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Title: Understanding the effect of particle size and processing on almond lipid bioaccessibility through microstructural analysis: from mastication to faecal collection

Author
item MANDALARI, GIUSEPPINA - University Of Messina
item PARKER, MARY - The Quadram Institute Bioscience
item GRUNDY, MYRIAM - The Quadram Institute Bioscience
item GRASSBY, TERRI - University Of Surrey
item SMERIGLIO, ANTONELLA - University Of Messina
item BISIGNANO, CARLO - University Of Messina
item RACITI, ROBERTO - University Of Messina
item TROMBETTA, DOMENICO - University Of Messina
item Baer, David
item WILDE, PETER - The Quadram Institute Bioscience

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2018
Publication Date: 2/14/2018
Citation: Mandalari, G., Parker, M.L., Grundy, M.M., Grassby, T., Smeriglio, A., Bisignano, C., Raciti, R., Trombetta, D., Baer, D.J., Wilde, P.J. 2018. Understanding the effect of particle size and processing on almond lipid bioaccessibility through microstructural analysis: from mastication to faecal collection. Nutrients. 10. https://doi.org/10.3390/nu10020213.
DOI: https://doi.org/10.3390/nu10020213

Interpretive Summary: We have previously shown that the fat found in almonds is not readily available to the body for digestion. In the present study, we measured the amount of fat released during simulated chewing (artificial mastication) from four almond meals: natural raw almonds, roasted almonds, roasted diced almonds and almond butter from roasted almonds. The amount of fat released after chewing ranged from 6% for almond butter to 12% for whole and chopped roasted almonds. These data were used to validate a previously published theoretical model of fat availability from almonds. In comparison, the total fat available for digestion is estimated to be 94% in almond butter, and represents the freely available fat resulting from the initial sample processing (making butter) and the further small amount (6%) of fat released from the intact almond particles during chewing. Particle size distributions measured after chewing in natural raw almonds, roasted almonds, and roasted diced almonds showed most of the particles had a size of 1000 µm and above, whereas the almond butter mainly contained small particles (< 850 µm). Fecal samples were collected from volunteers who consumed the four forms of almonds (natural raw almonds, roasted almonds, roasted diced almonds and almond butter from roasted almonds) and microstructural analysis was performed. This analysis confirmed that some lipid in natural raw almonds, roasted almonds, and roasted diced almonds remained encapsulated within the plant tissue throughout digestion, whereas complete digestion was observed in the almond butter sample. We conclude that the structure and particle size of the form of almonds are the main factors in regulating fat availability in the gut.

Technical Abstract: We have previously reported on the low lipid bioaccessibility from almond seeds during digestion in the upper gastrointestinal tract (GIT). In the present study, we quantified the lipid released during artificial mastication from four almond meals: natural raw almonds (NA), roasted almonds (RA), roasted diced almonds (DA) and almond butter from roasted almonds (AB). Lipid release after mastication (8.9% from NA, 11.8% from RA, 12.4% from DA and 6.2% from AB) was used to validate our theoretical mathematical model of lipid bioaccessibility. The total lipid potentially available for digestion in AB was 94.0%, which included the freely available lipid resulting from the initial sample processing and the further small amount of lipid released from the intact almond particles during mastication. Particle size distributions measured after mastication in NA, RA and DA showed most of the particles had a size of 1000 µm and above, whereas AB bolus mainly contained small particles (<850 µm). Microstructural analysis of faecal samples from volunteers consuming NA, RA, DA and AB confirmed that some lipid in NA, RA and DA remained encapsulated within the plant tissue throughout digestion, whereas almost complete digestion was observed in the AB sample. We conclude that the structure and particle size of the almond meals are the main factors in regulating lipid bioaccessibility in the gut.