Double Emulsions: Emerging Delivery System for Plant Bioactives

Bioactives have shown excellent protective effect against chronic diseases such as cancer, cardiovascular diseases and metabolic disorders. However, many of the bioactives like anthocyanins, carotenoids, flavonoids, vitamins and essential fatty acids are sensitive to surrounding environment stresses like pH, ionic strength, light, temperature, oxygen and gastro-intestinal (GI) conditions during transit. Hence, the functionality diminishes upon exposure to such unfriendly environment and leads to reduction in bioavailability. Double emulsions are designed to provide protection to bioactives in the innermost compartment through encapsulation and prevent loss of functionality in food matrix as well as during the GI transit. This article reviews the work done on double emulsion for food applications, covering various aspects of double emulsion like its matrix, constituents (aqueous phase, oil phase, emulsifiers, and other additives) and properties (viscosity, particle size, electrical conductivity and zeta potential). In addition to the stability of double emulsion, various means to express and modern techniques to measure it, the review also elucidates the role of newer emulsifiers and additives in improving the stability of double emulsion. The developments in target delivery of bioactives through double emulsion are highlighted. In vitro and in vivo studies proved target delivery of bioactives through double emulsion; however, confirmation through human trial is still pending.