Aqueous and Enzymatic Extraction of Oil and Protein from Almond Cake: A Comparative Study

Abstract

The almond cake is a protein- and oil-rich by-product of the mechanical expression of almond oil that has the potential to be used as a source of valuable proteins and lipids for food applications. The objectives of this study were to evaluate the individual and combined effects of solids-to-liquid ratio (SLR), reaction time, and enzyme use on oil and protein extraction yields from almond cake. A central composite rotatable design was employed to maximize the overall extractability and distribution of extracted components among the fractions generated by the aqueous (AEP) and enzyme-assisted aqueous extraction process (EAEP). Simultaneous extraction of oil and protein by the AEP was favored by the use of low SLR (1:12.82) and longer reaction times (2 h), where extraction yields of 48.2% and 70% were achieved, respectively. Increased use of enzyme (0.85%) in the EAEP resulted in higher oil (50%) and protein (75%) extraction yields in a shorter reaction time (1 h), compared with the AEP at the same reaction time (41.6% oil and 70% protein extraction). Overall, extraction conditions that favored oil and protein extraction also favored oil yield in the cream and protein yield in the skim. However, increased oil yield in the skim was observed at conditions where higher oil extraction was achieved. In addition to improving oil and protein extractability, the use of enzyme during the extraction resulted in the production of skim fractions with smaller and more soluble peptides at low pH (5.0), highlighting possible uses of the EAEP skim 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.

Effects of Processing Conditions on the Simultaneous Extraction and Distribution of Oil and Protein from Almond Flour

“…However, increased SLR led to a reduction in the protein yield in the cream as demonstrated by the negative and significant effect (−0.58) (p < 0.05) at 40 min (Table 3). Overall, our results are in agreement with the ones presented by Rosenthal et al [18], De Moura et al [11] and Souza et al [16] in which higher protein extraction yields have been achieved by the use of lower SLR. The comparison of our results with the ones in the literature is challenging due to the differences in the starting material used.…”

“…The higher DH of the EAEP 1 skim is likely due to the higher enzyme activity at pH 6.5 (95% of its maximum activity), compared with its activity at pH 9.0 (50% of its maximum activity, as described by the manufacturer). Our results are in agreement with the literature where the use of enzyme for a longer time, until a certain extent, resulted in higher DH [11,16,34].…”

“…The comparison of our results with the ones in the literature is challenging due to the differences in the starting material used. However, a similar trend has been observed by Souza et al [16], which reported significant increment in protein extractability from the almond press cake (41 to 47% for the AEP and 60 to 75% for the EAEP) when SLR was reduced from 1:7.18 to 1:12.82. Similarly, Esteban et al [28] reported higher protein extractability when using a solvent/almond meal ratio of 2000:1 (vol/wt) for a single extraction.…”

“…No protein extraction yields were reported for both studies. The simultaneous extraction of oil and protein from the almond press cake has been recently reported by Souza et al [16]. In their study, oil extraction yields of 42 and 50% were achieved for the AEP and EAEP, respectively.…”

“…Skim, cream, insoluble, and starting material were evaluated for oil, protein, and solids content. Total oil and protein extraction yields, which represent all oil and protein extracted from the almond flour, and the distribution of the extracted compounds among the fractions generated by the EAEP were calculated as described by Souza et al [16]. Total oil extraction yield (TOE), oil distribution in the fractions (free oil yield, oil yield in the cream, oil yield in the skim, and oil yield in the insoluble), total protein extraction yield (TPE), and protein distribution in the fractions (protein yield in the cream, protein yield in the skim, and protein yield in the insoluble) were determined according to Equations (1), (2), (3) and (4), respectively.…”