Bioaccessibility, gut microbial metabolism and intestinal transport of phenolics from 100% Concord grape juice and whole grapes are similar in a simulated digestion and fecal fermentation model

Phenolic rich 100% grape juice has been associated with many health benefits, but its place in dietary guidance is controversial relative to whole fruit. Direct comparisons of phenolic profiles and bioavailability between these food forms are needed. Phenolic bioaccessibility and metabolism from Concord (CG) and Niagara (NG) grapes and corresponding 100% juices were investigated using an in vitro digestion coupled with anaerobic gut fermentation model. Intestinal transport of resulting bioaccessible phenolics and microbial metabolites was estimated using a Caco-2 cell model. Total bioaccessible phenolics from both upper and lower digestion were similar (P > 0.05) between NG (400.9 ± 26.3 μmol per 100 g) and NGJ (349.5 ± 8.3 μmol per 100 g) and significantly different (P < 0.05) between CG (417.2 ± 24.4 μmol per 100 g) and CGJ (294.3 ± 45.4 μmol per 100 g) total cellular transport of phenolics was similar (P > 0.05) between whole grapes (89.4 ± 5.3 μmol per 100 g for CG, and 71.8 ± 2.4 μmol per 100 g for NG) and 100% juices (88.0 ± 5.6 μmol per 100 g for CGJ, and 85.3 ± 9.4 μmol per 100 g for NGJ). Differences were observed between the location of phenolic metabolism, bioaccessibility and subsequent cellular transport of individual phenolics between grapes and juice matrices. Specifically, greater amounts of phenolics were transported from grape juices than whole grapes from the upper tract. However, cumulative bioaccessibility and transport from upper and lower GI digestion/fermentation together indicates that the absorbable phenolics from 100% grape juice is similar to that of whole grapes, suggesting that phenolic-mediated health benefits from consumption of whole fruit and juice may be similar.

Bioaccessibility and intestinal cell uptake of carotenoids and chlorophylls differ in powdered spinach by the ingredient form as measured using in vitro gastrointestinal digestion and anaerobic fecal fermentation models

Insights into food matrix factors impacting bioavailability of bioactive carotenoids and chlorophylls from fruits and vegetable ingredients are essential to understanding their ability to promote health. The stability and bioaccessibility of carotenoids and chlorophylls were assessed from dehydrated, spray-dried, freeze-dried and fresh spinach ingredient forms using in vitro models simulating upper gastrointestinal (GI) digestion and lower GI anaerobic fecal fermentation. Intestinal transport of bioaccessible bioactives from both upper and lower GI compartments was assessed using the Caco-2 human intestinal cell model. Differences in carotenoid and chlorophyll contents were observed between ingredient forms and these influenced bioaccessibility. Lower carotenoid and chlorophyll contents in spray dried spinach resulted in the lowest total bioaccessible content among all spinach treatments (5.8 ± 0.2 μmoles per g DW carotenoid and chlorophyll). The total bioaccessible content was statistically similar between freeze-dried (12.5 ± 0.6 μmoles per g DW), dehydrated (12.5 ± 3.2 μmoles per g DW), and fresh spinach (14.2 ± 1.2 μmoles per g DW). Post anaerobic fermentation, cellular accumulation of carotenoids was higher (17.57-19.52 vs. 5.11-8.56%), while that of chlorophylls was lower (3.05-5.27 vs. 5.25-6.44%), compared to those observed following upper GI digestion. Collectively, these data suggest that spinach forms created by various drying technologies deliver similar levels of bioaccessible spinach bioactives and that the lower GI tract may serve as a site for significant absorption fostered by interactions with gut microbial communities that liberate additional bioactives from the spinach matrix.

Comparative Assessment of Phenolic Bioaccessibility from 100% Grape Juice and Whole Grapes

Objectives

Grapes and their 100% juices are rich sources of health promoting phenolics. Juicing of grapes includes contact with phenolic rich seeds and skins that otherwise relies on mastication for phenolic release from fruit. To understand if 100% grape juice can provide a matrix with highly bioaccessible phenolics relative to whole fruit, differences in phenolic content and bioaccessibility from commonly consumed table, Concord (CG) and Niagara (NG) grapes and their 100% juices were compared.

Methods

Phenolic content in CG, NG, table grapes, 100% Concord grape juice (CGJ), and 100% Niagara grape juice (NGJ) were assayed by LC-MS prior to subjecting grapes and juices to in vitro digestion to determine phenolic bioaccessibility. Results are expressed as relative and absolute bioaccessible content of individual phenolic species and total phenolics as a sum of anthocyanins (AC), flavan-3-ols (FL3), flavonols (FV), stilbenoids, procyanidins, and phenolic acids (PA).

Results

Phenolic compounds were concentrated in CG and NG seeds as FL3 (304.1–390.7 mg/100 g dw). CG skins were rich in AC (1050.5 mg/100 g dw) and FV (80.8 mg/100 g dw). Grape product form had a significant impact on content (P &lt; 0.01), relative bioaccessibility, and absolute bioaccessibility (P &lt; 0.01). CG had a higher total phenolic content (21.9–50.7 mg/100 g fw) compared to CGJ (5.8 mg/100 g fw), though NG (4.9–10.8 mg/100 g fw) was similar in phenolic content as NGJ (9.4–10.8 mg/100 g fw). Absolute bioaccessibility of CGJ total phenolics (5.2 mg/100 g fw) was similar to CG (2.6–9.6 mg/100 g fw), while NGJ (5.1–5.7 mg/100 g fw) had higher bioaccessible phenolic content than NG (0.8–1.1 mg/100 g fw). Differences in initial content and bioaccessible fractions were driven by higher relative bioaccessibility of AC in CGJ (86–135%) compared to CG (14–39%) and FL3/PA in CGJ/NGJ (48–101; 39–85%) compared to CG/NG (0–3; 9–67%). Comparisons between juices and table grapes followed similar trends.

Conclusions

A greater fraction of grape skin and seed derived PA, AC, and FL3 are extracted through juicing and made bioaccessible relative to whole fruit. 100% juice may provide an improved matrix for delivery of grape phenolics and despite some processing losses, whole fruit and juice are similar in overall phenolic delivery to consumers.

Funding Sources

Welch Foods Inc.

Comparative assessment of phenolic bioaccessibility from 100% grape juice and whole grapes

Concord and Niagara grape juice have comparable or greater absolute bioaccessibility of major classes of phenolic compounds compared to masticated whole grapes.