The role of dietary fiber in regulating lipid bioaccessibility of almonds during mastication

Almonds contain phytochemicals and nutrients that potentially have positive health benefits in relation to heart disease, diabetes and obesity. One important mechanism associated with these benefits is the bioaccessibility (release) of lipids from the almond tissue during mastication and digestion. Indeed, it has been reported that in human subjects on almond-rich diets, a significant proportion of lipid remains undigested, mainly caused by the entrapment of lipid by intact cell walls (dietary fiber). However, the bioaccessibility of almond lipid has not yet been quantified. We have studied this by performing a mastication trial in healthy human volunteers (n = 15). The particle size distribution of chewed almonds was measured using mechanical sieving and laser diffraction methods. Lipid release from ruptured almond cells was estimated using a theoretical model based on the particle size of the chewed almond tissue and the diameter of the lipid-rich cells. Our results showed that laser diffraction was the most reliable and efficient method. Lipid release from masticated almonds was estimated to be ~30% of total lipid and originated from the ruptured cells of the fractured tissue. This indicates that the majority of almond lipid is unavailable for the early stages of digestion. Further work will extend to studies of lipid release and digestion at more distal sites of the gastrointestinal trac