Impact of Almond Roasting and Particle Size on the Simultaneous Extraction of Lipids and Proteins for Almond Milk Production

Almond milk consumption has increased as an alternative to dairy milk. However, its low nutrient density and presence of emulsifiers have negatively impacted its consumer perception. We evaluated two sustainable approaches: aqueous (AEP) and enzyme-assisted extraction processes (EAEP), to produce a more nutrient-dense and functional milk. The effects of almond roasting, particle size, and extraction methods (AEP vs. EAEP) were evaluated on protein and oil extractability and in vitro protein digestibility. Unroasted and “light” and “dark” roasted almonds were ground to different particle sizes (flour, butter, or paste). AEP and EAEP were carried out in triplicate at pH 9.0, 1:10 solids-to-liquid ratio, 120 rpm at 50 °C for 60 min, with the addition of 0.5% alkaline endoprotease (w/w) in the EAEP. A two-way ANOVA (p<0.05) was used to evaluate the significance of the variables’ effect. Although dark roasting significantly increased oil extractability to 79% from flour (300µm, particle size reduction from flour to butter (35µm) or paste (20µm) was more effective to increase oil extractability up to 96%, regardless of the roasting or extraction methods used (AEP or EAEP). Roasting facilitated grinding and significantly increased protein extractability from flour (46 to 62%), but reduced extractability from butter and paste (smaller particle sizes) from 81 to 71% in the AEP due to protein denaturation. EAEP significantly increased protein extractability up to 91.76%, regardless of roasting employed. While roasting did not alter protein digestibility, the use of enzymes in the EAEP significantly increased in vitro protein digestibility from 84.6 to 96.9%. Overall, light roasted butter could be used to produce almond milk with higher nutrient density (1.63% protein and 1.25% oil for AEP and 1.87% protein and 5.15% oil for EAEP). These results indicate that almond milk with increased nutritional and functional properties can be produced by AEP and EAEP.