干燥方式和粉碎程度对苹果皮全粉理化特性及酚类生物利用度的影响

为了充分回收加工副产物苹果皮中丰富的酚类物质,缓解因处理不当导致的环境污染,本研究采用真空冷冻干燥(FD)和65℃热泵干燥(HP)预处理苹果皮,然后将干燥的苹果皮粗粉碎,再经振动磨超微粉碎5 和25 min制备苹果皮全粉,探究不同制粉方式对苹果皮全粉色泽、微观结构、粉体行为特性以及模拟胃肠消化过程中酚类物质生物利用度的影响。结果表明,随着粉碎时间的延长,粉体粒径变小,色泽变亮变红(L^*和a^*值显著升高),颗粒外观趋于规则、光滑。与粗粉碎相比,超微粉碎使粉体容积密度显著增大,压缩性显著降低,同时也使得粉体性质变得不稳定,影响了粉体流动性。干燥方式和粉碎程度均会影响酚类物质的溶出,HP和超微粉碎显著降低了苹果皮全粉中绿原酸和表儿茶素的含量,而FD显著降低了金丝桃苷、芦丁和根皮苷的含量。在胃消化过程中,芦丁含量升高了1.05~1.47倍,并有新的酚类物质——儿茶素产生,而其他酚类物质约降解了10.53%~34.08%;小肠消化过程中酚类物质的降解程度是胃消化的2~8倍。经透析后测得儿茶素、芦丁、金丝桃苷和根皮苷的生物利用度分别约为237.07%、18.35%、29.52%和41.04%。本研究结果为副产物苹果皮的回收利用提供了一条新途径,为苹果皮制粉加工和新产品开发提供了理论依据。

Influence of Drying Methods and Grinding Degree on Physicochemical Properties and Phenolics Bioavailability of Apple Peel Powder

In order to fully recover the abundant phenolics in apple peel as a by-product of processing and alleviate environmental pollution caused by improper handling, apple peel powder was prepared by vacuum freeze drying (FD) and heat pump drying at 65℃ (HP), followed by coarse grinding and ultrafine grinding for 5 minutes and 25 minutes. The effects of different processing methods on color, microstructure, powder characteristics and phenolics bioavailability in in vitro gastrointestinal digestion of apple peel powder were investigated. The results showed that with the increase of the grinding time, the particle size of the powder was smaller, the color was brighter and redder (the values of L^* and a^* significantly increased), and the appearance of powder particle became more regular and smooth. Compared with coarse grinding, ultrafine grinding significantly increased the bulk density and reduced the compressibility of the powder, while the powder properties became unstable, which affected the fluidity of the powder. Moreover, both the drying method and grinding degree affected the dissolution of phenolics. HP and ultrafine grinding significantly reduced the contents of chlorogenic acid and epicatechin in the apple peel powder, while FD significantly reduced the contents of hypericin, rutin and phloridzin in it. During gastric digestion, the content of rutin increased by 1.05-1.47 times, and the catechin was newly detected, while the remaining phenolics were degraded by about 10.53%-34.08%. During the intestine digestion, the degradation degree of phenolics was 2 to 8 times that of gastric digestion. Finally, the bioavailabilities of catechin, rutin, hypericin and phlorizin which measured after dialysis were 237.07%, 18.35%, 29.52%, and 41.04%, respectively. The study could provide a new way for the recycling of apple peel by-product, and to provide a theoretical basis for grinding process and new product development of apple peel.