PhD Candidate University of California Davis Davis, California
Almond milk is a popular beverage despite its relatively low protein content. The use of aqueous (AEP) and enzyme-assisted extraction processes (EAEP) facilitate the simultaneous extraction of protein and lipids from almonds, producing a more nutrient-dense milk with the potential for tailored protein functionality. The effects of extraction method, roasting, and particle size were evaluated on protein and oil extractability as well as 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. Roasting increased protein extractability from flour (46 to 62%), but reduced extractability from butter and paste from 81 to 71% in the AEP due to protein denaturation. EAEP significantly increased protein extractability up to 91.76% regardless of roasting. While roasting did not alter protein digestibility, the use of enzymes in the EAEP increased in vitro protein digestibility from 84.6 to 96.9%. Enzyme use reduced α-helix structure % compared to AEP, as well as increased % β-sheet structures. Roasting did not greatly impact AEP protein structure, but darker roasting led to decreased % β-turns and increased % unordered structures in EAEP. These results agreed with an observed decrease in surface hydrophobicity with roasting in AEP as well as reduced H0 and mean zeta-potential of skim surface proteins overall in EAEP. Overall, light roasted butter produced almond milk with 1.63% protein and 1.25% oil for AEP and 1.87% protein and 5.15% oil for EAEP, indicating that almond milk with tailored nutritional and functional properties can be produced by AEP and EAEP.