Development of composite nanoemulsion gels as carriers for co-delivery of wheat germ oil and probiotics and their incorporation in yoghurt

Emulsion gels have received significant interest in the food industry as functional colloids due to their improved stability and encapsulated bioactive substances. Thus, in this study, four different emulsions (EM I–IV) were formed by emulsifying wheat germ oil (WGO) using two methods: without sonication for EM I and III (fortified with orange essential oil, OEo), and with sonication for EM II and IV (fortified with OEo). To produce four distinct forms of composite emulsion gels, the prepared emulsions were fortified with probiotics and then added to biopolymers (Gel I-IV). In the emulsions and gels, the WGO oxidative stability and the Lb. rhamonusus survival rate were assessed. The promising formulations were applied to yoghurt as a food model. The results showed that EM III (232.2 nm) and IV (153.9 nm) demonstrated a higher average size than their plain EM I (185.7 nm) and II (131.6 nm). EM IV and Gel IV, with an induction period of 8.35 h and 10.06 h, were the most promising formulations for postponing WGO oxidative degradation. Gel IV had the highest DPPH scavenging activity with 80.88%, while EM I significantly decreased the activity by 54.21%. The Lb. rhamonusus survival rates in Em IV and Gel IV are 94.49% and 97.66%, respectively. Yoghurt incorporated with Gel IV enhanced the stability of pH and acidity throughout the storage period, decreased the syneresis value, and enhanced all parameters of texture profile analysis. Based on the results, emulsion gels could be used to deliver probiotics, nutraceuticals, and food additives.