Inclusion of 100% Concord grape juice reduces glucose release following in vitro digestion of a model carbohydrate rich meal

Abstract

Growing evidence suggest that phenolics from fruits and juices including 100% grape juice (GJ) may impact glucose homeostasis by independently inhibiting carbohydrate digestion and modulating intestinal glucose transport. However, the extent to which these effects are extendable to 100% GJ in the context of interaction within a meal remains unclear. To determine the influence of 100% GJ from purple American grapes (V. labrusca; Concord) on starch digestion and intestinal glucose release from a meal, GJ was combined (5 and 10% w/w) with a milk and cornstarch‐based pudding (MSP) providing protein and complex carbohydrates simulating a meal. This combination was introduced to an in vitro digestion model mimicking oral, gastric and small intestinal digestion. Phenolic bioaccessibility and extent of glucose release from starch were assessed following digestion. Concord GJ is rich in phenolic acids and flavonoids (806 to 845 μM total phenolics) including catechin, quercetin and isorhameritin, as well as anthocyanins (80 to 103 μM total anthocyanins) with cyanidin and delphinidin most abundant. Co‐digestion of GJ with MSP did not significantly impact bioaccessibility of total phenolics suggesting the food matrix did not impact digestive stability and ultimate bioaccessibility in the GI tract. Total glucose content in final digesta was decreased by 12% following co‐digestion of MSP with 10% Concord GJ (~55 μM phenolics) compared to sugar match control. No significant effect was observed from 5% Concord GJ. GJ phenolic extracts also demonstrated modest inhibition of a‐amylase at 500 μM phenolics (3.4–8.8%) and of glucoamylase activity at 300 and 500 μM phenolics (4.9 and 9.3%, respectively). Combined these data suggest that consumption of 100% GJ, compared to a sugar sweetened beverage, with a carbohydrate‐rich meal may delay digestive release of glucose in the upper GI through inhibition of glucoamylase leading to a modest reduction in glycemic response from a meal.Support or Funding InformationFunding support by Welch Foods