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ARS Home » Northeast Area » Beltsville, Maryland (BHNRC) » Beltsville Human Nutrition Research Center » Food Components and Health Laboratory » Research » Publications at this Location » Publication #331082

Title: Food processing and structure impact the metabolizable energy of almonds

item GEBAUER, SARAH - Food And Drug Administration(FDA)
item Novotny, Janet
item BORNHORST, GAIL - University Of California
item Baer, David

Submitted to: Food & Function
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2016
Publication Date: 9/20/2016
Citation: Gebauer, S.K., Novotny, J., Bornhorst, G.M., Baer, D.J. 2016. Food processing and structure impact the metabolizable energy of almonds. Food & Function. 7:4231-4238.

Interpretive Summary: Almonds are a rich source of certain vitamins and minerals, including some shortfall nutrients (nutrients that Americans do not consume in sufficient quantities). However, the perception that nuts contain a large number of calories may inhibit their consumption. But our previous research has demonstrated that calories from whole nuts are more difficult to digest and absorb than calories from other foods, though some evidence suggests that processed nuts (chopped, slivered, or buttered) may be more digestible. Therefore, we conducted a human feeding study to measure the calorie value of almonds in different forms. The calories available in whole natural almonds, whole roasted almonds, and chopped almonds were lower than the food label value, while the calorie value of almond butter was similar to the label value. Further, the calorie value of natural almonds was lower than the calorie value of whole roasted almonds, demonstrating that roasting can affect digestibility. We tested the hardness of the whole almonds to find that the natural almonds fractured into larger particles than the roasted almonds, which may explain the difference in digestibility. These results will be useful to scientists and health professionals.

Technical Abstract: The measured metabolizable energy (ME) of whole almonds has been shown to be less than predicted by Atwater factors. However, data are lacking on the effects of processing (roasting, chopping or grinding) on the ME of almonds. A 5-period randomized, crossover study in healthy individuals (n=18) was conducted to measure the ME of different forms of almonds (42 g/day), as part of a controlled diet: whole, natural almonds; whole, roasted almonds; chopped almonds; almond butter; and control (0 g/day). After 9 days of adaptation to each diet, participants collected all urine and fecal samples for ~9 days. Diets, urine, and feces were analyzed to determine ME. Fracture force and fracture properties of whole and chopped almonds were measured. Measured ME (kcal/g) of whole natural almonds (4.42), whole roasted almonds (4.86), and chopped almonds (5.04) was significantly lower than predicted with Atwater factors (P<0.001); ME of almond butter (6.53 kcal/g) was similar to predicted (P=0.08). The ME of whole roasted and chopped almonds was lower than almond butter (P<0.0001). ME of whole natural almonds was lower than whole roasted almonds (P<0.05). This may be due to lower hardness of whole roasted (298±1.3 N) compared to whole natural almonds (345±1.6 N) (P<0.05), and to whole natural almonds fracturing into fewer, larger particles, thus inhibiting the release of lipids. Atwater factors overestimate the ME of whole (natural and roasted) and chopped almonds. The amount of calories absorbed from almonds is dependent on the form in which they are consumed.