In vitro digestion effect on CCK and GLP-1 release and antioxidant capacity of some plant-based milk substitutes

Abstract

Recently, plant-based milk substitutes, as an emerging industry, are receiving more attention. Despite that, these dairy alternatives have not been adequately studied for their functional properties. Thus, the current research was devoted to study the satiety potential through in vitro secretion of cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1), and the antioxidant capacity of these dairy alternatives after in vitro digestion. The enteroendocrine cell line, STC-1, was used to measure satiety hormones release (CCK and GLP-1) by enzyme-linked immunoassay (ELISA). Also, total phenolic and flavonoid contents and antioxidant capacity (using oxygen radical absorbance capacity [ORAC], ferric reducing antioxidant power [FRAP], and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid [ABTS] assays) were measured before and after in vitro digestion. The results demonstrated that CCK secretion was significantly (p < 0.05) higher for cow's milk (350.64 pg ml^-1 ) as compared to plant-based milk substitutes. Among the plant-based milk substitutes, tiger nut milk showed the highest CCK stimulant (228.96 pg ml^-1 ), followed by hazelnut milk (220.04 pg ml^-1 ). Concerning GLP-1 release, the data exhibited that spelt milk was the food with the highest induction of GLP-1 hormone secretion, followed by cow's milk (910.17 and 876.59 pg ml^-1 , respectively), but without any significant differences between them. total phenolic content (TPC) values strongly increased after in vitro digestion, cow's milk and soymilk being the samples with the highest TPC values after in vitro digestion (165.76 and 153.71 mg GAE/100 ml, respectively). In line with TPC values, soymilk had the highest ORAC, ABTS, and FRAP values after in vitro digestion (25.41, 8.17, and 2.51 µmol TE/ml, respectively). Thus, these dairy alternatives could be an adequate substitute for cow's milk, according to its satiety and antioxidant capacity. PRACTICAL APPLICATION: The first study deals with the efficacy of plant-based milk substitutes as satiating foods. Spelt milk was the highest stimulant for GLP-1 secretion. Tiger nut milk showed the highest CCK stimulant, followed by hazelnut milk. TPC and total antioxidant capacity increased after digestion.

Keywords: CCK; GLP-1; STC-1; antioxidant capacity; cow's milk; in vitro digestion; plant-based milk substitutes.