Color and bioaccessibility of antioxidants and calcium of freeze-dried apples impregnated with sea buckthorn juice and calcium lactate: An in vitro digestion study

Color (L-, a-, and b-values); total phenolic content (TPC, mg gallic acid equivalent/100 g product); antioxidant activities (mg Trolox equivalent/100 g product) by ABTS, DPPH, oxygen radical absorbance capacity (ORAC), and photochemiluminescence assay including antioxidant capacity of lipid-soluble substances (PCL-ACL), water-soluble substances (PCL-ACW), and integral antioxidant capacity (PCL-IAC); phenolic and carotenoid composition by high-performance liquid chromatography (HPLC) (mg/100 g product); and calcium content (mg/100 g product) of freeze-dried Gala apple products - fresh apple (FA), fresh apple dipped in 1% ascorbic acid (FA+AA), and those prepared by atmospheric (AI), vacuum (VI), and ultrasound-assisted impregnation (USI) using sea buckthorn juice and calcium lactate, during in vitro digestion. The bioaccessibility values are expressed as percentages (%). Digestion stages 0–5 correspond to undigested, oral, gastric, duodenum, jejunum–ileum, and large intestine stages, respectively.