Impact of wheat endogenous lipids on the quality of fresh bread: Key terms, concepts, and underlying mechanisms

While wheat (Triticum aestivum L.) flour contains only low levels of lipids (2.0% to 3.0%), they tremendously affect fresh bread quality. They are either starch (30% to 40%) or nonstarch (60% to 70%) lipids. While the former are important in bread staling, they affect neither bread loaf volume nor crumb structure as they are only set free at the very end of the baking process and prior to that they are not available because of their location inside starch granules. This review mainly focuses on wheat nonstarch lipids and how they impact on bread quality. Traditional approaches for investigating their role in bread making have been to use flours varying in bread making quality, to defat and reconstitute flour with (fractions of) the extracted lipids and/or to supplement flour with lipids from wheat or other sources. More recently, lipases have been successfully applied to investigate how wheat lipids affect bread making. It is generally accepted that their impact on bread loaf volume and crumb structure largely if not entirely relates to that on bread dough gas cells stability. However, today there are still different views and hypotheses on the mechanism(s) whereby they impact fresh bread quality. This review first defines and introduces the key terms, concepts, and theories related to lipids, lipases, and bread making. Next, the effects that wheat endogenous lipids and their enzymatically released hydrolysis products have on fresh bread properties and the mechanisms whereby they exert these effects are reviewed.