Addition of milk to coffee beverages; the effect on functional, nutritional, and sensorial properties

To date, there exists a debate on the effect of milk added to coffee infusions/beverages concerning the nutritional quality of coffee and the functional properties of its phenolic compounds. Yet, the full nutritional quality and functional properties of a coffee beverage without a significant negative impact on its sensorial profile are highly desired by the consumers. Negative/masking, positive, and neutral effects of milk on the antioxidant activity and bioavailability of coffee phenolics (particularly, chlorogenic acids) have been reported. Some potential factors including the type and amount of milk added, type of coffee beverage, the composition of both milk (protein and fat) and coffee (phenolic compounds), preparation method, assays used to measure antioxidant properties, and sampling size may account for the various reported findings. Interactions between phenolic compounds in coffee and milk proteins could account as the main responsible aspect for the reported masking/negative impact of milk on the antioxidant activity and bioaccessibility/bioavailability of coffee bioactives. However, considering the interactions between milk components and coffee phenolics, which result in the loss of their functionality, the role of milk fat globules and the milk fat globule membrane can also be crucial, but this has not been addressed in the literature so far.Highlights In most cases, milk is added to the coffee beverages in several various ways. Effect of milk on the nutritional/functional properties of coffee is controversial. Enough evidence suggests negative effects of milk addition on properties of coffee. Interactions of coffee phenolics and milk proteins could account as the main aspect. The role of milk fat globules and milk fat globule membrane may also be crucial.