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

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

Food & function (2020-07-03)
Zulfiqar Mohamedshah, Sydney Chadwick-Corbin, JoLynne D Wightman, Mario G Ferruzzi
ABSTRACT

Juicing of grapes includes contact with phenolic rich seeds and skins that otherwise rely on maceration for phenolic release. 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. Phenolic contents in whole grapes and 100% juices were assayed by LC-MS prior to in vitro digestion to determine phenolic bioaccessibility. Phenolic compounds were concentrated in CG and NG seeds as flavan-3-ols (222.2-285.5 mg per 100 g fw). CG skins were rich in anthocyanins (201.4 mg per 100 g fw) and flavonols (15.5 mg per 100 g fw). Product form had a significant impact on content (p < 0.01), relative bioaccessibility, and absolute bioaccessibility (p < 0.01). CG had a higher total phenolic content (21.9-50.7 mg per 100 g fw) compared to CGJ (5.8 mg per 100 g fw), though NG (4.9-10.8 mg per 100 g fw) was similar in phenolic content to NGJ (9.4-10.8 mg per 100 g fw). Absolute bioaccessibility of total phenolics from CGJ (5.2 mg per 100 g fw) was similar to CG (2.6-9.6 mg per 100 g fw), while NGJ (5.1-5.7 mg per 100 g fw) had higher bioaccessible phenolic content than NG (0.8-1.1 mg per 100 g fw). Differences in bioaccessible content were driven by high relative bioaccessibility of anthocyanins in CGJ (86-135%) compared to CG (14-39%) as well as for flavan-3-ols and phenolic acids from CGJ/NGJ (48-101; 39-85%) compared to CG/NG (0-3; 9-67%). Comparisons between juices and table grapes followed similar trends. A greater fraction of skin and seed phenolics was extracted through juicing and made bioaccessible, making 100% grape juice and whole fruit similar in phenolic delivery to consumers.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Bile extract porcine
Sigma-Aldrich
Phentolamine hydrochloride, ≥98% (TLC), powder
Sigma-Aldrich
Mucin from porcine stomach, Type II
Sigma-Aldrich
Pepsin from porcine gastric mucosa, powder, ≥400 units/mg protein
Sigma-Aldrich
Lipase from porcine pancreas, Type II, ≥125 units/mg protein (using olive oil (30 min incubation)), 30-90 units/mg protein (using triacetin)
Sigma-Aldrich
α-Amylase from porcine pancreas, Type VI-B, ≥5 units/mg solid