rate of anthocyanins in the 1:1:1 freeze-dried extract+maltodextrin+whey protein(P2),1:2 freeze-dried extract+maltodextrin(P3),and 1:4 freeze-dried extract+maltodextrin(P6)groups increased in contrast to the other groups,indicating improved digestive stability of the polyphenol extract from mulberry pomace.