Novel approaches in anthocyanin research - Plant fortification and bioavailability issues

Background: Anthocyanins are a major class of plant phenolic pigments, responsible for the red, purple or blue color of leaves, flowers, tubers, fruits and certain vegetables. They are considered the largest and most important group of water-soluble pigments in nature and have been described to have multiple health-promoting properties. However, the bioavailability of anthocyanins is reportedly extremely low, affected by factors inherent to the molecule's characteristics, as well as by the effect of food processing, transformations during the digestive process and their levels in fruits. Scope and approach: This review aims to discuss current knowledge regarding the effects of technological processes used in the food industry on the stability, bioavailability and biological effect of anthocyanins. In addition, a review of new trends in the improvement of anthocyanin production in plants is presented, which outlines what has been reported about genes involved in the regulation and its expression. Key findings and conclusions: The alterations that anthocyanins suffer, which can affect their bioavailability and biological effects, do not take place solely during the digestion process, caused mainly by pH and intrinsic and bacterial enzymes, but also during the different processing methods that food-containing anthocyanins can undergo. Factors such as thermal and non-thermal processing, storage, oxidative degradation and encapsulation systems have been shown to closely influence anthocyanins' stability and biological effects. In recent times, genetic manipulation aiming at upregulating the gene expression of metabolic pathways has been used to improve fruit quality and anthocyanin content in plant foods, and may also contribute towards counteracting some of the indicated limitations.