Impact of Pleurotus ostreatus beta-glucans on oxidative stability of active compounds encapsulated in powders during storage and In vitro digestion

Polyunsaturated fatty acids and -tocopherol were encapsulated in powders by spray drying using maltodextrins DE 12 as wall material and different emulsifiers (Tween®20, acacia gum or beta-glucans-rich extracts from Pleurotus ostreatus). The aim was to study the effects of the surfactants on: (a) the oil droplet size distribution and alpha-tocopherol stability during in vitro digestion, and (b) the oxidative stability during 15 days of accelerated storage. Acacia gum sample had the most stable particle size distribution up to the gastric phase, but showed a significant alpha-tocopherol degradation prior to the intestinal stage. On the contrary, beta-glucan-samples displayed a bimodal distribution in the oral and gastric phases but retained alpha-tocopherol up to the beginning of the intestinal stage. At the end of intestinal stage, no alpha-tocopherol was found in the samples. The storage study showed that beta-glucans improved the oxidative stability of the powders, which displayed 82% alpha-tocopherol retention after 5 days under accelerated conditions (60 °C), corresponding to 310 days at 20 °C, while acacia gum and Tween® 20 did not delay alpha-tocopherol degradation. Results highlight the potential antioxidant activity of beta-glucans used as emulsifying agents during in vitro digestion and accelerated aging conditions.