Abstract
The enzyme-assisted aqueous extraction process (EAEP) is an environmentally friendly strategy that simultaneously extracts oil and protein from several food matrices. The aim of this study was to investigate the effects of pH (6.5–9.5), temperature (45–55 °C), solids-to-liquid ratio (SLR) (1:12–1:8), and amount of enzyme (0.5–1.0%) on the extraction and separation of oil and protein from almond flour using a fractional factorial design. Oil and protein extraction yields from 61 to 75% and 64 to 79% were achieved, respectively. Experimental conditions resulting in higher extractability were subsequently replicated for validation of the observed effects. Oil and protein extraction yields of 75 and 72% were achieved under optimized extraction conditions (pH 9.0, 50 °C, 1:10 SLR, 0.5% (w/w) of enzyme, 60 min). Although the use of enzyme during the extraction did not lead to significant increase in extraction yields, it did impact the extracted protein functionality. The use of enzyme and alkaline pH (9.0) during the extraction resulted in the production of more soluble peptides at low pH (5.0), highlighting possible uses of the EAEP skim protein in food applications involving acidic pH. The implications of the use of enzyme during the extraction regarding the de-emulsification of the EAEP cream warrant further investigation.
Highlights
The intrinsic composition of almonds, which has long been recognized as nutritious and healthy, has enabled its use in a wide range of applications such as nutritive snacks, bakery, and confectionery ingredients, and as a feedstock to produce almond milk, yogurt, and oil [1,2,3]
Our results are in agreement with the literature where the use of proteases resulted in the production of proteins with higher solubility at lower pH [5,16,34,38]
EAEP2 skim protein solubility was significantly higher than the solubility of AEP2 skim proteins (45 vs. 23%), regardless of the extraction time evaluated
Summary
The intrinsic composition of almonds, which has long been recognized as nutritious and healthy, has enabled its use in a wide range of applications such as nutritive snacks, bakery, and confectionery ingredients, and as a feedstock to produce almond milk, yogurt, and oil [1,2,3]. Major downstream processing challenges in the fractionation of oil-bearing materials into added-value compounds (oil, protein, and carbohydrates) are usually associated with the simultaneous attainment of high extraction yields and adequate product functionality [5,6]. Oil-bearing materials can be extracted by the use of screw pressing or by solvent extraction. While the former leads to the production of specialty oils, extraction yields (70–90%) are not as high as the ones obtained by Processes 2019, 7, 844; doi:10.3390/pr7110844 www.mdpi.com/journal/processes. Processes 2019, 7, 844 solvent extraction (usually > 95%) [7,8]. Higher extraction yields are achieved by solvent extraction, the use of flammable solvents such as hexane has raised several safety and environmental concerns [9], which has prompted the search for the development and use of more environmentally friendly extraction strategies [10,11,12]
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